Functional electrical stimulation (FES) has proven
to be an effective method for improving health and regaining
muscle function for people with limited or reduced motor skills.
Closed-loop control of motorized FES-cycling can facilitate
recovery. Many people with movement disorders (e.g., stroke)
have asymmetries in their motor control, motivating the need
for a closed-loop control system that can be implemented
on a split-crank cycle. In this paper, nonlinear sliding mode
controllers are designed for the FES and electric motor on
each side of a split-crank cycle to maintain a desired cadence
and a crank angle offset of 180 degrees, simulating standard
pedaling conditions. A Lyapunov-like function is used to prove
stability and tracking of the desired cadence and position for
the combined cycle-rider system. One experimental trial on an
able-bodied individual demonstrated the feasibility and stability
of the closed-loop controller, which resulted in an average
cadence error of 2.62 ± 3.54 RPM for the dominant leg and
an average position and cadence error of 39.84±10.77 degrees
and −0.04 ± 8.79 RPM for the non-dominant leg.
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Electromechanical delay during functional electrical stimulation induced cycling is a function of lower limb position
Introduction: Functional electrical stimulation (FES) induced cycling has been shown to be an effective rehabilitation for those with lower limb movement disorders. However, a consequence of FES is an electromechanical delay (EMD) existing between the stimulation input and the onset of muscle force. The objective of this study is to determine if the cycle crank angle has an effect on the EMD.
Methods: Experiments were performed on 10 participants, five healthy and five with neurological conditions resulting in movement disorders. A motor fixed the crank arm of a FES-cycle in 10 degree increments and at each angle stimulation was applied in a random sequence to a combination of the quadriceps femoris and gluteal muscle groups. The EMD was examined by considering the contraction delay (CD) and the residual delay (RD), where the CD (RD) is the time latency between the start (end) of stimulation and the onset (cessation) of torque. Two different measurements were used to examine the CD and RD. Further, two multiple linear regressions were performed on each measurement, one for the left and one for the right muscle groups.
Results: The crank angle was determined to be statistically relevant for both the CD and RD.
Conclusions: Since the crank angle has a significant effect on both the CD and RD, the angle has a significant effect on the EMD. Therefore, future efforts should consider the importance of the crank angle when modelling or estimating the EMD to improve control designs and ultimately improve rehabilitative treatments.
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- Award ID(s):
- 1762829
- NSF-PAR ID:
- 10231084
- Date Published:
- Journal Name:
- Disability and Rehabilitation: Assistive Technology
- ISSN:
- 1748-3107
- Page Range / eLocation ID:
- 1 to 6
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1080/17483107.2021.1878295
