What makes the Gait Torque lacrosse head a favorite among veteran players. How does its design enhance offensive gameplay and face-off performance. Why is the Gait Torque considered a powerful weapon for midfielders.
The Legacy and Appeal of the Gait Torque Lacrosse Head
The Gait Torque lacrosse head has earned its place as a beloved piece of equipment among seasoned players. Its enduring popularity stems from a combination of innovative design features and versatile performance capabilities. But what exactly sets this head apart from others on the market?
At its core, the Gait Torque is engineered to be a formidable tool for offensive midfielders seeking to dominate the field. The head’s design philosophy prioritizes quick ball release, pinpoint accuracy, and customizable stringing options. These attributes make it particularly appealing to players who value precision and adaptability in their gameplay.
Key Features that Define the Gait Torque
- Channeled ball stringing track for centered pocket placement
- Drop Scoop technology for enhanced ground ball pickup
- Gait Canted Technology in the sidewalls for maximum offset
- Flexible construction suitable for face-off specialists
- Reinforced throat for durability during intense play
The combination of these features creates a lacrosse head that excels in offensive situations while also offering utility for face-off middies. This versatility has contributed significantly to the Torque’s long-standing popularity among players at various positions and skill levels.
Scoop Design: Enhancing Ball Control and Accuracy
One of the standout features of the Gait Torque is its innovative scoop design. The incorporation of Drop Scoop technology sets this head apart from many of its competitors. But how does this design element translate to on-field performance?
The Drop Scoop allows players to string their pockets with a pronounced channel. This channeling effect serves two primary purposes:
- It creates a quicker release point for passes and shots
- It enhances overall accuracy by providing a more consistent ball path
Beyond these performance benefits, the lowered scoop profile also facilitates easier ground ball pickups. This dual functionality makes the Gait Torque an excellent choice for midfielders who need to excel in both offensive plays and ground ball situations.
Customization Potential of the Scoop
The aggressive and strong scoop design of the Gait Torque offers players significant customization options. By adjusting the pocket stringing in relation to the scoop, players can fine-tune their stick to match their individual playing style and preferences. This level of customization allows for precise control over factors such as:
- Ball release point
- Shot trajectory
- Pass accuracy
- Ground ball handling characteristics
The ability to tailor these aspects of performance gives players using the Gait Torque a distinct advantage on the field, particularly in high-pressure offensive situations where split-second decisions and actions can make the difference between scoring and turning over possession.
Sidewall Engineering: Maximizing Power and Versatility
The sidewalls of a lacrosse head play a crucial role in determining its overall performance characteristics. In the case of the Gait Torque, the sidewalls incorporate several key design elements that contribute to its reputation as a versatile and powerful offensive tool.
Gait Canted Technology: Unlocking Shot Power
At the heart of the Torque’s sidewall design is Gait’s proprietary Canted Technology. This innovative approach gradually cants the lower rail of the head, creating a maximum offset profile. But what tangible benefits does this design provide to players on the field?
- Increased shot velocity: The offset created by the canted rails allows for more whip in the pocket, translating to harder, faster shots.
- Enhanced ball control: The gradual cant helps cradle the ball more securely, improving overall ball retention during high-speed maneuvers.
- Improved accuracy: The offset profile contributes to a more consistent release point, aiding in shot and pass accuracy.
These performance enhancements make the Gait Torque particularly well-suited for offensive midfielders who need to generate quick, powerful shots with minimal wind-up time.
Stringing Options and Pocket Customization
Another standout feature of the Gait Torque’s sidewalls is the abundance of stringing holes—15 in total. This generous selection of stringing points offers players and stringers a wide array of options for pocket customization. But how does this translate to on-field performance?
The multiple stringing holes allow for:
- Precise pocket placement to match individual playing styles
- Fine-tuning of pocket depth and shape
- Creation of specialized pockets for different game situations (e.g., face-off vs. offensive play)
- Easy adjustment and maintenance of pocket performance over time
This level of customization potential ensures that players can adapt their Gait Torque to meet the specific demands of their position and playing style, further enhancing its versatility on the field.
Flexibility and Face-Off Performance
While the Gait Torque is primarily marketed as an offensive midfielder’s head, its design characteristics also make it a viable option for face-off specialists. The head’s flexibility plays a crucial role in this dual functionality. But how exactly does this flexibility translate to face-off performance?
Benefits of Flexibility in Face-Off Scenarios
The Gait Torque’s flexible construction offers several advantages during face-offs:
- Improved “give” during clamps, allowing for better ball control
- Enhanced ability to maneuver around opponent’s stick during face-off battles
- Reduced risk of breakage under the intense pressure of face-off situations
- Faster recovery to normal shape after face-off, facilitating quick transitions to offense
These characteristics make the Gait Torque an attractive option for FOGO (Face-Off, Get-Off) players who need a head that can withstand the rigors of face-offs while still performing well in offensive situations.
Balancing Flexibility and Durability
While flexibility is advantageous for face-offs, it’s crucial to consider the long-term durability of a flexible head. How does the Gait Torque address this potential concern?
The head’s design incorporates several features to enhance durability without sacrificing flexibility:
- Reinforced throat with two support columns
- High-quality plastic composition that resists fatigue
- Strategically placed structural elements to distribute stress
These design choices help ensure that the Gait Torque can withstand the demands of both face-off play and regular offensive use, making it a versatile option for midfielders who engage in both aspects of the game.
Throat and Neck Design: Enhancing Stability and Compatibility
The throat and neck of a lacrosse head play crucial roles in its overall performance and usability. In the case of the Gait Torque, these elements have been carefully designed to enhance both stability during play and compatibility with a wide range of shafts.
Reinforced Throat for Durability
The throat of the Gait Torque features two reinforcing columns located on the front of the head. This design choice serves several important functions:
- Increased structural integrity during face-offs
- Enhanced resistance to warping and deformation
- Improved overall durability in high-impact situations
These reinforcements ensure that players can confidently engage in face-offs and aggressive play without worrying about compromising the integrity of their head.
Neck Design for Versatile Shaft Compatibility
The neck of the Gait Torque boasts a unique design that enhances its versatility and ease of use. Key features of the neck include:
- A skinny but elongated base
- Tight fit against a wide variety of shaft types
- No need for additional taping or modifications
This design ensures that players can easily pair the Gait Torque with their preferred shaft without concerns about looseness or instability. The secure fit also contributes to improved performance in crucial areas such as ground ball scooping and face-off maneuvers.
Addressing the Warp Factor: Longevity and Maintenance
One aspect of the Gait Torque that merits discussion is its potential for warping over time, particularly when used frequently for face-offs. While this is a common concern with many lacrosse heads, it’s important to understand the specific implications for the Torque and how players can mitigate this issue.
Understanding Warp Potential
The flexibility that makes the Gait Torque effective for face-offs also contributes to its susceptibility to warping. Factors that can influence warping include:
- Frequency and intensity of face-off use
- Exposure to extreme temperatures
- Storage practices
- Overall playing style and stick handling habits
It’s important to note that while warping is a potential issue, it’s not unique to the Gait Torque and is a consideration for most lacrosse heads on the market.
Strategies for Minimizing Warp
Players can take several steps to reduce the likelihood and severity of warping in their Gait Torque head:
- Proper storage: Keep the head in a cool, dry place when not in use
- Regular maintenance: Check for signs of warping and address them early
- Rotation: Consider alternating between multiple heads for face-offs
- Temperature awareness: Avoid leaving the head in hot cars or direct sunlight for extended periods
- Stringing technique: Ensure the pocket is strung to distribute stress evenly across the head
By implementing these practices, players can significantly extend the life and performance of their Gait Torque head, ensuring it remains a reliable tool on the field.
Field Position Suitability: Excelling in Offensive Midfield Play
While the Gait Torque has proven its versatility across multiple positions, it truly shines in the hands of offensive midfielders. The head’s design philosophy and feature set are particularly well-suited to the demands of this dynamic position. But what specific attributes make the Torque such an effective tool for offensive middies?
Optimal Characteristics for Offensive Midfield Play
The Gait Torque incorporates several key features that cater to the needs of offensive midfielders:
- Quick release capabilities for fast, accurate passes
- Customizable pocket for personalized ball control
- Lightweight design for agile stick handling
- Strong scoop for efficient ground ball pickups
- Durability to withstand the physical demands of midfield play
These characteristics allow offensive midfielders to excel in various aspects of their role, from initiating fast breaks to creating scoring opportunities in settled offensive sets.
Adapting to Different Offensive Styles
One of the Gait Torque’s strengths is its adaptability to different offensive playing styles. Whether a midfielder prefers a run-and-gun approach or a more methodical, possession-based game, the Torque can be customized to support their preferred style of play.
Key customization options include:
- Adjusting pocket depth and placement for optimal ball retention or quick release
- Modifying stringing patterns to enhance shooting or passing performance
- Fine-tuning the overall head shape through selective tightening or loosening of sidewall strings
This adaptability ensures that the Gait Torque can serve as a reliable tool for offensive midfielders across a wide spectrum of playing styles and skill levels.
Final Verdict: The Gait Torque’s Place in Modern Lacrosse
After a comprehensive analysis of its features, performance characteristics, and versatility, it’s clear that the Gait Torque continues to hold a significant place in the world of lacrosse equipment. But how does it stack up against more recent head designs, and who stands to benefit most from choosing the Torque?
Strengths and Potential Drawbacks
The Gait Torque offers several compelling strengths:
- Exceptional customization potential
- Versatility across multiple positions
- Proven durability and performance
- Strong suits for both offensive play and face-offs
However, potential drawbacks to consider include:
- Susceptibility to warping with heavy face-off use
- May not incorporate the very latest materials or manufacturing techniques
- Some players may prefer more specialized heads for specific positions
Ideal Players for the Gait Torque
The Gait Torque is particularly well-suited for:
- Offensive midfielders who value versatility and customization
- Face-off specialists who also contribute to offensive play
- Players who appreciate time-tested designs with proven performance
- Those who enjoy fine-tuning their equipment for optimal personal performance
For these players, the Gait Torque offers a compelling blend of tradition and performance that continues to make it a relevant choice in today’s lacrosse landscape.
In conclusion, the Gait Torque lacrosse head has earned its reputation as a versatile and effective tool for players across multiple positions. Its enduring popularity is a testament to its thoughtful design and adaptability to various playing styles. While newer heads may offer incremental improvements in specific areas, the Torque’s well-rounded performance and customization potential ensure its continued relevance in modern lacrosse.
Gait Torque Lacrosse Head Review
The Gait Torque lacrosse head has withstood the test of time and is coveted by veteran players. The Torque is a powerful weapon for an offensive middie looking to dominate the playing field.
The channeled ball stringing track allow you to seat the pocket in the middle of the head providing an accurate, quick release giving you the advantage in the offensive game.
Scoop
The scoop of the Torque features Gait’s Drop Scoop technology. This aspect of the lacrosse head gives the ability for players to string their pockets with a channel for a quicker release point and increased accuracy.
This aggressive, strong scoop gives the opportunity to customize your pocket to your own advantage and control your accuracy to a much greater extent. All while being able to pick up ground balls with ease due to the lowered scoop.
Sidewalls:
The sidewalls of the Gait Torque introduce “Gait Canted Technology” which creates maximum offset by gradually canting the lower rail.
The 15 stringing holes and the offset created by the canted rails will give you ultimate customization in pocket capabilities, while also creating the maximum shot velocity achievable so your shots will be harder than ever.
The sidewalls flexibility is also another aspect of the head that should not be overlooked. The Gait Torque is extremely flexible which makes it a viable option for your faceoff game to take the next big step.
Throat
The throat of the Torque is reinforced with two columns located on the front of the lacrosse head. You will have no problem taking face-offs and won’t worrying about the durability of the head.
Neck
The neck has a skinny but long base that holds tight against any shaft. You can be assured that during gameplay you won’t have any problem scooping ground balls like a pro or applying demanding flexibility at the faceoff position.
Warp Factor
The warp factor of the Gait Torque lacrosse can be a bit of a problem.
If you are planning on facing off with the Torque, it will be put under a lot of bending constantly. There are always ways you can avoid the warping of a lacrosse head and I see no problem with the Gait Torque being able to overcome the stress of being warped.
