Research On Coordinated Control For Linear-motor-driven Biaxial Gantry System

Linear-motor-driven multi-axis motion system has been widely used in contour machining of mechanical manufacturing due to the characteristics of simple structure,high acceleration,fast response and low noise and so on.However,the product manufacturing error is attributed by servo lag,dynamic characteristics mismatch among the servo axes,coupling among the axes,external disturbances and so on.It has always been a hot topic in control community that how to improve the contour tracking accuracy of multi-axis motion system.In this thesis,the subject investigated is a linear-motordriven biaxial gantry system,and a lot of researches indulge in improving the coordination of servo axes in motion system and dealing with the influence of uncertainties,external disturbances and actuator faults.The main contents and results of this thesis are as follows.Firstly,according to the structure and working principle of permanent magnet linear synchronous motor,the basic structure and working principle of the linear-motor-driven biaxial gantry system are introduced.On this basis,the nonlinear mathematical model of the linear-motor-driven biaxial gantry system in Cartesian coordinate frame is established,which takes into account uncertainties and external disturbances in the system.It lays the foundation for the subsequent controller design.Secondly,two kinds of cooperated controllers are proposed for contour tracking problem of the linear-motor-driven biaxial gantry system in the presence of parametric uncertainties and external disturbances.Via introducing task coordinate frame,the system dynamics in Cartesian coordinate frame is transformed into task coordinate frame resulting in contour error dynamics.Based on the transformed model,the first robust adaptive coordinated controller is proposed using the certainty equivalence principle.In addition,in order to further improve the transient tracking performance and steady-state tracking accuracy of the system and realize the performance-oriented control,the second robust adaptive cooperated controller based on immersion and invariance is proposed,which is combined with the idea of immersion and invariance manifold based on noncertainty equivalence principle.The advantages of the control algorithm compared with the first algorithm are analyzed from the perspective of Lyapunov theory.Furthermore,the effectiveness of the proposed two control algorithms is verified by a series of numerical simulations and experiments on a linear-motor-driven biaxial gantry machine tool.Finally,a robust adaptive fault-tolerant coordinated control method is proposed for the contour tracking problem of the linear-motor-driven biaxial gantry system with uncertainties and external disturbances in the presence of unknown time-varying actuator faults.The system dynamics with actuator faults is firstly transformed into task coordinate frame with the aid of the introduced task coordinate frame,and then the controller is designed based on the transformed model.Specifically,the actuator faults and external disturbances are dealt with by bound estimation approach with the help of two introduced smooth functions;the adaptation law is designed using the certainty equivalence principle to estimate the unknown parameters in the system and improve the steady-state tracking accuracy.In addition,the parameter estimates are modified by smooth projection to enhance the robustness and rapidity response of the system.Theoretical analysis,numerical simulation and experimental results demonstrate that the proposed control algorithm can effectively deal with the influence of actuator faults,parametric uncertainties and external disturbances,and guarantee the closed-loop system with satisfying contour tracking accuracy.There are 31 figures,9 tables and 66 references in this thesis.