Nonlinear Neuromuscular Electrical Stimulation Tracking Control of a Human Limb

Abstract

Abstract-A high-level objective of neuromuscular electrical stimulation (NMES) is to enable a person to achieve some functional task. Towards this goal, the objective of the current effort is to develop a NMES controller to produce a knee position trajectory that will enable a human shank to track any continuous desired trajectory (or constant setpoint). A nonlinear control method is developed to control the human quadriceps femoris muscle undergoing nonisometric contractions. 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 (e.g., spasticity, delays, fatigue). The performance of the controller is demonstrated through a series of closed-loop experiments on human subjects. The experiments illustrate the ability of the controller to enable the leg shank to track single and multiple period trajectories with different periods and ranges of motion, and also track desired step changes with changing loads.

Design of Closed-Loop Fuzzy FES Controller and Tests in Controlling Knee Extension Movements

“…If the delay in muscle response causes any problems, feedforward control has to be implemented with the closed-loop control. Although another study showed good tracking control performance [11], it used total knee-joint dynamics model at the sitting position and the disturbance included in the model is considered to significantly affect on practical application such as FES cycling.…”

A novel modulation strategy to increase stimulation duration in neuromuscular electrical stimulation

“…A computer was used to collect data from the encoders and execute a closed-loop RISE (robust integral of the sign of the error) controller. 13 The RISE controller calculates the voltage required at any given time for a subject's knee joint/shank to follow a given desired trajectory. The desired trajectory was selected as a sinusoid ranging from 5 to 35 with a period of 1.5 seconds.…”

“…Leg angle was controlled using the closed-loop nonlinear control strategy 13 to adjust the voltage (i.e., amplitude modulation). To reduce the effect of day-to-day variability in muscle response to stimulation, the control gains were adjusted to minimize the baseline tracking error.…”

“…The purpose of this study is to examine the effect of feedback-based frequency modulation on the closed-loop performance of the quadriceps femoris muscle group during repeated dynamic contractions with the goal of enabling more successful contractions, quantified by limb position error. A recently developed NMES control method 13 is implemented through amplitude modulation with constant pulse width and different constant-frequency settings. The respective results are compared with those obtained by implementing the same controller with amplitude modulation and a feedback-based varied-frequency modulation scheme that adjusts the frequency to maintain the limb position tracking error within a specified range.…”

Robust compensation of electromechanical delay during neuromuscular electrical stimulation of antagonistic muscles

“…NMES artificially contracts muscle groups by applying external stimulation current. Closed-loop control of NMES can be used to generate advanced functional tasks (in this case NMES is also called functional electrical stimulation (FES)) such as walking [2,3], single leg extension [4][5][6][7][8][9], and upper extremity grasping and reaching [10][11][12].…”