Every lacrosse player knows that warp cannot be avoided and the Gait Torque performs as well as any other head. This is an excellent lacrosse head for you to dominate the field with and no warp can take that away from the Torque.
Shaft fit
The elongated neck of the Gait Torque provides a perfect fit for all lacrosse shafts. You will not need to tape the stick on, that’s a pain that the Torque doesn’t require. You will have no problem finding your favorite shaft and fitting the Torque on to it.
Field Position
The Gait Torque is designed for the offensive midfielder that is looking to dominate the field in the offensive end. The Torque also appeals to the faceoff midfielders or FOGO’s that are looking to help their teams score goals consistently.
No other head offers the ability to customize the pocket as much as the Torque. Providing quick release and maximum accuracy, this head has offense in mind.
Summary
The Gait Torque is an awesome head for your typical on the run offensive midfielder. The sidewall stringing options along with the low dropped scoop can create a pocket perfect for quick release and prime accuracy. With these two things you will be able to make incredible feeds from anywhere on the field with the confidence that your passes will reach their mark.
For the faceoff middie, the Torque has incredible flexibility making clamps and rakes easier than ever. You will be dominating the middle of the field helping your team gain possession at all costs. The Gait Torque is the head to use to take your game to the next level.
Gear Review: Torque Head by Gait Lacrosse
[rwp-review id=”1″]
Company: Gait Lacrosse / Product: Torque Head / Price: $49.
99
The Gait Torque is really a classic by now. It’s been out for years, it’s tried, tested, and true, and those that swear by it, love it to death. It’s the bigger, better, younger brother of the Triton, and it’s been a popular head, for a long time, for good reason. It’s just the first of many reviews coming up for the product Gait sent our way to test out:
Appearance… +7.5
The fully offset Torque is pretty smooth looking. Rounded, semi-square stringing holes dot the entire sidewall, and three big openings present themselves on the sidewall. It’s sleek and streamlined, and is as cut down and minimalist as possible. It looks light, and it is.
Stringing… +7.5
The Gait Torque is wonderful to string. There are inside and outside sidewall wings towards the top of the head, which means you can create a wide or narrow channel. The sidewall holes themselves are large and there are a ton of them. Even the scoop is laden with stringing holes, creating as many options for customization as possible.
The head naturally creates a good pocket with even a basic mesh string job. Overall, the design is a winner!
So why does it get a 2.0 deduction? One reason, plain and simple: the sharper edges of the plastic sidewall holes create a point of wear and tear for your strings, and this means that the sidewalls can wear out faster than they might otherwise. It is the only knock on this head’s stringability, and if you use thicker sidewall, you can avoid it for the most part.
Stiffness… +8.0
Stiffness is a tough category to really gauge because sometimes a lot of stiffness is good (say, for a defenseman), and sometimes it’s bad (say, for a FoGo). So since the Torque is really an all-around head for the high school player, I’ll gauge it as that: all around. For defenseman, it might be a little thin. However, for the defender looking for a light head, the Torque could be a nice choice. For middies and attack, it’s right up your alley and will get the job done.
Overall, I’d say that’s about a 8 in stiffness, wouldn’t you? Moving right along.
Durability… +8.0
Once again, due to the thin nature of the head and minimalist approach to plastic, the Torque can get a little tweaked over time. It might warp just a shade or pinch in or out, but from my experience, it won’t break. I just dyed the first Torque I ever got and gave it away to a kid. It’s still in great shape, and totally playable… six years later.
If you’re worried about the head making it through a season, you probably shouldn’t be. These heads should definitely be able to stand up to a good year’s worth of abuse. Everyone breaks a head every once in a while, but the Torque is pretty tough.
Value… +10
At a penny under $50 this is one of the best values I’ve seen in a while. If this head had been $50 when it came out I would have bought 6 of them… and then only needed the first one. It’s a fantastic value and since these are HS legal, I expect a lot of guys to snap them up.
They’re also great for box lacrosse and can be pinched pretty easily, so that’s nice.
Overall… 8.4/10
Overall the knocks on the Gait Torque are really quite small. It’s a light head that provides a ton of stringing options and can work for almost any position on the field. At $50 it’s a steal and while it might not be brand new, it’s a classic, and more importantly, it works.
Abnormal joint torque patterns exhibited by chronic stroke subjects while walking with a prescribed physiological gait pattern | Journal of NeuroEngineering and Rehabilitation
Subjects
Ten chronic hemiplegic stroke subjects (age: 51–65, avg 56.5 yrs, SD 4.9) with mild to moderate lower limb impairments (Fugl-Meyer lower limb scores 16–31 avg 21.1, SD 5.3) were tested along with five healthy subjects with no known neurological impairments or gait disorders (age: 51–69, avg 58.8, SD 6.7). Stroke inclusion criteria included unilateral lesion of the cortex or subcortical white matter with an onset greater than one year prior to testing.
Subjects were excluded from the study if they presented with severe osteoporosis, contracture limiting range of motion, significant muscle tone, cardiac arrhythmia, or significant cognitive or communication impairment which could impede the understanding of the purpose of procedures of the study (less than 24 on the Mini Mental State Exam [25]). All experimental procedures were approved by the Institutional Review Boards of Medstar Research Institute and the Catholic University of America. Informed consent was obtained prior to each test session.
Motor impairment was evaluated in the paretic lower extremity using the Fugl-Meyer (FM) scale [26], which ranges from 0 to 34 with the maximum score indicating no observable deficits in function. In order to study hemiparetic stroke patients with mild to moderate impairment levels, we targeted subjects having a FM score in the range of 10–30.
Instrumentation
A Codamotion active marker system (Charnwood Dynamics LTD, UK) was used to track the leg kinematics of each subject in the same manner as Neckel and Hidler [27].
Tracking kinematic patterns using a motion capture system was necessary since subject’s legs are not rigidly coupled to the Lokomat and therefore do not move through the same trajectory as the system’s linkages [28]. Thus relying on the Lokomat potentiometers to measure leg kinematics is highly inaccurate. Custom marker clusters were used such that the cuffs that fix the subject to the Lokomat would not interfere with the placement of the 24 active markers used. First, rigid plastic bases with foam undersides were inserted under the Lokomat leg cuffs. The motion tracking marker clusters were then fixed to rigid plastic caps that fit firmly on top of both the base and Lokomat leg cuff strap with Velcro straps. The Codamotion camera was placed approximately 2 meters in front of the Lokomat. The marker positions were recorded at 100 Hz and exported to the software package Visual 3D (C-Motion INC, Rockville MD) where a customized model of each subject was created from anthropometric data. From this model limb segment center of mass, segment acceleration, joint centers and limb angles were derived and exported to the software package Matlab (Mathworks, Natick MA) for further filtering and processing.
An ADAL split-belt instrumented treadmill (TECHMACHINE, Andrézieux France; see Belli et al., 2001 for detailed description [29]) was used below the Lokomat, which allowed for ground reaction forces to be recorded for each leg in the vertical, anterior-posterior, and medial-lateral axes. Each of the six Lokomat cuff brackets that couple the subject’s leg to the device were instrumented with 6 degrees of freedom loadcells (JR3 Inc, Woodland CA) that measured the interaction forces and torques applied to the subject’s legs by the Lokomat. The Lokomat is equipped with optional footstraps that lift the forefoot up so that the toes can clear the ground during swing. These footstraps were used on the affected leg of all stroke subjects, where the tension in each strap was measured with uniaxial force sensors (MLP-50, Transducer Techniques, Temecula CA). A photograph of the loadcell setup along with a schematic of the measured forces can be seen in Figure 1.
Figure 1
Setup of instrumentation.
The photograph on the left shows the loadcells on the leg cuffs of the Lokomat which measure the interactions between the subject and the device. The graphic on the right represents the recorded forces acting on a subject’s right limb – ground reaction force, footstraps, and loadcells. Graphic adapted from Visual 3D (C-Motion INC, Rockville MD).
Electromyographic (EMG) recordings were collected from the tibilias anterior, gastrocnemius, biceps femoris, vastus medialis, rectus femoris, gluteus maximus, gluteus medius, and adductor longus of both limbs in stroke subjects and the left limb of four of the five control subjects (one subject was improperly grounded and their EMG data was not analyzed) using two Bagnoli-8 EMG system (Delsys, Inc., Boston, MA). EMG data, along with the forces and torques from the loadcells, were anti-alias filtered at 500 Hz prior to sampling at 1000 Hz using a 16-bit data acquisition board (Measurement Computing, PCI-DAS 6402, Middleboro, MA) and custom data acquisition software written in Matlab and stored for later analysis.
Force plate data was further low-pass filtered using a zero-delay fourth order Butterworth filter with a 25-Hz cutoff frequency.
Protocol
The stroke subjects were first fitted with a harness so that a portion of their body-weight could be supported while control subjects did not wear the harness. Subjects were led into the Lokomat and with the help of a physical therapist the device was adjusted so that the Lokomat hip and knee centers lined up with those of the subject. After being correctly aligned, the marker clusters were applied to the subject’s feet, shanks, and thighs. A neoprene band was tightly wrapped around the subject’s waist and individual motion tracking markers were affixed to the boney landmarks of the pelvis.
After the subject was in the Lokomat, an experienced physical therapist conducted a practice session for up to 2–3 minutes to allow the subject to acclimate to the device. Stroke subjects began walking suspended above the treadmill and the amount of body weight support provided by the accurate and constant Lokolift system [30] was reduced until a minimum level that produced an appropriate gait pattern was found.
Inappropriate gait patterns were judged by the physical therapists and included such factors as impaired limb buckling during stance, toe dragging through swing, and excessive trunk movements that would not be analogous to a healthy gait pattern. The levels of minimum body weight support ranged from 11.5 to 25.6 percent of total body mass.
Following the acclimation period, the speed of the Lokomat was randomly adjusted to one of 4 different speeds (1.5, 2.0, 2.5, and 3.0 km/hr), and after allowing the subject to acclimate to the new speed 30-seconds of data was collected. The subject was told to try and match the kinematic pattern of the Lokomat to the best of their ability. It should be noted that the Lokomat was run with 100% guidance force under these trials, meaning the device was in a pure position control mode rather than an impedance mode. While the Lokomat has the ability to change the amount of subject assistance, our goal was to determine whether subjects assisted through physiological gait patterns produce symmetric, normal joint torques.
For this, position control mode was more appropriate than an impedance mode. The remaining 3 speeds were tested in the same manner. Adequate rest breaks were taken throughout the experiment to minimize fatigue. For the purposes of this paper, only trials run at 2.5 km/hr are reported.
Following all trials, a precision digitizing arm (MicroScribe MLX, Immersion, San Jose CA) was used to accurately locate the position of the Lokomat, load cells, and foot lifter locations with respect to anatomical landmarks. This information was necessary to determine the location of the Lokomat forces acting on the subject’s lower extremities when computing the joint torques throughout the gait cycle [24].
Data analysis
The vertical ground reaction forces were used to mark the heel strike of each step, measured as the point were the force exceeded 50 N. All experimental data (including that calculated in Visual 3D) over the 30-second trials were broken up into individual strides (from heel strike to heel strike in the same leg), which were then resampled to the same signal length.
The subject kinematics calculated from Visual 3D (limb segment center of mass location, segment acceleration, joint center locations and limb segment locations) were combined with all the forces and torques acting on the subject – the ground reaction forces from the split-belt instrumented treadmill, as well as at the Lokomat leg cuffs (location of the loadcells calculated from the Lokomat potentiometers and digitized Lokomat limb lengths) – into a custom inverse dynamics model [24]. This model was then used to calculate joint torques that the subjects were generating throughout the trial in both the frontal and sagittal planes, as well as the torques that the Lokomat were inducing on the subject. For each subject, the data generated for all steps within a 30-second trial was averaged for each limb.
Statistical analysis
A total of 5 kinematic and 5 kinetic measures of the profiles of the impaired, unimpaired, and control limbs (left limb) were compared using a single factor ANOVA.
