Extended state sliding mode observer of PMSM and estimation of rotor position plus speed

In order to solve the chattering phenomenon in PMSM back EMF sliding mode observer (SMO), adaptive hybrid SMO was presented based on the PMSM extended state equation, of which the state variables were current and flux. The error between real and observed current was selected as sliding hyperplane. When the sliding mode occurred, the error was zero, and the equivalent control signals contained the information about the flux observation error. The error converged to zero when the equivalent signals were inputted to flux equation. The chattering phenomenon was suppressed well in the flux observation, from which the rotor angle can be calculated directly without filter. The influence of speed estimation error to flux observation was analyzed, and feedback matrix was calculated based on the analysis. The speed adaptive scheme was established, which was proved by Lyapunov theory. Simulation and experimental results show that the proposed method can precisely calculate the position and speed of the rotor, and the system has good dynamic and static performances.