Research On Robust Repetitive Control Strategy For Slow Tool Servo System

Slow tool servo(STS)driven by ironless permanent magnet linear synchronous motor(ILPMLSM)is taken as the research object of this thesis.Repetitive control strategy,linear matrix inequality(LMI),linear fractional transformation and high-order repetitive control theory are taken as the theoretical basis of this thesis.Aiming at the problem of parameter perturbation and other uncertainties affecting the performance of slow tool servo system in high precision machining,the displacement tracking control of slow tool servo system is studied to meet the dual requirements of robustness and tracking performance of slow tool servo system.The main contents are as follows.Firstly,the basic structure and operation principle of the slow tool servo system are studied and analyzed,and the mathematical model of the slow tool servo system is given.Secondly,in the application of linear motor servo system to slow tool servo of ultra-precision machine tools,it is required that the system not only has good tracking ability for periodic input instructions,but also has certain restraint ability for uncertainties such as system parameter changes.To solve this problem,a robust repetitive control strategy based on linear matrix inequality is adopted.The robust repetitive control strategy adopted in this thesis is a LMI-based static feedback control law derived from Lyapunov-Krasovskii theory.This control strategy can guarantee the robust performance and tracking ability of the system.The slow tool servo system is modeled and simulated by using MATLAB/Simulink,and compared with repetitive control under different working conditions.The simulation results verify the feasibility and effectiveness of the control strategy.Finally,the input instructions of the slow tool servo system are usually periodic.When tracking the periodic input instructions,the system has the problem of poor robustness and tracking performance due to disturbance factors such as system parameter perturbation.In order to improve the robustness and tracking performance of the system,a high-order repetitive control strategy is introduced.The control strategy adopts a systematic,semidefinite programming based approach to compute high-order repetitive controllers that yield an optimal trade-off between robustness and stability,thereby improving the robustness and tracking performance of the system.The simulation results show that the strategy can effectively track the periodic input signal and suppress the disturbance of parameter perturbation in the slow tool servo system.