Performance of a Dual Three-Phase Permanent Magnet Machine for a Steer-by-Wire System Under Healthy and Faulty Conditions

Electric power steering (EPS) is now widely used in the automotive sector to give driver assistance. More recently interest has grown in steer-by-wire (SbW) systems which dispense with the conventional mechanical linkage between steering wheel and steering rack. Dual three-phase permanent magnet machines offer a fault tolerant solution for SbW systems. The healthy operation mode has been widely studied in the literature but faulty operation has received much less attention. Therefore, this manuscript focuses on studying post-fault operation from thermal and electromagnetic points of view. A 12 stator-slot/10 rotor-pole (12s/10p) interior permanent magnet (IPM) motor has been investigated using finite elements (FE) for the electromagnetic analysis and a lumped parameter thermal network (LPTN) for the thermal study to investigate the coupled behavior. In addition, a prototype has been built for the validation of the electromagnetic model and for the calibration of the LPTN. The results confirm that up to about 70% of rated torque can be obtained in the faulted condition.