| XY motion platform which is driven by permanent magnet liner synchronous motor in order to realize planar positioning and planar feed is widely used in boring,milling,drilling machine and various machining centers.The precision of the platform mainly depends on its servo system and mechanical structure.As the mechanical structure of XY motion platform has entered its mature stage,it is necessary to conduct a thorough research on its servo system in order to improve the machining precision.To reduce contour error in repetitive tasks,the fractional order iterative learning position controller for single axis servo system is designed,as well as the cross-coupling fractional order iterative learning position controller for biaxial system,which aims at improvement of contour accuracy in repetitive tasks.First of all,this thesis introduces the structure and working principle of XY motion platform.The tracking error and the contour error of the platform are defined.The expressions of contour error are deduced,respectively under the condition of straight trajectory,circle trajectory and any profile trajectory.The principal factors which affect the accuracy of the platform is analyzed.Then,in view of XY motion platform under the condition of the repetitive tasks can produce tracking error and contour error,the PID iterative learning position controller and PI speed controller are designed,using fractional order calculus theory which is a hot research subject in recent years,the improved iterative learning controller learning law,fractional order PD~?type of fractional order iterative learning controller is designed,improve the tracking performance of the single axis servo system.For traditional cross-coupling controller and uniaxial feedback controller are independently designed,which has problem in lacking of a systematic,uniaxial fractional order iterative learning control system and biaxial cross coupling structure of iterative learning control system are designed.Tracking and contour accuracy of uniaxial servo system and biaxial system are improved.The coordination control of XY motion platform is highly achieved.Finally,set up a simulation model for XY motion platform under Matlab/Simulink.Write the process of iterative learning control.Verify the effective of the design for fractional order iterative learning controller and cross coupling iterative learning controller.By comparing and analyzing to the uniaxial integer order iterative learning controller and cross-coupling integer order iterative learning controller,testify that the design of fractional order controller is viable and effective in improving contour accuracy of XY motion platform. |
