Research On PMSM Sensorless Speed Control Technology

The permanent magnet synchronous motor(PMSM) has been widely used in the industry,agriculture,military affairs and civilian for many advantages such as simple structure, small size,light weight,high power density,high efficiency, easy of control,wide speed range and so on. The operation of a PMSM requires the rotor position information,which is usually provided by a mechanical position sensor.Unfortunately,the use of these sensors will increase the overall cost and the complexity of the systems,and also reduce the reliability and noise immunity of the systems. Therefore, the sensorless control technology has become a hotspot in the field of motor control technology in recent years.Sensorless speed control method is divided into two types:one type applies to standstill or very low speed condition;another is applicable to medium and high speed condition.In this paper, fluctuating high frequency signal injection suitable for low speed and MRAS suitable for high speed are researched detailedly.Firstly, the current research and development trend of the permanent magnet synchronous motor sensorless speed control system,the coordinate transformation theory,the mathematic model of PMSM and vector control theory is introduced in this paper.On this basis the paper introduces some commonly used vector contol strategies and analyze the advantages and disadvantages of the various control and the applicable occasions.Secondly, the basic principle and classification of high frequency signal injection method is introduced in this paper.Then,the rotor position estimation algorithm of PMSM,based on the fluctuating high frequency signal injection strategy is deeply studied.The extracting process of the rotor position information is elaborated in detail. In order to verify the proposed control scheme,simulation is carried out.Howerver,this method requires to inject harmonic signal continuously,easily leading to torque ripple,especially can not track dynamic processes at high speed.And the high speed performance of MARS is relatively good. We consider the respective advantages of both,establishing a composite sensorless control system. The fluctuating high frequency signal injection is used at low speed, ensuring measurement accuracy of rotor position and speed,while MARS is used at high speed to ensure fast dynamic response. In order to verify the proposed control scheme,simulation is carried out.And the simulation results confirm that this method is effective to estimate rotor position and speed correctly.Finally, in the basis of the simulation, the hardware platform based on the TI’s TMS320F2812DSP is used to build a sensorless speed control system of PMSM.The experiment of static and dynamic performance of system is carried out.The experimental results show the effectiveness and feasibility of the composite method.