Research On Compensation Method Of Thrust Fluctuation Of Linear Motor System Based On DOB And ADRC

With the rapid development of aerospace and other industries,the demand for complex curved surface parts of various metal materials is increasing,which puts forward higher requirements for slow tool servo machine in terms of dynamic response and low speed stability.As the main power source of high-end CNC machine tools,linear motors affect the tracking performance of the system directly.Because the linear motor eliminates the intermediate transmission link of the rotating electrical machine and realizes the direct-drive movement,the error caused by the intermediate transmission link is eliminated.However,the way of direct-drive movement also causes interference such as thrust fluctuations to affect the linear motor directly,which has affected the accuracy of the linear motor motion platform seriously,and has become an indispensable factor affecting the tracking performance of the machine tool.Therefore,studying how to reduce the influence of disturbances such as thrust fluctuations on linear motors is the key to achieving high dynamic response and low speed stability of slow tool servo machining.This thesis uses the method of optimizing the control system to compensate the thrust fluctuations.First,the theoretical model of the linear motor is derived,an open-loop sweep experiment is designed,and an approximate model of the linear motor is obtained through system identification.Starting from the cause of the linear motor thrust fluctuations,a mathematical model of the thrust fluctuations is established,using the method of constant speed and pulling to collect the data of thrust fluctuations,and obtained the mathematical model of thrust fluctuations by identification.Secondly,the disturbance observer is used to study the thrust fluctuation compensation,and feedforward is added to the disturbance observer.The simulation results show that the disturbance observer + feedforward control can play a good role in compensating the thrust fluctuations,but the disturbance observer has a high requirement for model identification accuracy.Thirdly,the method of compensating thrust fluctuations for auto disturbance rejection control is deeply studied.It is proposed to replace the classic nonlinear tracking differentiator with a full-range fast nonlinear tracking differentiator.Aiming at the delay problem of the tracking differentiator,differential prediction compensation is added,and the differential tracker is used in the feedback loop to replace the first two of the extended state observer.Finally,the feed-forward control is added,and the simulation results verify the effectiveness of the improved strategy.Finally,on the basis of theoretical analysis,a linear motor motion platform based on Power UMAC is built.Disturbance observers and auto disturbance rejection controllers is used to compensate the thrust fluctuations.The performance of the control algorithm before and after the improvement in dynamic response and low-speed stability is compared.The experimental results verify the effectiveness of the improvement strategy.