Patent ID: 7233139
Filing Date: 2007-06-19
Classification: G01D

Abstract:
1. An angular position sensor for sensing an angle of rotation of a target object, the angular position sensor comprising: magnetic field generator means for producing a magnetic field; and magnetic sensor means having a first magnetic sensor element, a second magnetic sensor element, and a third magnetic sensor element each for providing an output signal depending on a direction of the magnetic field, computing means for calculating the angle of rotation of the target object based on output signals of the three magnetic sensor elements, wherein one of the magnetic field generator means and the magnetic sensor means rotates in conjunction with the target object, the first, second, and third magnetic sensor elements are located so as to provide output signals having different phase differences by allowing the magnetic sensor means to rotate relative to the magnetic field generator means, and the first, second, and third magnetic sensor elements are located based on predetermined angular relationships therebetween such that each magnetic sensor element outputs an output signal having a phase different from an inverted phase of an output signal of any other magnetic sensor element; the computing means determines an offset by which an output from each of the magnetic sensor elements is corrected to zero when the magnetic field is absent, and the computing means makes a correction to a gain of an output from at least one of the first magnetic sensor element and the second magnetic sensor element so that the outputs from the first magnetic sensor element and the second magnetic sensor element coincide with each other at a rotational angular position of the target object at which the third magnetic sensor element provides an output of zero when the magnetic field is present, the correction being made in accordance with an ideal output ratio between the outputs from the first magnetic sensor element and the second magnetic sensor element, the ideal output ratio being defined by an angle between the first magnetic sensor element and the third magnetic sensor element and by an angle between the second magnetic sensor element and the third magnetic sensor element with respect to a rotational direction of the target object; and the computing means calculates an angle of rotation of the target object through a trigonometric inverse operation in accordance with the offset-corrected and gain-corrected outputs from the first and second magnetic sensor elements.