JPH10227657A - Position detector with error correction function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constantly detect a DC component and to detect a position accurately by utilizing a property that the mutual difference between square sums indicating the radius of a circle increases in the case of a gear eccentricity and adding a correction to a bi-phase signal using only an accurate DC component detection value when the amplitude fluctuation is small. SOLUTION: When a retention signal dh of the output of an amplitude fluctuation detection part 11 is zero, DC components Va and Vb detected by a DC component detection part 10 are outputted as they are. When hen the retention signal dh is 1, DC components Va and Va immediately before are retained and continue to be outputted. As a result, when the amplitudes of bi-phase signals (x) and (y) fluctuate and an operation for detecting the DC components Va and Vb becomes inaccurate, a DC component that is detected by an operation immediately before continues to be used. Then, by performing a correction by subtracting DC components Va and Vb outputted from the DC component retention part 18 using substracting 19a and 19b, an ideal bi-phase AC signal that does not contain any DC component can be obtained without any DC component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a rotational position detecting device used for detecting a rotational position and a rotational speed of a main shaft of a machine tool, and more particularly to a position detecting device having an error correcting function.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing the principle of detection of a conventional rotational position detecting device. In the figure, reference numeral 1 denotes a gear attached to a detection body such as a rotating shaft, which is generally made of a magnetic material such as iron. Reference numeral 2 denotes a sensor, which includes a magnetoresistive element and a bias magnet, and outputs a change in magnetic flux generated based on the teeth of the gear 1 as the gear 1 rotates as electric signals x and y. These electric signals x and y are generally two-phase AC signals,
And Equation 2.

X = V · sin θ + Va

Y = V · cos θ + Vb where V is the amplitude of the two-phase signal, Va is the DC component included in the signal x, and Vb is the DC component included in the signal y. is the phase of the two-phase signal, and when the rotation angle of the gear 1 is φ and the number of teeth of the gear 1 is n, the phase θ is expressed by the following equation (3).

[Equation 3] θ = n · φ

[0003] These two-phase signals x and y are A /
Instantaneous value (x, y) by D converters 3a and 3b
And input to the divider 6. In the conventional general rotational position detecting device, the DC components Va and Vb shown in the above equations (1) and (2) are neglected. At this time, the output of the divider 6 is expressed as follows.

X / y = sin θ / cos θ = tan θ The output of the divider 6 is inversely converted from the tan function by the converter 7, and the rotational position θ is detected as follows.

## EQU5 ## θ = tan ^-1 (x / y) = tan ^-1 (tan θ)

The rotational position θ detected as described above is a minute position where one tooth of the gear 1 has one cycle. On the other hand, the two-phase signals x and y are converted into pulse signals by the comparators 4a and 4b and input to the counter circuit 5. The counter circuit 5 counts the pulse signals xa and ya to obtain 1 of the rotational position θ.
The upper digit ud of the rotational position exceeding the period is detected.
The upper digit ud of the rotational position and the rotational position θ are added by an adder 8.
And the rotational position detection value φ over the entire circumference of the gear 1 is obtained. Generally, a portion indicated by a dotted line in FIG. 5 is processed by software using a microprocessor or the like.

[0005]

In the above-described rotational position detecting device, the DC components Va and Vb included in the two-phase signal are neglected, but the output signal of a general sensor is generated due to a temperature change or the like. DC component
This causes an error in the position detection value. With respect to such a problem, the present applicant has already proposed in Japanese Patent Application Laid-Open No. 3-54416 a position detecting device for detecting and correcting a DC component included in a two-phase signal. In such a conventional position detecting device, the amplitude V of the two-phase signal is assumed to be constant, and the instantaneous values (x1, y1) to (x4, y) of the two-phase signal used for detecting the DC component are used.
Unless the amplitudes V are equal for each of 4), accurate detection of a DC component cannot be performed. However, since the signal amplitude of a general sensor output signal changes in inverse proportion to the distance between the gear and the sensor, when the gear is mounted eccentrically with respect to the rotation axis, the amplitude V is changed according to the rotation. Will change. On the other hand, in the above-described conventional position detection device, when extracting the instantaneous values (x1, y1) to (x4, y4) of the two-phase signal, the change in the amplitude V is not considered at all, so that the gear is biased. If the user is in mind, a set of instantaneous values having different amplitudes V is extracted, so that the detected value of the DC component becomes inaccurate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to always accurately detect a DC component even when the amplitude of a two-phase signal fluctuates due to gear eccentricity. As a result, an object of the present invention is to provide a position detection device with an error correction function capable of performing accurate position detection.

