An Intelligent Control Scheme to Facilitate Abrupt Stopping on Self-Adjustable Treadmills

The control problem in self-adjustable treadmills is to keep the position of the user at a reference position. The position error is the key obstacle in facilitating the abrupt stopping on self-adjustable treadmills. Another difficulty in this application is the oscillatory response of the closed-loop system. The conventional control methods utilize a high-gain observer to estimate the user velocity and exploit this information beside feedback signals to decrease the position error. Utilizing the high-gain observer, however, applies anomalous force (AF) to the user, leading to an unnatural feeling, and does not guarantee an oscillation-free response for the output. This paper aims to alleviate these problems by proposing a supervisory control scheme. First, a RISE controller is utilized for walking/running stage to compensate for slowly varying uncertainties in the system model without applying a large AF. Then, a positive-output controller is exploited for the stopping stage to guarantee the convergence of the position error without oscillation. Using the estimated intentional velocity and acceleration, a supervisory system is designed to switch between the controllers. Experimental results show the superiority of the proposed approach over the existing methods.