The kinematic measures were ankle, knee and hip range of motion (ROM), maximum vertical pelvic displacement from heelstrike, and the time in the gait cycle at which the minimum pelvic displacement occurred. The kinetic measures were maximum vertical ground reaction force, maximum ankle dorsiflexion torque, magnitude of knee extension torque at the midpoint of the initial swing phase (68.5% gait cycle), the time at which the maximum hip extension torque occurred, and the magnitude of the hip adduction torque at mid swing (80% gait cycle). A Bonferroni correction was used to reduce the risk of Type I errors, so that with 10 measures tested, a α = 0.005 was used for all comparisons.
The EMG activity from the selected muscle groups was band-pass filtered (20–450 Hz), full-wave rectified, and then smoothed using a 200-point RMS algorithm. For each muscle recorded, the EMG traces were normalized to that subject’s highest value recorded across all trials to allow for inter-subject comparison.
The mean normalized EMG trace for each subject was broken up into seven phases of the gait cycle (initial loading 0–12%, mid-stance 12–30%, terminal-stance 30–50%, pre-swing 50–62%, initial-swing 62–75%, mid-swing 75–87%, terminal-swing 87–100%) and each section integrated as in Hidler and Wall [31].
Gait Torque Device | Device alleviates the curre…
About
Gait Torque Device
BSU File Reference #140
Abstract
There are very few current products that can assist patients with rotational foot problems that cause impediments in their gait. Currently the only tools that are available to achieve the desired effects are therapeutic bands that are wrapped around the leg, connecting to the patient’s belt and shoe. This current technique constricts blood flow in the leg and provides a major inconvenience to the patient.
Boise State University has developed a Gait Torque Device that alleviates the problems associated with the current treatments.
Our apparatus assists the human gait by providing a rotational force on the leg/hip in order to bring the leg/hip to a straight “toes-forward” position. It works by using three components; the belt component, the shoe component and the component that attaches the shoe to the belt. The attachment from the shoe to the belt can be manipulated to provide varying levels of torque on the foot of the patient. The direction of the torque can also be controlled to the extent that the rotational force can be applied either clockwise or counterclockwise on the patient’s foot.
This is a non-intrusive apparatus that does not constrict the blood flow in the leg, like therapeutic bands. Even more, the Gait Torque Device can be removed and attached by any person and to most shoe types. The amount of force applied to the foot can also be varied for comfortable adjustment to any patient. The ability to manipulate the force of the torque is a key to therapeutic recovery.
The patient, or care provider, can raise or lower the amount of torque force, according to the patient’s need. This allows the patient to make more neurological connections with the brain, as they get stronger, helping facilitate a lasting correction to their gait. It also has the dual potential for occupational “at home” use as well as clinical use in rehabilitation clinics.
Advantages
• Easy to use apparatus allows for at home and clinical use.
• Non-intrusive design that doesn’t constrict blood flow.
• Multidirectional torque.
• Adjustable torque for comfortable and effective use.
Boise State is looking for a Licensee for this technology.
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Here’s your chance for a great price on a lacrosse head! Drop-V scoop channels the pocket allowing for improved accuracy and a quicker release point. Multi Hole stringing system allows for multiple string patterns..
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High torque realization of the stepping over gait for a humanoid .
..: Ingenta Connect
Purpose
This paper aims to propose a pulsing type joint servo driver-based obstacle surmounting method for a humanoid robot according to the whole-body dynamics model, which fully takes into account the relationship between
the whole-body stability margin and instantaneous torque.
Design/methodology/approach
First, the authors designed a new practical instantaneous large torque strategy for a pulsing type joint servo driver by modeling
the whole-body dynamics of the humanoid robot. The work also considered joint angle planning based on the dynamic model for crossing obstacles. Second, in the simulation and experimentation, the instantaneous torque of the driver is used to realize successful crossing of obstacles by the humanoid
robot. This verifies the correctness of the whole-body dynamics model and the feasibility of the method for crossing obstacles.
Findings
The experimental data and results are described and analyzed, showing that the
proposed method is feasible and effective through simulation and implementation.
Originality/value
The main contribution is the humanoid robot’s actuation control technology and humanoid action realization, which
could be used for squatting and moving heavy objects to help a humanoid robot adapt effectively.
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Keywords:
Humanoid robot;
Obstacle surmounting;
Servo drive;
Whole body dynamic modeling
Document Type: Research Article
Affiliations:
1:
School of Information Engineering, Southwest University of Science and Technology, Mianyang (Sichuan), China
2:
Automation Research Institute Co., Ltd. of China South Industries Group Corporation, Mianyang (Sichuan), China
Publication date:
June 15, 2020
Relationship between Asymmetry of Gait and Muscle Torque in Patients after Unilateral Transfemoral Amputation
Many studies have shown that unilateral transfemoral amputation involves asymmetric gait.
Transfemoral amputation leads to muscle atrophy in a tight stump resulting in asymmetry in muscle torque between the amputated and intact limb. This research is aimed at verifying if a relationship between torque values of hip joint flexors and extensors and gait asymmetry in patients with TFA exists. Fourteen adult subjects with unilateral TFA took part in the experiment. Gait symmetry was evaluated based on the ground reaction force (GRF). Measurements of muscle torque of hip flexors and extensors were taken with a Biodex System. All measurements were taken under isokinetic (60°/s and 120°/s) and isometric conditions. The symmetry index of vertical GRF components was from 7.5 to 11.5%, and anterio-posterior GRF from 6.2 to 9.3%. The symmetry index for muscle torque was from 24.3 to 44% for flexors, from 39 to 50.5% for extensors, and from 28.6 to 50% in the flexor/extensor ratio. Gait asymmetry correlated with muscle torque in hip joint extensors. Therapy which enhances muscle torque may be an effective form of patient therapy.
The patient needs to undergo evaluation of their muscle strength and have the therapy programme adjusted to their level of muscle torque deficit.
1. Introduction
People with unilateral transfemoral amputation (TFA) have lost their knee and ankle joint. Frequent complications observed within the amputated limb are muscle atrophy and decrease in muscle contractions in the thigh stump [1]. These lead to a decrease in the muscle torque which stabilizes the hip joint of the amputated limb [2]. Gait asymmetry is reported in range of motion, stride length and width, time variables of the gait cycle, and component values of ground reaction forces (GRF) [3–5].
Many studies have reported that values of the vertical ground reaction force components (vGRF) of an amputated limb in the support phase are lower than for the intact limb [6–8]. Also, the component of the anterior-posterior ground reaction force (a-pGRF) is 50% smaller in the intact limb [9]. Asymmetrical GRF distribution results from the subject’s willingness to protect the amputated limb by decreasing the load.
Therefore, subjects with TFA shift their centre of mass (CoM) toward the intact limb, which decreases load on the amputated limb [10]. Prolonged asymmetrical loading was found to be a predictor of atrophy in tight stump muscles, overloading, and degenerative changes [11]. Patients with TFA develop compensatory strategies in order to decrease asymmetry, such as the vaulting strategy or hip hiking [12, 13].
Studies on healthy human gait have shown that gait asymmetry may correlate with muscle torque asymmetry [14]. Research evaluating patients with transtibial amputation (TTA) shows statistical significant differences between muscle torque asymmetry of the intact and amputated limbs, 33 ± 20% for extensors and 22 ± 23% for flexors [15]. Moirenfeld et al. [2] pointed to the existence of 49.7 Nm deficit muscle torque in amputed limbs for extensors and 35.1 Nm for flexors of the hip joint in patients with TTA. Hip muscle torque asymmetry between intact and amputed limb can be assumed to point to gait asymmetry.
It is important to decrease the asymmetry reported between muscle strength in hip joints because significant differences between the intact and amputated limb may lead to strain and quicken degenerative changes [16]. The ability to decrease muscle torque asymmetry was described in studies comparing symmetry in torque flexors and extensors of subjects with TFA engaged in sports and those physically inactive. The authors concluded that physical activity improves the strength of the muscles that affect the hip joint [17].
This study evaluated gait asymmetry based on the symmetry index of GRF components. Many research papers have examined this problem [18]. The symmetry index can be a criterion differentiating correct and pathological movement patterns, as well as a tool to evaluate the rehabilitation process [14, 19]. It has been hypothesized that an increase in strength ability of hip joint muscles may improve gait symmetry. This can be obtained by introducing resistance exercises to the rehabilitation process of patients with TFA.
The correlation between hip joint muscle strength and asymmetry of kinetic gait variables in people with TFA has not been studied. However, there has been some research on subjects with below-knee amputation. Researchers have shown a correlation between gait asymmetry and muscle torque in patients with TTF [10, 20–22]. We expected to observe the same correlation in patients with TFT. That is why this research is aimed at identifying a relationship between torque values, symmetry of muscle torque of hip flexors and extensors of an intact and amputated limb, and a degree of gait asymmetry in patients with TFA.
2. Material and Methods
2.1. Recruitment and Inclusion Criteria
Fourteen adult subjects with unilateral TFA (mean age: 46 ± 14 years, mean height: 1.76 ± 09 m, mean body mass: 79.6. ± 18.3 kg) took part in the experiment. All participants were subject to gait analysis, but only eight participated in muscle torque evaluation. Six patients did not participate in muscle torque evaluation because their stump was too short (Table 1).
Some were physically active and participated in sports like wheelchair tennis, sitting volleyball, swimming, and body building. The patients’ body height, mass, age, and amputation characteristics are presented in Table 1. Prior to the research, all participants were informed about its aim and their ability to terminate participation at any stage without providing a reason. All participants provided written, informed consent. Only adults were selected for the research. All subjects used prostheses every day and did not use any other gait aid device. Each participant had been using a prosthetic limb for six months, minimum. The exclusion criteria of the study were stump or lower limb pain and chronic illnesses, which might have influenced motor organ performance.
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R: right side; L: left side; +: patients who participated in muscle torque measurement. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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63The research project was approved by the university ethics committee.
2.2. Data Processing
2.2.1. Gait
A 6 m walking distance at a self-selected speed enabled the recording of 3 to 4 complete gait cycles. The protocol was run 6 times. Ground reaction force (GRF) data was collected with the use of two Kistler 9286AA-A plates with the frequency of 1 kHz situated at the centre of a pathway [23, 24].
In addition, mean gait speed was computed for each patient and key moments (heel strike and toe-off) acquired for each measurement trial using SMART-E motion analysis system (BTS Bioengineering, Milan, Italy).
Raw GRF measurements were filtered by a 2nd order Butterworth filter with a cut-off frequency of 6 Hz. For the main Cartesian components of GRF vector, such as vertical ground reaction force (vGRF) or horizontal anterior-posterior (a-pGRF) (Figure 1), the researchers conducted a parametrization by computing the following:
(i)vF1: maximal vGRF of overweight at the initial weight acceptance phase(ii)vF2: minimal vGRF of underweight during middle stance(iii)vF3: maximal vGRF of overweight during terminal stance(iv)a-pF1: maximal braking a-pGRF at initial stance(v)a-pF2: maximal push-off a-pGRF at terminal stance
2.3. Torque Measurement
Measurements of speed-strength abilities in hip joint muscles in flexion (FL) and extension (EXT) were taken with a Biodex System 4 Pro device. The measurement setup was comprised of a chair with an adjustable back angle and seat height, and straps to stabilize the trunk (2 straps) and pelvis (1 strap).
An adjustable arm had a strap to stabilize the lower limb or a thigh stump. Prior to measuring, subjects removed their orthopaedic limb and underwent a thigh-skin evaluation of the remaining limb. The subjects’ supine position and angular velocities were selected on the basis of the manufacturer’s recommendations (Figure 2). All individuals were allowed to familiarize themselves with the type and resistance of movement to be performed. A thigh stump could not be shorter than 22 cm measured from the trochanter. The design of the device enabled the alignment of the dynamometer axis of rotation with the axis of hip-joint movement. All measurements were taken in the sagittal plane under isokinetic (angular velocity 60°/s and 120°/s) and isometric conditions. Flexors (FL) and extensors (EXT) of the hip were studied in sets of 5 repetitions. The time interval between each measurement (rest time) was 1 minute. The following variables were studied: peak torque for FL and EXT under isometric condition, peak torque for FL, and EXT under isokinetic conditions.