[0007]

According to the present invention, two-phase signals x = V.cos .theta. + Va, y = V having predetermined phases according to the position of the object to be detected and having mutually different phases by 90 degrees. The present invention relates to a position detecting device that detects the position of the object using sin θ + Vb. The object of the present invention is to provide an instantaneous value of at least three or more different points on the circumference of the locus of the two-phase signal. (x1, y1), (x2, y2),
(x3, y3), and the instantaneous value (x1, y1), (x2, y2), (x x3, y3), a DC component detection unit that calculates DC component detection values Va, Vb as the center of the trajectory circle, a DC component holding unit that holds the DC component detection values Va, Vb, and the instantaneous value ( x1, y1), (x2, y2), for each of (x3, y3), the sum of squares R1 = x1 ² + y representing the radius of the circle
1 ² , R2 = x2 ² + y2 ² , R3 = x3 ² + y3 ² and sum of squares R1, R2, R3
When the mutual difference is equal to or more than a predetermined value, an amplitude fluctuation detection unit that outputs a holding signal to the DC component holding unit, and the DC component detection values Va and Vb held by the DC component holding unit.
This is achieved by providing a position detection unit that detects the position of the object to be detected based on a difference signal between the two-phase signal and the two-phase signal.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a position detecting apparatus according to the present invention, a plurality of instantaneous values (x1, y1), (x2, y2), which are three or more different points on the circumference of a locus of a two-phase signal, are described. ), (against x3, y3) respectively, the sum of squares amplitude variation detecting section represents a radius of the circle ^{R1 = x1 2 + y1 2,} R2 = x2 2 + y2 2, R3 = x3 2 + y3 2 If the gear is eccentric, the sum of squares R1, R2, R3
Of the amplitude V is detected by utilizing the fact that the difference between the two becomes larger. When a change in the amplitude V is detected, the DC component detection unit predicts that the DC component detection unit cannot output an accurate DC component detection value, and the DC component holding unit sets the DC component detection value V
hold a and Vb. As a result, the two-phase signal can be corrected using only the accurate DC component detection value calculated when the fluctuation of the amplitude V is small.

FIG. 1 is a block diagram showing an embodiment of a position detecting device with an error correcting function according to the present invention.
The same components as those of the conventional position detecting device are denoted by the same reference numerals, and the description thereof will not be repeated. The instantaneous value holding unit 9 obtains four sets of instantaneous values (x1, y1), based on the following equation 6 from the instantaneous values (x, y) of the two-phase signals output from the A / D converters 3a and 3b. (x2, y2), (x3, y3), (x4, y
4) is extracted and held in four buffers. In a specific embodiment, when a data register, a microprocessor, or the like is used, a memory can be used as the buffer.

(X1, y1) is x ≧ 0 and y ≧ 0 and | x | ≧ | y | (x2, y2) is x ≧ 0 and y <0 and | x | <| y | (x3, y3 ) Is x <0 and y <0 and | x | ≧ | y | (x4, y4) is x <0 and y ≧ 0 and | x | <| y |

The instantaneous value (x1, y
1), (x2, y2), (x3, y3), (x4, y4) are represented as points on the circumference which is the locus of the two-phase signal as shown in FIG. That is,
Divide the circumference into eight areas, of which four are not adjacent
This is an algorithm that extracts instantaneous values of two regions. By extracting the instantaneous values of the non-adjacent areas in this way, it is possible to ensure the accuracy in the DC component calculation described later. It should be noted that, based on an operation such as the following equation 7 in addition to the above equation 6, an instantaneous value in an area not shown in FIG. 2 can be extracted, but the contents are completely equivalent.

(X1, y1) is x ≧ 0 and y ≧ 0 and | x | <| y | (x2, y2) is x ≧ 0 and y <0 and | x | ≧ | y | (x3, y3 ) Is x <0 and y <0 and | x | <| y | (x4, y4) is x <0 and y ≧ 0 and | x | ≧ | y |

The instantaneous value (x1, y) held in the instantaneous value holding unit 9
Using (1), (x2, y2), (x3, y3), and (x4, y4), the DC component detection unit 10 calculates the DC component Va included in the two-phase signal based on the calculation of Expressions 8 and 9 below. , Vb.

