Abstract
A novel optimal tracking control (OTC) strategy using an adaptive second order sliding-mode control (SOSMC) scheme for a ball-screw feed drive system actuated by permanent-magnet synchronous motor (PMSM) to realize high precision-positioning is proposed in this paper. First, the SOSMC is employed for minimizing the chattering phenomenon and stabilizing the ball-screw feed drive system. Due to the dynamic uncertainties, nonlinearities of backlash, friction force and exterior disorder can affect the control performance of ball-screw feed drive system seriously. Additionally, the conventional choice of the SOSMC gains may destroy the dynamic performance of the ball-screw feed drive system. Therefore, to enhance the dynamic performance and to achieve the robustness and optimality of the ball-screw feed drive system characteristics using the SOSMC, a direct heuristic dynamic programming (HDP) approach is employed to tune the SOSMC gains optimally. Thus, critic and actor neural networks are adopted to solve the Hamilton-Jacobi-Bellman (HJB) equation online. At the same time, actor neural network provides the optimal control performance. Furthermore, the stability of the closed-loop control system is guaranteed via Lyapunov theory. The verification of the control system performance using experimental results proves the superiority of the proposed optimal adaptive SOSMC (OASOSMC) approach for the ball-screw feed drive system in spite of indefinite uncertain dynamics and external disturbances.