Nonlinear Muscle Length-Tension Curves Affect the Control of Electrically Stimulated Antagonist Muscles

Robust controller designs for electrically stimulated muscle systems critically depend on muscle nonlinearites. Experimental and mathematical modelling results are presented which demonstrate that nonlinear muscle length-tension curves cause magnitude dependent stability conditions for proportional closed-loop positioning systems. These results have applications to the design of clinical neural prostheses for returning function to spinal cord injured persons.