Control of wheel motors for the provision of traction and steering of railway vehicles

This study presents the development of a control system for permanent magnet motors embedded in railway wheels for integrated traction and steering of rail vehicles. The overall control scheme and the control strategies for the provision of traction and wheelset steering are presented, but a main focus of this study will be concerned with the development of a new sensor-less position detection technique that overcomes the difficulties of position detection at zero and very low speed using the back-emf-based methods. The new technique does not require the injection of high frequency harmonics, and detects the motor position from simple measurements of the neutral point voltage of the motor influenced by the variation of inductances with respect to rotor position. Both theoretical development and experimental verifications are provided.