An Experimental Powered Lower Limb Prosthesis Using Proportional Myoelectric Control

2014 ◽  
Vol 8 (2) ◽  
Author(s):  
Stephanie Huang ◽  
Jeffrey P. Wensman ◽  
Daniel P. Ferris
Keyword(s):  
Lower Limb ◽  
Muscle Activity ◽  
Plantar Flexion ◽  
Myoelectric Control ◽  
Artificial Muscles ◽  
Plantar Flexors ◽  
Force Output ◽  
Prosthetic Socket ◽  
Pneumatic Artificial Muscles ◽  
Powered Prosthesis

One way to provide powered lower limb prostheses with greater adaptability to a wearer's intent is to use a neural signal to provide feedforward control of prosthesis mechanics. We designed and tested the feasibility of an experimental powered ankle-foot prosthesis that uses pneumatic artificial muscles and proportional myoelectric control to vary ankle mechanics during walking. The force output of the artificial plantar flexor muscles was directly proportional to the subject's residual gastrocnemius muscle activity. The maximum force generated by a pair of artificial muscles fixed at nominal length was 3513 N. The maximum planter flexion torque that could be generated during walking was 176 Nm. The force bandwidth of the pneumatic artificial muscles was 2 Hz. The electromechanical delay was 33 ms, the time to peak tension was 48 ms, and the half relaxation time was 50 ms. We used two artificial muscles as dorsiflexors and two artificial muscles as plantar flexors. The prosthetic ankle had 25 deg of dorsiflexion and 35 deg of plantar flexion with the artificial muscles uninflated. The intent of the device was not to create a commercially viable prosthesis but to have a laboratory prototype to test principles of locomotor adaptation and biomechanics. We recruited one unilateral transtibial amputee to walk on a treadmill at 1.0 m/s while wearing the powered prosthesis. We recorded muscle activity within the subject's prescribed prosthetic socket using surface electrodes. The controller was active throughout the entire gait cycle and did not rely on detection of gait phases. The amputee subject quickly adapted to the powered prosthesis and walked with a functional gait. The subject generated peak ankle power at push off that was similar between amputated and prosthetic sides. Our results suggest that amputees can use their residual muscles for proportional myoelectric control to alter prosthetic mechanics during walking.

scholarly journals Design and Control of a 1-DOF Robotic Lower-Limb System Driven by Novel Single Pneumatic Artificial Muscle

2019 ◽  
Vol 10 (1) ◽  
pp. 43 ◽  
Author(s):  
Tsung-Chin Tsai ◽  
Mao-Hsiung Chiang
Keyword(s):  
Lower Limb ◽  
Artificial Muscle ◽  
Robotic System ◽  
Artificial Muscles ◽  
Prototype System ◽  
Pneumatic Artificial Muscle ◽  
Torsion Spring ◽  
Pneumatic Artificial Muscles ◽  
Control Response ◽  
Spring Mechanism

This study determines the practicality and feasibility of the application of pneumatic artificial muscles (PAMs) in a pneumatic therapy robotic system. The novel mechanism consists of a single actuated pneumatic artificial muscle (single-PAM) robotic lower limb that is driven by only one PAM combined with a torsion spring. Unlike most of previous studies, which used dual-actuated pneumatic artificial muscles (dual-PAMs) to drive joints, this design aims to develop a novel single-PAM for a one degree-of-freedom (1-DOF) robotic lower-limb system with the advantage of a mechanism for developing a multi-axial therapy robotic system. The lower limb robotic assisting system uses the stretching/contraction characteristics of a single-PAM and the torsion spring designed by the mechanism to realize joint position control. The joint is driven by a single-PAM controlled by a proportional pressure valve, a designed 1-DOF lower-limb robotic system, and an experimental prototype system similar to human lower limbs are established. However, the non-linear behavior, high hysteresis, low damping and time-variant characteristics for a PAM with a torsion spring still limits its controllability. In order to control the system, a fuzzy sliding mode controller (FSMC) is used to control the path tracking for the PAM for the first time. This control method prevents approximation errors, disturbances, un-modeled dynamics and ensures positioning performance for the whole system. Consequently, from the various experimental results, the control response designed by the joint torsion spring mechanism can also obtain the control response like the design of the double-PAMs mechanism, which proves that the innovative single-PAM with torsion spring mechanism design in this study can reduce the size of the overall aid mechanism and reduce the manufacturing cost, can also improve the portability and convenience required for the wearable accessory, and is more suitable for the portable rehabilitation aid system architecture.

