Treffer: Designing an FES Control Algorithm: Important Considerations.

One of the most crucial aspects of closed-loop control of upright mobility using functional electrical stimulation (FES)-evoked muscle contractions is the development of a robust control algorithm. The need for compliance with certain safety requirements when FES-evoked movements are deployed to neurological patients is essential, and the computational tools employed play a fundamental role in this task. This paper reports on some new developments regarding closed-loop control of upright mobility and discusses some important issues concerning FES control design. Our laboratory has focused on the restoration of mobility in spinal cord-injured individuals by means of FES-evoked muscle contractions, and currently we deploy a Pocket PC to control an ambulatory neuromuscular stimulator, while movement feedback data is collected from portable motion sensors. Programmed in Matlab Simulink, the control algorithm is structured with sensor feedback (thighs and shanks kinematic data) acting as the model input and the stimulator channels (gluteus, quadriceps and common peroneal nerve) as the model output. In both input and output components, properties such as sampling rate and stimulation parameters are handled. The functions of standing up, sitting down and stepping are designed as finite-state models and grouped into different subsystems, thereby assuring that conditions of ‘worst-case' system behavior can be identified and treated independently. The operator initiates the changes between states via button presses. The two major control actions of the model's algorithm are the modulation of quadriceps stimulation to avert knee buckle during stance and the stimulation of the common peroneal nerve to refine swing leg motion during stepping. This control algorithm has proven to meet the differing requirements of both the clinical and research environments, by achieving flexible programming with a fast algorithm development, real-time operation, reliable processing of heavy mathematical calculations and the ability to counteract external disturbances or unexpected behavior. [ABSTRACT FROM AUTHOR]

Copyright of World Congress on Medical Physics & Biomedical Engineering 2006 is the property of Springer eBooks and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)