Sensorless observer based hysteresis control of a transverse flux machine at low speed

DYNAX is a transversal flux machine developed for high torque density. Fields of application are the drive train of hybrid and electric vehicles and automotive auxiliary equipment. Because of the high number of pole-pairs, the rotor angle measurement requires ambitious sensor technology. For cost sensitive series applications, a sensorless angle computation would be desirable. So the objective of actual research activities is the creation of an observer based, hysteresis current control that enables sensorless operation over the whole speed range. The hysteresis control strategy avoids typical problems of vector control, for example subharmonics and full modulation. The observer provides highly dynamic current data and permits a stable hysteresis current control without sensor. It compensates limited bandwidth of current sensor and other time delays in the signal path. Focus of this paper is the angle estimation at standstill and low speed, which is the most critical aspect.