Research On Long-distance Speed Control System Of Brushless DC Motor

In some places such as oil fields and mines where the operation space is not ideal and the laying of lines is difficult,or in the environment of building electrical renovation and intelligent home where it is difficult to rebuild the network,the long-distance speed control of brushless DC motor(BLDCM)needs to consider the technical and cost problems of laying signal lines or wireless communication modules separately.In this thesis,a method of sending speed control signal while providing power in the form of controllable rectified wave is proposed.Controllable rectified wave consists of several single-cycle AC waves and rectified full waves.Through the digital signal coding technology,the single cycle AC wave and the single cycle rectified full wave are set to correspond to the binary signal code 0,1,or 1,0 respectively.The signal code is composed of two parts: the guide code and the data code,in which the guide code serves as a reminder to receive,and the data code contains information about the speed,direction and start-stop of the motor.The transmission and reception of controllable rectified wave are realized by the transmission circuit and the reception circuit of controllable rectified wave velocity signal respectively.Controllable rectifiedr wave velocity signal transmitting circuit controls the orderly switching on and off of bidirectional thyristors in the controllable rectified module circuit according to the given speed,and sends out a group of controllable rectified waves.After long-distance transmission by two special controlled power lines,it is received and recognized by the speed signal receiving circuit.The design and Simulation of BLDCM control system are also carried out in this thesis.In order to improve the speed control accuracy,a double closed-loop speed control system is designed,in which the optimized fuzzy PI speed control algorithm is adopted in the speed loop,and the motor speed control system model is built and simulated with the help of MATLAB/Simulink simulation platform.The feasibility of sending and receiving speed control signals in the form of controllable rectified waveform is verified by setting up an experimental circuit for transmitting and receiving speed control signals of controllable rectified wave.The simulation results of BLDCM speed control system show that the adjusting time of the fuzzy PI speed control system is 1.9 s and the system response overshoot is 2.6%.It meets the design requirement that the starting overshoot should not exceed 5% when the motor is stable to a given speed within 3 seconds and no load.