[Equation 8] Va = 1/2 · [{(x1 ² -x3 ² ) (y2-y4)-(x2 ² -x4 ² ) (y1-y3)
+ (y2-y4) (y1-y3) (y1 + y3-y2-y4)} / {(x1-x3) (y2-y4)-(x2-
x4) (y1-y3)}]

[Equation 9] Vb = 1/2 · [{(y2 ² -y4 ² ) (x1-x3)-(y1 ² -y3 ² ) (x2-x4)
+ (x2-x4) (x1-x3) (x2 + x4-x1-x3)} / {(x1-x3) (y2-y4)-(x2-
x4) (y1-y3)}] In FIG. 2, the line segment connecting the point (x1, y1) and the point (x3, y3) and the point (x2, y2) and the point (x4, y4) in FIG. This is an operation to obtain the intersection coordinates of the vertical bisectors of the line segments, and the obtained coordinate points (Va, Vb) are the center points of the circle in FIG. 2 and coincide with the DC components of the two-phase signal.

As shown in FIG. 2, when the points (x1, y1) to (x4, y4) are all present on the same circumference, the calculation based on the above equations (8) and (9) is correctly performed. Can be requested.
However, when the gear 1 shown in FIG. 1 is mounted eccentrically with respect to the rotation shaft, the amplitude of the two-phase signal changes due to a change in the interval between the sensor 2 and the gear 1.
When the amplitude changes in this way, as shown in FIG.
The result is that the instantaneous value holding unit 9 holds the instantaneous values on the circumferences having different radii. At this time, the DC component detection unit 10 cannot correctly obtain the center point of the circle. For this reason, in the present invention, the amplitude fluctuation detection unit 11 uses the instantaneous values (x1, y1) to (x4, y4) held in the instantaneous value holding unit 9 to calculate the square of the radius of the circle by the following equation (10). Calculate the sum.

[Number 10] ^{R1 = x1 2 + y1 2 R2} = x2 2 + y2 2 R3 = x3 2 + y3 2 R4 = x4 2 + y4 2

Using R1 to R4 calculated by the above equation (10),
It is determined whether or not the difference between them is equal to or less than an allowable value. If the difference exceeds the allowable value, it is determined that the amplitude has fluctuated, and a DC component holding signal dh is output. The operation of outputting the holding signal dh, that is, the configuration of the amplitude fluctuation detecting unit 11 is as shown in the block diagram of FIG.
That is, the squares of x1 to y4 are calculated by the multipliers 12a to 12h, and the squares of the x component and the y component are added by the adders 13a to 13d, respectively, and the sum of squares of the radius is calculated.
Calculate R1 to R4. The subtractors 14a to 14c calculate the difference between the sums of the squares of the radii R1 to R4.For example, the subtractor 14a calculates R1 calculated by (x1, y1) and R4 calculated by (x4, y4). Is obtained. Next, the comparators 15a to 15c determine whether or not the difference D1 to D3 between R1, R2, R3, and R4 output from the subtracters 14a to 14c is greater than or equal to a predetermined value by comparing the difference with the reference voltage 16. In the embodiment shown in FIG.
The output logic of 15c indicates that the difference is less than a predetermined value when it is "1" and that it is more than a predetermined value when it is "0". The outputs of the comparators 15a to 15c are logically synthesized by the NAND circuit 17, and the difference D1 to D3 between R1, R2, R3, and R4 is calculated.
If at least one of them is equal to or larger than a predetermined value, the holding signal dh is output.

The DC component holding unit 18 is realized by a sample and hold circuit. When the holding signal dh output from the amplitude fluctuation detecting unit 11 is "0", the DC component detecting unit 1
The DC components Va and Vb detected as 0 are output as they are, and when the holding signal dh becomes "1", the DC components Va and Vb immediately before that are held and the output is continued. As a result, the amplitudes of the two-phase signals x and y fluctuate and the DC component Va
When the calculation for detecting Vb and Vb becomes inaccurate, the DC component detected by the immediately preceding calculation can be used as it is. Since the DC component included in the two-phase signal is generally caused by a temperature change or the like, it does not rapidly change in a short time region. Therefore, the value held by the DC component holding unit 18 may be continuously used. Next, the DC components Va and Vb output from the DC component holding unit 18 are subtracted by the subtracters 19a and 19b.
If the correction is made by subtracting from the two-phase AC signal in b, the DC components included in Equations 1 and 2 disappear, and an ideal two-phase AC signal containing no DC component can be obtained. Note that, in FIG.
It is also possible to realize by software using a microprocessor or the like.

