Predictive Position Synchronization Control Of Multi-axis Motion System Based On Extended State Observer

Multi-motor high-precision control systems are widely used in high-end equipment such as CNC machine tools and robots.As the number of motors increases,the tracking trajectory becomes complicated,and the parameters difference between the motors and external disturbances affects the position control accuracy,which in turn affects the coordination and synchronization between the drive axes and increases the contour error.It is of great significance to study the multi-axis system synchronization control strategy under complex disturbances.To this end,this paper deduces the state space equations under different control and prediction domains,and uses model predictive control(MPC)to design the position-current prediction controller,adding contour error,tracking error and control increment in the value function.The current time control law is obtained by minimizing the value function.Based on the model predictive control,the extended state observer(ESO)is designed to observe the disturbance term in the second-order differential model of multi-axis motion system.The equivalent friction force,q-axis current tracking error and the external disturbance term of position loop are regarded as a time-varying disturbance,and the compensation proportional amount is obtained by the linear proportional differential feedback control law.The current control quantity is optimized in real time by the compensation control quantity,and the form of the feedforward compensation is compensated to the current control law,which solves the problem of tracking the complex trajectory.In order to make the system have better dynamic performance and reduce the amount of calculation,an offline gain optimization method is proposed.The reference gain matrix corresponding to different trajectories is calculated offline,and the calculation results are run online in real time.The proposed control strategy is experimentally verified on the experimental platform of multi-axis motion control system and compared with the cross-coupling control algorithm.The experimental results show that the proposed control strategy can not only accurately track the contour trajectory at steady state,but also achieve good tracking effect in transient state.