JP3092100B2 - Position detector 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 position detecting device used for detecting a rotation angle of a servomotor and the like. The present invention relates to a position detection device with an error correction function that detects various error components included in an AC signal and automatically corrects the error to detect a position.

[0002]

2. Description of the Related Art An example of a conventional position detecting device is shown in FIG. A gear 2 made of a magnetically permeable material is attached to a rotating body 1 of the detected object, and magnetic sensors 3 and 4 and a magnet 5 are disposed to face the gear 2, and outputs of the magnetic sensors 3 and 4 are provided. V
x and Vy are respectively input to the sample and hold circuits 11 and 12 in the instantaneous value detection unit 10 and also to the comparison arithmetic units 21 and 22 in the position upper digit detection circuit 20. The outputs of the sample and hold circuits 11 and 12 are input to A / D converters 13 and 14, respectively. The digital instantaneous values x = cos θ and y = sin θ that have been A / D converted are input to a divider 31 and the division result y / X is tan
^-1 circuit 32. This tan ^-1 circuit 3
2 indicates that the rotation angle corresponding to one tooth of the gear 2 is 2π (r
This is a result of interpolation detection of a minute position θ in one tooth in the case of (ad). The outputs of the comparators 21 and 22 are input to the pulse counter 23, and the upper digit data TN of the counted position is input to the adder 33 in the position detector 30. The adder 33 obtains the rotation angle position PS of the rotating body 1 by adding the position θ detected by interpolation within one tooth and the upper digit data TN of the position. In such a configuration, the processing in the position detection unit 30 may be realized by software processing using a microprocessor or the like. The operation of the software in this case is
This is as shown in the flowchart of FIG.

[0003]

In the conventional position detecting device, the outputs Vx and Vy of the magnetic sensors 3 and 4 have the same amplitude, the phase difference is exactly 90 °, and the DC offset component is 0. Are dealing. However, in general, the DC offset is often treated as a fixed value that is known in advance even if it is not 0. Even in this case, in the internal processing of the position detection unit 30, the fixed DC offset that is known is also used. Is subtracted from Vx and Vy, so that the DC offset is treated as 0 as described above. However, in an actual position detecting device, an offset or a fluctuation of an offset occurs in an actual two-phase AC signal output from the magnetic sensors 3 and 4, each amplitude is different, and a phase difference is 90%.
°, the signal was detected as a value different from V · sin θ and V · cos θ to be detected. Since the calculation is performed on the basis of the detection value including such an error, there has been a problem that the position cannot be detected with high accuracy conventionally.

Conventionally, in such a case, there has been a case where the above error correction circuits are provided to cope with the problem. However, since each error correction circuit requires adjustment of a variable resistor or the like,
Due to artificial adjustment errors, characteristic changes due to circuit element temperature fluctuations and the like, and characteristic deterioration due to aging, it has not been possible to always perform highly accurate position detection. Further, the applicant of the present invention has proposed in Japanese Patent Application Laid-Open No. Hei 3-170011 an error detection method for detecting each of the above errors from a plurality of sets of instantaneous values of the two-phase AC signals Vx and Vy. However, in an actual position detecting device, there are problems that an arithmetic circuit becomes expensive and that a desired detection accuracy cannot be obtained depending on how to select a plurality of sets of instantaneous values. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to simultaneously and accurately detect each of the above errors by a simple and inexpensive arithmetic processing circuit.
It is still another object of the present invention to provide a position detection device with an error correction function that can always perform accurate position detection by automatically correcting the position.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a position detecting device having an error correcting function, and an object of the present invention is to provide a position detecting device having first and second phases different in phase according to a moving distance .theta. A detection unit that outputs two-phase sine wave signals x and y; x = 1 / A · (cos θ
−K · sin θ) + C, and the second sine wave signal is represented by y = s
When expressed as inθ + d, instantaneous values y ₁ and y ₂ of y at the time when x = 0, instantaneous values x ₁ and x ₂ of x at the time of y = 0, and | x | = | y | x or y instantaneous value _{x 3} and _{x 4} in at the time made, or _{y 3} and _{y 4} and storage means for storing a; _y 1 stored in the storage _means, y _2, x _{1, x} 2, x ₃ or y ₃ , x ₄ or y ₄ to calculate the amplitude of the two-phase sinusoidal signals x and y .
A representing the difference is obtained by the operation of Equation 1, and the two-phase sine wave is obtained.
K representing the phase difference between the signals x and y is calculated by the equation (2).
And the DC offset of the two-phase sinusoidal signals x and y
An operation for finding C and d to be expressed by the operations of Expressions 3 and 4.
Means ; C obtained simultaneously by the error calculating means,
Using d, A, and K, the third and fourth two-phase sine wave signals x '= 90 ° differing in phase from each other, have the same amplitude, and have no DC offset component from the two-phase sine wave signals x and y. error correcting means for obtaining cos θ and y ′ = sin θ; the third and fourth two-phase sine wave signals x ′ and y ′
And a position detection unit for calculating the moving distance θ of the moving body based on the calculation of θ = tan ⁻¹ (y ′ / x ′). The storage means stores the y ₁ , y when the moving speed of the moving body is equal to or higher than a predetermined value.
_{2, x 1, x 2,} x 3, x 4 holds without updating the said when the moving speed of the moving body is equal to or less than the predetermined value is the _{y 1, y 2, x 1} , x 2 , X ₃ , x ₄ at the time when x = 0, y = 0, | x | = | y
At the time of |, the data is sequentially updated and stored.

