This application is based upon and claims the benefit of priority from prior Japanese patent application No. 2018-194096, filed on Oct. 15, 2018, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a rotation angle detection device, a rotation angle detection method and a program.

2. Related Art

In the related art, known is a device having a magnetic field generation unit provided on a rotating body, and configured to detect a rotation angle of the rotating body, based on magnetic field components measured around the rotating body (for example, Patent Document 1).

Patent Document 1: Japanese Patent No. 6,191,840B

SUMMARY

In the rotation angle detection device, the rotation angle is corrected, based on error information about the rotation angle acquired in advance. For this reason, it is preferably to acquire the error information about the rotation angle with accuracy.

In order to solve the above problem, a first aspect of the present invention provides a rotation angle detection device configured to detect a rotation angle of a magnetic field generation source, based on a magnetic field in at least two directions detected by a magnetic field detection device. The rotation angle detection device may include a correction value calculation unit configured to calculate a correction value of the rotation angle. The rotation angle detection device may include an angle output unit configured to output an angle output signal indicative of the rotation angle of the magnetic field generation source, based on a magnetic field detection signal to be output from the magnetic field detection device and the correction value. The rotation angle detection device may include a filter unit capable of selecting a first filter characteristic, which is to be used for outputting the angle output signal, and a second filter characteristic, which is to be used for calculating the correction value and is different from the first filter characteristic.

A band of the first filter characteristic through which a signal is to pass may be narrower than a band of the second filter characteristic through which a signal is to pass.

The angle output unit may include a first computing unit configured to output a first computing signal corresponding to the magnetic field detection signal. The angle output unit may include an angle update unit configured to output the angle output signal, based on the first computing signal. The angle output unit may include a feedback unit configured to generate a magnetic field correction signal and to output the same to the first computing unit. The filter unit may be configured to input a signal, which is to be obtained by filtering an output from the first computing unit, to the angle update unit. When the rotation angle detection device calculates the correction value, the first computing unit may be input with the magnetic field detection signal and may output the first computing signal. The angle update unit may be input with a signal filtered using the second filter characteristic and may generate an uncorrected angle signal. The correction value calculation unit may calculate the correction value, based on the uncorrected angle signal. When the rotation angle detection device generates the angle output signal, the first computing unit may be input with the magnetic field detection signal and the magnetic field correction signal and may output the first computing signal. The angle update unit may be input with a signal filtered using the first filter characteristic and may generate the angle output signal. The feedback unit may calculate the magnetic field correction signal by inputting the angle output signal and the correction value, and feed the same back to the first computing unit.

The angle output unit may include an angle computing unit configured to output an angle signal, which corresponds to a magnetic field detection signal corresponding to a magnetic field detected by the magnetic field detection device and the correction value. The correction value calculation unit may be configured to calculate a correction value, based on the angle signal output by the angle computing unit without using the correction value. When calculating a correction value of the rotation angle, the filter unit may input a signal, which is obtained by filtering the angle signal by using the second filter characteristic, to the correction value calculation unit. When generating the angle output signal by using the correction value, the filter unit may output a signal, which is obtained by filtering the angle signal by using the first filter characteristic, as the angle output signal.

The angle output unit may include an angle computing unit configured to output an angle output signal, based on a magnetic field detection signal corresponding to a magnetic field detected by the magnetic field detection device. The correction value calculation unit may be configured to calculate a correction value, based on the angle output signal output by the angle computing unit without using the correction value. When calculating the correction value, the filter unit may input a signal, which is obtained by filtering the magnetic field detection signal by using the second filter characteristic, to the angle computing unit. When generating the angle output signal by using the correction value, the filter unit may input a signal, which is obtained by filtering the magnetic field detection signal by using the first filter characteristic, to the angle computing unit.

The correction value calculation unit may be configured to calculate a correction value, based on the angle output signal generated by the angle update unit without using the correction value, and a reference angle signal having passed through a filter having a preset delay characteristic.

A second aspect of the present invention provides a rotation angle detection method of detecting a rotation angle of a magnetic field generation source, based on a magnetic field in at least two directions detected by a magnetic field detection device. The method may include correction value calculating of calculating a correction value of a rotation angle, based on a signal having passed through a filter unit for which a second filter characteristic is selected in the filter unit in which a first filter characteristic and the second filter characteristic different from the first filter characteristic can be selected. The method may include angle outputting of outputting an angle output signal indicative of a rotation angle of the magnetic field generation source, based on a signal having passed through the filter unit for which the first filter characteristic is selected and the correction value.

A third aspect of the present invention provides a program for causing a computer to execute the rotation angle detection method in accordance with the second aspect.

A third aspect of the present invention provides a program for causing a computer to execute the rotation angle detection method in accordance with the second aspect.

In the meantime, the summary of the present invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above.

