Sliding mode control for offshore parallel antenna platform with large orientation workspace

Abstract

A novel sliding mode control strategy is proposed to solve the trajectory tracking control problem of an offshore antenna platform, which uses a Stewart-type parallel mechanism and has a large orientation workspace. To obtain comprehensive posture parameters of the offshore antenna platform, a posture compensation algorithm using the information of azimuth and elevation is proposed. Considering known limb lengths, a state observer which based on a super-twisting algorithm is presented to obtain limb velocities. To solve the trajectory-tracking control problem of the platform, a modified nonsingular terminal integral sliding mode controller is proposed. To reduce chattering, the sliding mode controller is equipped with a higher order super-twisting algorithm. The Lyapunov theory was used to prove its stability. Simulation results on a large-orientation workspace offshore antenna platform demonstrate its superiority over three other controllers. Compared with the traditional sliding mode controller with super-twisting algorithm, the integral of the squared error of the proposed control strategy is 49.49% lower.