scholarly journals Soft Pneumatic Artificial Muscles With Low Threshold Pressures for a Cardiac Compression Device

2013 ◽  
Author(s):  
Steven C. Obiajulu ◽  
Ellen T. Roche ◽  
Frank A. Pigula ◽  
Conor J. Walsh
Keyword(s):  
Response Times ◽  
Local Stress ◽  
Artificial Muscles ◽  
Force Output ◽  
Stress Concentrations ◽  
Nylon Mesh ◽  
Cardiac Compression ◽  
Pneumatic Artificial Muscles ◽  
Low Threshold ◽  
Actuator Design

In this paper, we present the design, fabrication and characterization of fully soft pneumatic artificial muscles (PAMs) with low threshold pressures that are intended for direct cardiac compression (DCC). McKibben type PAMs typically have a threshold pressure of at least 100 kPa and require rigid end fittings which may damage soft tissue and cause local stress concentrations, and thus failure points in the actuator. The actuator design we present is a variant on the McKibben PAM with the following key differences: the nylon mesh is embedded in the elastomeric tube, and closure of the end of the tube is achieved without rigid ends. The actuators were tested to investigate the effects of mesh geometry and elastomer material on force output, contraction, and rise time. Lower initial mean braid angles and softer elastomer materials provided the best force, contraction, and rise times; Up to 50 N of force, 24% contraction, and response times of 0.05 s were achieved at 100 kPa. The actuators exhibited low threshold pressures (<5 kPa) and high rupture pressures (138 kPa – 720 kPa) which suggest safe operation for the DCC application. These results demonstrate that the actuators can achieve forces, displacements, and rise times suitable to assist with cardiac function.

scholarly journals Changes in Muscle Activity with Assistance Level During Exoskeletal Gait in Acute Stroke

2021 ◽  
Author(s):  
Ben P.F. O'Callaghan ◽  
Matthew W. Flood ◽  
Michele Tonellato ◽  
Caitríona Fingleton ◽  
Madeleine M Lowery ◽  
...  
Keyword(s):  
Acute Stroke ◽  
Lower Limb ◽  
Muscle Activity ◽  
Stroke Care ◽  
Acute Stage ◽  
Plantar Flexors ◽  
Post Stroke ◽  
Paretic Side ◽  
Gait Parameters ◽  
Cord Injury

Abstract BackgroundThe level of assistance provided to the user is an important decision in rehabilitation training using robotic devices. Both fully assistive and assist-as-needed paradigms have shown benefits in functional outcomes in healthy individuals and users with chronic stroke and spinal cord injury. The effect of assistance level on muscle activity and kinematic gait parameters has not yet been directly examined during overground exoskeletal gait in a stroke population. Furthermore, it is not clear whether an assist-as-needed approach could elicit increased voluntary activity in individuals in the acute stages of stroke. The aim of this study was to examine the effect of assistance level on muscle activity and kinematic parameters during exoskeleton gait in individuals in the acute stage of stroke care.MethodsNine individuals in the acute stage of post-stroke care performed walking tasks in the EKSO GTTM exoskeleton using both maximal assistance and adaptive assistance control paradigms. Temporal gait parameters and muscle activity were recorded using accelerometers and surface EMG on the lower limb muscles.ResultsShorter swing times and longer double support times were observed on the non-paretic side during adaptive assist mode than with maximum assist mode (p<0.0065). No significant effect of exoskeleton mode was observed on the remaining temporal gait parameters. On the paretic side, proximal lower limb muscles (RF and ST) and plantar-flexors (SO) (p<0.00125) exhibited greater activation in adaptive assist mode than in maximum assist mode. On the non-paretic side however, the lower limb distal muscles (TA and SO) displayed greater activity during maximum assist mode than adaptive assist mode (p<0.00125). ConclusionsThe level of assistance provided by an exoskeleton in the acute stages of stroke care is an important clinical decision. The results indicate that an adaptive or assist-as-needed approach elicits higher levels of activation in muscles acting around the knee joint and plantar-flexors on the paretic side than a maximal, fixed assistance paradigm, in the acute stage post-stroke. Increased activity around the ankle joint during maximum assistance mode was also noted. Improved understanding of the effect of assistance level can help inform future control paradigms for exoskeleton gait in acute stroke.