Ratio of the FL to EXT torques (F/E ratio) for the intact and amputated limbs was calculated. GRF data and muscle torque were normalized to body weight (BW). The following equation was used to compute the symmetry index for gait variables and muscle torque:
Symmetry index designates symmetry (low values) or asymmetry (high values) for an x variable between uninvolved (un) and involved (amputated) sides and is expressed in percents.
2.4. Statistics
Normal distribution of the variables was determined by implementation of the Kolomogorov-Smirnov and Lilliefors tests. Not all values were normally distributed; thus, the Wilcoxon signed-rank test was applied to determine differences between the amputated limb and intact limb. The relationship between muscle torque and gait asymmetry was evaluated with the use of Spearman’s rank correlation coefficient. The statistical significance level was set as .
3. Results
Gait symmetry was evaluated based on the vertical ground reaction force (vGRF) and the anterior-posterior (a-p GRF) ground reaction force (Table 2).
In addition, due to differences observed between patients in regard to their morphological parameters, statistical analysis was carried out for ground reaction forces normalized to body weight (%BW) and normalized muscle torque to body mass (Nm/kg). Variables were statistically smaller for the amputated limb in regard to values of GRF by 7.7%BW () in the support phase (vF1), 12.3%BW () in terminal stance (vF3), and 12.0%BW () for posterior braking force at initial stance (a-pF1). Values of the vertical component of GRF during underweight in middle stance (vF2) were on average 5.8%BW higher () for the amputated limb.
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1
90 ± 0.78Muscle torque of hip joint flexors and extensors in all measurement conditions was statistically significantly lower for the amputated limb (Table 2). Specifically, the differences between the two limbs were 0.28 Nm/kg () for FL and 0.45 Nm/kg () for EXT in isometry, 0.44 Nm/kg () for FL and 0.47 Nm/kg () for EXT in isokinetic 60°/s, and 0.37 Nm/kg () for FL and 0.24 Nm/kg () for EXT in isokinetic 120°/s. There were no statistically significant differences between flexors and extensors (F/E ratio) due to the high variability (high standard deviation).
The next stage of this research was to find correlations between gait symmetry index and muscle torque symmetry index in hip joint flexors and extensors. The analysis showed a positive correlation between the symmetry index of the horizontal GRF in the support phase (vF1) and torque symmetry index of hip joint extensors in isometric conditions (Table 3). The remaining gait phases illustrated a correlation of GRF symmetry with the torque symmetry index of hip joint extensors at 120°/s. In this research, no statistically significant differences were found between GRF symmetry and the flexor to extensor ratio (F/E ratio).
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12Analysis of correlations between gait asymmetry and torque in hip joint flexors (Table 4) showed a statistically significant relationship only in muscles of the amputated limb.
The results revealed a positive correlation between the symmetry index in maximal posterior braking a-pGRF at initial stance (a-pF1) and muscle torque of hip joint flexors in isometric conditions. A statistically significant correlation between gait asymmetry and muscle torque of the intact and amputated limb extensors was observed for isometric and isokinetic measurements (120°/s). In detail, the muscle torque of extensors obtained in isometric conditions at 120°/s showed a negative correlation with braking force (a-pF1) and positive with propulsion force (a-pF2) for the amputated limb. There was a negative correlation between muscle torque in isometric conditions and vertical underweight force (vF2) observed in the intact limb. Also, a negative correlation was observed between muscle torque in isokinetic conditions at 60°/s and braking force (a-pF1) and positive correlation with propulsion force (a-pF2). Additional correlations were observed between the F/E ratio. A correlation between the ratio of the amputated limb for maximal muscle isometric force was positive for braking force (a-pF1) and negative for propulsion force (a-pF2). There was a positive correlation between maximal muscle isometric force and vF2 for the intact limb, and a negative correlation between maximal isokinetic force at 60°/s with propulsion force (a-pF2).
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3.1. Individual Results
The subjects differed in terms of age, body mass and height, and level of physical activity. Therefore, there were two statistical analyses conducted by the researchers: one of data collected for the entire group and one of variables related to the individuals. They compared muscle torque in subjects with the results of healthy people at the same age range.
Patient’s data was standardized and adjusted individually in respect to age, height, and mass using regression equations provided by Harbo et al. [25].
Results obtained by healthy subjects in the selected age groups were normalized to 100% and presented in Figure 3. Patient S1 (46 years old) obtained higher muscle torque values of the hip joint flexor of the intact and amputated limbs than his peers. The same conclusion was drawn for hip joint extensors. Muscle torque values obtained by the intact limb were twice as high, which resulted in great asymmetry between the intact and amputated limb. This patient showed a high level of muscle strength which was related to quite a significant level of gait asymmetry (163.5%) during the anterior push-off a-pGRF at terminal stance. Similar muscle torque was obtained by patient S12 (age 58) who showed greater asymmetry between vertical GRF components.
4. Discussion
There are many factors having influence on gait asymmetry in people with unilateral TFA such as age, patient’s physical fitness, time post amputation, type of a prosthetic limb, and rehabilitation program. Prolonged time asymmetric loading of the lower limb—intact and amputated—results in atrophy of stump muscles, degenerative changes in the joints of the intact limb, and lower back pain. Consequently, participation in therapy aiming at reducing gait asymmetry seems justifiable. It has been hypothesized that there is a correlation between strength of hip joint muscles and gait asymmetry assessed on the basis of the ground reaction force (GRF) components. Confirmation of this hypothesis was illustrated by a selection of exercises strengthening hip joint muscles in patient therapy [1, 10].
4.1. Gait
The typical M-shape observed in healthy people was also characteristic for the vertical (vGRF) component of amputated limbs of the patients [23, 24]. All analyzed GRF variables showed quantitative differences between the amputated and intact limb. They pointed to a significant load on the intact limb, which may in turn cause degenerative changes. This problem has been highlighted by a number of authors [26, 27]. Lower relative GRF values in all gait phases (vF1, vF3, a-pF1, and a-pF2) except in the middle stance (vF2) were observed for the amputated limb. de Castro et al. [28] observed similar values of a relative vGRF (101.6 for vF1 and 97.9 for vF3) in a group of patients aged 56.7 ± 11.7 years. However, relative anterior-posterior ground reaction force (a-pGRF) component values assessed by de Castro et al. [28] at initial stance and terminal stance were lower in comparison to our patients (7.12 for a-pF1 and 7.4 for a-pF2). Schaarschmidt et al. [29] showed similarities to our results of vGRF in the middle stance (in the underweight phase) and terminal stance (in the overweight phase). Furthermore, they concluded that vF2 values of an amputated limb decreased along with an increase of gait velocity. Lower vGRF values in the intact limb in the final support phase could occur as an adaptive mechanism to increase the foot clearance of the prosthetic foot, otherwise also known as the vaulting [13]. The results obtained in this research, when compared with those obtained by different authors, showed that vF1, vF3, and a-pF1 GRF of the intact limb were identical for healthy people, while the values for the amputated limbs were much smaller [30, 31].
Research showed that asymmetry in walking over many years with greater loading on the intact limb may be the cause of degenerative changes to weight-bearing joints [32]. Therefore, many authors are interested in gait asymmetry in amputees. This research showed the greatest vGRF asymmetry between the limbs in the terminal stance (vF3): 11.5%. Nolan et al. [5] in their research on the relationship between vF1 asymmetry and gait velocity (at velocities of 0.5, 0.9, and 01.2 m/s) showed that gait symmetry indices were on average 29.4, 28.9, and 26.0% and were higher than those obtained by our patients (7.5%), presumably, because our patients were physically active. The symmetry index in healthy people depends on gait speed but does not exceed 10% and decreases along with a decrease in speed [5, 33].
4.2. Muscle Torque
One of the main causes of gait disturbance in patients after TFA is the imbalance of muscles acting on the hip joint following removal of the femoral ends of major muscles, such as the hamstrings, adductors, rectus femoris, and sartorius muscles. Burger et al. [1] (using electrical stimulation and measurement of muscle belly displacement) illustrated an important function of the gluteus maximus (GM) in improving the quality of gait. They found that atrophy of GM proved by decease of muscle belly displacement of the amputated limb of TFA patients requires programmes of physical therapy directed at strengthening the muscle. These slow down thigh motion at the end of the swing phase and hold the knee joint straight in the support phase [34]. Muscles acting on the hip joint are presumed to have influence on the transfer of weight to the prosthetic limb, similar to people with below-knee amputations [21].
Except for a single case study, we have not found any published research involving torque evaluation of hip joint flexors and extensors in patients with TFA [17]. We had access only to studies regarding patients and these on muscle torque hip abductors [15, 35]. Our research has hypothesized that there is a relationship between gait asymmetry and muscle strength of hip joint flexors and extensors. Evaluation of these muscles was of interest due to the fact that an increased symmetry index of the hip joint flexors and extensors in healthy people causes lower back pain [36]. In this research, relative values of muscle torque of an amputated limb computed for all measurement conditions were significantly lower than those for an intact limb, which resulted in a high value of symmetry index. Relative values of muscle torque of an amputated limb were lower for hip joint flexors than extensors. Also, hip joint extensors were stronger than flexors of an intact limb. An exception was measurements obtained in isokinetic conditions for 120°/s where both groups reached similar relative torque values. There were no statistically significant differences in F/E ratio between intact and amputated limbs. In patients with unilateral TFA, the symmetry index of muscles acting on these joints was quite high. Moreover, the symmetry index computed for flexors increased along with angular velocity (from 24.3% to 43.9%). The opposite behaviour was found for the extensors, and the highest symmetry index was obtained in isometric conditions (50.5 ± 19%). Equally high (50 ± 16%) symmetry indexes between the limbs were observed in the F/E ratio. A similar study was carried out for patients with TTA [15]. The symmetry index between intact and amputated limbs was significantly greater for hip extensors (33% at 30°/s) than flexors (22%). In healthy people, the symmetry index of muscle torque of hip joint flexors and extensors ranges from 1.3 to 5.6% for flexors and 2.3% for extensors [37]. Bae et al. [38], using the electromyography technique (EMG), showed asymmetry in strength of intact and amputated limbs. They concluded that EMG activity in the major muscles for the intact leg was lower than for healthy persons—20.5% for quadriceps and 87.9% for hamstring. But the EMG muscle activities of the tibialis anterior and gastrocnemius were greater than for healthy subjects—14.5% and 15.5%, respectively.
4.3. Correlation between Gait Asymmetry and Muscle Torque of Hip Joint Flexors and Extensors
A correlation between gait asymmetry and muscle torque of hip joint muscles in people with TFA was not previously studied. Therefore, it prevents us from comparing our results with those of different authors. Our results showed that a correlation between gait asymmetry and muscle torque exists only for the a-pGRF components. Strong hip flexors and extensors were associated with smaller asymmetry of the anterior-posterior component at the initial stance (a-pF1), while weaker flexors and extensors of the amputated limb were associated with smaller asymmetry of the anterior-posterior at the terminal stance (a-pF2). This analysis showed a lack of relationship between vertical components of the ground reaction force and muscle torque of hip joint flexors, except in one case. On the other hand, there were many statistically significant correlations between gait asymmetry and muscle torque asymmetry of extensors in regard to an intact and amputated limb.
4.4. Case Study Analysis
The group of patients studied was not homogeneous. They differed both in age and physical activity practice. It was observed in terms of muscle torque values of patients with TFA compared to healthy people in the same age. Torque values of the amputated limb obtained in isokinetic conditions (60°/s) for professional athletes (S1, S14, and S12) were similar to or higher than the values for healthy people. Special attention was paid to S1 patient who was a professional athlete in body building. Muscle torque of his hip joint flexors and extensors of the amputated limb was similar to normative values for healthy people, while his intact limb was much stronger, with much higher normative values than those of healthy subjects at the same age (46 years old). Also, the muscle torque value obtained by patient S12 in some conditions was similar or higher than those obtained by healthy people. It can be presumed that therapy through sport activity may improve the mobility of patients with TFA. The study on the positive effect of therapy through sports activity has confirmed greater dynamics in generating maximal muscle torque [17]. Although some tested subjects did not declare sports activity, their muscle torque values were still similar to normative one. A growing body of evidence suggests that muscle torque measurements obtained in isometric conditions should be used in diagnostics of patients with TFA [39].
