Rotation angle detection device and electric power steering system

摘要

Bridge circuits have half bridges formed of sensor elements, which vary respective impedances in accordance with a rotating magnetic field generated by a rotary object. A control unit acquires output signals produced from intermediate points of the half bridges, and calculates a rotation angle of the rotary object based on the output signals. The control unit determines that the output signal is abnormal, if a calculation value of the output signal calculated based on at least four output signals is outside a predetermined range. The control unit thus determines which one of the output signals has become abnormal due to failure or the like.

主权项

1. A rotation angle detection device comprising:
a plurality of bridge circuits including a plurality of half bridges, each of the half bridges including a sensor element varying an impedance thereof in response to rotating magnetic field generated by rotation of a reference part and the half bridges generating output signals from intermediate points, respectively; and a control unit including a signal acquisition section for acquiring the output signals of the bridge circuits, a rotation angle calculation section for calculating a rotation angle of the reference part based on the output signals acquired by the signal acquisition section, and an abnormality determination section for determining an abnormal signal, which is one of the output signals having abnormality, wherein the signal acquisition section acquires at least four output signals, which include sine-system signals, which are a sine signal and a −sine signal, and cosine-system signals, which are a cosine signal and a −cosine signal, wherein the abnormality determination section calculates calculation values by using the at least four output signals and determines the abnormal signal among the output signals, the abnormal signal causing the calculation value to be outside a predetermined range, and wherein the rotation angle calculation section calculates the rotation angle of the reference part based on the sine-system signals and the cosine-system signals, which are other than the abnormal signal, wherein: the abnormality determination section calculates a plurality of first values, which comprise at least four square values of the output signals so that the square values of the sine signal, the −sine signal, the cosine signal and the −cosine signal are each calculated and calculates a plurality of second values by adding two of the first values so that the plurality of second values comprise at least four sum values; the abnormality determination section determines the abnormal signal based on by which one of the output signals the second value is caused to be outside the predetermined range; and wherein the abnormality determination section determines the abnormal signal based on which one of the four square values causes two of the four sum values to be outside the predetermined range.