The Research Of Robust H_∞ Control Theory In Linear High Precision Servo System

A new kind of robust H∞ control tactic based on IP controller for dynamical and rapid high-precision-feed in a single axis is proposed in this paper, and the problem of H2/H∞ is also introduced, in which a constraint condition on Y is deduced. The background of the paper is "Theory of Dynamic Precision synchronization Traverse and Research of Realization Methods for Linear Servo Dual Position Loops System (NO.50075057)", which is supported by National Natural Science Foundation of China.The linear permanent magnet synchronous motor(LPMSM) has avoided the effects of the mechanical transmission chains from rotary motions to linear ones, and has strong electromagnetism thrust, lower cost, small electrical time constant and rapid response etc., which becomes one of the best executive machines in the high-precision and micro-feed servo system. In this project, using LPMSM as driving parts in modern mechanical systems involved high-precision synchronized feed technology such as gantry-moving type milling machine is first proposed so as to bring their high-speed dynamic response ability into play for realizing dynamically synchronized feed.The innovative ideas in this paper are that robust H∞control theory based on conventional IP controller is applied to the high-precision feed of a single axis, and the controlled plant is composed of IP velocity loop and two-order model of linear motor. A constraint condition on Y in the problem of H2/H∞ is deduced from the frequency criterion of Riccati equation, which makes the repeated computation on r simple. Considering the two-loops control problem, the H∞state feedback controller based on IP controller as the inner controller is applied to satisfy the velocity performance of the system, and a PI controller, the external controller, is used to satisfy the positionperformance. The controllers have considered all sorts of imperceptible factors affecting the servo performances in a LPMSM servo system, which include the parametric uncertainties brought by the changes of the mobile mass, frictional coefficient, the thrust fluctuations aroused by the varieties of the magnetic density distributions and the time harmonic. The H∞state feedback controller restrains disturbances and uncertainties to keep the robust and stable performance. The IP controller, which has the ability of rapid response, is applied to satisfy the rapid performance. Both the inner controller and external controller are used to satisfy the required tracking performance.The proposed control scheme has a rigorous theoretic base. The controllers designed not only guarantee the stability robustness and performance robustness of the system but also the tracking performance of the system. The simulation results show that the design is reasonable and effective.