5. Conclusions
This research showed consistent evidence of a significant correlation between hip joint extensors and gait asymmetry. Conclusions drawn on the basis of the study mean group for patients with TFA are limited by errors caused by many factors. We therefore believe that statistical analysis used in such a heterogeneous group may have errors. For this reason, all data for the patients have been included with our analysis. Although statistical analysis showed some correlations, it is the analysis of individual cases that can be useful in improving patients’ mobility and quality of life. Sports training which enhances muscle torque may be an effective form of patient therapy. However, prior to commencement, a patient needs to undergo evaluation of their muscle strength and have the therapy programme adjusted to their level of muscle torque deficit.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
decoding of salamander locomotion / Habr
Our planet is inhabited by species with a variety of characteristics. Some live in the depths of the ocean, others almost never leave heaven. Depending on the habitat and behavior characteristics of the species, its gastronomic preferences, appearance, characteristics of the organism, including its motor functions, are formed. It is quite logical why a dolphin needs paws if it lives in water. But, as the naive bird from the cartoon “Wings, Legs and Tails” showed, sometimes the paws still exceed the wings, especially if there are four of them.Scientists from Tohoku University (Japan) decided to examine in detail the locomotion (i.e. movement) of the salamander, which is able to overcome difficult routes due to the unique coordination of the body and limbs. What is so special about the salamander’s gait, how complex was the mathematical model of its locomotion, what role does the nervous system play in this, and how can the obtained data be applied in the human world? We will find answers to these questions in the report of scientists. We ran. Let’s go.
Basis of research
It is not surprising that many four-legged animals are very mobile and well adapted to the heterogeneity of terrestrial conditions.One of the decisive factors affecting this is the coordination between body parts at the moment of movement: head, torso, tail, paws. For example, flexing the cheetah’s body increases its speed, the nodding of the horse reduces metabolic costs, and the waviness of the salamander’s tail promotes dynamic balance.
Salamander on a treadmill.
Scientists answer why they chose this amphibian for their research. The fact is that salamanders have extremely high body and limb flexibility, which changes depending on the speed of movement.This allows a better view of their locomotion and a better understanding of body-limb coordination.
At low movement speed, salamanders demonstrate a lateral sequence (L-S gait) gait with standing waves of lateral undulating body movements. At this moment, the body vibrates, and some points of the body act as “nodes” and do not move at all.
At higher speeds, they demonstrate a gait at a trot * with standing waves at first (at medium speeds) and then with traveling waves (at high speeds) of lateral undulating body movement.At this moment, all parts of the body vibrate from side to side, spreading waves rostrocaudally (i.e. from head to tail).
Lynx * – the movement of an animal when it alternately rearranges pairs of legs located diagonally.
It may seem that such a varied locomotion requires a developed control system, but salamanders have a simpler nervous system than many mammals (they have fewer neurons with less differentiated structures). Therefore, the mechanism of locomotion of salamanders should be simple but effective.
Locomotion of salamanders and other vertebrates is controlled by distributed neural networks called central pattern generators * (CPG from central pattern generators ), and sensory feedback from peripheral nerves.
Central generator of ordered activity * – a neural network that delivers rhythmically ordered motor signals without feedback.
In particular, experiments with salamander decerebration have shown that the neural connection between CPGs is responsible for coordinating axial and limb movements.Numerous studies have been conducted on the basis of this data, but they have focused on limb coordination rather than body-limb coordination.
To fill this knowledge gap, the scientists decided to create a mathematical model of the salamander’s movement and then run several simulations. Thus, they wanted to find out what mechanisms underlie the coordination between the salamander’s body and its limbs.
Mathematical modeling
At the first stage of modeling, it was necessary to recreate the body of a salamander, consisting of n segments of the body and four legs (image No. 1).
Image # 1
The segments are connected by means of pivot joints with a combination of rotary actuators yaw * , passive spring and passive damper. The front and hind legs are attached on both sides at the level of k and l segments, respectively. Each share has two rotary yaw and roll * drives, controlled by phase oscillators.
Yaw * – the angular movement of the object relative to the vertical axis.
Roll * – rotation of an object around its longitudinal axis.
There is a force transducer at each tip of the foot, and each torso node has angle and torque transducers. Angle sensors determine the angle of the j-th node of the trunk from the head (θ
b j
). When the trunk node bends to the right, the variable θ
b j
becomes positive. Torque sensors measure the torque generated by the rotary actuators in the torso assembly.
Next, it was necessary to describe the locomotion control algorithm. The controller consists of oscillators, which are CPGs. To focus on the potential role of sensory feedback as a synchronization mechanism, this work does not model connections between oscillators. Instead, nearby body parts are connected through sensory feedback (image # 2).
Image # 2
Sensory feedback consists of the following four aspects of feedback:
- limb-to-limb force feedback;
- body-to-limb torque feedback;
- limb-to-body force feedback;
- body-to-body angular feedback.
The first aspect is responsible for the coordination of the four legs as they move forward, supporting the body. The second and third aspects involve cross-feedback, which establishes self-organized body-limb coordination. The fourth aspect coordinates the lateral (lateral) undulating movements of the multi-segment trunk.
Each leg has a phase oscillator, the phase of which determines the target angle of the rotary actuators in the yaw and roll directions as follows:
where θ y i and θ r i are the target angles; C y 0 and C r 0 – neutral angles; C y amp and C r amp are the amplitudes of the yaw and roll drives; φ i – the phase of the oscillator with the index i indicating a specific paw (1 – left front, 2 – right front, 3 – left back and 4 – right back).
The temporal evolution of the phase is described as follows:
where ω (rad / s) is the intrinsic angular velocity of the phase oscillators; σ LL (rad / s), ρ LL (1 / N), σ BL (rad / s) and ρ BL [1 / (N · m)] are the weights of the sensory feedback; N i (N) is the normal force found at the tip of the foot. And τ b k and τ b l is the torque created by the k and l drive (rad – radian, s – second, N – newton, m – meter).
Formula # 3 refers to limb-limb feedback. Based on the sensory feedback effect, the phase of the oscillator is modulated to 3π / 2 when N i > 0. When the foot supports the body, the foot receives a higher force from the support, that is, a higher value of N i . Thus, this feedback means that the paw remains on the ground while supporting the body.
Local sensory information (N i ) describes the extent to which a particular paw provides support to the body, and also indicates how much the other paws are currently contributing to body support.Through this sensory information, the feedback can generate adaptive interlimb coordination without neural communication between the paws.
Formula # 4 refers to the feedback between the body and limbs ( 3A and 3B ).
Image # 3
When the torso drive k flexes the body to the right (τ b k > 0), the oscillator phase of the left front leg is modulated to π / 2 for raising the legs, and the oscillator phase of the right front leg is modulated up to 3π / 2 to put the paws on the ground.As the phase changes, the left front foot is lifted off the ground and the right front foot is lowered toward the ground.
This allows the drive k to bend the body to the right (θ b k > 0), and the salamander model moves forward when the fixed legs (e on the ground) act as an axis of rotation. Likewise, the oscillator phases of the hind legs are modulated by the drive torque l.
Torques on the torso drives are described as follows:
where θ b j is the actual angle of inclination of the drive; σLB (Nm) and ρLB (1 / N), σBB (Nm) and ρBB (1 / rad) are the weights of the sensory feedback.
Formula 6 refers to limb-body feedback. The sensory feedback effect is such that the k and l trunk segments flex in response to ground contact (3A and 3C). When the left front leg is on the ground (N 1 > 0), the drive k bends the body to the left (τ b k <0). Similarly, when the right front paw is on the ground (N 2 > 0), the drive k bends the body to the right (τ b k > 0).
The interaction of body-to-limb and limb-to-body sensory feedback establishes a relationship between the legs and torso, providing longer strides and more powerful ground offsets.
Formula # 7 is responsible for body-body feedback. The local feedback rule is based on curvature derivative control. It creates a torque proportional to the derivative of the curvature of the body, so that the lateral undulating movements of the body propagate backward.
Simulation results
After creating a mathematical model, scientists conducted a series of computer simulations, where the gait of a salamander and other four-legged animals was simulated. For this, the open source library
Open Dynamics Engine
(rigid body dynamics;
library site
) was used.
Each test was conducted on level ground for 60 seconds, with the oscillator phases initially being set randomly. The size and weight of the model corresponded to those of the robot salamander, developed by the authors of the study in a previous work (A Salamander Robot Driven by Cross-Coupled Sensory Feedback Control between Legs and Trunk).
The angular frequency and amplitude of the paws were selected with physically plausible values. Other parameters were determined by trial and error.The time step of the model was 0.01 s, and the control commands were updated at each such step.
In order to understand whether the model can reproduce the change in gait of the salamander, taking into account the change in speed, the simulation was carried out with a change in the parameters ω from 1.8 π to 3.8 π (rad / s) at time 16 s, and then from 3.8 π to 1.8 π at the moment time 22 sec.
Image # 4
The upper graph of image # 4 shows lateral flexion of the trunk node, with the colored area indicating the period when the node flexes to the right (θ b j > 0).The bottom graph shows a gait chart where the colored area represents the period when the foot is in contact with the ground (N i > 0).
Video # 1: Results of modeling the variable gait of a salamander.
For ω = 1.8π, the bend of the body (j = 3-6) is antiphase to the bend of the tail (j = 7-10). The feet then begin to touch the ground in the following order: Right Hind (RH), Right Front (RF), Left Hind (LH), and Left Front (LF).
The mean and standard deviation of fill factor * was 69.3 and 0.55%, respectively. And the mean and standard deviation of of the diagonal * were 21.9 and 1.26%, respectively.
Duty factor * – The proportion of the time the foot is in the stance phase during the gait cycle.
Diagonal * is the fraction of the cycle period when the left / right hind foot precedes the left / right front foot.
According to the Hildebrand gait classifier, this gait was defined as such with a lateral sequence (L-S).In nature, such a gait is observed at a low speed of movement of the salamander.
For ω = 3.8π, the flexion duration shifted posteriorly (backward) and continuously, indicating a traveling wave. The step pattern is such that the diagonally opposite feet are almost synchronized. The mean and standard deviation of the fill factor was 64.5% and 9.74×10 -2 , respectively. The mean and standard deviation of the diagonal was 48.0 and 1.97%, respectively.
From these data it follows that this gait is classified as a trot.Consequently, this gait was observed at higher speeds of movement of the salamander.
At the moment ω changed from 1.8 π to 3.8 π at the 16th second, the gait pattern smoothly changed from L-S step with a standing wave to a trot with a traveling wave. The opposite picture was observed when ω changed from 3.8 π to 1.8 π at the 22nd second, when the trot switched to a slow step.
A similar thing was observed for any initial phase of the oscillator in all 10 runs. It follows from this that the developed model perfectly copes with the task of modeling the speed-dependent gait of salamanders by simply changing the parameter ω.
Next, a comparison was made of the lateral bend waveform of each type of gait in the model and in the salamander.
Image # 5
Above is a comparison of the model and salamander Dicamptodon teneborosus . The figures on the left were created by combining the lateral positions of the body segments from the shoulder (j = 3) to the thigh (j = 7) in the model for ω = 1.8π ( 5A ) and ω = 3.8π ( 5B ), respectively. A 5C and 5D correspond to the gait of a real salamander.
5A shows a body waveform alternating between two stable curve configurations. And the curve represents half the wavelength from the shoulder and hip. This pattern is a standing wave with knots at the shoulder and hip and is similar to the walking of a real salamander ( 5C ).
5B shows that the body waveform has no knots and the trunk does not follow a simple side-to-side bending pattern (as in 5A ).This model is a running wave similar to that of a salamander during the trot ( 5D ).
From the data of the comparative analysis, it follows that the model is capable of reproducing two types of waves (standing and traveling), i.e. corresponds to that observed during the gait of the salamander.
Further, the scientists decided to show that their model can reproduce the locomotion pattern of not only salamanders, but also other tetrapods.
Desert iguana (Dipsosaurus dorsalis).
Certain lizard species, such as Dipsosaurus dorsalis , also exhibit speed-dependent gait transitions. They use standing waves at lower speeds and traveling waves at higher speeds, similar to the gait of a salamander.
