Research On Sensorless Control System Of Brushless DC Motor On DsPIC

Brushless direct current motor(BLDCM) has good characteristics of small size, good speed control performance, high output efficiency, so it is widely used in electric vehicles, aerospace and other fields. Usually, the brushless direct current motor detects rotor position with position sensor. The position sensor accuracy and reliability will be greatly reduced in some special work environments such as high temperature, corrosive environments, vibration, etc.The sensorless control method of back EMF zero crossing detection reduce the volume of the motor and the production cost. At the same time, the rotor position signal is more stable, the reliability and environmental adaptability is enhanced.So this research has important significance for the control of brushless DC motor in bad conditions.According to the operating principle of the brushless DC motor in this paper,and its mathematical model is established. Speed loop uses fuzzy PI control, the current loop uses the traditional PI control, to achieve double closed loop control.Starting motor which uses "three-step" approach. Construction of control system model and simulation Matlab/Simulink toolbox, receiving better control effect.In view of the simulating verification of the system design scheme, design hardware circuit and software of sensorless control system of brushless DC motor which used the digital signal processor dsPIC as the core. The hardware circuit is mainly constituted by BEMF detecting circuit, current sampling circuit,isolation drive circuit and power supply circuit etc. And also designed the board of this hardware circuit and completed the welding. The software of the control system was designed using C-language in MPLAB development environment based on modular design ideals.Set up experimental platform of brushless DC motor control system. In the PC interface can view change of motor speed, and real-time monitoring machineoperation. After optimization of parameter modification and application,traditional PI control and fuzzy PI control experiments at the speed of mutation and load conditions are carried out and compared. The results show that the sensorless brushless DC motor fuzzy PI control system has quick response speed,high control precision, strong anti-interference ability, good dynamic the performance and static performance. The fast startup, speed regulation and speed setting function are realized, verify the rationality of the design scheme. The research has a high application value for high accuracy applications, poor working conditions and other fields.