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Lower-limb Cycling in Paraplegia using Functional Electrical Stimulation: the role of feedback control, and a review of health-related benefits

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Abstract:
In the first half of the 1980s it was established that people with a spinal cord injury are able to produce cyclical leg motion by means of controlled sequential stimulation of the large leg-actuating muscles (`FES-cycling'). A number of subsequent investigations have studied the physiological adaptations which can occur in response to regular cycling exercise. Significant improvements in cardiopulmonary status (as indicated by increased peak oxygen uptake and faster oxygen uptake response kinetics) and in tibial bone density have been observed, along with several additional benefits. This talk will focus on the development of methods and protocols for FES-cycling which allow precise determination of the key indices of cardiopulmonary fitness, and will describe the key role of feedback control in achieving high testing sensitivity. Our study investigated feedback control strategies for integration of electric motor assist and functional electrical stimulation for paraplegic cycling, with particular focus on development of a testbed for exercise testing, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. 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. We provide experimental results showing physiological response profiles from a submaximal exercise step test and a maximal incremental exercise test, as facilitated by the control strategy. These results show that 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 characterisation of physiological response profiles and estimation of key parameters of aerobic function. References: K. J. Hunt et al, "Control Strategies for Integration of Electric Motor Assist and Functional Electrical Stimulation in Paraplegic Cycling: utility for exercise testing and mobile cycling", IEEE Trans. Neural Sys. Rehab. Eng., 12 (1), 89-101, 2004. T. Schauer, K. J. Hunt, N.-O. Negard, M. H. Fraser and W. Stewart, "Regelung der Trittgeschwindigkeit beim Liegedreiradfahren von Querschnittsgelahmten", Automatisierungstechnik, 50 (6), 271-278, 2002. C. Ferrario, B. Stone, K. J. Hunt, S. A. Ward, A. N. McLean and M. H. Fraser, "Oxygen cost of different stimulation patterns for FES cycling", Proc. 9th Ann. Conf. Int. Functional Electrical Stimulation Soc., Bournemouth, England, 171-173, 2004. E. S. Idso, T. A. Johansen and K. J. Hunt, "Finding the metabolically optimal stimulation pattern for FES-cycling", Proc. 9th Ann. Conf. Int. Functional Electrical Stimulation Soc., Bournemouth, England, 239-241, 2004.

http://fesnet.eng.gla.ac.uk/CRE/
Type of Seminar:
Public Seminar
Speaker:
Professor Ken Hunt Director
Centre for Rehabilitation, Engineering, University of Glasgow & Honorary Professor in Spinal Injuries, Queen Elizabeth National Spinal Injuries Unit, Glasgow
Date/Time:
Dec 15, 2004   17:15
Location:

ETH Zentrum, Gloriastr. 35, Zurich, Building ETZ, Room E6
Contact Person:

Prof. R. Riener
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Biographical Sketch:
Ken Hunt is Wylie Professor of Mechanical Engineering and Director of the Centre for Rehabilitation Engineering at Glasgow University (appointed at Glasgow in January 1998). He is also a Clinical Research Professor at the National Spinal Injuries Unit at Glasgow's Southern General Hospital. The Centre for Rehabilitation Engineering (http://fesnet.eng.gla.ac.uk/CRE) carries out basic and applied research in assistive technologies for function restoration. Previously, from 1992-1997, he was a research scientist and project leader with Daimler-Benz Systems Technology Research Berlin, part of Daimler-Benz corporate research. From 1989-1992 he held a Royal Society of Edinburgh Personal Research Fellowship, and during that period was with the Department of Mechanical Engineering at the University of Glasgow. From 1987-1989 he was a Research Scientist with BBN Systems and Technologies (the European division of Bolt, Beranek and Newman Inc.). Professor Hunt obtained a 1st class honours BSc in Electrical and Electronic Engineering in 1984 and a PhD in Control Theory in 1987, both from the University of Strathclyde, Glasgow. He is a member of the IEEE . In 1997 he was awarded the IEE's Young Engineer's Award for achievement, and in 2002 he received the IEE Coales Premium for a paper published in the IEE Proceedings.