A Design Of High-speed And High-precision Linear Motor Servo Control System

Compared to screw linear drive system,permanent magnet synchronous linear motor(PMLSM)has no complicated intermediate transmission mechanisms,and electromagnetic thrust acts on the load directly,which makes it possible to get higher speed and position accuracy.This feature makes PMLSM play an increasingly important role in high speed and high precision applications.However,there are still many problems in the practical application of linear motors,such as frictional nonlinearity,sensor noise,and magnetic resistance,which limit the improvement of control performance.Designing an advanced servo control system can overcome such problems,and it is of great significance to exert the structural advantages of linear motors and ensure high speed and high precision performance.In this paper,the linear motor dynamics model is obtained by analyzing the magnetic resistance,friction force and current loop by mechanism modeling method.Then,the parameters of the model in macro and micro friction states and the magnetic resistance disturbance information are identified by various identification methods based on the kinetics analysis.The model information is used to design the controller of the linear motor,and the disturbance information is used to design the current loop feedforward compensation strategy to eliminate the effects of magnetic resistance.Velocity loop controller uses a two-degree-of-freedom_?controller design method.One of the degrees of freedom of the controller is using_?mixed sensitivity design method to accomplish the objectives of disturbance suppression and noise resistance,and the other degree of freedom controller could improve the tracking performance without any loss on the ability of disturbance suppression and noise resistance.A feedforward+feedback+controller switching control strategy is proposed in position loop.The feedforward controller ensures most of the tracking performance through the input shaping design method.The tracking error caused by the remaining model uncertainty is eliminated by feedback and the feedback controller can employ the LQR or disturbance observer design method.In addition,a controller switching strategy is added near the end of the position command to solve the smearing phenomenon caused by nonlinear friction.The position loop control strategy can guarantee the tracking accuracy in the high-speed tracking process under the limitation of bandwidth,and greatly reduce the adjustment time.Besides,a detailed experimental verification of the rationality of the control scheme is carried out in this paper.The velocity loop step response experiment shows that the two-degree-of-freedom_?controller design method can ensure better noise suppression performance and improve response speed compared with PI controller.High-speed S-shaped trajectory tracking experiments show that the control effect of the position loop control strategy adopted in this paper is at the same level as the high-end servo driver in terms of tracking accuracy,and the adjustment time is also greatly reduced.In addition,the control method proposed in this paper has certain versatility and is not limited to a specific linear motor model.It has a high reference value for solving the engineering control problem of permanent magnet synchronous linear motor.