Sliding-mode control-based adaptive PID control with compensation controller for motion synchronization of dual servo system

The synchronous control of multi-motors is essential in multi-axis motion control system. Compared to single-axis tracking error, the synchronization error, responsible for final machining accuracy, is more important. There is correlation among axes, which can lead to mismatch in speed and position among axes when different load disturbances or other factors of each axis emerge. That means appropriate synchronous control methods should be designed. This paper have designed an adaptive PID control (APID) method based on sliding mode control (SMC) for motion synchronization of dual servo system. The synchronization error model with lumped uncertainties is established based on a transformation matrix and single-axis tracking error, introducing coupling factors between two axes to controller. Then, a sliding mode surface is established based on synchronization error model. Furthermore, the adjustment laws of gain parameters of PID controller are derived based on gradient descend method according to sliding mode surface. Last, in order to compensate the output of APID controller and guarantee the stability of the control system, a compensation controller is designed. The simulation results indicate that, compared to conventional PID controller, the single-axis tracking error and synchronization error are both effectively reduced by the control strategy designed, and the control system has a strong ability to resist parameters variation and external disturbances.