The Research On Permanent Magnet Synchronous Motor Position Sensorless Control Strategy

With the advantages of small size, high efficiency, small moment of inertia and thehigh adaptability to the environment, permanent magnet synchronous motor (PMSM) arewidely used in high-performance servo fields, such as CNC machine tools, industrialrobots and so on. At the same time, because of its advantages of low cost and goodreliability, the sensorless control of permanent magnet synchronous motor become one ofresearch hot spot in the current motor control field.Based on the traditional double closed-loop vector control system of permanentmagnet synchronous motor, this paper presents a new sensorless control strategy, and dosome further research for the key problems. The mainly research work this articlesummarized as follows:First of all, on the basis of analysis of permanent magnet synchronous motormathematical model, this paper analyses the interior of the permanent magnetsynchronous motor electromagnetic constraint relations, expounds the principles of vectorcontrol of permanent magnet synchronous motor, established the space voltage vectorpulse width modulation (SVPWM) model, and analyses the traditional double closed-loopvector control system of permanent magnet synchronous motorSecond, on the basis of existing double closed-loop vector control system, this paperproposes a new sensorless control strategy, the current estimation and speed estimation arejoin to the system respect to the traditional current loop and speed loop. Based on the innercurrent loop, the current estimation which can estimate three-phase inverter output currentby dc bus current are established. At the same time, this paper analyzes the dead timeimpact on current estimates, and proposes solutions to solve the problem. On the otherhand, respect to the outer speed loop, the speed estimation which used by back-EMF areestablished. At the same time, aiming at the problem that speed estimation algorithm isinaccurate at the zero speed or low speed, this paper proposes the half closed loop strategywhich can avoid the rotor out of step and can realize real-time online optimal estimate forrotor position angle and rotational speed.Finally, the control strategy combining current estimation and speed estimation areapplied to the sensorless control of permanent magnet synchronous motor in the system.In Matlab/Simulink environment, the traditional double closed-loop vector control systemand sensorless control system are simulate respectively, results show that the controlstrategy adopted in this article has excellent characteristics for rotor position and speedtracking and can response quickly and smoothly with small speed overshoot. At the sametime the system have strong load disturbance resistance and have good controlperformance.