Investigation of the Hammerstein hypothesis in the modeling of electrically stimulated muscle

Hunt, K.J., Munih, M., Donaldson, N.D. and Barr, F.M.D. (1998) Investigation of the Hammerstein hypothesis in the modeling of electrically stimulated muscle. IEEE Transactions on Biomedical Engineering, 45(8), pp. 998-1009.

Abstract

To restore functional use of paralyzed muscles by automatically controlled stimulation, an accurate quantitative model of the stimulated muscles is desirable. The most commonly used model for isometric muscle has had a Hammerstein structure, in which a linear dynamic block is preceded by a static nonlinear function, To investigate the accuracy of the Hammerstein model, the responses to a pseudo-random binary sequence (PRBS) excitation of normal human plantarflexors, stimulated with surface electrodes, were used to identify a Hammerstein model but also four local models which describe the responses to small signals at different mean levels of activation. Comparison of the local models with the Linearized Hammerstein model showed that the Hammerstein model concealed a fivefold variation in the speed of response. Also, the small-signal gain of the Hammerstein model was in error by factors up to three. We conclude that, despite the past widespread use of the Hammerstein model, it is not an accurate representation of isometric muscle. On the other hand, local models, which are more accurate predictors, can be identified from the responses to short PRBS sequences. The utility of local models for controller design is discussed.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: UNSPECIFIED
• Authors: Hunt, K.J., Munih, M., Donaldson, N.D., and Barr, F.M.D.
• Subjects: R Medicine > R Medicine (General)
• College/School: College of Science and Engineering > School of Engineering > Systems Power and Energy
• Journal Name: IEEE Transactions on Biomedical Engineering
• Publisher: IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
• ISSN: 0018-9294
• Copyright Holders: © Copyright IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
• First Published: First published in IEEE Transactions on Biomedical Engineering
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher