FIELD

The present disclosure relates to operations performed using a periodic sensor signal representing a varying rotation angle detected by a rotation angle sensor and, to be more specific, to the generation of an output signal based on such a periodic signal and/or to the determination whether an update of an offset register of a rotation angle sensor is to be performed.

BACKGROUND

Generally, rotation angle sensors may be used to detect a rotation angle of an object. For example, a magnetic field sensor may be used to detect a varying magnetic field generated by a rotating object. The rotating object may be a magnetic field source, such as a pole wheel, or may be a toothed wheel of a ferromagnetic material, which is arranged relative to a magnet in order to influence the magnetic field generated by the magnet. The output of the magnetic field sensor may be a periodic sensor signal indicating the rotation of the rotating object. The rotating object may be attached to a wheel of a vehicle so that the rotation of the wheel may be detected and so that the output of the magnetic field sensor may be indicative for the wheel speed. Such rotation angle sensors may be regarded as representing wheel speed sensors.

Rotation angle sensors may generate output signals according to different signal protocols. In a so-called AK protocol, at each zero crossing of a periodic sensor signal a pulse pattern is generated. In a so-called high-resolution AK protocol, a pulse pattern is generated each time the periodic sensor signal passes one of a number of thresholds. The pulse pattern may include a first pulse of a larger amplitude and a number of information bits representing pulses of a lower amplitude. Ina so called PWM protocol (PWM=pulse width modulation), pulses of different widths may be generated each time the periodic sensor signal passes one or more thresholds. Independent of the protocol used, the pulse pattern may include information on the direction of the detected rotation.

SUMMARY

It would be desirable to make rotation angle sensors more robust with respect to vibrations.

Examples of the present disclosure provide an apparatus for generating an output signal based on a periodic sensor signal representing a varying rotation angle detected by a rotation angle sensor, the apparatus being configured to:

compare the periodic sensor signal to a number of thresholds to detect threshold crossings of the periodic sensor signal;

generate the output signal including a pulse pattern at the time of a threshold crossing if the direction of rotation has not changed since an immediately preceding threshold crossing; and

generate the output signal not including a pulse pattern at the time of the threshold crossing if the direction of rotation has changed since the immediately preceding threshold crossing.

Examples of the present disclosure provide an apparatus for determining whether an update of an offset register of a rotation angle sensor is to be performed, the apparatus being configured to:

compare a periodic sensor signal of the rotation angle sensor to a number of thresholds to detect threshold crossings of the periodic sensor signal;

count a number of consecutive threshold crossings which take place without a change in the direction of rotation;

decide that an update of the offset register is not to be performed if the number of consecutive threshold crossings which take place without a change in the direction of rotation is less than the number of thresholds; and

decide that an update of the offset register is to be performed if the number of consecutive threshold crossings which take place without a change in the direction of rotation is equal to or higher than the number of thresholds.

Examples of the present disclosure permit the output signal of a rotation angle sensor to be robust against vibrations of an amplitude lower than a specific amplitude. To be more specific, in examples pulse patterns, so-called protocols, in the output signals are prevented if a rotation does not cause the periodic signal to pass more than one threshold in the same direction. In examples, offset correction of the rotation angle sensor may be made robust against vibrations by performing an update of an offset register only if a number of consecutive threshold crossings which take place without a change in the direction of rotation is equal to or higher than the number of thresholds to which the periodic signal is compared. In other words, an update of the offset register is not performed if there was not a movement of a full magnetic period in one direction.