[0015]

As described above, in the present invention,
Even when the amplitude of the two-phase signal fluctuates because the gear is mounted eccentrically with respect to the rotating shaft, the DC component included in the two-phase signal is not detected incorrectly,
The position can always be detected by accurately correcting the DC component, and a highly accurate position detecting device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment of a position detecting device according to the present invention.

FIG. 2 is a diagram for explaining a principle of detecting a DC component.

FIG. 3 is a diagram for explaining a DC component detection operation when the amplitude fluctuates.

FIG. 4 is a block diagram illustrating an internal configuration of an amplitude fluctuation detection unit.

FIG. 5 is a block diagram showing an example of a system configuration of a position detecting device according to the related art.

[Explanation of symbols]

 Reference Signs List 1 gear 2 sensor 3 A / D converter 4 comparator 5 counter circuit 6 divider 7 converter 8 adder 9 instantaneous value holding unit 10 DC component detecting unit 11 amplitude fluctuation detecting unit 12 multiplier 13 adder 14 subtractor 15 comparator 16 Reference voltage 17 NAND circuit 18 DC component holding unit

Claims (3)

[Claims] 1. A two-phase signal x = V · cos θ + Va, y having a predetermined phase and having a phase difference of 90 degrees according to the position of an object to be detected.
= V · sinθ + Vb, in the position detecting device for detecting the position of the detected object, the locus of the two-phase signal, at least three or more different points on the circumference of the instantaneous value (x1, y1), (x2, y2),
(x3, y3), and the instantaneous value (x1, y1), (x2, y2), (x x3, y3), a DC component detection unit that calculates DC component detection values Va, Vb as the center of the trajectory circle, a DC component holding unit that holds the DC component detection values Va, Vb, and the instantaneous value ( x1, y1), (x2, y2), for each of (x3, y3), the sum of squares R1 = x1 ² + y representing the radius of the circle
1 ² , R2 = x2 ² + y2 ² , R3 = x3 ² + y3 ² and sum of squares R1, R2, R3
When the mutual difference is equal to or more than a predetermined value, an amplitude fluctuation detection unit that outputs a holding signal to the DC component holding unit, and the DC component detection values Va and Vb held by the DC component holding unit.
A position detection unit for detecting a position of the object to be detected based on a difference signal between the two-phase signal and the two-phase signal. 2. The position detection device with an error correction function according to claim 1, wherein said instantaneous value holding section is configured such that (x1, y1) is x ≧ 0 and y ≧ 0 and | x | ≧ | y |, (x2, y2) is x ≧ 0 and y <0 and | x | <| y |, (x3, y3) is x <0 and y <0 and | x | ≧ | y |, (x4, y4) is an operation consisting of x <0 and y ≧ 0 and | x | <| y |, or (x1, y1) is x ≧ 0 and y ≧ 0 and | x | <| y |, (X2, y2) are x ≧ 0 and y <0 and | x | ≧ | y |, (x3, y3) are x <0 and y <0 and | x | <| y |, (x4, y4 ) Is an instantaneous value (x1, y1) to (x4) of the two-phase signal, which is a different point on the circumference of the trajectory based on the calculation of x <0 and y ≧ 0 and | x | ≧ | y | , y4) are extracted and held, and a position detection device with an error correction function is provided. 3. The position detection device with an error correction function according to claim 1, wherein the DC component detection unit performs a Va based on instantaneous values (x1, y1) to (x4, y4) of the two-phase signal. = 1/2 ・ [{(x1 ² -x3 ² ) (y2-y4)-(x2 ² -x4 ² ) (y1-y3) + (y2-y4)
(y1-y3) (y1 + y3-y2-y4)} / {(x1-x3) (y2-y4)-(x2-x4) (y1-y
3)}] Vb = 1/2 ・ [{(y2 ² -y4 ² ) (x1-x3)-(y1 ² -y3 ² ) (x2-x4) + (x2-x4)
(x1-x3) (x2 + x4-x1-x3)} / {(x1-x3) (y2-y4)-(x2-x4) (y1-y
3)}, wherein the DC component detection values Va and Vb are calculated based on the calculation consisting of: