Research On Control Technology And Anti-disturbance Strategy Of High Speed Direct Drive Feed System

In the field of high-speed machining,high-speed direct-drive feed systems are gaining more and more favor due to their excellent dynamic characteristics of high speed and high acceleration.Compared with the traditional feed system in the form of a ball screw,the direct drive feed system uses a linear motor to directly drive the feed axis.Although the error introduced by the transmission structure is eliminated,the motor is directly affected by cutting forces and other external disturbances.This will affect the tracking accuracy of the feed axis.In addition,there is a unique thrust fluctuation phenomenon in the linear motor,which causes periodic interference to the feed axis.This thesis starts from the design level of the control system of the high-speed direct-drive feed system,with the goal of improving the tracking accuracy of the feed axis,and has carried out the following work:(1)The advantages of the direct drive feed system are analyzed,the mathematical model of the linear motor is established,and the inverse M sequence is selected as the input signal for system identification.The PI controller of the current loop is designed,and the corresponding Simulink simulation model is established with the overall model of the linear motor and the current loop as the controlled object,and the approximate transfer function of the linear motor is obtained through system identification.(2)Aiming at the susceptibility of the direct-drive feed system to disturbances,a composite control strategy that combines active disturbance rejection technology with a two-degree-offreedom controller is proposed.A non-linear tracking differentiator is introduced to suppress the overshoot of the motor in the starting phase,and it is used to extract the differential value of the signal.Based on the approximate model obtained by system identification,a modelassisted full-order linear extended state observer is designed,and stability analysis is performed.Aiming at the problem of lag in feedback regulation,a two-degree-of-freedom controller based on feedforward and PD state feedback is designed.Facing the difficult situation of LESO parameter setting,a method of LESO parameter tuning based on differential evolution is proposed.Finally,a simulation experiment is carried out to verify the effectiveness of the proposed algorithm.(3)The thrust fluctuation phenomenon of the linear motor is analyzed,and a simplified mathematical model of the identifiable end effect is established.Aiming at the scene where the end effect disturbance model is constant and the parameters are time-varying,the recursive least square method and the forgetting factor least square method are used to identify and compensate the end effect disturbance online.A nonlinear dynamic forgetting factor is introduced,and the robustness of the dynamic forgetting factor least square method is verified by simulation.