scholarly journals Encouraging Volitional Pedaling in Functional Electrical Stimulation-Assisted Cycling Using Barrier Functions

2021 ◽  
Vol 8 ◽  
Author(s):  
Axton Isaly ◽  
Brendon C. Allen ◽  
Ricardo G. Sanfelice ◽  
Warren E. Dixon
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Power Output ◽  
Barrier Function ◽  
Control Method ◽  
Lyapunov Theory ◽  
Target Point ◽  
Worst Case ◽  
Barrier Functions ◽  
Uncertain Dynamics

Stationary motorized cycling assisted by functional electrical stimulation (FES) is a popular therapy for people with movement impairments. Maximizing volitional contributions from the rider of the cycle can lead to long-term benefits like increased muscular strength and cardiovascular endurance. This paper develops a combined motor and FES control system that tasks the rider with maintaining their cadence near a target point using their own volition, while assistance or resistance is applied gradually as their cadence approaches the lower or upper boundary, respectively, of a user-defined safe range. Safety-ensuring barrier functions are used to guarantee that the rider’s cadence is constrained to the safe range, while minimal assistance is provided within the range to maximize effort by the rider. FES stimulation is applied before electric motor assistance to further increase power output from the rider. To account for uncertain dynamics, barrier function methods are combined with robust control tools from Lyapunov theory to develop controllers that guarantee safety in the worst-case. Because of the intermittent nature of FES stimulation, the closed-loop system is modeled as a hybrid system to certify that the set of states for which the cadence is in the safe range is asymptotically stable. The performance of the developed control method is demonstrated experimentally on five participants. The barrier function controller constrained the riders’ cadence in a range of 50 ± 5 RPM with an average cadence standard deviation of 1.4 RPM for a protocol where cadence with minimal variance was prioritized and used minimal assistance from the motor (4.1% of trial duration) in a separate protocol where power output from the rider was prioritized.

EVALUATION OF CLOSED-LOOP CONTROL SYSTEM FOR RESTORING STANDING AND SITTING FUNCTIONS BY FUNCTIONAL ELECTRICAL STIMULATION

2005 ◽  
Vol 17 (01) ◽  
pp. 19-26 ◽  
Author(s):  
CHENG-LIANG LIU ◽  
CHUNG-HUANG YU ◽  
SHIH-CHING CHEN ◽  
CHANG-HUNG CHEN
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Closed Loop ◽  
Spinal Cord Injuries ◽  
Control Method ◽  
Control Strategies ◽  
Evaluation Process ◽  
Closed Loop Control ◽  
Loop Control ◽  
Loop Control System

Functional electrical stimulation (FES) is a method for restoring the functional movements of paraplegic or patients with spinal cord injuries. However, the selection of parameters that control the restoration of standing up and sitting functions has not been extensively investigated. This work provides a method for choosing the four main items involved in evaluating the strategies for sit-stand-sit movements with the aid of a modified walker. The control method uses the arm-supported force and the angles of the legs as feedback signals to change the intensity of the electrical stimulation of the leg muscles. The control parameters, Ki and Kp, are vary for different control strategies. Four items are collected through questionnaires and used for evaluation. They are the maximum reactions of the two hands, the average reaction of the two hands, largest absolute angular velocity of the knee joints, and the sit-stand-sit duration time. The experimental data are normalized to facilitate comparison. Weighting factors are obtained and analyzed from questionnaires answered by experts and are added to evaluation process for manipulation. The results show that the best strategy is the closed-loop control with parameters Ki=0.5 and Kp=0.

scholarly journals Home-Based Functional Electrical Stimulation of Human Permanent Denervated Muscles: A Narrative Review on Diagnostics, Managements, Results and Byproducts Revisited 2020

Diagnostics ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 529 ◽  
Author(s):  
Helmut Kern ◽  
Ugo Carraro
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Cauda Equina ◽  
Quadriceps Muscle ◽  
Ultrastructural Organization ◽  
Force Output ◽  
Case Scenario ◽  
Worst Case ◽  
Home Based ◽  
Cord Injury

