The Design And Research Of Sensorless Control System For Brushless DC Motor

The brushless dc motor(BLDC motor) has been widely used in national production and living in all areas because it has so many advantages such as high efficiency, low noise, great longevity, compact construction, convenient maintenance and high performance etc. It is different from the traditional DC motor using commutator and brush to commutate, BLDC motor is inherently electronically controlled and requires rotor position information for proper commutation of currents. However, the application of rotor position sensors increases the motor's size, costs and reduces reliability. So it's necessary for further research on sensorless control of the BLDC motor.To obtain the commutation signals from observable signals of motor without position sensor can be regard as a nonlinear system identification process. The cerebellar model articulation controller (CMAC) is a kind of learning structure for simulating cerebellum, it provides a capability that can multidimensional nonlinear map from inputs to outputs. It has strong nonlinear function approximation and generalization ability, and can learn fast, So CMAC can be used to build the nonlinear relationship between the stator voltages and commutation signals.This paper research on sensorless control of BLDC motor, and proposes using CMAC as control strategy in sensorless control system. From analysis of the structure, this paper discusses the operation principle and the mathematical model for BLDC motor, a detailed analysis about sensorless control methods have been made. Then the structure of sensorless control system for BLDC motor is designed. The principle and implementation of sensorless controls based on back-EMF crossing zero point method and flux linkage function method are discussed. For their problems, this paper presents the theory and implementation of a novel sensorless control method based on CMAC. To verify these three methods, the simulation platform of is designed for BLDC motor. And the above three methods are verified on it. The simulation comparison experiments are developed for these methods. Simulation results show that the proposed method can provide accurate commutation signals and realize position sensorless control. Finally, the real-time control system is designed based on STM32 microprocessor.