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Control of thumb force using surface functional electrical stimulation and muscle load sharing.
Ard J Westerveld1, Alfred C Schouten, Peter H Veltink
1Laboratory of Biomechanical Engineering, MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, 7500 AE Enschede, The Netherlands. h.vanderkooij@utwente.nl.
Journal of Neuroengineering and Rehabilitation
|October 10, 2013
Summary
Surface functional electrical stimulation (FES) can help stroke survivors regain thumb control for object manipulation. This study shows FES can accurately predict and control thumb forces, especially with feedback, improving hand function.
Area of Science:
- Rehabilitation Engineering
- Neuroprosthetics
- Biomechanics
Background:
- Stroke survivors frequently experience challenges with hand object manipulation.
- Effective thumb control is crucial for dexterous object manipulation.
- Surface functional electrical stimulation (FES) offers a potential method to assist hand movements.
Purpose of the Study:
- To investigate the control of 2D thumb force using FES.
- To predict thumb muscle forces based on sigmoidal recruitment curves and force direction.
- To develop and evaluate a closed-loop force controller for thumb movement assistance.
Main Methods:
- Recruited five able-bodied and five stroke subjects for experiments.
- Measured thumb forces in response to FES applied to three thumb muscles.
- Developed force vector maps and a closed-loop controller utilizing load sharing for 2D force control.
Main Results:
- Force vector prediction model demonstrated low RMS errors (0.22 ± 0.17 N healthy; 0.17 ± 0.13 N stroke).
- Stroke subjects exhibited a limited workspace due to reduced muscle force production.
- Feedback control significantly improved force control accuracy, particularly for stroke subjects, by reducing stationary errors.
Conclusions:
- Thumb muscle responses to FES can be modeled using sigmoidal recruitment curves and a single force direction.
- Load sharing among redundant muscles enables generation of forces in desired directions.
- Subject-specific force vector maps are effective for feedforward and feedback control, with feedback enhancing accuracy.
