Sensorless control for surface mounted PM machine with a high inertial load

PM machine or Permanent magnet synchronous motor (PMSM) is a nonlinear system with multivariable couplings. To achieve the sensorless control of a PMSM with high inertial load, a modified current observer, using PI regulator instead of sliding mode switching function, is proposed in this paper. The modified current observer can solve the chattering and phase delay problem while still maintaining the robust advantages of sliding mode system in position estimation. In addition, a new phase-locked loop (PLL) based angle switching strategy is designed to ensure the motor can smoothly switch from I-F control to closed-loop sensorless vector control in startup stage with a high inertial load. The simulation and experimental results show that the control system of PMSM with proposed ideas has fast response speed, accurate rotor position estimation, stable state switching and good system robustness under high inertia load.