Robust Continuous Finite-Time Tracking Control with Finite-Time Observer for a Stewart Platform

Abstract

In this paper, a third-order sliding mode control (SMC) with a super-twisting finite time observer is proposed for the position control of a Stewart platform. The Stewart platform is a parallel robotic manipulator with a fixed base platform connected to a movable top platform with the help of six actuator legs. The proposed control makes the movable platform track a reference trajectory in finite time while rejecting matched disturbances. Conventional SMC offers robustness towards matched disturbances, but will induce chattering in the system. The proposed third-order SMC can ease out the chattering problem and achieve finite-time tracking. Furthermore, a robust super-twisting observer is designed, which converges to the actual states in finite time, such that the proposed control can be computed from the system output using the observer. A simulation study of the Stewart platform is done for the proposed robust continuous finite-time control with the finite-time observer. The results using the proposed control are compared with conventional SMC, PID control and twisting control.