Angle detection method and angle detection device
One aspect of an angle detection device of the present invention includes: three magnetic sensors that detect a change in magnetic flux due to rotation of a rotation shaft; and a signal processing unit that processes signals output from the three magnetic sensors. The signal processing unit acquires sensor signals output from three magnetic sensors, extracts 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, generates a linear function θ(Δx) representing a straight line connecting the intersection point adjacent to each other and the zero-cross point, calculates a deviation between a mechanical angle θ calculated based on the linear function θ(Δx) for a plurality of points on the straight line and a mechanical angle θe acquired from an encoder installed on a rotation shaft as a first angle error, and generates a first angle error function for calculating a first angle error corresponding to an arbitrary point on the straight line based on the first angle error calculated for the plurality of points on the straight line.
1 . An angle detection method for detecting a mechanical angle of a rotation shaft, the angle detection method comprising:
acquiring signals output from three magnetic sensors that detect a change in magnetic flux due to rotation of the rotating shaft as sensor signals, the three sensor signals having a phase difference of 120° in an electrical angle;
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.
2 . The angle detection method according to claim 1 , further comprising:
calculating, as a second angle error, a deviation between a value obtained by subtracting the first angle error calculated based on the first angle error function from the mechanical angle θ calculated based on the linear function θ(Δx) and the mechanical angle θe acquired from the encoder for a plurality of points on the straight line;
storing the second angle error calculated for a plurality of points on the straight line as a learned value; and
generating a second angle error function for calculating a second angle error corresponding to an arbitrary point on the straight line based on the second angle error calculated for a plurality of points on the straight line.
3 . The angle detection method according to claim 1 , wherein intervals between a plurality of points on the straight line are equal intervals.
4 . 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.
5 . The angle detection device according to claim 4 , wherein
the signal processing unit is configured to further execute:
calculating, as a second angle error, a deviation between a value obtained by subtracting the first angle error calculated based on the first angle error function from the mechanical angle θ calculated based on the linear function θ(Δx) and the mechanical angle θe acquired from the encoder for a plurality of points on the straight line;
storing the second angle error calculated for a plurality of points on the straight line as a learned value; and
generating a second angle error function for calculating a second angle error corresponding to an arbitrary point on the straight line based on the second angle error calculated for a plurality of points on the straight line.
6 . The angle detection device according to claim 4 , wherein intervals between a plurality of points on the straight line are equal intervals.