The Sensorless Rotor Position Detection And Torque Ripple Minimization For Synchronous Motor

ESM has many significant advantages compared with other motors. However,real-time rotor position is needed to realize accurate control of the ESM. Theapplication of the mechanical sensor to detect the rotor position causes many otherproblems. And thus, the method to detect the rotor position without mechanicalsensor is needed.This paper realizes the detection of the rotor position without using mechanicalsensor. The rotor position in static position can be derived by imposing theexcitation current within a short time and detecting the resulting three-phase EMF.In the high speed stage, rotor position can be detected by analyzing the cross-zeropoints of the detected EMF. In the low speed stage, the rotor position detection canbe realized with the method of self-providing pulse pre-positioning. In this way, thegoal of detecting the rotor position in the whole speed region is achieved.Self-providing pulse method, however, induces some other potential problems,which damage the motor rotor. To avoid these problems, a novel rotor positiondetection strategy is proposed based on high-frequency signal injection method.This strategy can be implemented by injecting high-frequency signal into theexcitation current. The resulting high-frequency EMF can be sampled to contributeto the detection of the rotor position. The injection methods are investigated in thispaper deeply. Finally, the voltage pre-estimation algorithm is adopted to deal withcommutation current distortion problem and increases the rotor positioningaccuracy.This paper tries to suppress the torque ripple problem, from three differentperspectives: mathematical model of the motor, commutation angle, andhigh-frequency signal injecting. Based on the mathematical model, a definition ofthe commutation current is given and the relation between the commutation momentand torque ripple can be derived. The commutation moment for minimum torqueripple is the moment when the EMF crosses the zero point. From schematic of thepractical motor driving system, the conclusion can be gotten that the smaller thecommutation lead angle is, the smaller the torque ripple is. Finally, the influence ofhigh-frequency injection signal is taken into account and the comparison resultshows that the influence of it can be neglected.The MATLAB simulation result proves the viability of the proposed method.The practical hardware setup is built and the proposed method is applied into it. Thepractical experiment result shows good performance, which proves that the proposed method can be used to detect the rotor position of the ESM in practice.