| Linear Motor is a kind of linear driving equipment that transforms power into linear movement directly. Metro vehicle driven by the linear motor is one of the most advanced urban rail transport, which has been adopted by cities in many countries as the proposal of urban traffic system in the 21st century. Nowadays, the linear motors used for metro vehicles are linear induction motors (LIM). 70% of the core technologies, which used in the linear motor driven control system for metro vehicles, need be imported. In order to localize the core technologies, and to further improve the control performance, it's very necessary to research on the linear induction motor control system.When linear motor driven vehicles are in operation, the air gap between primary and secondary will change, and the motor characteristics change accordingly. The changes of characteristic parameters will influence the accuracy of building the motor mathematical model. In order to ensure the propulsion, to decrease the energy consumption, to improve the efficiency, and to ensure the safety, stability as well as the economy of the Metro bus, first of all, the theoretical research and validating experiments on building the mathematic model of the linear inductor motor should be carried out. Then, the control methods as well as control strategies to the control system of the linear induction motor should be reasonable and advanced adopted. The domestic control technology research for linear induction motor is still in the stages of exploration in application areas, and analysis on the characteristics, design and manufacturing. If the establishment of the mathematic model of linear induction motors has been tested, the control methods and control strategies have been right and advanced apllied, the control technology of linear induction motor absolutely makes a great step on both its theory and actual practice.The input current in the primary windings includes the electromagnetic thrust component and the excitation component. Since the excitation circuit of Linear Induction Motor is non-independent, it's very troublesome to control it. Vector Control which based on the object model is a control scheme for dynamic performance AC motor's speed control system. Under the basic idea of Vector transformation control, through vector transformation matrix, the current in the primary of linear induction motor can be decomposed into two non-coupled parts: the excitation current and the armature current. By controlling excitation current and armature current, the secondary magnetic flux and the electromagnetic thrust can be controlled, so as to the motor speed.There are three main control methods for Linear Induction Motors: slip frequency control, direct electromagnetic thrust control and direct magnetic field oriented control. Among the above-mentioned control methods, in the case of the velocity mutation, direct magnetic field oriented control responds the fastest and with no oscillations; in the case of the velocity mutation while the velocity is in low range, direct thrust control and direct magnetic field oriented control respond faster, but there is a steady-state error existed in direct thrust control. In general, direct magnetic field oriented vector control methods have outstanding performance, particularly the high precision in speed control and location control.According to the direct magnetic field oriented vector control method, linear induction motor control system adopts velocity and magnetic flux closed-loop control. In order to restrain the cross-coupling still existed between the rate of the excitation current and the armature current in the primary windings, current hysteresis control is used, so that the actual current can track a given value. Also an additional thrust closed-loop is designed following the velocity loop to reduce or avoid the impact on the thrust because of the flux closed-loop mutation. Thus, a kind of vector control system made up of a velocity closed-loop, a magnetic flux closed-loop and an inner thrust loop is created.As rotary motor, the control technology development of linear motor has also gone through three stages: the traditional classical control theory (such as PID control) --modern control theory (variable structure control, robust control) -- Intelligent Control (neural network control, fuzzy control). It is a good method to introduce the fuzzy control technology into linear motor control. Some research work has been carrying out on applying this method to Linear motor control field. When using fuzzy control to the linear motor, in order to satisfy the AC drive on the dynamic response and steady-state accuracy requirement, the fuzzy controller should have self-contained control rules. The quantifiable factors and scale factors in conventional or composite fuzzy controller are fixed, but they largely influence the performance of the fuzzy controller. By selecting a group setting can not meet the requirements both in dynamic and static state. So, the fuzzy controller is designed based on self-adjusting fuzzy control technology which can adjust its quantifiable factors, scale factors and fuzzy control rules. In allusion to the characteristics of the linear induction motor used by metro vehicles, This paper introduces direct magnetic field oriented vector control method and self-adjusting fuzzy control strategy to the linear induction motor control system. The main items researched in this paper are as following:1. Summarize the commonly used theory analytical methods and control methods for linear induction motor. Analyze the vector control technology applied in the linear motor. Provide the equivalent circuit considering the end effect of the linear induction motor. Based on the equivalent circuit, provide the linear induction motor model in the dq synchronous rotating coordinate system.2. In accordance with the characteristics of an operating linear induction motor: multivariable, nonlinear, strong coupling and difficult to establish its accurate dynamic model; propose a magnetic field oriented vector control method. The control system is made up of a velocity closed-loop, a magnetic flux closed-loop and an inner thrust loop. Design the linear induction motor vector control system based on this control method. In terms of control strategy, put forward a self-adjusting fuzzy control strategy and design the corresponding self-adjusting fuzzy controller.3. Establish the linear induction motor simulation model considering the end effect in dq coordinate system by using MATLAB software, and apply the model to the simulation for linear induction motor control system. Establish the linear induction motor vector control system simulation model based on self-adjusting fuzzy, and do experiments by virtue of computer simulation. Simulation results show that compared to the PI control system, the vector control system of the linear motor based on self-adjusting fuzzy is more robust, the system's steady-state and dynamic performance has been greatly increased.4. Test the model of the linear induction motor.
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