Nonlinear tracking control of a human limb via neuromuscular electrical stimulation

Abstract

A nonlinear control method is developed in this paper that uses neuromuscular electrical stimulation to control the human quadriceps femoris muscle undergoing nonisometric 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.

Nonlinear Neuromuscular Electrical Stimulation Tracking Control of a Human Limb

“…To facilitate the subsequent stability analysis, the open-loop error system for (13) can be determined as (14) where denotes the unmeasurable auxiliary term (15) To further facilitate the analysis, another unmeasurable auxiliary term, , is defined as…”

“…An open-loop error system for a general uncertain nonlinear muscle model is developed in this paper (and in the preliminary results in [14]) by grouping terms in a manner that facilitates the development of a new continuous feedback method (coined RISE for robust integral of the sign of the error in [15], [16]). Through this error-system development, the continuous RISE controller is proven (through a Lyapunov-based stability analysis) to yield an asymptotic stability result despite the uncertain nonlinear muscle model and the presence of additive bounded disturbances (e.g., muscle spasticity, fatigue, changing loads in functional tasks, and delays).…”

RISE Controller Tuning and System Identification Through Machine Learning for Human Lower Limb Rehabilitation via Neuromuscular Electrical Stimulation

“…In the literature one can find Stegath et al (2007Stegath et al ( , 2008 and Sharma et al (2009) as pioneers authors on developing the RISE controller for the lower limb tracking control. Afterward, Sharma et al (2012) presented an improvement of the RISE control method for the same application using an NN feedforward term.…”

“…Given the stability analysis and the gains sufficient condition initially provided by Stegath et al (2008) and Sharma et al (2009) for an uncertain nonlinear muscle model, one finds out gains inequalities leading to a very large combination within the set of feasible solutions in R + . Furthermore, when it comes to SCI rehabilitation via NMES/FES there exist several problems like muscle fatigue, due to incomplete tetanus and even from the electrical stimulus application itself.…”