Sensor device and method for determining a relative angular position between shaft halves of a rotary shaft

A method for determining a relative angular position between a first shaft half and a second shaft half of a rotary shaft, in particular a rotary motor drive shaft, the method comprising the steps of:

• transmitting between the first shaft half and the second shaft half via a torsion section which interconnects the first shaft half and the second shaft half to one another in an elastic manner,
• providing a first magnetic structure and a second magnetic structure having spatially different magnetic periodicities, wherein the first magnetic structure is mounted on the first shaft half and the second magnetic structure is mounted on the second shaft half such that respective magnetic fields generated and/or influenced by the first magnetic structure and the second magnetic structure superpose,
• providing at least four sensors mounted stationary with respect to a rotary movement of the rotary shaft such that the superposed magnetic field generated and/or influenced by the first magnetic structure and the second magnetic structure is detected by each of the at least four stationary sensors, and,
• by an electronic evaluation circuit, receiving measurement values corresponding to the detected superposed magnetic field from each of the at least four sensors, determining the relative angular position from the received measurement values of the at least four sensors, and determining an absolute angular position of the rotary shaft in relation to a predetermined rotary reference position from the received measurement values of the at least four sensors.