Research On Friction Compensation Of Linear Servo Drive System

With the development of morden technology,the requirements for the linear servo system increases.Nonlinear friction is the main factor that influences the static and dynamic performance of the servo motion control system.Friction compensation is an effect way to improve the performance of the servo system.Therefore,a thorough study of the friction compensation has the practical significance.In this paper,the model identification of the linear motion control system is made based on experimental regression method.Then,a control strategy is designed and the validity is verified by the experimental research.First,the control strategy of the linear servo drive system is designed.The theoretical model of the linear servo system is deduced based on its principle.The model is then simplified and the parameters are obtained by the system identification for the following research.Second,the research status of varieties of friction models are introduced and the LuGre Model is chosen for the nominal model of the system.Experiments are designed to obtain the static and dynamic parameters of the LuGre model.The model obtained in this part provides the basis for the friction compensation controller.Then,for the control of the linear servo system,four control schemes are proposed: PID controller,feedforward friction compensation controller,disturbance observer controller,combination of feedforward fiction compensation and disturbance observer controller.Feedforward friction compensation is based on the LuGre friction model,and disturbance observer controller is based on the model of the system.The controller is realized by programming in real-time control system dSPACE.The experiment results reveal that the feedforward compensation is effective in improving the jitter effects near zero velocity.Moreover,the disturbance observer is superior in displacement tracking.Considering the parameters of friction model could be changed with the variability of external environment,there are errors and uncertainty in the model.Therefore,the adaptive friction compensation method based on backstepping design is presented in this paper.This method could ensure the asymptotic stability of the close-loop system.The nonlinear friction is overcome and the tracking accuracy of the servo control system is enhanced accordingly.