Optimization and evaluation of a proportional derivative controller for planar arm movement

Area of Science:

• Rehabilitation Engineering
• Biomedical Engineering
• Control Systems

Background:

• Current functional electrical stimulation (FES) often uses open-loop control, limiting precision for complex movements.
• Upper extremity reaching requires precise control, necessitating feedback mechanisms.

Purpose of the Study:

• To develop and evaluate proportional derivative (PD) feedback controllers for precise upper extremity reaching using FES.
• To assess the generalizability and robustness of these controllers in a simulated musculoskeletal arm model.

Main Methods:

• Implemented three PD feedback controllers utilizing two joint angle sensors to stimulate six arm muscles.
• Optimized feedback gains by minimizing position errors and muscle forces.
• Evaluated controllers on a computational arm model, testing generalizability and robustness against muscle weakening, joint friction, and increased arm mass.

Main Results:

• Optimized PD controllers achieved fast, accurate, and robust reaching movements in simulations.
• Improper controller tuning resulted in oscillatory behavior.
• Controller performance showed slight improvement with increased feedback gain matrix complexity.

Conclusions:

• PD feedback control is effective for achieving precise and robust upper extremity reaching movements with FES.
• Controller optimization and tuning are critical for successful FES applications.
• This approach holds promise for enhancing FES-based rehabilitation and assistive technologies.