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Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: Utility for exercise testing and mobile cycling

Hunt, K.J., Stone, B., Negard, N.O., Schauer, T., Fraser, M.H., Cathcart, A.J., Ferrario, C., Ward, S.A. and Grant, S. (2004) Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: Utility for exercise testing and mobile cycling. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 12 (1). pp. 89-101. ISSN 1534-4320

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Abstract

AIM: The aim of this study was to investigate feedback control strategies for integration of electric motor assist and functional electrical stimulation (FES) for paraplegic cycling, with particular focus on development of a testbed for exercise testing in FES cycling, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. A second aim was to investigate the possible benefits of the approach for mobile, recreational cycling.

METHODS: A recumbent tricycle with an auxiliary electric motor is used, which is adapted for paraplegic users, and instrumented for stimulation control. We propose a novel integrated control strategy which simultaneously provides feedback control of leg power output (via automatic adjustment of stimulation intensity) and cycling cadence (via electric motor control). Both loops are designed using system identification and analytical (model-based) feedback design methods. Ventilatory and pulmonary gas exchange response profiles are derived using a portable system for real-time breath-by-breath acquisition.

RESULTS:We provide indicative results from one paraplegic subject in which a series of feedback-control tests illustrate accurate control of cycling cadence, leg power control, and external disturbance rejection. We also provide physiological response profiles from a submaximal exercise step test and a maximal incremental exercise test, as facilitated by the control strategy.

CONCLUSION: The integrated control strategy is effective in facilitating exercise testing under conditions of well-controlled cadence and power output. Our control approach significantly extends the achievable workrate range and enhances exercise-test sensitivity for FES cycling, thus allowing a more stringent characterization of physiological response profiles and estimation of key parameters of aerobic function.We further conclude that the control approach can significantly improve the overall performance of mobile recreational cycling.

Item Type: Article
Copyright, Publisher and Additional Information: Copyright © 2004 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Keywords: cardiopulmonary exercise testing, control systems, functional electrical stimulation (FES), lower limb cycling, spinal-cord injury (SCI) rehabilitation
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Biological Sciences (Leeds) > Institute of Membrane and Systems Biology (Leeds)
Depositing User: Sherpa Assistant
Date Deposited: 14 Mar 2006
Last Modified: 09 Jun 2014 12:45
Published Version: http://dx.doi.org/10.1109/TNSRE.2003.819955
Status: Published
Refereed: Yes
Identification Number: 10.1109/TNSRE.2003.819955
URI: http://eprints.whiterose.ac.uk/id/eprint/714

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