JP6204000B2 - Position detection device - Google Patents

Description

  The present invention relates to an improvement in a position detection device used for detecting a rotational position and a rotational speed of a spindle of a machine tool.

  Conventionally, a position detection apparatus as described in Patent Document 1 is known. FIG. 3 is a block diagram showing the detection principle of the position detection device disclosed in Patent Document 1. In FIG.

A gear 1 attached to a detection object such as a rotating shaft is made of a magnetic material such as iron. The sensor 2 composed of a magnetoresistive element and a bias magnet outputs a change in magnetic flux generated as a result of the rotation of the gear 1 as electric signals x and y. These electric signals x and y are generally two-phase alternating current signals and are expressed by the following equations 1 and 2.
x = V · sin θ + Va Equation 1
y = V · cos θ + Vb Equation 2

  Here, V is the amplitude of the two-phase signal, Va is a DC component included in the signal x, and Vb is a DC component included in the signal y. θ is the phase of the two-phase signal. If the rotation angle of the gear 1 is Φ and the number of teeth of the gear 1 is m, the phase θ is θ = m · Φ.

These two-phase signals x and y are converted into instantaneous values (x, y) by the A / D converters 3a and 3b, respectively, and input to the subtracters 19a and 19b and the instantaneous value holding unit 9. The instantaneous value holding unit 9 extracts four sets of instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4) that satisfy the following condition 1 or condition 2, Hold in 4 buffers.
<Condition 1>
(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 |
<Condition 2>
(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 DC component detection unit 10 extracts the DC from the four sets of instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4) extracted and held by the instantaneous value holding unit 9. Calculate the component. That is, when the amplitude V of the two-phase signal is constant and the phase θ of the x-phase and the y-phase always coincide, the locus of the two-phase signal (x, y) draws one circle and the center of the circle The coordinates are (Va, Vb). The central coordinates (Va, Vb) are perpendicular to 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). It can be obtained by calculation as the intersection of bisectors.

  When the subtractors 19a and 19b subtract the DC components Va and Vb calculated in this way from the two-phase signal, an ideal two-phase AC signal that does not include a DC component, x = V · sin θ, and y = V · cos θ. Is obtained. When this ideal two-phase AC signal is input to the divider 6, the output is x / y = sin θ / cos θ = tan θ.

The output tan θ of the divider 6 is subjected to inverse transformation of the tan function by the converter 7, and the phase θ = tan ⁻¹ (x / y) = tan ⁻¹ (tan θ) is detected. Then, the rotation angle Φ is calculated based on the obtained phase θ.

Japanese Patent No. 3391646

  Here, the technique described above is premised on the case where the amplitude V of the two-phase signal is constant and no phase difference is generated between the x-phase and the y-phase, and the locus of the two-phase signal is a circle. On the other hand, in the position detection device, the amplitude V of the two-phase signal may change with rotation due to an inclination when the detection device is attached. For example, in the sensor 2 of FIG. 3, when the sensor 2 is tilted in the direction of the arrow 2a, the amplitude of x is small and the amplitude of y is large. The locus is a vertically long ellipse. Further, when the phase θ of the two-phase signal is shifted due to displacement of the detection elements, for example, when the detection element on the y side is shifted in the direction of the arrow 2b in the sensor 2 of FIG. 3, the phase θ of y is delayed. Therefore, the locus of the two-phase signal on the plane with the horizontal axis x the vertical axis y is an ellipse inclined at 45 ° or −45 °. When the two-phase signal has both an amplitude error and a phase error, the locus becomes an ellipse having a certain inclination as shown in FIG. As described above, in the case of a two-phase signal in which the locus of the signal has an elliptical shape due to an amplitude error or a phase error, an accurate DC component cannot be obtained by the conventional method described above. In order to find the center of the ellipse as the intersection of the perpendicular bisectors from the instantaneous values of the four points on the ellipse, instantaneous values extracted at limited points such as the intersection with the major axis and minor axis of the ellipse are required. Become.

