Research On Trajectory Tracking Control Strategy Of Engraving Manipulator

The effective control of the trajectory error of the engraving manipulator in the machining process is an important way to improve the machining accuracy of the workpiece.In order to achieve trajectory tracking accurately,the single-axis position tracking error,synchronization error and contour error are considered in a multi-axis engraving manipulator system.This thesis,focusing on the direct drive H-type engraving manipulator applied to PCB board engraving,the uniaxial tracking control,synchronous control and contour control under uncertain factors are studied by adopting a variety of control strategies to reduce the single-axis position error,the coaxial-axis synchronous error and the non-coaxial-axis contour error,so as to improve trajectory tracking accuracy of the H-type engraving manipulator.Based on the principle and mathematical model of permanent magnet synchronous linear motor,taking direct drive H-type engraving manipulator as the controlled object,the mathematical model of H-type engraving manipulator is constructed.According to the force analysis on the X-axis of H-type engraving manipulator during PCB board engraving,the mathematical model of H-type engraving manipulator considering the uncertain factors is derived.As for the problem that the position tracking accuracy of the traditional single-axis control strategy is not sensitive to uncertain factors,which leads to an inaccurate tracking accuracy easily,an integral sliding mode controller based on a novel approach rate is proposed to control the position of the single-axis system.A novel approach rate is designed to reduce chattering in uniaxial position.By using the single-axis position error and its derivative,the integrated sliding mode surface is designed to reduce the chattering phenomenon of the sliding mode control.Meanwhile,the gain related to disturbance is introduced into control law to suppress the influence of uncertain factors on the single-axis system.Using Lyapunov stable theory,the stability of a single-axis system based on a novel approach rate integral sliding mode controller is proved.Through simulation comparison,the effectiveness of the proposed control strategy is verified.Aiming at the problem of asynchronism between Y1 axis and the Y2 axis due to parameter perturbation and uneven force,a synchronization controller is designed to improve the synchronization tracking accuracy between the two axes.A fractional-order integral sliding mode cross-coupling synchronization controller is designed to reduce the synchronous error.The correction error is constructed by using cross-coupling structure,and is introduced into the sliding mode controller.The integral term of the sliding mode surface is replaced by fractional calculus.The introduction of fractional-order makes the control more flexible and the synchronization tracking performance improved.On the basis of the improved mean coupled structure,a fractional-order mean-value coupling synchronization controller is proposed to further improve the convergence speed.Based on Lyapunov stable theory,the stability of the coaxial system with synchronous control is analyzed.The validity of the synchronous control strategy is verified by simulation results.The most intuitive representation of trajectory tracking is in the machining contour,and the contour error affects the PCB engraving accuracy.To deal with contour error problem between X axis and Y axis under complex working conditions,a cooperative controller based on disturbance observer is designed to improve contour tracking accuracy.For purpose of solve the problem that the control input depends on the upper bound of uncertain error in sliding mode controller,a disturbance observer is constructed to observe and estimate the comprehensive disturbance under complex working conditions immediately,and improve the anti-disturbance performance of the system.Based on the disturbance observer,analyzing that contour error is related to uniaxial position error and synchronous error,a fractional-order sliding mode contour cooperative controller in non-coaxial axis is proposed.By using Lyapunov stable theory,it is proven that the stability of H-type engraving manipulator system with proposed control strategy.The simulation results are proposed to verify the validity of the control strategy of the non-coaxial axis.