JP3391646B2 - Position detection device with error correction function - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a rotational position detecting device used for detecting the rotational position and rotational speed of a spindle 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 detection principle of a conventional rotational position detecting device. In the figure, reference numeral 1 denotes a gear attached to a rotary detection body such as a rotary shaft, which is generally made of a magnetic material such as iron. Reference numeral 2 denotes a sensor, which is composed of a magnetoresistive element and a bias magnet, and when the gear 1 rotates, changes in magnetic flux generated based on its teeth are output as electrical signals x and y. These electrical signals x and y are generally two-phase alternating current signals, and
And expressed as in Equation 2.

[Equation 1] x = V · sin θ + Va

## EQU00002 ## y = V.cos.theta. + 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. θ 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 Equation 3 below.

[Equation 3] θ = n · φ

These two-phase signals x and y are respectively A /
Instantaneous value (x, y) by the D converters 3a and 3b
Is 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 ignored, and the output of the divider 6 at this time is expressed as follows.

## EQU00004 ## x / y = sin .theta. / Cos .theta. = Tan .theta. The output of the divider 6 is the inverse of the tan function converted by the converter 7, and the rotational position .theta. Is detected as follows.

[Equation 5] θ = tan ⁻¹ (x / y) = tan ⁻¹ (tan θ)

The rotational position θ detected as described above is a minute position with one tooth of the gear 1 as 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 the rotational position θ of 1
The upper digit ud of the rotational position in the range exceeding the cycle is detected.
This upper rotational position digit ud and the above rotational position θ are added by the adder 8
Is added to obtain the rotational position detection value φ over the entire circumference of the gear 1. Incidentally, the portion indicated by the dotted line in FIG. 5 is generally processed by software using a microprocessor or the like.

[0005]

In the above-described rotational position detecting device, the DC components Va and Vb contained in the two-phase signal are ignored, but the output signal of a general sensor is generated by a temperature change or the like. DC component to
Therefore, an error occurs in the position detection value. To solve such a problem, the present applicant has already proposed in JP-A-3-54416 a position detecting device for detecting and correcting a DC component contained 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 when detecting the DC component are used.
For each of 4), if the amplitude V is not the same, the direct current component cannot be detected accurately. However, since the signal amplitude of the output signal of a general sensor changes in inverse proportion to the distance between the gear and the sensor, when the gear is mounted eccentrically with respect to the rotation shaft, the amplitude V changes depending on the rotation. It will change. On the other hand, in the above-mentioned conventional position detecting device, since the change in the amplitude V is not taken into consideration when extracting the instantaneous values (x1, y1) to (x4, y4) of the two-phase signal, the gear is biased. If so, 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 under the circumstances as described above, and an object of the present invention is to always accurately detect a DC component even when the amplitude of a two-phase signal changes due to eccentricity of a gear. As a result, it is an object of the present invention to provide a position detection device with an error correction function that can perform accurate position detection.

[0007]

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

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the position detecting device of the present invention, a plurality of instantaneous values (x1, y1), (x2, y2), which are three or more different points on the circumference, which is the locus of a two-phase signal, are used. ), for each of (x3, y3), sum of squares R1 = x1 ² + y1 ² , R2 = x2 ² + y2 ² , R3 = x3 ² + y3 ^{2 in} which the amplitude fluctuation detection section represents the radius of the circle. If the gear is eccentric, the sum of squares R1, R2, R3
The fluctuation of the amplitude V is detected by utilizing the fact that the difference between the two becomes large. When the fluctuation of the amplitude V is detected, the DC component detecting unit predicts that the DC component detecting value cannot output an accurate DC component detecting value, and the DC component holding unit detects the DC component detecting value V.
Holds a and Vb. As a result, it is possible to correct the two-phase signal by 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 of 1 are given the same reference numerals, and the description thereof will be omitted to avoid duplication. The instantaneous value holding unit 9 calculates four sets of instantaneous values (x1, y1) from the instantaneous values (x, y) of the two-phase signals output from the A / D converters 3a and 3b based on the calculation of the following equation 6. (x2, y2), (x3, y3), (x4, y
4) is extracted and stored in 4 buffers. It should be noted that the buffer may be a memory or the like when a data register, a microprocessor, or the like is used in a specific embodiment.

(6) (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 extracted by the above equation 6
1), (x2, y2), (x3, y3), and (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 8 areas, which are not adjacent 4
This is an algorithm that extracts the instantaneous values of two areas. By extracting the instantaneous values of the areas that are not adjacent to each other in this way, it is possible to ensure the accuracy in the DC component calculation described later. Note that, based on the calculation of the following Expression 7 in addition to the above Expression 6, the instantaneous value of the area not shown in FIG. 2 can be extracted, but the contents are completely equivalent.

(7) (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
1), (x2, y2), (x3, y3), (x4, y4), the DC component detecting unit 10 calculates the DC component Va included in the two-phase signal based on the following equations 8 and 9: , Vb is calculated.

[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)}]

[Expression 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 above operation connects the line segment connecting the point (x1, y1) and the point (x3, y3) and the line segment connecting the point (x2, y2) and the point (x4, y4). This is a calculation for obtaining the coordinates of the intersection of the vertical bisectors of each line segment, and the obtained coordinate point (Va, Vb) is the center point of the circle in FIG. 2 and coincides with the DC component of the two-phase signal.