But it is curious that these lizards also use “intermediate” waves while moving with an intermediate speed, i.e. not walking, but also not running. The shape of such waves has elements of both standing and traveling waves.
In order to convey this intermediate state in the model, scientists set the value of ω equal to 2.3π, i.e. between about 1.8 π and 3.8 π (like salamanders).
Image # 6
On 6A , a lateral flexion and gait diagram are shown. The step pattern was L-S. The mean and standard deviation of the fill factor were 66.8 and 0.23%, and the mean and standard deviation of the diagonal were 29.0 and 0.35%.
Video # 2: Desert iguana gait simulation results.
During wave propagation, irregularity is observed in the thigh area (j = 7). 6B and 6C show the lateral displacement of each body part in the direction of movement of the model and lizard D. dorsalis , respectively.
At 6B , the point of minimum lateral displacement moves backward, like traveling waves. However, there are several points in the same position (behind the shoulder), as if knots were present, which resembles standing waves.Consequently, the form of this intermediate wave ( 6C ) consists of elements of both standing and traveling waves.
As in the case of salamanders, here the model was also able to successfully reproduce the gait patterns of D. dorsalis due to a change in only one parameter – ω.
Madrei Alligator Lizard (Gerrhonotus kingii).
The next object of consideration was lizards of the species G. kingii . The peculiarity of this lizard is that it uses traveling waves not only when trotting (like a salamander), but also when moving at a slower pace.
For the simulation, the ω value was set to 2.3π, and the limb-body (σLB = 4.5) and body-to-body (σBB = 5.0) feedback coefficients were lower than those used in the salamander simulation.
Image # 7
On 7A the lateral flexion and gait patterns are shown. The step pattern was L-S. The mean and standard deviation of the fill factor was 64.2% and 5.28×10 -2 , and the mean and standard deviation of the diagonal was 38.7 and 0.13%.
Video # 3: The results of modeling the gait of the Madreian alligator lizard.
At 7B and 7C , the lateral displacement of each body part in the direction of movement of the model and lizard G. kingii , respectively, is shown. At 7B , the point of minimum lateral displacement is continuously shifted backward. The waveform is a traveling wave ( ° C ), in which there is no node.
As in the previous two cases, modeling of locomotion G.kingii was successful.
It remains to understand how the feedback affects locomotion. For this, modeling was carried out with a change in the values of the parameters, including the feedback force. Two metrics were used to quantify gait: diagonal and waveform index (W).
Image # 8
The color diagrams above show two indices when the proper angular velocity ω is between 1.5π and 4.0π and the limb-to-limb feedback force (σ LL ) is 0.00 to 7.50. At 8A and 8B , the control parameters σ LB and σ BB are 7.0 and 7.7, respectively. At 8C , 8D , the control parameters σ LB and σ BB are 4.5 and 5.0, respectively.
Oscillations in the upper left part of 8C and 8D indicate that unstable locomotion has occurred and gait has not been assessed correctly.
According to the diagrams at 8A and 8B , the diagonal and the W index increase with increasing ω.Consequently, a trot with a traveling wave occurs at large values of ω. In this case, both parameters decrease with increasing σ LL , and at large values of σ LL , an L-S pattern of standing wave gait appears.
At the same time, the diagonal and W values for 8C and 8D are usually higher than those for 8A and 8B . Consequently, at small σ LB and σ BB , a trot with a traveling wave occurs even at a relatively small value of ω.This pattern is consistent with that observed in locomotion of G. kingii , using exclusively traveling waves, even at very low speeds.
Finally, the scientists decided to check how changes in the parameters of mass and body size will affect the simulation results.
Image # 9
On 9A you can see that the diagonal is higher if the size or weight of the body is larger. And at 9B it can be seen that the waveform index increases, i.e.That is, the waveform is more similar to a traveling wave if the body is larger.
For a more detailed acquaintance with the nuances of the study, I recommend that you look into the report of scientists.
Epilogue
In this work, scientists have transformed the gait of the salamander (and not only) into a mathematical model, thereby describing the dynamics of animal locomotion and the aspects that affect its change.
But the main goal of the work was to confirm the hypothesis that the exchange of sensory information plays an important role in locomotion, which makes it possible to control the movements of the body and limbs.The theory was confirmed in practice by converting a mathematical model into a computer one.
The research data is a valuable resource for robotics. To create a robot that can move like a salamander or any other creature, you need to fully understand its locomotion. What seems natural and understandable to us (for example, our gait) is an impossible task for a robot if all the nuances are not taken into account in its development. Suffice it to recall how awkward humanoid robots were decades ago, and how they were improved thanks to the analysis of human locomotion.As they say, the devil is in the little things, and for the world of science this phrase has a special meaning.
Friday off-top:
Once upon a time, Boston Dynamics robots could not climb one step, but now they dance better than many people (certainly better than me).
Thanks for your attention, stay curious and have a great weekend, guys! 🙂
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Clinical Study Multiple Sclerosis: Robotic Gait Training, Conventional Therapy – Clinical Trials Registry
This is a prospective, randomized, blind, controlled trial. Ninety-eight MS subjects will be recruited upon subject identification in U.O. Rehabilitation Medicine and Center for Rare Diseases and Neuroimmune Diseases, IRCCS Neurosciences & quot; Bellaria & quot; (BO).
After eligibility has been assessed and informed consent is obtained, patients will be enrolled and randomized into two groups using the randomization and stratification method. Subjects will be grouped into strata determined by the degree of impairment (for example, using results from the Extended Disability Status Scale or EDSS) and then randomized separately to each stratum according to block randomization and assigned one of two treatment group options:
1.Robotic gait training (experimental group)
2. Traditional therapy (control group)
Robotic gait training:
Patients will undergo 12 RAGT trainings over 4 weeks (3 sessions per week). During these sessions, participants will wear harness straps attached to the system to provide body weight support and they will walk on the treadmill using a robotic walking orthosis. The legs are controlled according to the physiological gait.The torque of the knee and hip actuators can be adjusted from 100% to 0% for one or both legs. The treadmill speed can be adjusted from 0 km / h to approximately 3 km / h and maintain body weight from 0% to 100%. In the first lesson, we will set these learning parameters in accordance with the subject. characteristics and level of demand. As the training progresses, adjustments in assistance are provided by the guided gait orthosis, the amount of body weight support and the speed of the treadmill will be made.The workouts will last an hour with 30 minutes of real walking. time, since the installation of the object in the device takes about 30 minutes.
Conventional therapy:
The control group will receive 12 conventional therapy sessions over 4 weeks (3 sessions per week) that will focus on gait training. Subjects will receive 1 hour of individualized routine physiotherapy per session. During the first 5-10 minutes, subjects will perform stretching exercises for the lower limbs and core to increase muscle flexibility; then they will engage in exercises to strengthen the muscles of the lower extremities, adapted to their initial conditions of characteristics (10 minutes).This will be followed by a walking workout with an assistant. done.
Evaluation of results Evaluation of results will be carried out one week before the start of treatment. (T0), after two weeks (T1), after 4 weeks (T2) and after 3 months of observation (T3). Staff Blinded to treatment will appreciate the effect of the intervention.
Choice of screwdriver
Unscrewing a couple of screws once a year is a task that can be easily solved with a regular screwdriver. Carrying out several dozen operations with fasteners during home repairs or professionally assembling furniture are problems of a different scale that require special equipment.Our material will help you find the right screwdriver in seven steps.
Screwdriver: Briefly about the main thing
A screwdriver is a hand-held tool used to work with fasteners. The device allows you to quickly tighten or unscrew a large number of screws and other fasteners. Models with advanced functionality, drills and screwdrivers can also drill holes.
The electric screwdriver is made on the basis of a motor that drives a spindle through a gearbox with a chuck installed on it.The torque and screw-in depth are adjusted by means of a special coupling. An electronic unit is used to control the device.
7 steps to choose screwdriver
So, we decided that a screwdriver is vital for productive work and maintaining peace of mind. Online stores and offline retail outlets offer such choices that make your eyes run wild. And advertising of some models is brighter than others, and the seller advises something there, talks about benefits and discounts.Stop. Don’t panic. Exhale. We remove our hands from the nonsense with the “-200%” sticker and choose the really necessary thing in seven steps.
Step 1: define the tasks and scope of work
Before going to the store, it’s good to understand why we need a screwdriver specifically for us. Any standard tool can twist-unscrew fasteners. For universal drilling applications, a drill / driver is best. However, it should be borne in mind that the product will lose in terms of the power of a full-fledged drill.
For home use, assembling cabinets, installing baseboards and other not particularly difficult tasks, a household device will be enough. Perhaps its performance and power are not very great, but the balance of price, quality and available features will be optimal. If you need to perform all the same operations a hundred times a day for a long time, we go to the professional equipment department with a confident gait. Devices will be more expensive, but wear resistance, performance and other parameters will be higher.
Step 2: Choice of location and type of power supply
The type of power supply of our ideal tool depends on the place where labor feats are performed with the help of a screwdriver. If electricity is supplied to the location and the presence of a long cord does not bother you, you can safely choose a network tool. Due to the lack of a battery, the unit weighs less than battery counterparts, and can also work without interruption for a long time.
If the benefits of civilization in the form of an ordinary outlet are not available, we take a model with a battery, or better with two at once: while one battery is being charged, with the help of the second one you can safely continue your studies.Independence fee – limited runtime and need to recharge.
If the future is so vague that it is impossible to speak with confidence about the place of work, our option is a universal fighter with a battery and a power cord.
Step 3: Power Parameters
With network products, everything is simple: we pay attention to the characteristics of the electrical network, and also make sure that the length of the cord is sufficient for convenient use. With battery and combined options, things are more complicated: performance depends on the type, capacity and voltage of the battery.
The battery voltage influences the drive power and the maximum torque value. Manufacturers offer models with voltages ranging from 9 to 36 volts. The latter are found in professional devices. An average value of 12 – 14.4 volts is quite enough for an inhabitant of a household toolbox.
The capacity of the power supplies is also different. If the product is to be switched on sporadically, and most of the time to rest on the shelf, a battery with a capacity of up to 2 Ah is sufficient for it.If the intensity of work is higher, we add at least 1 Ah.
Screwdrivers are most often equipped with four types of batteries: lithium-ion (Li-Ion), lithium-polymer (Li-Pol), nickel-cadmium (Ni-Cd) and nickel-metal hydride (Ni-MH).
- Li-Ion batteries withstand more than 3000 charge / discharge cycles, have no memory effect, and are distinguished by high charge capacity and power density. However, lithium-ion batteries are expensive, they do not know how to charge at negative temperatures and “from scratch”.
- Li-Pol are ahead of competitors in terms of capacity, but quickly fail.
- Ni-Cd batteries are faithful companions for mid-range instruments. They are inexpensive, they are not afraid of full discharge, they tolerate cold staunchly. At the same time, the specific capacity of the batteries is not very high. In addition, nickel-cadmium batteries have a memory effect and a bad habit of self-discharge.
- Ni-MH batteries are the closest relatives of Ni-Cd batteries.They have a less pronounced memory effect and increased capacity. In addition, NiMH products are more compact. Batteries of this type withstand no more than 500 operating cycles, are afraid of frost and cannot be stored completely discharged.
Step 4: Max Torque and RPM
The maximum torque, expressed in newton meters, characterizes, in simple terms, the force that the tool exerts on the fastener when twisting or on the surface when drilling.
If the responsibilities of the master and the screwdriver include only the repair of furniture, appliances, toys and other minor operations, then a device with a maximum torque of about 10 N • m will be sufficient. Although such a tool will be considered, rather, an electric screwdriver. Values of 20 – 30 N • m are sufficient for screwing fasteners into various surfaces, and over 30 N • m – for drilling fairly hard materials.
Specialized exclusively in screw-unscrew operation, the tools perform less than 800 rpm.The drilling function is available for devices with a rate of 800 to 1300 rpm. Anything that spins faster than 1500 rpm can be classified as a professional product.
