The Research On Fault Diagnosis Method And Sensorless Control Methods At Low Speed For Switched Reluctance Motor

Switched reluctance motor(SRM) has features of simple structure, low cost, flexible control, good performance, strong tolerance, etc. It has been widely used in areas of aeronautics and astronautics, electrical vehical, demostic appliances and industrial applications. SRM cannot operate normally without the information of rotor position. But the fact that traditional position sensors such as photoelectric and hall sensors are installed with the motor will increase the cost and volume of the system. Worse still, those sensors are very likely to break down when the machine is working in the environment of high temperature, damp or with dust. Therefore, it will enhance the applications of SRM to research the fault diagnosis and tolerant control of position sensors, and the sensorless control.Through the analysis of the square wave position signals of SRM, a new fault diagnosis method of position signals based on the predictions of the edges is proposed. Three adjacent edges are used to predict the fourth edge, which is compared to the actual one to judge whether fault happens or recovers. This method can diagnose each position signal separately, and can be applied to conditions when acceleration or deceleration happens frequently. It can also be extended to the fault diagnosis of other motor's square wave position signals. The corresponding fault tolerant control method is also researched. Finally, simulations and experiments are carried out to prove its validity and reliability.When all the position sensors break down, then no position signals can be obtained. Hence, this paper researches the sensorless control algorithm based on high frequency injection. The high frequency model is established, and the estimation procedure is worked out. Through a series of filters and coordinate transformation, the realtime position information can be acquired. Low speed experiments using this method are realized.The method mentioned above has some inherent drawbacks, and a new sensorless method based on PWM control is proposed to tackle them. PWM signals are used to drive the motor, which can be equivalent to the injected high frequency signals. The generation and the principle of PWM signals are introduced. Phase shift with substraction is applied to simplify the estimation procedure while ensuring the accuracy. Simulations and experiments verify the feasibility of this method.