Research On Sensorless Control Of Brushless DC Motor Based On Improved Sliding Mode Observer

Brushless DC motor is a kind of high-efficiency and energy-saving motor,which has achieved great development in recent years and its market share is continuously rising.Due to the existence of position sensors,the control system of brushless DC motor with position sensors needs to reserve positions for the position sensors during production and installation,which is difficult to realize miniaturization,complex system structure,low reliability,etc.At the same time,the position sensor is easy to be affected by the external environment in the use process,the detection result is easy to produce deviation,which reduces the reliability of the system.Therefore,aiming at the above problems,the research on the brushless DC motor position sensor technology is carried out.In this paper,the brushless DC motor sensorless control technology is the main research content.Firstly,the basic structure,operation principle and mathematical model of the brushless DC motor are analyzed,and the motor simulation model is built in Matlab/Simulink environment.Then,the control principle and method of the brushless DC motor with no position are analyzed,and the inaccurate result of detecting the rotor position by using the traditional sliding mode observer brushless DC motor system is studied.In this paper,a sensorless control method of the brushless DC motor with a global fast terminal sliding mode observer is proposed.The rotor position is estimated by using the linear back EMF,and then the commutation time point is determined.The method saves a lowpass filter and can effectively compensate the influence of phase delay.Compared with the traditional sliding mode switching,the switching surface of the method can quickly converge the state point to the equilibrium point in a global range and in a limited time.Then the traditional sliding mode observer and the proposed new sliding mode observer are simulated and verified in Matlab/Simulink environment.The correctness and effectiveness of the improved method are verified by comparing the line back EMF waveform,rotor position waveform and torque waveform under sudden load.Finally,DSP/TMS320F2812 is used as the main control chip,peripheral circuits are designed,and an experimental platform is built.the control programs of the traditional sliding mode observer and the global fast terminal sliding mode observer are respectively written in CCS environment,and the two control methods are compared.The results show that the global fast terminal sliding mode observer can make the rotor position detection more accurate,and can track the rotor better at the moment of sudden load change,which verifies the effectiveness and practicability of the global fast terminal sliding mode observer.