Step 5: Looking for Hidden Talent
When we have almost decided on the main parameters, it turns out that there are a lot of devices with the given characteristics. All other things being equal, tools with additional modes and functions win. So, the presence of the shock mode makes it possible to work with capricious hard surfaces, and the impulse mode makes it possible to cope with sour compounds and the twisting of elements, the size of which exceeds the standard.Backlighting can be another nice bonus. The light source is located under the socket or on the handle. The latter option is preferable if the work area needs bottom lighting.
Step 6: Weigh
In addition to performance, when choosing a tool, you need to consider its convenience. Not in an abstract sense, but for a very specific master: a model that fits perfectly into a wide palm is not suitable for a narrow one, and the remote location of the control buttons will surely upset the owner of not the longest fingers.Therefore, choosing “the world’s best screwdriver”, we will focus on our own feelings. The weight, the shape of the handle, the location of the buttons – all this helps or interferes with long-term work with the tool.
Step 7: add the buns
When the most important is taken into account, we can afford to pick and choose and finish off the consultant with questions about the number of replaceable attachments, the availability of a case, belt, holster for storing and carrying wealth, as well as inquire about the availability of other “goodies”, including a discount.
Galloping Horse Inspired These Trotboots Lego Mindstorms ?
In my last post on trotbots, I mentioned that I will be incorporating the Lego Mindstorms EV3 brick in new versions. I have now posted instructions for two walkers rated for the weight of an EV3 brick: the robust Klann mechanical spider and the TrotBot Ver 2 with retractable fingers. The latter increases the contact of the feet with the ground and reduces the power requirements of the robot to support the weight.
Assembling the functional walker from heavy EV3 bricks is a good test of the walking mechanism’s capabilities.This can reveal flaws in projects like partial scaling.
TrotBot Version 2
TrotBot Feet Background
The main focus of our TrotBot project is on developing active legs to improve gait and reduce the number of legs required. We found that when the TrotBot had only eight legs, a lot of torque was required for the walkers to walk smoothly and the robot to rise from the bottom of the gait. We didn’t want to start over with a revision of the 12-foot version, so instead we explored ideas for active feet that could smooth out the TrotBot’s 8-step gait.
Using the galloping horse for inspiration, we aimed to add some sort of second leg to each leg that would mimic how the hind legs and then the front legs land in pairs. This led to what we call the TrotBot heel. This increased the contact of the TrotBot’s feet with the ground by about 10%, reduced foot slip and increased the height of the steps in the TrotBot’s hind legs. Below is a video comparing the TrotBot and its heels to a prancing horse.
Then we looked at adding some kind of active toes that would press down on the ground when the foot began to rise, just like people use their toes to walk.We installed one of these ideas on our larger TrotBot. They gave the robot a smoother gait, but since they were attached to their legs at a fixed angle, they tended to catch obstacles. Fishing on obstacles sometimes blocked communication and caused the mechanisms to grind or break. Unfortunately, this finger violated our main goal – to create a mechanism that could walk over rough terrain!
Taking another look at the galloping horse for inspiration, we began experimenting with grip configurations that mimicked horses pushing their hooves back and then holding them folded back as they lifted their legs to hit the ground again.We found several variants that mimic this action and they increased the TrotBot’s foot contact by another 10% while maintaining a high path. The TrotBot ver 2 in the video below uses a LEGO approximation of one of these finger variants.
Klann’s Mechanical Spider
Klann Linkage, designed by Joe Klann, is one of the most popular and functional pedestrian links in the engineering world, and several huge versions visit Burning Man occasionally.
There were several issues in completing this build:
1.It was difficult to get close to Clann’s Lego connection using the images Clann provided. I found the published patent details a little confusing, so instead I took the coordinates at each end of the mechanism rods in Clann’s images, calculated the rod lengths using the Pythagorean theorem, and chose the Lego beams that approximated them most closely. My final path looks pretty close to Joe Clann, and as you can see in my video below, it’s a beast!
2.Walkers require stronger frames than wheeled vehicles (especially those with heavy EV3 bricks), so finding ways to incorporate triangles into their frames was critical to success. However, neither Clann’s nor TrotBot’s link sizes work with integer right-angled triangles like 3,4,5 or 6,8,10, and Lego integer-length beams don’t seem like viable choices for frame triangles. So, I used the Pythagorean theorem and found approximate right-angled triangles that worked with their bond sizes.
3. Since the pairs of inner and outer legs are always 180 ° out of phase, this walker does not have a differential to prevent the legs from sliding during turns and should therefore be built as narrow as possible. I reduced the Clann’s width by placing an EV3 brick on its side and reduced the TrotBot’s width by placing an EV3 brick under the frame.
4. My Clann build requires an 11 hole beam for the lower leg. If not supported, this beam risks bending or breaking under the weight of the EV3 frame.My solution was to make the lower leg section in a triangle as shown in the photo below:
Train Humanoid Walker
This example shows how to model a humanoid robot with Simscape Multibody ™ and train it using any genetic algorithm (which requires a Global Optimization Toolbox license) or reinforcement learning (which requires the Deep Learning Toolbox ™ and Reinforcement Learning Toolbox ™ licenses).
Walker’s humanoid model
This example is based on a humanoid robot model.You can open the model by entering sm_import_humanoid_urdf at the MATLAB® command line. Each section of the robot is torque-driven by articulations at the frontal hip, knee, and ankle. Each arm has two passive articulations at the frontal and sagittal shoulder. During simulation, the model detects contact forces, torso position and orientation, joint states, and upright position. The figure shows a Simscape Multibody model at different levels.
Contact Simulation
The model uses Contact Force Spatial Blocks to simulate contact between feet and ground.To facilitate contact and speed up the simulation, red spheres are used to represent the lower parts of the robotic legs. For more information, see Use Contact Proxy to Simulate Contact.
Combined Controller
The model uses a stiffness-based feedback controller to control each connection [1]. Model the joints as first-order systems with coupled stiffness (K) and weakening (B) , which can be set to make the joint behavior critically weakened.The torque is applied when the target value θ0 differs from the current combined position θ:
T = Bθ • + K (θ0-θ).
Spring setpoint θ0 can be varied to detect feedback to move the joint. The figure shows a Simulink model of the controller.
Train Humanoid Walker
The purpose of this example is to train a humanoid robot to walk, and various methods can be used to train the robot. The example shows reinforcement learning methods and a genetic algorithm.
Traversal objective function
This example uses an objective function to evaluate different traversal styles. The model gives a reward (rt) in each clock cycle:
rt = w1 vy + w2ts-w3 p-w4 Δz-w5 Δx
Here:
vy – Transfer (rewarded) speed
p – Power consumption (penalized)
Δz – Vertical offset (penalized)
Δx – Lateral displacement (penalized)
w1 ,…, 5: Weights that represent the relative importance of each term in the premium function
Also, no fall is rewarded.
Therefore, the total reward (R) for bypassing the trial is
Here T is the time at which the simulation ends. You can change the premium weights in the sm_humanoid_walker_rl_parameters script. The simulation ends when the simulation time is reached or the robot falls. The fall is set as:
The robot falls below 0.5 m.
The robot moves from the side more than 1 m.
The body of the robot rotates more than 30 degrees.
Learn with the Genetic Algorithm
To optimize the robot traversal, you can use the Genetic Algorithm. A genetic algorithm solves optimization problems based on a natural selection process that mimics biological evolution. Genetic algorithms are especially suited for problems where the objective function is discontinuous, non-differentiable, stochastic, or highly non-linear.For more information see ga (Global Optimization Toolbox).
The model sets the angular demand for each join to a repeating pattern, which is like the central pattern generators seen in nature [2]. The repeating pattern gives to the open loop controller. The signal frequency is the gait period, which is the time taken to complete one full step. In each gait period, the signal switches between different angular demand values.Ideally, the humanoid robot walks symmetrically, and the control pattern for each joint in the right leg is transmitted to the corresponding joint in the left leg with a delay of half the gait period. The pattern generator seeks to determine the optimal control pattern for each connection and to maximize the target traversal function.
To train a robot with a genetic algorithm, open the sm_humanoid_walker_ga_train script. By default, this example uses the pretrained humanoid Walker.To train humanoid Walker, set trainWalker to true .
Train with reinforcement learning
Alternatively, you can also train the robot with the Deep Deterministic Policy Gradient (DDPG) reinforcement learning agent. The DDPG agent is the agent’s reinforcement learning agent who calculates optimal policies that maximize long-term rewards. DDPG agents can be used in systems with continuous actions and states.For more information on DDPG agents, see rlDDPGAgent (Reinforcement Learning Toolbox).
To train a robot with reinforcement learning, open the sm_humanoid_walker_rl_train script . By default, this example uses the pretrained humanoid Walker. To train humanoid Walker, set trainWalker to true .
References
[1] Kalveram, Karl T., Thomas Schinoer, Steffen Bairle, Stefanie Richter and Petra Jansen-Osmann.“Parallelizing Neural Feedforward into Mechanical Spring: How Physics Uses Biology in Limb Control”. Biological Cybernetics 92, no. 4 (April 2005): 229-40. https://doi.org/10.1007/s00422-005-0542-6.
[2] Jiang Shan, Cheng Junshi and Chen Jieping. “Design of a Central Template Generator for a Humanoid Robot Walking Based on a Multipurpose GA”. In Continuations. 2000 IEEE / RSJ International Conferences on Intelligent Robots and Systems (IROS 2000) (CAT.00Ch47113), 3: 1930–35. Takamatsu, Japan: IEEE, 2000. https://doi.org/10.1109/IROS.2000.895253.
An in vivo Rodent Model of Contraction-induced Injury and Non-invasive Monitoring of Recovery
1. In vivo damage model and isometric torque measurement.
- These procedures can be used for rats or mice 7,17,18. First, place the animal’s back under inhalation anesthesia (~ 4-5% isoflurane for induction in the induction chamber, then ~ 2% isoflurane through the head for maintenance) using a precision vaporizer (Cat # 91103, Vet Character, Inc, Pleasanton, California).Apply sterile ophthalmic creams (Paralube Vet Ointment, PharmaDerm, Floham Park, NJ) to each eye to protect the cornea from drying out. During the procedure, the animal is kept warm through the use of heat, lamps are located outside the cage and kept at least 6 inches away from the animal at all times.
- Prepare the skin by removing hair and cleansing with alternating scrubs of betadine and 70% alcohol to prevent bacteria from seeding the skin into soft tissues or bones. Confirmation of proper anesthesia by lack of deep tendon reflexes (no leg withdrawal in response to foot pinching).The needle is manually placed through the proximal tibia to stabilize the limb on the rig (25G and 27G for the mouse). The needle should not enter the front leg compartment.
- Lock the needle in a fixed position so that the animal is lying down and the fingers are straight up. A custom device is used to protect the needles and thereby stabilize the foot.
- The footrest is made to order with a footrest (fig. 1). An axle footrest is attached to a stepper motor (model T8904, NMB Technologies, Chatsworth, Calif.) And a torque sensor (model QWFK-8M, Sensotec, Columbus, OH).The foot should initially be positioned so that it is orthogonal to the tibia, as shown in Figure 1.
- Use of percutaneous electrodes (723742, Harvard Apparatus, Cambridge, MA) or subcutaneous electrodes (J05 needle electrode needle, 36BTP, Jari power electrode, Gilroy , California) to stimulate the peroneal nerve near the fibular neck, where the nerve lies in a superficial position. Visually confirm isolated flexion by performing a series of twitches (0.1 ms pulse for mouse and 1 ms pulse for rat) before the legs are secured.Once the leg is attached to the footboard with duct tape, an increase in the amplitude of the twitch in response to the increased tension, confirms that the opposite muscles (plantarflexors) are not simultaneously stimulated.
- Before injury, and at selected time points after injury, the maximum force produced by the dorsiflexors is recorded as “maximum isometric torque” (torque without changing muscle length) Torque measurements are taken at the same setup that is used to induce injury.Before recording the maximum isometric torque, the pulse amplitude is adjusted to optimize twitch tension and the optimal ankle position is determined by assigning twitches at various dorsiflexors lengths. After obtaining the torque curve angle to determine the optimal length of dorsiflexors (resting length, aka Lo), the torque frequency plot is obtained by gradually increasing the pulse frequency over a 200 ms train pulse. The maximum contraction of fused tetanic is obtained usually at 90-100 Hz.Three separate twitches and tetanic contractions are recorded and saved for later analysis.
