Predictive Contour Control Of Multi-axis Motion System Driven By Permanent Magnet Synchronous Motors

The multi-axis motion system driven by permanent magnet synchronous motors has broad application prospects in the field of high-speed and high-precision modern numerical control technology due to its advantages in power density,operating efficiency and response speed.However,the traditional contour control strategy for the multi-axis motion system always suffers the problems that the control structure is redundant,the controller parameter adjustment is cumbersome,the dynamic response speed is slow and the contour error is large at the trajectory turning point.To solve the above problems,this paper proposes and establishes an integrated synchronous control architecture based on the idea of unified modeling,and propose three improved predictive contour control strategies under this control architecture.An integrated synchronous control architecture based on the idea of unified modeling is proposed to regard the motion mechanism,the multiple inverters and multiple permanent magnet synchronous motors as a whole to build a compact non-cascaded predictive controller.This method can unify the loop controller of each axis and merge the multiple nested control loops in the multiple motor control into one loop.It has the advantages of intuitive modeling and simple structure.The three improved predictive contour control strategies proposed below are all designed based on this control architecture.A generalized predictive contour control strategy for the multi-axis motion system is proposed.Through synthesizing the advantages of online parameter estimation,multi-step prediction,rolling optimization and feedback correction in generalized predictive control,the tracking error and the contour error are simultaneously introduced into the cost function to seek the optimal control input signal which makes the performance of the tracking error and the contour error to be optimal coordinately.Simultaneously,the constraint problem is considered to design a dynamic limiter.This control strategy can solve the problems that the control structure is redundant,etc in the traditional control strategy,and reduce the contour error while improving the system transient contour tracking performance.A model predictive contour control strategy based on state space for the multi-axis motion system is proposed.The tracking error,the contour error,thecontrol increment and the position increment are introduced into the cost function simultaneously to realize the multi-variable collaborative optimization control.At the same time,a method of real-time adaptive adjustment of the position increment weight coefficient and the control increment weight coefficient is proposed to suppress the current increment fluctuation at the turning point of the trajectory.This control strategy can solve the problems that the control structure is redundant,etc in the traditional control strategy,take the smoothness of the tracking path into account and improve the system dynamic,steady-state contour tracking performance.A finite control set model predictive contour control strategy for the multi-axis motion system is proposed.The appropriate candidate voltage vectors are determined by taking the tracking error as the main index,and a unified cost function of the multi-axis motion system is established by regarding the contour error,the motor operating performance and the current amplitude limit as the evaluation indexes to realize multi-variable collaborative optimization control.Then the optimal voltage vectors are selected from the candidate vectors by the principle of minimizing the cost function.This control strategy can solve the problems that the control structure is redundant,etc in the traditional control strategy,and improve the system dynamic response speed and contour accuracy.A high-reliable multi-axis motion system prototype is conducted to research the control performance of the traditional cascade control strategy and the three improved control strategies based on unified modeling.The results show that the three improved control strategies can effectively solve the problems that the control structure is redundant,the controller parameter adjustment is cumbersome,the dynamic response speed is slow and the contour error is large at the trajectory turning point in the traditional contour control strategy.And the correctness of the theoretical analysis and the effectiveness of the control strategies are proved.