the rotor an actuation of motor m requires a transformation of the current vector from the system rotating along with rotor r into a stationary system having the axes ia and ib this requires knowledge of angle w at all times which varies with the rotation of rotor r and is referred to as commutation angle w the transformation is also referred to as a park transformation it should be noted that such motors m frequently have a multiplicity of magnetic periods i e pole pairs so that a complete movement of the current vector or rotor r through a magnetic period corresponds to only a partial mechanical rotation a motor m having two pole pairs has mechanically rotated only about 180 degrees when rotor r has traversed a complete magnetic period it is important to note that commutation angle w must be known at all times for the park transformation it can be acquired with the aid of position measuring device e provided the mechanical position of rotor r has previously been put in relation to the position of rotor r within a magnetic period of motor m conventional methods that are used for this purpose have been mentioned above example embodiments of the present invention are based on european published patent application no 0 784 378 mentioned above in which a commutation offset is adjusted with the aid of a controller structure greater deflections of the rotor being avoided in so doing however such methods fail under certain conditions in that no stable commutation angle comes about even after a longer period of time in particular systems featuring with low friction bearings and an initial speed that differs from zero are.