  Four sets of instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4) satisfying the conditions 1 and 2 are the instantaneous value and center of an extraction region on the ellipse of the locus. There is a possibility that the position of the instantaneous value of the region facing the center shifts from 180 ° to ± 45 °. As shown in FIG. 4, the position calculated by the instantaneous value has a large error from the center position of the ellipse.

  The present invention has been made in order to solve the above-mentioned problems, and the present invention relates to the phase error of the two-phase signal due to the amplitude error of the two-phase signal due to the inclination at the time of mounting the detector or the deviation of the arrangement of the detector elements. An object of the present invention is to provide a position detection device with an error correction function that can always detect a direct current component with high accuracy even when there is an error, and as a result, can perform accurate position detection.

The position detection apparatus of the present invention detects the position of the detection object based on the two-phase signals x = V · cos θ + Va and y = V · sin θ + Vb, which vary according to the change of the detection object and differ in phase by 90 degrees. In the position detection device, when φ is an arbitrary angle and α is a minute angle, among the instantaneous values (x, y) of the two-phase signal, φ−α ≦ tan ⁻¹ (y / x) ≦ An instantaneous value satisfying φ + α is (x1, y1), an instantaneous value satisfying φ + 90−α ≦ tan ⁻¹ (y / x) ≦ φ + 90 + α is (x2, y2), φ + 180−α ≦ tan ⁻¹ (y / x) ≦ An instantaneous value holding unit that holds an instantaneous value satisfying φ + 180 + α as (x3, y3) and an instantaneous value satisfying φ + 270−α ≦ tan ⁻¹ (y / x) ≦ φ + 270 + α as (x4, y4), and the two-phase signal The direct current coincides with the center of the circle or ellipse drawn by the locus of A direct current component detector that calculates the value of the minute (Va, Vb) based on the four sets of instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4); A position detection unit that detects the position of the detected object based on a difference signal between the DC component (Va, Vb) calculated by the DC component detection unit and the two-phase signal (x, y). It is characterized by that.

  According to the position detection device of the present invention, even when the detection device is attached so as to have an amplitude error and a phase error in the two-phase signal, the DC component included in the two-phase signal is accurately detected and corrected. A position can be detected, and a highly accurate position detection device can be realized.

It is a block diagram which shows an example of the system configuration | structure of the position detection apparatus which is embodiment of this invention. It is a figure for demonstrating the direct current | flow component detection operation in embodiment of this invention. It is a block diagram which shows an example of the system configuration | structure of the conventional position detection apparatus. It is a figure for demonstrating DC component detection operation by a prior art.

In the position detection apparatus of the present embodiment, instantaneous values (x1, y1), (x2, y2), (x3, y3), four different points on an ellipse that are loci of two-phase signals having different amplitudes and phases, By limiting the extraction region in the extraction of (x4, y4), the accuracy of detecting the DC component is increased. More specifically, when φ is an arbitrary angle, only a range of minute angles of ± α ° from each position of φ, φ + 90 °, φ + 180 °, and φ + 270 ° is limited as an extraction region. In other words, in this embodiment, (x1, y1) to (x4, y4) are extracted so that tan ⁻¹ (y / x) is shifted by 90 °. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing an example of a system configuration of a position detection apparatus according to an embodiment of the present invention. FIG. 2 is a diagram for explaining a DC component detection operation in the present embodiment.

In FIG. 1, reference numeral 1 denotes a gear attached to an object to be detected such as a rotating shaft, and is generally composed of a magnetic material such as iron. A sensor 2 includes a magnetoresistive element and a bias magnet. When the gear 1 rotates, magnetic flux changes generated based on the teeth are output as electrical signals x and y. These electric signals x and y are generally two-phase AC signals, and are expressed as x = V · cos θ + Va and y = V · sin θ + Vb .

  Here, V is the amplitude of the two-phase signal, Va is a DC component included in the signal x, and Vb is a DC component included in the signal y. θ is the phase of the two-phase signal. If the rotation angle of the gear 1 is Φ and the number of teeth of the gear 1 is m, the phase θ is θ = m · Φ.