Spinal cord injury (SCI) produces muscle wasting that is especially severe after complete and permanent damage of lower motor neurons, as can occur in complete conus and cauda equina syndrome. Even in this worst-case scenario, mass and function of permanently denervated quadriceps muscle can be rescued by surface functional electrical stimulation using a purpose designed home-based rehabilitation strategy. Early diagnostics is a key factor in the long-term success of this management. Function of quadriceps muscle was quantitated by force measurements. Muscle gross cross-sections were evaluated by quantitative color computed tomography (CT) and muscle and skin biopsies by quantitative histology, electron microscopy, and immunohistochemistry. Two years of treatment that started earlier than 5 years from SCI produced: (a) an increase in cross-sectional area of stimulated muscles; (b) an increase in muscle fiber mean diameter; (c) improvements in ultrastructural organization; and (d) increased force output during electrical stimulation. Improvements are extended to hamstring muscles and skin. Indeed, the cushioning effect provided by recovered tissues is a major clinical benefit. It is our hope that new trials start soon, providing patients the benefits they need.

scholarly journals Evaluation of Functional Electrical Stimulation to Assist Cycling in Four Adolescents with Spastic Cerebral Palsy

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Ann Tokay Harrington ◽  
Calum G. A. McRae ◽  
Samuel C. K. Lee
Keyword(s):  
Cerebral Palsy ◽  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Power Output ◽  
Cycling Performance ◽  
Cardiovascular Fitness ◽  
Spastic Cerebral Palsy ◽  
Surface Electrodes ◽  
Future Work

Introduction. Adolescents with cerebral palsy (CP) often have difficulty participating in exercise at intensities necessary to improve cardiovascular fitness. Functional electrical stimulation- (FES-) assisted cycling is proposed as a form of exercise for adolescents with CP. The aims of this paper were to adapt methods and assess the feasibility of applying FES cycling technology in adolescents with CP, determine methods of performing cycling tests in adolescents with CP, and evaluate the immediate effects of FES assistance on cycling performance.Materials/Methods. Four participants (12–14 years old; GMFCS levels III-IV) participated in a case-based pilot study of FES-assisted cycling in which bilateral quadriceps muscles were activated using surface electrodes. Cycling cadence, power output, and heart rate were collected.Results. FES-assisted cycling was well tolerated (n=4) and cases are presented demonstrating increased cadence (2–43 rpm), power output (19–70%), and heart rates (4-5%) and decreased variability (8–13%) in cycling performance when FES was applied, compared to volitional cycling without FES assistance. Some participants (n=2) required the use of an auxiliary hub motor for assistance.Conclusions. FES-assisted cycling is feasible for individuals with CP and may lead toimmediateimprovements in cycling performance. Future work will examine the potential for long-term fitness gains using this intervention.

scholarly journals Control of functional electrical stimulation for restoration of motor function

2017 ◽  
Vol 30 (3) ◽  
pp. 295-312
Author(s):  
Dejan Popovic
Keyword(s):  
Biological Control ◽  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Control Method ◽  
Level Structure ◽  
Open Loop ◽  
Model Based Control ◽  
Model Based ◽  
Assistive Systems ◽  
Artificial Control

An injury or disease of the central nervous system (CNS) results in significant limitations in the communication with the environment (e.g., mobility, reaching and grasping). Functional electrical stimulation (FES) externally activates the muscles; thus, can restore several motor functions and reduce other health related problems. This review discusses the major bottleneck in current FES which prevents the wider use and better outcome of the treatment. We present a control method that we continually enhance during more than 30 years in the research and development of assistive systems. The presented control has a multi-level structure where upper levels use finite state control and the lower level implements model based control. We also discuss possible communication channels between the user and the controller of the FES. The artificial controller can be seen as the replica of the biological control. The principle of replication is used to minimize the problems which come from the interplay of biological and artificial control in FES. The biological control relies on an extensive network of neurons sending the output signals to the muscles. The network is being trained though many the trial and error processes in the early childhood, but staying open to changes throughout the life to satisfy the particular needs. The network considers the nonlinear and time variable properties of the motor system and provides adaptation in time and space. The presented artificial control method implements the same strategy but relies on machine classification, heuristics, and simulation of model-based control. The motivation for writing this review comes from the fact that many control algorithms have been presented in the literature by the authors who do not have much experience in rehabilitation engineering and had never tested the operations with patients. Almost all of the FES devices available implement only open-loop, sensory triggered preprogrammed sequences of stimulation. The suggestion is that the improvements in the FES devices need better controllers which consider the overall status of the potential user, various effects that stimulation has on afferent and efferent systems, reflexive responses to the FES and direct responses to the FES by non-stimulated sensory-motor systems, and the greater integration of the biological control.

