A Study On Indirect Iterative Learning Control Of Linear Motor Drive H-type Platform

he technical level of precision machining equipment plays a crucial role in the development of national science and technology level.The numerical control machine tool because of the speed is fast,the processing ability is accurate and so on the merit,it has been attracting the attention of the industry in recent years.The permanent magnet linear synchronous motor(PMLSM)cancels the driving mode of "rotating motor ball screw" in the structure,and replaces it with the direct driving mode,and is widely used in high-grade CNC machine tools,lithography machines and other industries.The H-type motion platform driven by linear motor has the advantages of large working space and good flexibility,which can be widely used in many fields,such as precision machining,CNC machine tools and so on.However,due to the problem of mechanical coupling between the motors of the two parallel axes,a series of factors,such as uneven force on the parallel axes caused by the reciprocating motion of the movers on the beam,will cause the uniaxial position tracking error,the biaxial synchronization error and the contouring error of the H-type motion platform,which will not only affect the working accuracy,but also cause system damage and even personal security.As a result,it is very important to improve the accuracy of uniaxial tracking,biaxial synchronization and triaxial contouring for H-type motion platform.Here,three aspects of uniaxial tracking control,biaxial synchronous control and triaxial contouring control are studied.The machining accuracy of H-type motion platform is improved by designing a controller with good performance.Firstly,by consulting the domestic and foreign literature about the H-type platform,this paper introduces the domestic and foreign development status of the H-type platform and the related control strategies,and also introduces the development status of contour control and the specific estimation method of contouring error.By introducing the structure and principle of permanent magnet linear synchronous motor,and considers the influence of the X axis promoter on the torsion pendulum force in the direction of the Y axis,deduces and establishes the mathematical model of the H-type motion platform.Secondly,because the H-type motion platform is easily disturbed by uncertain factors in its work,and there is still mechanical coupling between the biaxial,therefore,the BP neural network controller is designed in this paper to improve the tracking accuracy of the system and suppress the high frequency jitter.In order to improve the synchronization accuracy of the two axes,a cross-coupled synchronization controller is added between the two axes,which combines the uniaxial position tracking error with the uniaxial speed tracking error to form the cross-coupled synchronization error to achieve mechanical decoupling.MATLAB/Simulink is used to simulate the designed controller.Finally,in order to reduce the contouring error of the three-axis system of the H-type motion platform,an indirect iterative learning controller is designed on the basis of not changing the controller of the two-axis system.The local controller of the inner ring adopts proportional control,the iterative learning law of the outer ring adopts P-type iterative learning law,and the controller gain of the local controller is optimized through iterative learning,thus improving the contouring accuracy of the system.MATLAB/Simulink is used to simulate the designed controller.