Position and Speed Detection Method Based on Cross-Decoupling Network Filtering for Gearless Traction Motor Drives at Low-Speed Operation

This article proposes a position and speed detection method based on the cross-decoupling network filtering (CDNF) method combined with phase-locked loop (PLL). This method is used to enhance the detection precision of position and reduce the speed fluctuations at low-speed operation for gearless traction motor drives with an ordinary-resolution encoder. The harmonic distributions of the discontinuous orthogonal position signal in low-speed region are analyzed. On this basis, the position and speed detection method based on CDNF with PLL is presented to obtain the harmonics of the discontinuous position signal adaptively for eliminating the position detection error and improving the accuracy of the speed feedback. The criteria of the filter parameter design are presented based on the maximum phase margin theory to maintain the stability of the system. Experiments were carried out on an 11.7 kW permanent magnet gearless traction motor drive with an ordinary-resolution encoder installed. The experimental results verify the effectiveness of the proposed method at low-speed operation.