A cascade load force control of a hydraulically driven 6-DOF parallel robot manipulator based on input-output linearization

Abstract

In this paper, we consider the problem of tracking control of a hydraulically driven 6-DOF parallel robot manipulator. To drive the upper moving platform, hydraulic systems composed of the six valvecontrolled asymmetric pistons are used as actuators. In order to realize the trajectory tracking control of the parallel robot manipulator, a cascade control algorithm based on input-output linearization in the legspace is proposed. We applied the cascade controller, which consists of an inner loop and an outer loop, in order to separate the hydraulic dynamics from the mechanical part. Thus, the inner-loop control has the objective of controlling the actuator load force using the input–output linearization, independent of the resulting motions of the load. The outer–loop control is aimed at controlling the actuator load and rejecting external disturbance of the system. To facilitate the realization of the proposed cascade control concept, the MATLAB/Simulink model is devised. In order to show the effectiveness of the proposed cascade control algorithm, the comparative simulation results are made between proposed concept and the classical control strategy for this kind of manipulator.