Electromyographic and Safety Comparisons of Common Lower Limb Rehabilitation Exercises for People With Hemophilia

2019 ◽  
Author(s):  
Joaquín Calatayud ◽  
Sofía Pérez-Alenda ◽  
Juan J Carrasco ◽  
Adrián Escriche-Escuder ◽  
Carlos Cruz-Montecinos ◽  
...  
Keyword(s):  
Lower Limb ◽  
Muscle Activity ◽  
Plantar Flexion ◽  
Rectus Femoris ◽  
Knee Extension ◽  
Activity Levels ◽  
External Resistance ◽  
Elastic Resistance ◽  
Ankle Plantar Flexion ◽  
Gastrocnemius Lateralis

Abstract Background Ankles and knees are commonly affected in people with hemophilia and thus are targets for prevention or rehabilitation. However, to our knowledge, no studies have evaluated muscle activity and safety during exercises targeting the lower limbs in people with hemophilia; this lack of information hinders clinical decision-making. Objective The aim of this study was to compare the tolerability of, safety of, and muscle activity levels obtained with external resistance (elastic or machine)–based and non–external resistance–based lower limb exercises in people with hemophilia. Design This was a cross-sectional study. Methods Eleven people who had severe hemophilia and were undergoing prophylactic treatment participated. In a single experimental session, participants performed knee extension and ankle plantar flexion during 3 exercise conditions in random order: elastic band–based resistance (elastic resistance), machine-based resistance (machine resistance), and no external resistance. Exercise intensities for the 2 external resistance–based conditions were matched for perceived exertion. Muscle activity was determined using surface electromyography (EMG) for the rectus femoris, biceps femoris, gastrocnemius lateralis, and tibialis anterior muscles. Participants were asked to rate exercise tolerability according to a scale ranging from “very well tolerated” to “not tolerated” and to report possible adverse effects 24 and 48 hours after the session. Results No adverse effects were reported, and exercise tolerability was generally high. In the knee extension exercise, the rectus femoris normalized EMG values during the elastic resistance and machine resistance conditions were similar; 29% to 30% higher activity was obtained during these conditions than during the non–external resistance condition. In the ankle plantar flexion exercise, the gastrocnemius lateralis normalized EMG value was 34% higher during the machine resistance condition than without external resistance, and the normalized EMG values during the elastic resistance and other conditions were similar. Limitations The small sample size and single training session were the primary limitations of this study. Conclusions Exercises performed both with elastic bands and with machines at moderate intensity are safe, feasible, and efficient in people with severe hemophilia, providing comparable activity levels in the agonist muscles.

Passive and Active Control Strategies of a Leg Rehabilitation Exoskeleton Powered by Pneumatic Artificial Muscles

2017 ◽  
Vol 31 (10) ◽  
pp. 1759021 ◽  
Author(s):  
Chen Su ◽  
Ao Chai ◽  
Xikai Tu ◽  
Hongyu Zhou ◽  
Haiqiang Wang ◽  
...  
Keyword(s):  
Lower Limb ◽  
Sliding Mode ◽  
Control Strategies ◽  
Low Cost ◽  
Gait Training ◽  
Interaction Force ◽  
Gait Rehabilitation ◽  
Artificial Muscles ◽  
Model Free ◽  
Pneumatic Artificial Muscles

Nerve injury can cause lower limb paralysis and gait disorder. Currently lower limb rehabilitation exoskeleton robots used in the hospitals need more power to correct abnormal motor patterns of stroke patients’ legs. These gait rehabilitation robots are powered by cumbersome and bulky electric motors, which provides a poor user experience. A newly developed gait rehabilitation exoskeleton robot actuated by low-cost and lightweight pneumatic artificial muscles (PAMs) is presented in this research. A model-free proxy-based sliding mode control (PSMC) strategy and a model-based chattering mitigation robust variable control (CRVC) strategy were developed and first applied in rehabilitation trainings, respectively. As the dynamic response of PAM due to the compressed air is low, an innovative intention identification control strategy was taken in active trainings by the use of the subject’s intention indirectly through the estimation of the interaction force between the subject’s leg and the exoskeleton. The proposed intention identification strategy was verified by treadmill-based gait training experiments.