scholarly journals Functional electrical stimulation of permanently denervated muscles, updated 2020

2020 ◽  
Vol 97 (3) ◽  
pp. 130-136 ◽  
Author(s):  
U. Carraro ◽  
H. Kern ◽  
G. Albertin G. ◽  
S. Masiero ◽  
A. Pond ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Cauda Equina ◽  
Quadriceps Muscle ◽  
Ultrastructural Organization ◽  
Force Output ◽  
Case Scenario ◽  
Cross Sectional ◽  
Worst Case ◽  
Cord Injury

Spinal cord injury produces muscle wasting, which is especially severe after the complete and permanent damage of lower motor neurons that occurs in complete Cauda Equina Syndrome. Even in this worst-case scenario, we have shown that permanently denervated Quadriceps muscle can be rescued by surface Functional Electrical Stimulation and a purpose designed home-based rehabilitation regime. Here, our aim is to show that the effects are extended to both antagonist muscles and the skin of the thighs. Before and after 2 years of electrical stimulation, mass and structure of Quadriceps and Hamstrings muscles were quantitated by force measurements. Muscle gross cross section were evaluated using color computed tomography, muscle and skin biopsies by quantitative histology and immunohistochemistry. The treatment produced: a) an increase in cross-sectional area of stimulated muscles; b) an increase in muscle fiber mean diameter; c) improvements in ultrastructural organization; and d) increased force output during electrical stimulation. The recovery of Quadriceps muscle force was sufficient to allow 25% of the compliant subjects to perform stand-up and step-in place trainings. Improvements are extended to hamstring muscles and skin. Indeed, the cushioning effect provided by recovered tissues is a major clinical benefit. It is our hope that, with or without our advice, trials may start soon in Europe and Russia to provide persons-in-need the help they deserve.

RESIDUAL CAPABILITIES OF HEMIPLEGIC PATIENTS TO RESTORE HAND FUNCTIONS VIA A NON-INVASIVE FUNCTIONAL ELECTRICAL STIMULATION SYSTEM

2006 ◽  
Vol 18 (05) ◽  
pp. 255-263
Author(s):  
YING-HAN CHIOU ◽  
JER-JUNN LUH ◽  
SHIH-CHING CHEN ◽  
JIN-SHIN LAI ◽  
TE-SON KUO
Keyword(s):  
Electrical Stimulation ◽  
Functional Electrical Stimulation ◽  
Control Strategy ◽  
Control Method ◽  
Control Strategies ◽  
Hand Function ◽  
Loop Control ◽  
Non Invasive ◽  
Hand Functions ◽  
Electrical Stimulator

Control strategies are the chief attraction in the field of rehabilitation engineering, and especially in a functional electrical stimulation (FES) system, a reliable control method is important for paralyzed patients to restore lost their functions. In this paper, we have presented a demonstration of the control strategy, which is based on the patient-driven loop, used in a non-invasive FES system for hand function restoration. With the patient-driven loop control, hemiplegic patients could use their residual capabilities, such as shoulder movements in their sound extremities, the myoelectric signals generated from different muscles, etc, to operate the FES system. Here we have chosen the most common and acceptable signals as the input sources, i.e. electromyographic (EMG) signals, to control a non-invasive FES system, generating the electrical stimuli to excite the paralyzed muscles. In addition, EMG signals recorded by the sensors in the electrical stimulator can serve both as the trigger of the system and as the adjustment of the electrical stimulation parameters, thereby improving the system's performance and reliability. From the experimental results, subjects can successfully use their residual capabilities to control the FES system and restore their lost hand functions as well. On the other hand, from the viewpoints of rehabilitation and psychology, hemiplegics will benefit greatly by using their residual capabilities to regain their lost functions. It is believed that the patient-driven loop control is very useful, not only for the FES system in this study, but also for other assistive devices. By the control strategy proposed in this paper, we deeply hope that patients will benefit greatly and regain their self-confidence.

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