Integrated Uncertainty/Disturbance Compensation With Second-Order Sliding-Mode Observer for PMLSM-Driven Motion Stage

The permanent magnet linear synchronous machine driven motion stage for the semiconductor manufacturing equipment and machine tools has the basic requirement of high-dynamic response and high position accuracy. However, due to the direct-drive structure, the effect of parameter uncertainty, including the electrical and the mechanical one, and external disturbance will be directly exerted to the stage. In this paper, an integrated compensation scheme of the overall uncertainty and disturbance is proposed based on the second-order sliding-mode observer (SOSMO). First, an extended state model for considering the disturbance dynamics is established for both the electrical and the mechanical subsystems. To obtain high-dynamic current performance, the predictive current control (PCC) is utilized to design the current controller, and the SOSMO is integrated to compensate the main problem of a parameter mismatch for the PCC. Furthermore, the SOSMO is also configured to estimate the force ripple, and then the observation term is applied in parallel to the velocity controller. With this integrated scheme, the disturbance of the motion stage can be simply and effectively compensated. Experiments are demonstrated to show the effectiveness of the integrated method on both the PCC and force ripple suppression.