Nonlinear tracking control of a human limb via neuromuscular electrical stimulation

A nonlinear control method is developed in this paper that uses neuromuscular electrical stimulation to control the human quadriceps femoris muscle undergoing non- isometric contractions. The objective of the controller is to position the lower limb of a human along a time-varying trajectory or a desired setpoint. The developed controller does not require a muscle model and can be proven to yield asymptotic stability for a nonlinear muscle model in the presence of bounded nonlinear disturbances. Performance of the controller is illustrated in the provided experimental results.