Abstract It is noted that in a conventional sliding mode observer (SMO), the discontinuity terms of the sliding mode control (SMC) law can cause undesirable chattering problems, and the amplitude of the chattering is proportional to the sliding mode gain. In order to suppress the chattering problem caused by the discontinuity terms and the variations of system operating conditions, this paper proposes an enhanced adaptive sliding mode observer (ASMO) for sensorless control of surface‐mounted permanent magnet synchronous motor (SPMSM). The strategy can automatically adjust the sliding mode gain according to the system states to ensure system stability and chattering suppression. In addition, considering that the tracking performance of a linear low‐pass filter (LPF) included in the conventional SMO can be limited by the sampling time, Levant's differentiator is adopted to replace the LPF for a more precise estimation of the back electromotive force (EMF). Rigorous Lyapunov theory demonstrates the stability of the proposed algorithm, and the effectiveness and feasibility of the method are verified on an experimental platform with a 1.5 kW SPMSM.
Cao et al. (2026) studied this question.