Finite-Time Lyapunov-based Second-Order Sliding Mode Control for a Parallel Robot for Automobile Electro-Coating Conveying

To attain the high performance tracking control of a parallel robot for automobile electro-coating conveying, a finite-time Lyapunov-based second-order sliding mode control (SOSMC) is studied. By introducing a linear correction term into the traditional nonlinear supertwisting algorithm, an improved continuous SOSMC law is obtained, which is not only robust to the strong disturbance near the origin, but also available to suppress the linearly growing disturbance away from the origin. Furthermore, a fast terminal sliding variable in the form of a piecewise function is designed to avoid the singularity problem, and the finite time convergence of the tracking error is realized to improve the tracking performance. The finite time convergence of the sliding variable and its derivative is proved by Lyapunov theory, the convergence time and the explicit relationship of the controller parameters are provided in the paper. Finally, the validity of the proposed finite-time Lyapunov-based SOSMC is verified by simulation and experiment on the prototype system of the parallel robot.