Sliding Mode Control for Electric Power Assist Systems

Abstract

This paper presents a nonlinear controller for electric power assist systems based on the sliding mode control. The proposed sliding mode controller is designed to achieve desired nonlinear properties including gravitational effect with robustness against disturbances such as friction force and modeling errors. Furthermore, so-called reaching phase is positively utilized so that the operator can feel disturbance torque of relatively large amplitude which should be noticed as information about environment, for example, when hitting an obstacle accidentally. Although the reaching phase can be designed from several points of view, the dynamics in the reaching phase is linearlized in order to use fruitful linear control theories such as H-infinity theory.

Integral Sliding Mode Control with Anti-windup Compensation and its Application to a Power Assist System

“…Considering a desired assist rate, maneuverability and so on, a desired closed-loop dynamics can be designed as follows (Yokoyama et al, 2006): …”

“…J e : equivalent inertia including all rotating parts, : arm angle, M: equivalent mass of load and arm, g: gravitational constant, l: arm length, T h : operational torque by operator, T a : assist torque, T d : disturbance torque, n: gear ratio, K t : torque constant of motor, K : back emf constant, R: resistance, u: input voltage Using the state vector, x 4 [ 3 ] T , the state space model of the plan is represented by Considering a desired assist rate, maneuverability and so on, a desired closed-loop dynamics can be designed as follows (Yokoyama et al, 2006):…”