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

摘要

AIM: The aim of this study was to investigate feedbackudcontrol 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 wasudto investigate the possible benefits of the approach for mobile, recreational cycling.udududMETHODS: 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 areuddesigned 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.udududRESULTS: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.ududCONCLUSION: The integrated control strategy is effective in facilitatingudexercise testing under conditions of well-controlled cadenceudand power output. Our control approach significantly extends theudachievable workrate range and enhances exercise-test sensitivityudfor FES cycling, thus allowing a more stringent characterizationudof physiological response profiles and estimation of key parametersudof aerobic function.We further conclude that the control approachudcan significantly improve the overall performance of mobile recreationaludcycling.udud