A Novel Fundamental PWM Excitation-Based Rotor Position Estimation Method for Precision Sensorless Control of IPMSMs

In sensorless control of interior permanent magnet synchronous motors (IPMSMs), the fundamental PWM excitation (FPE)-based methods use PWM signals excitation and measure the derivative of the stator current as responses to estimate the rotor position. As the signal injection is no more required, the FPE-based methods have the potential to simplify the controller and achieve precision sensorless servo control. However, the current derivative is hard to measure accurately. Therefore, existing FPE-based methods usually suffer from significant position estimation errors. In this paper, a novel FPE-based rotor position estimation method is proposed with high stability and accuracy. Different from existing methods which usually sample current derivative only 2 times per PWM cycle, the proposed method takes 2 to 6 samples, depending on the amplitude and direction of the voltage vector. To make full use of all recent sample points, a first-in-first-out (FIFO)-based least squares algorithm is proposed. The optimal rotor position estimation can be obtained with only a small amount of computation since the analytical solution is given. Simulation results demonstrate that the rotor position can be estimated with an accuracy of 1 electrical degree under various speed and load. Sensorless closed-loop trajectory tracking control based on the proposed method is realized, which shows an exciting prospect of sensorless control in high-performance servo systems.