Sensorless control of permanent magnet synchronous motor based on fixed-time terminal sliding mode observer

In the sensorless control of a sliding mode observer (SMO)-based permanent magnet synchronous motor (PMSM), a large gain is required to ensure the stability of the sliding motion. Nonetheless, this can lead to the unexpected chattering and degrade the precision of position estimation. To overcome this trouble, we have proposed a fixed-time nonsingular terminal SMO (NTSMO). The convergence time is independent of the initial value. Firstly, a fixed-time nonsingular terminal sliding mode surface is designed so that the current observation error fixed-time converges to zero, and the singularity issue can be averted. Secondly, via the phase-locked loop tactic, the rotor position and speed are calculated from the measured back electromotive force. Thirdly, a Lyapunov function-based proof is utilized to assure the stability of the observer. Finally, the validity of this method is confirmed by simulation tests and experiment results.