As shown in FIG. 2, the calculation by the above equations 8 and 9 is correct when the points (x1, y1) to (x4, y4) are all present on the same circumference. Can be asked.
However, when the gear 1 shown in FIG. 1 is mounted eccentrically with respect to the rotating shaft, the amplitude of the two-phase signal changes due to the change in the distance between the sensor 2 and the gear 1.
When the amplitude changes in this way, as shown in FIG.
The instantaneous value holding unit 9 holds the instantaneous values on the circumferences having different radii, and at this time, the DC component detecting unit 10 cannot accurately find the center point of the circle. Therefore, 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 formula 10. Calculates the sum.

[Equation 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 less than a predetermined allowable value. If the difference exceeds the allowable value, it is determined that the amplitude fluctuates, and the DC component holding signal dh is output. Here, the allowable value is determined based on the maximum value of the assumed DC components Va and Vb, and as an example, the maximum value of 2
Set about double. An operation of outputting the holding signal dh,
That is, the configuration of the amplitude fluctuation detecting section 11 is as shown in the block diagram of FIG. That is, the multiplier 12a
.About.12h calculate the squares of x1 to y4, and adders 13a to 13d add the squares of the x component and the square of the y component, respectively, to calculate the sum of squares R1 to R4 of the radii. The subtracters 14a to 14c calculate the mutual difference of the sums of squares R1 to R4 of the radius. For example, the subtracter 14a calculates R1 calculated by (x1, y1) and R4 calculated by (x4, y4). The difference D1 from Next, the comparators 15a to 15
In c, it is compared with the reference voltage 16 whether or not the mutual differences D1 to D3 of R1, R2, R3 and R4 output from the subtractors 14a to 14c are equal to or more than a predetermined value corresponding to the predetermined allowable value. Judge by In the embodiment of FIG. 4, the output logic of the comparators 15a to 15c indicates that the difference between them is less than a predetermined value when it is "1" and is more than the predetermined value when it is "0". The outputs of these comparators 15a-15c are set to N
The AND circuit 17 logically synthesizes and outputs a holding signal dh when at least one of the differences D1 to D3 among R1, R2, R3, and R4 is a predetermined value or more.

The DC component holding unit 18 is realized by a sample and hold circuit, and when the holding signal dh output from the amplitude fluctuation detecting unit 11 is "0", the DC component detecting unit 1 is used.
The detected DC components Va and Vb of 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 continuously used as it is. Since the DC component contained in the two-phase signal is generally caused by a temperature change or the like, it does not change rapidly 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 from the subtracters 19a and 19a.
When the correction is performed by subtracting from the two-phase AC signal in b, the DC component contained in the equations 1 and 2 disappears, and an ideal two-phase AC signal containing no DC component can be obtained. In addition, in FIG. 1, a portion indicated by a dotted line is
It can also be realized 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 changes due to the gear being mounted eccentrically with respect to the rotating shaft, the DC component contained in the two-phase signal is not detected inaccurately,
The DC component can always be corrected accurately to detect the position, and a highly accurate position detection device can be realized.

[Brief description of 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 the principle of DC component detection.

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

FIG. 4 is a block diagram showing 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 a conventional technique.

[Explanation of symbols]

1 gear 2 sensors 3 A / D converter 4 comparator 5 counter circuit 6 divider 7 converter 8 adder 9 Instantaneous value storage 10 DC component detector 11 Amplitude fluctuation detector 12 multiplier 13 adder 14 Subtractor 15 Comparator 16 Reference voltage 17 NAND circuit 18 DC component holder

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01D 5/00-5/62 G01B ⁷ /00-7/34 G01P 1/00-3/80

Claims (2)

(57) [Claims] 1. A two-phase signal x = V.cos.theta. + Va, which has a predetermined phase depending on the position of an object to be detected, and has a phase difference of 90 degrees from each other.
In a position detection device that detects the position of the detected object using y = V · sin θ + Vb, instantaneous values (x1, y1), (of four different points on the circumference of the locus of the two-phase signal) x2, y2), (x3, y3), (x4,
y4) and the instantaneous value holding unit that holds the instantaneous value (x1, y1), (x2, y2), (x3, y3) because the DC component of the two-phase signal and the center of the circle of the locus coincide with each other. ), (x4, y4), the DC component detection unit that calculates the DC component detection value Va, Vb as the center of the circle of the locus, the DC component holding unit that holds the DC component detection value Va, Vb, the Instantaneous value (x1, y1), (x2, y2), (x3, y3),
For each of (x4, y4), the sum of squares representing the radius of the circle R1 = x1 ² + y1 ² , R2 = x2 ² + y2 ² , R3 = x3 ² + y3 ² , R4 = x4 ² + y4 ² If the mutual difference of the sum of squares R1, R2, R3, R4 is greater than or equal to a predetermined value, an amplitude fluctuation detection unit that outputs a holding signal to the DC component holding unit, and the DC DC component detection values Va and Vb held by the component holding unit and the above-mentioned 2
A position detection device with an error correction function, comprising a position detection unit that detects the position of the detected object based on a difference signal from a phase signal. 2. The position detecting device with an error correcting function according to claim 1, wherein the instantaneous value holding unit calculates the instantaneous values x and y of the two-phase signals from (x1, y1) to x ≧ 0 and y ≧. 0 and | x | ≧ | y |, (x
2, 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
Operation consisting of |, or (x1, y1) is x ≧ 0 and y ≧ 0 and | x
| <| Y |, (x2, y2) is x ≧ 0 and y <0 and | x | ≧ | y |, (x3, y3)
X <0 and y <0 and | x | <| y |, (x4, y4) is x <0 and y ≧ 0
And the instantaneous values (x1, y1) to (x of the two-phase signals, which are different points on the circumference of the locus, based on the calculation of | x | ≧ | y |
A position detection device with an error correction function, which is characterized by extracting and retaining (4, y4).