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Modelling the optimal control of cyclical leg movements induced by functional electrical stimulation
P H Veltink1, H M Franken, J A Van Alsté
1Department of Electrical Engineering, University of Twente, Enschede, The Netherlands.
The International Journal of Artificial Organs
|December 1, 1992
Summary
This study proposes an optimal control strategy for functional electrical stimulation (FES)-induced leg movements in paraplegics. The findings suggest precise timing of quadriceps and flexion reflex stimulation can achieve cyclical leg movements, aiding mobility.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Rehabilitation Robotics
Background:
- Paraplegia results in impaired lower limb function.
- Functional Electrical Stimulation (FES) offers a potential method to restore movement.
- Cyclical leg movements, like those in gait, are crucial for mobility.
Purpose of the Study:
- To develop an optimal control strategy for FES-induced cyclical leg movements in paraplegics.
- To determine optimal stimulation patterns for quadriceps and flexion withdrawal reflex.
- To achieve desired movement parameters including hip angle, foot clearance, and knee extension.
Main Methods:
- Development of a dynamic model of the neuromuscular-leg system.
- Application of an optimization criterion based on desired movement and minimal stimulation duration.
- Computer simulations to determine optimal timing and duration of stimulation bursts.
- Parameter identification using preliminary experiments and literature.
Main Results:
- Optimal timing predicted: flexion reflex ~150 ms before forward swing, quadriceps ~200 ms before end of forward swing.
- Predicted cycle duration of 1300-1500 ms.
- Feasibility of achieving functional leg movements with only two stimulation channels.
Conclusions:
- An optimal control strategy using FES can generate cyclical leg movements for paraplegics.
- Precise timing of stimulation is key to achieving functional gait-like movements.
- This approach lays the groundwork for adaptive control strategies to manage muscle fatigue.