- Using commercial software (LabVIEW version 8.5, National Instruments, Austin, TX) to synchronize contractile activation, ankle rotation initiation, and torque collection data. Stimulation of the dorsiflexor muscles occurs while a computer-controlled motor simultaneously moves the footrest in plantar flexion, which leads to lengthening contractions (also called “eccentric” contractions, which causes muscle damage).The specific protocol depends on the desired amount of injury desired by the investigator. The amount of injury or tissue damage can be adjusted by manipulating variables such as angular velocity, muscle activation time, range of motion, and the number of lengthening contractions.
- To cause injury, impose lengthening contraction with maximal isometric contraction, altering range of motion, lengthening rate, and stimulation timing as needed. For example, the maximum isometric contraction is obtained by dorsiflexors and after 200 ms, they lengthen at the selected speed to approximate normal movement (900 ° / sec).We have previously shown that activation before movement and the degree of elongation are important factors in injury 14. Most of the torque produced by dorsiflexors from TP 11 and we have shown earlier that this model leads to injuries so that this muscle 5. 13-15. The T. remains stimulated throughout the lengthening.
- After injury, the animal is removed from the apparatus. The tibial contact is removed, the legs are cleaned again, and the animal is returned to the cage (placed on a temperature-controlled heating block at 37 ° C) and monitored until it recovers.This includes waiting until the animal sleeps and a cell phone. Animals suffer no pain during the procedure and there are no visible changes in gait (eg, lameness) after injury induced by lengthening contractions. However, appropriate anti-pain treatment is continued (buprenorphine 0.05 – 0.1 mg / kg every 12 hours for 48 hours after surgery).
2. In situ measurements of total muscle tension.
- The animal is prepared and the tibia is stabilized as described above in section 1.1 to 1.3. All instruments are turned on at least 30 min prior to testing to ensure correct calibration and to minimize thermal drift of the force transducer.
- Cut the skin in front of the ankle and tear the tendons of the tibialis anterior (TBA). Carefully tie a 4.0 Ethicon silk non-absorbable suture to the tendons and attach the Vicryl suture to the strain gauge using the provided S-hook (weight = 0.1 g), Model FT03, Grass Instruments, Warwick, RI). In addition, a custom clamp (weight = 0.5g) can be used to attach the tendon to the Vicryl suture (Fig.2).
- The sensor is mounted on a micromanipulator (Kite Manipulator, World Precision Instruments Inc, Sarasota, Florida) so that the TA can be adjusted with resting length and aligned properly (straight tension line between departure and insertion points). TA is protected from cooling the heat of the lamp and from dehydration by oil products. The signals from the sensor (calibrated before each test) are fed through a DC amplifier (Models P122, Grass Instruments, Warwick, RI) for the A / D board to be collected and stored in the acquisition software (PolyView version 2.1, Grass Tools, Warwick, RI).
- Attach a TP transducer and apply a single twitch (rectangular pulse of 1 ms) at different muscle lengths to determine L 0. Muscle rest length, measured using calipers, is defined as the distance between the tibial tuberosity and the myotendinous junction. At this length, gradually increase the pulse amplitude and then the pulse frequency to create the target frequency ratio. The maximum fused tetanic contraction is obtained at about 90-100Hz (300ms train duration consists of 0.1ms or 1ms pulses).Use 150% of maximum stimulation intensity to activate TA to induce maximum contractile activation (P 0). Maximum tetanic contractions can be performed repeatedly and expressed as a percentage of P 0, providing a fatigue index at any desired point in time.
3. In vivo MRI and / or spectroscopy of rodent skeletal muscle.
All MRI and MRI scans are performed on Bruker BioSpin (Billerica, M.A.) 7.0 Tesla MR system equipped with a 12 cm gradient insert (660 mT / m maximum gradient, 4570 t / m / s maximum slew rate), powered by Paravision 5.0 software.
- The animal was anesthetized with vaporized isoflurane as described above in section 1.1. An MR-compatible small animal monitoring and gating system (SA Instruments, Inc.) is used to monitor respiration rate and body temperature. The body temperature of the mouse is maintained at 36-37 ° C using a warm water circulator.A custom holder is used to position the mouse in a supine position with both legs parallel to the opening of the magnet from knee to foot. The four-channel receive-only surface coil is within a 72mm linear 1H resonator. The resonator coil is tuned and matched to the sample.
- MRI: After the localizers, the following MR scans are performed: T1-weighted rapid acquisition with relaxation enhancement (rare) with the following parameters: TE = 9.52 ms, TR = 1800, echo train length = 4, in-plane resolution 100×100 µm, and slice thickness = 750 µm.Double echo PD / T2 is rare: TE = 19.0 / 57.1 ms, TR = 5000 ms, echo train length = 4, in-plane resolution 100×100 µm, and slice thickness = 750 µm. Spin echo (SE) of the diffusion tensor of the image data using 12 non-collinear directions: b-value = 350 s / mm 2, TE = 26 ms, TR = 4500 ms, in-plane resolution 150×150 μm, and slice thickness = 750 microns. Multi-slice multi-echo (MSME) T2 parametric data display using 16 MGE = 11.4 ms to 182.5 ms with ΔTE = 11.4 ms, TR = 10000 ms, in-plane resolution 150×150 μm, and slice thickness = 750 microns.
- Imaging: Tensor reconstruction diffusion and tractography is performed using TrackVis (Martinos Center for Biomedical Imaging; Massachusetts General Hospital, Boston, MA) to create mean diffusion coefficient (MD), fractional anisotropy (PA) images, and map tractography. T2 mapping is done using custom software written in MAT LAB (Mathworks; Natick, MA) using nonlinear least squares for the measured data at each point to the canonical T2 signal equation.Regions of interest are measured to assess the values of the parameters in the TP.
- 1H spectroscopy: Automated spacers are carried out on 1 x 1 x 4 mm 3 voxels in TP. Point-resolved spectroscopy (PRESS) of a pulse train (TR / TE = 2000/18 ms) is used to obtain spectra of the same voxel with 1024 averages. Data collection is 34 minutes per leg. Spectral data are processed using 16 LCModel package. 31P Spectroscopy: Dual tuned (1H, 31P) coil surfaces are used to perform non-localized (single-pulse experiment) or localized spectroscopy using an image sampled in vivo spectroscopy (ISIS) pulse sequence.
4. Collection and storage of muscles.
TP is collected after, at the end of the experiment, weighed, the rigs are frozen in liquid nitrogen and then stored at -80 ° C. This can be done at any time after experiments in vivo. Muscles are harvested immediately after experiments in situ, as this is the terminal of the procedure. To obtain detailed morphological studies, animals were fixed in 4% paraformaldehyde by perfusion through the left ventricle.
5. Representative results.
Figure 3 shows representative data from rats in in vivo in apparatus. in vivo. apparatus is used to obtain the maximum torque generated by the dorsiflexor muscles; It is also used to cause damage to these same muscles. Due to the length of muscle tension, maximum isometric torque usually occurs when the ankle joint is located at approximately 20 ° plantarflexion (with the legs orthogonal to the lower leg is considered 0 °).After maximum isometric torque is obtained, the legs can be placed in any position to initiate the injury protocol. Figure 3 presents an injury protocol from 30 reps with an arc of motion from 0 ° – 70 °. Note the steady decrease in torque from the isometric phase (filled arrow) and the lengthening of the phase (open arrow) during compression caused by protocol trauma. Torque is recorded in units of Nmm, but the absolute value depends on the size of the animal and its condition (for example, muscle injury, muscle fatigue, muscle fatigue, or lack of certain proteins due to homologous recombination).
Figure 4 shows representative data from rats at in place of the apparatus. Our apparatus at site does not imply lengthening of contractions, but rather allows us to isolate, properly align, and measure the maximum tension produced by individual muscles at a known length. Figure 4 shows the gradual loss of strength that occurs during a fatigue test in the tibialis anterior muscle of a rat. In this particular example, the titanic melee was conducted once per second for 5 minutes.Stress (forces) are usually written in newtons (or grams), but like torque, the absolute value depends on the size and condition of the animal. Because muscle mass is obtained immediately after this procedure, the forces can be normalized (called “specific force”) to the muscle’s cross-sectional area.
Figure 5 shows representative data from in vivo mouse images such as T1-T2 and parametric imaging (), 3D tractography from diffusion tensor tomography (B), 1 H-spectroscopy (C), and 31 P spectroscopy.See the legend figure for details.
Figure 1: in vivo apparatus . * For injury, the shin is stabilized and the leg is attached to a motor-driven plate. The ankle dorsiflexors are stimulated through the peroneal nerve while the footrest forces the leg into plantar flexion (dotted arrow).
* Lovering & De Deyne, J Biomechanics 2005, used with permission.
Figure 2: In place of the apparatus the sensor is mounted on the micromanipulator so that the TA can be adjusted with resting length and aligned properly in X, Y, Z and directions.The distal T. tendon is attached to the load cell and a single twitch is induced at different muscle lengths to determine L 0. The maximum tetanic contraction is obtained to determine the maximum contractile activation (P 0). Maximum tetanic tension can be repeated and expressed as a percentage of P 0, providing a fatigue index at the desired point in time.
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Figure 3: Torque data in vivo apparatus Representative traces of torque recording from lengthening contractions in rats.In this particular example, the muscles were stimulated for 200 milliseconds to induce a peak isometric contraction (filled arrow) before elongation (open arrow) on the stretcher across a 70 ° arc of motion at an angular velocity of 900 ° / s
Figure 4: Tension data in-situ apparatus Representative data showing a decrease in maximum isometric tetanic tension upon re-stimulation of the tibialis anterior muscle (TA) in a rat. In this example, T.was isolated, corrected for optimal length (L 0), and then stimulated 200 ms tetanic contraction every second for 5 minutes.
Figure 5: in vivo images: images show a transverse (axial) T1-T2 section and a parametric display of the tibialis anterior (TP) muscle. A dotted red box surrounds the TA to show increased increased T2 injury (left) compared to intact (right side) B :…. Representative 3D tractography from diffusion imaging tensor (DTI) C: 1 H spectrum of mouse TA shows several lipid resonances detected; differentiation between intramyocellular (IMCL) and extramyocellular lipids (EMCL) peaks obtained by this method D: 31 P MR spectrum of rat TA shows phosphocreatine (PCR), inorganic phosphate (Pi), and three. resonances (α, β, γ) of adenosine-5′-triphosphate (ATP).
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Samsung achieves ISO certification for robotic personal care system with GEMS Hip – Samsung Newsroom Kazakhstan
Certification confirms the safety and quality of Samsung GEMS Hip products in the field of robotics for personal assistance
Samsung Electronics became the first company in Korea to receive the international ISO 13482 (Robots and Robotic Devices – Safety Requirements for Personal Care Robots) certification in Korea, a testament to the significant advancements in the GEMS Hip Personal Care Robot.
ISO 13482 is a globally recognized standard set by the International Organization for Standardization (ISO) in 2014 to ensure safety in the use of mobile robotic servants, robotic assistants and robotic porters. The certification officially confirms the safety and quality of Samsung GEMS Hip products in accordance with the requirements of ISO 13482.
By applying the appropriate torque to both hip joints according to the user’s movements, GEMS Hip can reduce the metabolic cost of walking by 24% while increasing the speed by 14%.Ultimately, with this support, a more energy efficient and stable gait can be achieved.
In addition to the ISO 13482 standard, Samsung has also obtained the ISO 13849 (Safety of Equipment – Safety Related Parts) certification for the GEMS Hip safety function, which limits the maximum torque of the engine.
“Product safety is critical to the widespread use of robotic assistants,” said Jung Il Moon, President of the Korea Robotics Development Institute (KIRIA).”We believe that efforts to meet the stringent criteria of global standardization demonstrated by this achievement will further advance the personal care robotics industry.”
“With this international safety certification, we are on the cusp of an important transformation,” said Sungchul Kang, Senior Vice President and Head of Robotics Center, Samsung Research. “The certification will allow us to bring robots closer to our daily life, increase their availability and usefulness.We will do our best to further research in the field of robotics. ”
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