A Non-Axisymmetric Winding-Based Sliding Mode Position Observer for Dual Three-Phase Permanent Magnet Motor Under Single Phase Open-Circuit Fault

After a single phase open-circuit fault occurs in dual three-phase permanent magnet synchronous motor, the remaining healthy windings form a group of non-axisymmetric five-phase winding, which makes it difficult to estimate the position information accurately while performing the sensorless control scheme. For addressing the issue, a sliding mode position observer designed according to the non-axisymmetric winding is proposes in this paper. Twice decoupling operations were carried out on the main inductance matrix, the resistance matrix and the leakage inductance matrix, then the decoupled voltage equation of the non-axisymmetric five-phase winding is derived. For suppressing the fluctuations of the back-EMFs caused by the asymmetric inductance matrix, a nonlinear restoring-force coefficient sigmoid (RF-Sigmoid) is proposed to reduce the chattering of the estimated back-EMF. In addition, the stability analysis of the non-axisymmetric winding-based sliding mode position observer is also provided. The experimental and simulation results verify the effectiveness of the proposed method.