Based On The Quasi Sliding Mode Observer Of Sensorless Brushless Dc Motor Control Technology Research

Brushless DC motors(BLDCM) are widely used in every walk of life in view of its excellent qualities such as high operating efficiency, no spark during commutating, and good mechanical properties. Traditional BLDCM can get the exact rotor position signal to realize commutation and velocity modulation through mechanical position sensor. However, the mechanical position sensors may restrict BLDCM’s application in some areas, such as aerospace, automobile, and even can not be used in some cases with the position sensor. So sensorless control for BLDCM becomes a hot academic research in recent years.Sliding mode variable structure control is characterized with disturbance adaptive capacity, it can be used in motor speed control, position control. The sliding mode observer can not only evaluate the state of uncertain object, but also can get the real-time variable of the inner and outer disturbance. However, the traditional sliding mode observer have the problem of chattering and low accuracy, thus limiting the method in high performance drive applications. To solve the above problems, a method for sensorless control of BLDCM is designed on the basis of the new characteristics of sliding-mode variable-structure control.Firstly, the basic principles and control methods of sensorless brushless DC motors (BLDCM) are introduced in this paper, and the common rotor position detection techniques are researched. Secondly, on the basis of the analysis of the motor model and sliding-mode variable-structure principle, a novel quasi-sliding mode observer for sensorless control of BLDCM are proposed. The sliding surface is defined based on the errors between actual and estimated currents in this observer, and then estimated the rotor speed and the rotor position based on the mathematical relationship of electromotive force (EMF) and the rotor speed. The sign function is replaced by a saturation function, a valid boundary can solve the chattering problem, and then using the estimated speed which is got by the observer as the closed loop speed feedback., the real speed response is good. A sensorless control system for BLDCM based on the novel quasi-sliding mode observer is implemented. Simulation result shows that the proposed method can not only correctly estimate the speed and the position of the rotor, improve the accuracy of the estimation of the rotor position, but also can restrain the traditional sliding mode control chattering validly, enables the system with strong robustness. Finally, the hardware and software of the BLDCM control system are designed based on the dsPIC30F6010. And functions like BLDCM staring, voltage¤t sampling, speed regulating rotor position detecting are realized.