Research On Characteristic And Fuzzy Control Technology For Linear Induction Motor

Linear Induction Motor (LIM) is the linear driven equipment that transforms the power directly into the linear movement. Motro vehicles driven by the linear motor is one of the most advanced facilities of urban railway transportation, which has been adopted by cities in different countries as the proposal of urban traffic system in 21st century. When vehicles driven by LIM is running, the major forces existing between the primary motor and secondary sections of motor are the horizontal force and the perpendicular electromagnetic force. Those two forces changes with different air gaps. As the air gap of the linear motor changes during the vehicle running, motor features the changes accordingly, and its feature parameter changes too, thus it finally influences building the precise mathematic module. To ensure the certain propulsion force, to decrease the energy consuming, to improve the efficiency, and to ensure the safety, stability as well as the economical running of the metro vehicles, herein it is firstly to carry out the theoretical research of the mathematic module of the LIM and to verify it by experiment means,then, to introduce the reasonable and advanced control methods as well as control strategies to the control system of the LIM. It is no doubt once the established mathematic module of the LIM is verified,together with successful application of advanced and applicable control strategy and method, the control technology of LIM will make a great step on both its theory and actual practice.At present, as for the metro vehicles and AC electric transmission Locomotive, the major three ways of the control strategies adopted commonly on the traditional rotating induction motor are the following: slip frequency type control, field oriented control and the direct torque control. From the view point of principle, there's the generality existing between the linear induction and the traditional rotating induction motor, which all gain the driving force from the magnetic field formed by the three-phase currents. Therefore, the control strategy adopted by the traditional rotating induction motor can be also applied in the LIM. LIM control strategy is same as above-mentioned three ones.Since the alternating asynchronous linear motor and the rotating alternating asynchronous motor have the similarities like the strong coupling ability, non-linear, multi-variable system; moreover the LIM is sensitive to the perturbation motion and change of system parameters, urther the friction and propulsion makes the system have more apparent non-linear property, seeking out the more optimized arithmetic and performing the effective control become the most challenging research topic. Therefore, the questions like how to trace the parameters of the object being controlled, how to improve the robustness of the control system, and which control method whose arithmetic is not subject to the change of the parameters of object being controlled should be applied become the hot topics among the majority of scholars and on the field of present transmission control system.The handling methods of intelligent control theory is no longer a single mathematic module but an extensive module combining the mathematic module and knowledge system together, which is fully applied with human experience, wisdom and the judging ability to control the complicated system. The advantages of intelligent control has been improved and adopted in many occasions, which has stepped into the electrics and electronice field and the transmission control field. It can be foreseen that artificial intelligence will have the outstanding effects on the electrics and electronics and transmission fields.Comparatively speaking, the three typical intelligent control strategies are specified as the fuzzy control, the neural network and the expert control, which mainly solve the problems that are complicated and can hardly be solved by the traditional methods.This thesis firstly has some research on the object being controlled—the LIMr—by means of distributive-parameter electromagnetic field theory and the integrated-parameter equivalent circuit. Then the control options of the LIM is introduced. At the same time, based on the background of application of the LIM in the Metro Vehicles and Light Railway Vehicles, the research focuses on the control system of the LIM, the main items researched are as following:1,Since the specific problem existing on the air gap field of the LIM, the motor field becomes a non-even vortex field, the magnetic field distribution of which can not be easily found out by the traditional integrated parameter circuit. On this thesis, the three-dimensional field of the motor is transformed into the two-dimensional field; The two-dimensional electromagnetic field of single edging type of LIM is calculated by using of the IEA.Based on the above mentioned theory, the features of the LIM is simulated and analysed by adopting the professional software Ansoft Maxwell 2D, gained the curves of magnetic strength distribution curve, magnetic force lines curve, current density curve as well as the air gap magnetism density curve and etc.At some motor running moment, analyzed properties of LIM under rated voltage in terms of propulsion force, perpendicular force and variation curve of current vs.2,The mathematical model and simulation model of LIM at two-dimensional rotated coordinating (d.q)has been built considering its edging effect and vortex loss.3,Based on the vector control mathematical model of LIM and the slip frequency type vector control design methods with close loop of speed, open loop of magnetic flux. Considering the difficulties to configure the precise dynamic mathematic model of LIM, apply the fuzzy control method into slip frequency type vector control system of LIM. The speed fuzzy controller is designed, with slip frequency type vector control system where magnetic flux loop is open and speed-current loop is close. The computer simulation of the motor has been made in the case of starting and operating with load, and its results showed that the LIM slip frequency type vector control system with fuzzy control method has more Robustness than PI control system, and has great improvement in terms of system control performance.4,Although the slip frequency type vector control system features simple structure and easy to realize, however, the control of rotator magnetic flux is of open loop, and the direction of magnetic field is ensured by vector control formula, thus this system will have deviation for the dynamic status. In order to improve the control precision, the design scheme of fuzzy vector control system of LIM with close loop of speed and rotator magnetic flux, and inner loop of magnetic thrust has been proposed, in which, the speed and magnetic flux regulator is controlled by self-adapted fuzzy controller (SAFC). The controller adjusts the fuzzy rule base by adjusting the fuzzy controller parameters and the weights of each input variable, thus the function is optimized. Finally, to verify the feasibility of theoretical scheme, make computer simulation of this fuzzy vector control system of LIM with double-close-loop of speed and rotator magnetic flux, and inner loop of magnetic thrust in terms of the system performance tracing to given input signal. The result of simulation experiment shows that the dynamic and stable performance obtained by SAFC with close loop of speed and rotator magnetic flux is better than that by the slip frequency vector control with close loop of speed and open loop of magnetic flux.5,Measuring the LIM being analyzed linear motor and its experiment devices of the control system,it has been gotten that the various curves of the motor features under different controlling voltage,and comparison of the experiment results with that of IEA. The result verifies effectiveness of the IEA analyzing theory on LIM features and computer simulation results.