  These two-phase signals x and y are converted into instantaneous values (x, y) by the A / D converters 3a and 3b, respectively, and input to the subtracters 19a and 19b and the instantaneous value holding unit 9.

The instantaneous value holding unit 9 sequentially calculates tan ⁻¹ (y / x) from the instantaneous values (x, y) of the respective two-phase signals that are the outputs of the A / D converters 3a and 3b. Then, four sets of instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4) when the calculated tan ⁻¹ (y / x) satisfies the following condition 3 Are stored in four buffers. In the specific embodiment, the buffer uses a memory or the like when a data register or a microprocessor is used.
<Condition 3>
(X1, y1) is φ−α ≦ tan ⁻¹ (y / x) ≦ φ + α
(X2, y2) is φ + 90−α ≦ tan ⁻¹ (y / x) ≦ φ + 90 + α
(X3, y3) is φ + 180−α ≦ tan ⁻¹ (y / x) ≦ φ + 180 + α
(X4, y4) is φ + 270−α ≦ tan ⁻¹ (y / x) ≦ φ + 270 + α

Here, the lower limit of the minute angle α for extracting at least one instantaneous value in each angle region of the above condition 3 is the angular velocity of θ when the rotational speed of the gear 1 in FIG. 1 is n (min−1). 360 × m × n / 60 = 6 mn (° / sec), and if the instantaneous value extraction cycle is T (sec), the rotation angle per one instantaneous value extraction cycle is 6 mnT °. In order for the angle to fall within the instantaneous value extraction angle region ± α °, 6 m nT ≦ 2α, that is, 3 m nT ≦ α. Further, the upper limit of α where the instantaneous value extraction areas do not overlap is 45 °, but α << 45 ° because α is a minute angle. Accordingly, the range of α can be expressed as 3 mnT ≦ α << 45 °. In order to further reduce the error, it is desirable that the value of α is as small as possible, and it is desirable that there are no instantaneous values of two or more points in one angle region. For this purpose, α is preferably smaller than 6 m nT (α < 6 m nT).

The instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4) extracted by the above condition 3 are the points on the circumference as the locus of the two-phase signal in FIG. It is expressed as follows. The diagonal line in FIG. 2 represents the angle range from which the instantaneous value is extracted. Using the instantaneous values (x1, y1), (x2, y2), (x3, y3), (x4, y4) held in the instantaneous value holding unit 9, the DC component detection unit 10 uses the following equations 3 and 4. Based on the above calculation, the DC components Va and Vb included in the two-phase signal are calculated.
Va = 1/2 · [{(x1 ² −x3 ² ) (y2−y4) − (x2 ² −x4 ² ) (y1−y3) + (y1−y3) (y2−y4) (y1 + y3−y2−y4) )} / {(X1-x3) (y2-y4)-(x2-x4) (y1-y3)}] Equation 3
Vb = 1/2 · [{(y1 ² −y3 ² ) (x2−x4) − (y2 ² −y4 ² ) (x1−x3) + (x1−x3) (x2−x4) (x1 + x3−x2−x4) )} / {(Y1-y3) (x2-x4)-(y2-y4) (x1-x3)}] Equation 4

  In the above calculation, the vertical bisector of 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) in FIG. This is an operation to obtain the intersection coordinates of The obtained coordinate points (Va, Vb) are close to the center point of the ellipse in FIG. 2, and are similar to the DC component of the two-phase signal.

  Here, (x1, y1) to (x4, y4) used for calculating the intersection (Va, Vb) are instantaneous values extracted based on the condition 3 as described above. In this case, the instantaneous values (x1, y1) and (x3, y3), and (x2, y2) and (x4, y4) are always located on approximately 180 ° opposite sides with respect to the origin. In other words, there is no deviation near ± 45 ° as in the prior art. As a result, the finally obtained intersection (Va, Vb) can always have a value similar to the center of the ellipse.

