The Robust Control Research On Linear Servo System

The Permanent Magnet Linear Synchronous Motor(PMLSM) 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 operator in the high-precision and micro-feed servo system. Based on the research of the PMLSM mathematic model and control theory, a PMLSM feed system is established. The dynamics, optimization and control strategy as well as some key technologies of the PMLSM feed system are studied by combining theoretical analysis with computer simulations.PMLSM servo system is a dynamic complex nonlinear system with high precision and fast response characteristic, its main performances are the tracking ability to the input command and disturbances rejection ability to the disturbances. In the ideal case, the output is able to track the changes of the input command without delay and overshoot. It is difficult to meet together the requirement that is the tracking performance of the system to input signal and resistance disturbances performance to the uncertainty using conventional PID controller. So, the mixed linear quadric optimal control and robust H_∞control strategy is proposed to solve above-mentioned problem on the background of the normal H_∞control strategy.The controller is made of two parts, which are named of robust H_∞feedback controller and LQ optimal controller respectively. The former is used as the regulator for depressing disturbances, and the later is the regulator for tracking. The advantage of this control strategy is that, on the one hand it is used to assure the system performance of robustness by overcoming the modeling uncertainties and disturbances from external circumstance; on the other hand the linear feedback structure of the LQ controller is used to guarantee the tracking performance. The simulation results indicated that the scheme used is able to assure the robustness to parameter changes and disturbances of the system, while improving the tracking rapidity and precision. Because the LQ controller can be written into a unit analytic expression, and a simple state linear feedback control rule, it is easy to compute and also to achieve in project. When the math model is accurate, the LQ controller can be solved and got the closed loop formal analytic solution.In the thesis, the proposed control schemes have strict theoretical background and have been verified by simulation. The simulation results show that those methods are very effective, not only enhance the fast tracking performance in the linear servo system, but also have strong robustness to parameter variation, load disturbance and the uncertain factors.