Permanent-Magnet Synchronous Motor Sensorless Control Using Proportional-Integral Linear Observer with Virtual Variables: A Comparative Study with a Sliding Mode Observer

Quick convergence, simple implementation, and accurate estimation are essential features of realizing permanent-magnet synchronous motor (PMSM) position estimation for sensorless control using microcontrollers. A linear observer is often designed on real plant variables and is more sensitive to parameter uncertainty/variations. Thus, conventionally, a sliding mode observer (SMO)-based technique is widely used for its simplicity and convergence ability against parameter uncertainty. Although SMO has been improved for switching chattering and phase delay, it provides purely proportional gain, which leads to steady-state error and chattering in observation results. Different from conventional linear observer using real plant variables or SMO with proportional gain, a simple proportional-integral linear observer (PILO) using virtual variables is proposed in this paper. This paper also provides a comparative study with SMO. By introducing virtual variables without physical meaning, the PILO is able to simplify observer relations, get smaller phase shifts, adapt mismatched parameters, and obtain a fixed phase-shift relation. The PILO is not only simple, but also improves the estimation precision by solving the controversy between chattering and phase-delay, steady-state error. Moreover, the PILO is less sensitive to parameters mismatching. Simulation and experimental results indicate the merits of the PILO technique.