Angle detection method and angle detection device

An angle detection device that detects a mechanical angle of a rotation shaft, the angle detection device comprising:

• three magnetic sensors configured to detect a change in magnetic flux due to rotation of the rotation shaft;
• and
• a signal processing unit configured to process signals output from the three magnetic sensors, wherein
• the signal processing unit is configured to execute:
• acquiring signals output from the three magnetic sensors as sensor signals, the three sensor signals having a phase difference of 120° in an electrical angle from each other;
• extracting an intersection point at which two sensor signals among the three sensor signals intersect with each other and a zero-cross point at which each of the three sensor signals intersect with a reference signal level over one mechanical angle cycle;
• generating a linear function θ(Δx) representing a straight line connecting the intersection point and the zero-cross point adjacent to each other, wherein Δx is a length from a start point of the straight line to an arbitrary point on the straight line, and θ is a mechanical angle corresponding to an arbitrary point on the straight line;
• calculating, as a first angle error, a deviation between a mechanical angle θ calculated based on the linear function θ(Δx) and a mechanical angle Ve acquired from an encoder installed on the rotation shaft for a plurality of points on the straight line;
• storing the first angle error calculated for a plurality of points on the straight line as a learned value;
• and
• generating a first angle error function for calculating the first angle error corresponding to an arbitrary point on the straight line based on the first angle error calculated for a plurality of points on the straight line,
• wherein the first angle error function is expressed by the following expression,
• θ
• err
• =
• θ
• err
• ⁡
• (
• k
• +
• 1
• )
• -
• θ
• errk
• x
• norm
• 8
• ×
• (
• x
• -
• k
• ⁢
• x
• norm
• 8
• )
• +
• θ
• errk
• wherein,
• k is numbers from 0 to 8 assigned to nine attention points among the plurality of points on the straight line,
• Xnorm is a length from the 0th attention point to the 8th attention points,
• x has the same meaning as Δx, and is the length from the start point of the straight line to the arbitrary point on the straight line,
• θerr is the first angle error,
• θerr (k+1) is the first angle error at (k+1)th attention point,
• θerr k is the first angle error at kth attention point.