The Appling Research On Robust Control Theory--Robust Control System Design For Linear Induction Motor

Robust Control is brought out to deal with system uncertainty, whose research emphasis is to discuss the resistance of the system's certain characteristics or index to some disturbance. Supposing the system's transfer functions belong to a set, we judge the nature of the feedback system: given a controller, if all the objects in the set can fulfill the demands of the nature, we say that the controller is robustic to the nature. The general meaning of robustion is that all objects in a set can meet the requirements of inner-stability and other characteristics. Robust control includes the concept of weight function and augment-system, which leads to that the controlled system can take some natures, like model uncertainty, stability, sensibility, disturbance-resistance, into consideration at the same time. We do the applying research of robust control theory in this paper, choose Post Distribution System (PDS) using Linear Induction Motor (MM) as power source as the control object. The main work focus on modeling and control research, fi.tlfill the control demand of quick tracking, anti-loading disturbance and anti- model changing. In the current research situation, we still lack convenient and effective way to control LIM. Because LLM's magnetic poles are open, the magnetic chain is not closed, it has end effect and expose strong nonlinear characteristics if compared with Rotate Induction Motor (RIM). In the way of using, people normally only consider the static design characteristics, and don't consider the dynamic characteristics; In the control strategy, people only consider open-loop control. The above situation can't meet the need of the system, such as quick tracking, accurate position and proper push, can抰 make the LIM expose its advantages. In this paper, we explore a method to simplify the LIIM model, and we can use modern control method on this basis: 1) apply vector control, set up dynamic equation of the LIM, and linearize relation of the input and output; 2) establish and simplify the dynamic model of PDS using LIM as power system; 3) basing on this model, do some control research on this system. Because the establishment of the simplified LIM model, we get a big development in the LIM control strategy. We can control LIM according to the way of RIM control. And, the whole-design method of controller and object can optimize the design characteristics of the LIM. In the robust control research of this paper, we use H_∞ control theory and the concept of weighing function, system-augment to meet the need of velocity tracking, anti-disturbance, anti-model-change. We induce the inner model control to improve the system's dynamic nature, which is to add a special part into controller, and make the system has good anti-disturbance nature. We also do some research on robust pole assignment based on inner model method, and design two-degree of freedom controller. We also emulate the control systems designed by PID control method, robust pole assignment method, H_∞ Control, and compare their result and advantages.