Research On Contour Control Of H-type Platform Based On Double Circle Weighted Approximation Method

Under the background that the big countries all over the world attach great importance to the development of manufacturing industry,the accuracy of NC machining has been continuously improved,and the control requirements for the performance of AC servo system are also gradually improving.Contour accuracy is an important measurement index of NC machining,and the errors existing in the production process of the system are finally shown in the form of contour errors.This paper takes the direct drive H-type precision motion platform as the research object,in view of the fact that the servo system is easily affected by uncertain factors such as external disturbance and friction and the inaccurate estimation of the traditional contour error calculation model,the research on reducing the single axis tracking error and the overall contour error in the machining process of H-type platform are carried out.Firstly,the development status and main motion control strategies of direct drive H platform at home and abroad are introduced.According to the basic principle and operation characteristics of PMLSM,the mathematical model of direct drive H platform with uncertain factors such as external disturbance and friction are established,and the mechanism of tracking error and contour error are analyzed.Secondly,in order to improve the tracking accuracy of single axis,an adaptive robust controller of linear servo system based on Lugre friction model is designed.Adaptive control has the ability to identify parameters to achieve high tracking accuracy,but poor robustness;robust control has a strong anti-disturbance ability for external disturbances,but has a large steady-state error.Therefore,adaptive control is combined with robust control.Theoretical analysis shows that the adaptive robust controller can effectively overcome the effects of friction and external disturbances on the system performance,keep the tracking error within the required range,and ensure the tracking accuracy of the single axis and the anti-disturbance ability of the system.The contour accuracy is improved indirectly.Then,in order to further improve the contour accuracy of H-type platform,the problems that the traditional contour error estimation model has a large tracking error and the inaccurate calculation in the face of large curvature machining will lead to the decrease of contour accuracy are analyzed.A double circle weighted approximation method is proposed to estimate the profile error,which is closer to the real contour error by introducing the weighted coefficient contour error estimation value.At the same time,considering the synchronous drive of double parallel axes of H-type platform,it is necessary to ensure that the synchronization error between two parallel axes can not be too large while maintaining high precision in the process of contour machining,so as to prevent the phenomenon of machine jumping and avoid damage to the machine.therefore,a single neuron adaptive double-layer cross-coupling controller based on double-circle weighted approximation wheel profile error estimation model is designed.The contour error compensation is allocated to each servo axis to match the dynamic characteristics of each servo axis,and finally reduce the contour error.Finally,the control method designed above is simulated in Matlab/Simulink environment,and the simulation results show that the adaptive robust controller designed in this paper can effectively reduce the single-axis tracking error,and the double-layer cross-coupling controller based on double-circle weighted approximation method can reduce the contour error.