Voltage based sliding mode control of flexible joint robot manipulators in presence of uncertainties

Abstract

In this paper, a voltage-based sliding mode control (SMC) is presented to control the position of n rigid-link flexible-joint (RLFJ) serial robot manipulator in the presence of structured and unstructured uncertainties. In addition to good performance, the proposed method has three attracting properties: First, it has been developed for a class of RLFJ robot manipulators with a n degree of freedom (DOF). Second, the design process includes all the manipulator dynamical equations, the mechanical and the electrical part of the actuator. Third, the simple structure and low volume of computing make practical implementation possible. Using the idea of the independent joint control strategy, the system dynamic equations are decomposed into n independent subsystems. For each subsystem, three sliding surfaces are defined. Then using these sliding surfaces, control input laws are designed for all subsystems simultaneously. It is proved that the proposed method can guarantee the asymptotic stability of each subsystems and the global asymptotic stability of the closed-loop system in the presence of uncertainties. The results of simulations, as well as experimental results produced using MATLAB/Simulink external mode control on a flexible-joint electrically driven robot manipulator, illustrate high efficiency of the proposed control schemes.