Synchronous Robust Sliding Mode Control of a Parallel Robot for Automobile Electro-Coating Conveying

Abstract

This paper is devoted to improving the synchronization and robustness performance of a parallel robot used for automobile electro-coating conveying via a novel synchronous robust sliding mode control (SMC). A sliding surface is designed based on a composite error, which is composed of the tracking error of each joint and the synchronization errors among the joints. By incorporating a nonlinear disturbance observer into the finite-time SMC based on the composite error, the synchronous robust SMC of the parallel robot is realized. The finite-time Lyapunov stability of the sliding variable and the asymptotic convergence of the tracking error and synchronization error have been proved theoretically. The lumped disturbance in the system is estimated by the proposed scheme, and restriction on the change rate of the lumped disturbance has been relaxed. Due to the feedforward compensation with the disturbance estimation value, the switching gain of SMC required is merely larger than the upper bound of the disturbance estimation error, rather than the upper bound of the disturbance, resulting in chattering attenuation. Finally, the numerical simulation and experiment on the prototype system of the parallel robot are implemented to validate the effectiveness of the synchronous robust SMC.

Keywords

• Composite error
• disturbance observer
• parallel robot
• sliding mode control
• synchronization