Powering a Lower Limb Exoskeleton Using Pneumatic Artificial Muscles

2016 ◽  
Author(s):  
Jonathan M. Chambers ◽  
Craig R. Carignan ◽  
Norman M. Wereley
Keyword(s):  
Knee Joint ◽  
Lower Limb ◽  
Kinematic Model ◽  
Knee Joints ◽  
Transmission Model ◽  
Artificial Muscles ◽  
Lower Limb Exoskeleton ◽  
Actuation System ◽  
Pneumatic Artificial Muscles ◽  
Assembly Tasks

Passive leg exoskeletons are currently being investigated for offsetting the weight of tools and other loads from workers performing maintenance and assembly tasks. By providing power-assist to the knee joints with pneumatic artificial muscles (PAMs), a wider range of stances could be used by maintenance workers without drawing significant power. A simplified kinematic model of the exoskeleton is developed, and the array of potential user stance configurations is then bounded. A static analysis is performed to define the torque required for actuation of the knee joint to support the tool loads carried by the exoskeleton. Finally, an exemplary transmission model is used to verify that it is feasible for a PAM to provide the range of motion and forces required for knee joint actuation. Upon demonstration of the viability of PAM actuation, development of an exoskeleton leg prototype is underway to provide validation of the proposed scheme. The knee actuation system will be retrofit to the FORTIS exoskeleton, and tests on its effectiveness will be conducted.

Ultrasound reveals negligible cocontraction during isometric plantar flexion and dorsiflexion despite the presence of antagonist electromyographic activity

2015 ◽  
Vol 118 (10) ◽  
pp. 1193-1199 ◽  
Author(s):  
Brent J. Raiteri ◽  
Andrew G. Cresswell ◽  
Glen A. Lichtwark
Keyword(s):  
Cross Talk ◽  
Muscle Activity ◽  
Plantar Flexion ◽  
Medial Gastrocnemius ◽  
Electromyographic Activity ◽  
Plantar Flexors ◽  
Fascicle Length ◽  
Lateral Gastrocnemius ◽  
Muscle Fascicle

Because of the approximate linear relationship between muscle force and muscle activity, muscle forces are often estimated during maximal voluntary isometric contractions (MVICs) from torque and surface electromyography (sEMG) measurements. However, sEMG recordings from a target muscle may contain cross-talk originating from nearby muscles, which could lead to erroneous force estimates. Here we used ultrasound imaging to measure in vivo muscle fascicle length ( Lf) changes and sEMG to measure muscle activity of the tibialis anterior, medial gastrocnemius, lateral gastrocnemius, and soleus muscles during ramp MVICs in plantar and dorsiflexion directions ( n = 8). After correcting longitudinal Lfchanges for ankle rotation, the antagonist Lfat peak antagonist root-mean-square (RMS) amplitude were significantly longer than the agonist Lfat this sEMG-matched level. On average, Lfshortened from resting length by 1.29 to 2.90 mm when muscles acted as agonists and lengthened from resting length by 0.43 to 1.16 mm when muscles acted as antagonists (depending on the muscle of interest). The lack of fascicle shortening when muscles acted as antagonists indicates that cocontraction was likely to be negligible, despite cocontraction as determined by sEMG of between 7 and 23% MVIC across all muscles. Different interelectrode distances (IEDs) over the plantar flexors revealed significantly higher antagonist RMS amplitudes for the 4-cm IEDs compared with the 2-cm IEDs, which further indicates that cross-talk was present. Consequently, investigators should be wary about performing agonist torque corrections for isometric plantar flexion and dorsiflexion based on the antagonist sEMG trace and predicted antagonist moment.

scholarly journals Analysis and control of a parallel lower limb based on pneumatic artificial muscles

2017 ◽  
Vol 9 (1) ◽  
pp. 168781401668500 ◽  
Author(s):  
Feilong Jiang ◽  
Guoliang Tao ◽  
Qingwei Li
Keyword(s):  
Lower Limb ◽  
Artificial Muscle ◽  
Artificial Muscles ◽  
Pneumatic Artificial Muscle ◽  
Joint Movement ◽  
Obturator Internus ◽  
Pneumatic Artificial Muscles ◽  
Human Limb ◽  
Adaptive Control Algorithm ◽  
And Control

Most robots that are actuated by antagonistic pneumatic artificial muscles are controlled by various control algorithms that cannot adequately imitate the actual muscle distribution of human limbs. Other robots in which the distribution of pneumatic artificial muscle is similar to that of human limbs can only analyze the position of the robot using perceptual data instead of rational knowledge. In order to better imitate the movement of a human limb, the article proposes a humanoid lower limb in the form of a parallel mechanism where muscle is unevenly distributed. Next, the kinematic and dynamic movements of bionic hip joint are analyzed, where the joint movement is controlled by an observer-based fuzzy adaptive control algorithm as a whole rather than each individual pneumatic artificial muscle and parameters that are optimized by a neural network. Finally, experimental results are provided to confirm the effectiveness of the proposed method. We also document the role of muscle in trajectory tracking for the piriformis and musculi obturator internus in isobaric processes.

Sign in / Sign up

Export Citation Format

Share Document