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Identification and control of electrode arrays


Benjamin Hackl

Diploma/Master Thesis, WS 05/06

Functional Electrical Stimulation (FES) is a technique that uses electrical pulses to cause muscle contraction. FES is used for generating specific stimulation goals, especially long term management of functional movements. This treatment program can be used to increase the independency of a paralyzed person suffering from neurological disorders. FES is a technique where an external electric field depolarizes the cellular membrane and generates an action potential in the nerve, which then causes a muscle contraction. This project focuses on finding strategies to achieve best grasp by controlling the finger flexors and techniques to optimize the way of stimulating these muscles with transcutaneous FES. The muscles for finger flexion are located in the forearm and can be stimulated at so called activation points, these are areas, where when stimulation is applied, finger movement can be generated. In common Functional Electrical Stimulation, surface (transcutaneous) electrodes are placed over these activation points for a particular muscle group. For every patient these activation points have to be detected first using anatomical landmarks and visual observation. Such processes are time consuming and prone to misplacement. The electrical stimulation group at the Automatic Control Laboratory at the ETH Zürich has started developing transcutaneous electrode arrays that can dynamically change the size, shape and location of the stimulating current distribution. The larger electrode array can be used to cover most of the activation points on the forearm. This system enables the automatic optimization of the current distribution for different functional tasks; e.g. finger closure vs. wrist movement. Once the activation points are detected automatically with the electrode array, a control strategy is necessary for achieving best grasp and therefore a suitable model for the finger activation is needed. The project’s second goal was to find a model for describing the system behavior for the amplitude of the stimulation current at an activation point and the produced finger force. A theoretical mathematical model, derived from physical laws and physiological effects and the hands mechanical structure would be complicated and the parameters would have to be measured individually for each patient. System identification can therefore provide a method for online adaptation of parameters for a model for every patient.

Supervisors: Dr. T. Keller, Prof. M. Morari


Type of Publication:

(12)Diploma/Master Thesis

M. Morari

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% Autogenerated BibTeX entry
@PhdThesis { Xxx:2006:IFA_2821
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