When the DC components Va and Vb obtained by the calculation are corrected by subtracting them from the two-phase signals in the subtractors 19a and 19b, an ideal two-phase AC signal that does not contain a DC component can be obtained. When this ideal two-phase AC signal is input to the divider 6, the output is x / y = sin θ / cos θ = tan θ. The output tan θ of the divider 6 is subjected to inverse transformation of the tan function by the converter 7, and the phase θ = tan ⁻¹ (x / y) = tan ⁻¹ (tan θ) is detected. Then, the rotation angle Φ is calculated based on the obtained phase θ.

  That is, the detected rotational position θ is a minute position in which one tooth of the gear 1 is one cycle. On the other hand, the two-phase signals x and y are converted into pulse signals by the comparators 4 a and 4 b and input to the counter circuit 5. The counter circuit 5 detects the rotational position upper digit ud in a range exceeding one cycle of the rotational position θ by counting the pulse signals xa and ya. The rotational position upper digit ud and the rotational position θ are added by the adder 8 to obtain a rotational position detection value Φ over the entire circumference of the gear 1. In general, a portion indicated by a broken line in FIG. 1 is processed by software using a microprocessor or the like.

  As described above, the embodiment of the present invention has been described by taking the magnetic rotational position detection device as an example. However, the principle of the present invention is not limited to the magnetic rotational position detection device, and the linear movement type position detection device is exactly the same. Applicable. Further, the invention is not limited to the magnetic type using a gear, and for example, a detector using a two-phase sine wave signal such as a detector using a magnetized drum or an optical detector can be similarly applied.

  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 detection unit, 11 amplitude fluctuation detection unit, 18 DC component holding unit, 19 subtractor.

Claims (3)

A position detection device that detects a position of a detection object based on two-phase signals x = V · cos θ + Va and y = V · sin θ + Vb, which vary according to a change of the detection object and are 90 degrees out of phase with each other,
When φ is an arbitrary angle and α is a minute angle, among the instantaneous values (x, y) of the two-phase signal, an instantaneous value satisfying φ−α ≦ tan ⁻¹ (y / x) ≦ φ + α (x1 , Y1), an instantaneous value satisfying φ + 90−α ≦ tan ⁻¹ (y / x) ≦ φ + 90 + α (x2, y2), and an instantaneous value satisfying φ + 180−α ≦ tan ⁻¹ (y / x) ≦ φ + 180 + α (x3 , Y3), φ + 270−α ≦ tan ⁻¹ (y / x) ≦ φ + 270 + α, an instantaneous value holding unit that holds an instantaneous value as (x4, y4),
The values of the DC components (Va, Vb) that coincide with the center of the circle or ellipse drawn by the locus of the two-phase signal are represented by the four sets of instantaneous values (x1, y1), (x2, y2), (x3, y3). ), (X4, y4) based on a DC component detector,
A position detector that detects the position of the detected object based on a difference signal between the DC component (Va, Vb) calculated by the DC component detector and the two-phase signal (x, y);
A position detection apparatus comprising: The position detection device according to claim 1,
Said number detected body teeth m, a gear speed n (rpm), if the extracted period of the instantaneous value is T, then said small angle alpha, a 3m nT ≦ α«45 °, characterized in that A position detection device. The position detection device according to claim 1 or 2,
The direct current component detector is
Va = 1/2 · [{(x1 ² −x3 ² ) (y2−y4) − (x2 ² −x4 ² ) (y1−y3) + (y1−y3) (y2−y4) (y1 + y3−y2−y4) )}
/ {(X1-x3) (y2-y4)-(x2-x4) (y1-y3)}],
Vb = 1/2 · [{(y1 ² −y3 ² ) (x2−x4) − (y2 ² −y4 ² ) (x1−x3) + (x1−x3) (x2−x4) (x1 + x3−x2−x4) )}
/ {(Y1-y3) (x2-x4)-(y2-y4) (x1-x3)}],
A position detecting device that calculates DC component detection values Va and Vb based on the following formula.

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