Patent ID: 9518844
Filing Date: 2016-12-13
CPC Classification: G01D

Claim Text:
1. A rotation angle detection device comprising: a detection rotor rotating in accordance with rotation of a rotating body and provided with a plurality of magnetic poles; a first magnetic sensor outputting, in accordance with the rotation of the detection rotor, a first output signal that is a sinusoidal signal serving as a reference; and a second magnetic sensor outputting, in accordance with the rotation of the detection rotor, a second output signal that is a sinusoidal signal having a predetermined phase difference with respect to the first output signal; and detecting a rotation angle of the rotating body based on the first output signal and the second output signal of the first magnetic sensor and the second magnetic sensor, the rotation angle detection device further comprising: a memory configured to store angular widths of the plurality of magnetic poles measured in advance; and one or more processors programmed to: set, for each magnetic pole pair of the plurality of magnetic poles, a division corresponding to an angular width of the magnetic pole pair, identify, based on the first output signal, a magnetic pole sensed by the first magnetic sensor, compute, based on the first output signal, a first rotation angle that is a rotation angle within the division, compute, based on the second output signal, a second rotation angle that is a rotation angle within the division, compute a first absolute rotation angle of the detection rotor based on the computed first rotation angle, the angular widths of the plurality of magnetic poles stored in the memory, and the identified magnetic pole, compute a second absolute rotation angle of the detection rotor based on the computed second rotation angle, the angular widths of the plurality of magnetic poles stored in the memory, and the identified magnetic pole, and compute a rotation angle of the rotating body based on the computed first absolute rotation angle and the computed second absolute rotation angle, wherein the phase difference between the first output signal and the second output signal is 90°, the first rotation angle is computed based on the first output signal and a polarity of the second output signal, the second rotation angle is computed based on the second output signal and a polarity of the first output signal, and the one or more processors are further programmed to: compute the rotation angle of the rotating body based on the computed second absolute rotation angle when an absolute value of the first output signal is greater than or equal to a predetermined value, compute the rotation angle of the rotating body based on the computed first absolute rotation angle when an absolute value of the second output signal is greater than or equal to the predetermined value, and compute the rotation angle of the rotating body based on one of either or both of the computed first absolute rotation angle and the computed second absolute rotation angle when both the absolute value of the first output signal and the absolute value of the second output signal are less than the predetermined value.