[0007]

According to the present invention, the two-phase sine wave signals Vx and Vy output from the detector in accordance with the moving distance θ of the moving body.
Since there is an error in the amplitude of each other, the phase difference also has an error with respect to 90 °, and each contains a DC offset component,

Vx = V ₁ · (cos θ−K · sin θ) + a

Vy = V ₂ · sin θ + b The two-phase sine wave signals Vx and Vy are handled as numerical data x and y digitized by an A / D converter in the position detecting unit. The digitized numerical data x and y are calculated using a scaling factor Sf. Can be standardized as follows. That is,

Vx = Sf · x = V ₁ (cos θ−K · sin θ) + a

Vy = Sf ・ y = V ₂・ sin θ + b where the scaling factor Sf is a two-phase sine wave signal V
The amplitude of x and Vy, since a variable that can assume arbitrarily by the resolution or the like of the A / D converter, when thinking of a sine wave Vy as a reference amplitude assuming Sf = V _2, number 7 and number 8
Can be rewritten as follows:

[0008]

(Equation 9)

Y = sin θ + d where A = V ₂ / V ₁ , C = a / V ₂ , d = b / V _{2 In the} present invention, the instant of y at the time when x of the two-phase sine wave signal becomes 0 Using the instantaneous value of x at the time when y of the two-phase sine wave signal becomes 0 and the instantaneous value of x or y at the time when | x | = | y | K, C, and d, that is, the values of the amplitude error, phase error, and DC offset of the two-phase sine wave signals x and y are simultaneously calculated and detected. And
Using the detected error components, the two-phase sine wave signal x
And from y

X '= A (x-C) + K (yd) = cos
θ

[Mathematical formula-see original document] By the operation of y '= yd-sin [theta], the amplitudes are equal to each other and the phase difference is 90.
° and two-phase sine wave signals x 'and y' which do not include a DC offset can be obtained, and from these two-phase sine wave signals x 'and y'

## EQU13 ## θ = tan ^-1 (y '/ x') = tan ^-1
By the calculation (sin θ / cos θ), the moving distance θ of the moving body can be detected with high accuracy without errors.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. is there. The gear 2, the magnetic sensors 3, 4 and the magnet 5 attached to the rotating body 1 are the same as in the prior art.
The output of 4 is the amplitude error as shown in the above equations (5) and (6),
This is a two-phase sine wave signal including errors such as a phase error and a DC offset. The two-phase sine wave signals Vx and Vy are supplied to sample-hold circuits 11 and 12, and A / D converters 13 and 1, respectively.
4 is converted into digitized numerical data x and y. Note that x and y are represented by the above-described equations 9 and 10. As shown in FIG. 2, the two-phase sine wave signals x and y are sine waves having a rotation angle corresponding to one tooth of the gear 2 for one cycle, that is, 2π (rad). Includes amplitude error A, phase error K, DC offset C and d for the wave. Since these error amounts cannot be directly detected by such a position detecting device, these error amounts A, K, c, and d are calculated from the instantaneous values of the two-phase sine wave signals x and y. Think about detecting. First, transform equations 9 and 10

## EQU14 ## sin θ = yd

[Mathematical formula-see original document] cos [theta] = A (x-C) + K (yd) is obtained. Equations 14 and 15 are sin ² θ + cos ² θ =
Since the relationship of 1 holds,

(Y−d) ² + {A (x−C) + K (y−d) ² } = 1 is obtained. By transforming this equation 16,

Equation 17] ^{A 2 x 2 + (1 +} K 2) y 2 + 2AKxy-2A (AC + Kd) x -2 and ^{{(1 + K 2) d} + AKC} y + {(1 + K 2) d 2 + A 2 C 2 + 2AKCd-1} = 0 Become. Here, considering the phase error K, since the phase error K is designed and manufactured so as to be as small as possible in a general magnetic sensor,

(Equation 18) Can be approximated, and as a result, Equation 17 can be further considered as follows.

Equation 19] ^{A 2 x 2 + y 2 +} 2AKxy-2A (AC + Kd) X -2 (d + AKC) y + (d 2 + A 2 C 2 + 2AKCd-1} = 0 In this connection, the number 19 two-phase sinusoidal signals x and y When considered as a coordinate axis orthogonal to a two-dimensional plane, this is nothing but the equation of an ellipse on the xy plane.

Now, each of the error amounts A, K, C and d in Expression 19 is
It is an object of the present invention to calculate them at the same time , but simply from these instantaneous values of the two-phase sinusoidal signals x and y, these error amounts A, K,
Calculating C and d is not realistic because the calculation becomes very complicated. Therefore, in the present invention, it is considered that the calculation is performed using the instantaneous values of the two-phase sine wave signals x and y at the following three specific timings. That is, three timing is x = 0 and the instantaneous value _{y 1} of y when made and _y 2 y = 0 the instantaneous value of x when the become _{x 1} and _{x 2 | x | = | y} | become when x instantaneous value _x 3 = _{y 3} and _x 4 = a -y _4. Note that for the case of timing, the following operations be used instantaneous value y ₃ and y ₄ and y is obtained exactly the same results. Here, a specific example of a method for obtaining instantaneous values of the two-phase sine wave signals x and y at these specific timings will be described.

In FIG. 1, the two-phase sine wave signals x and y output from the instantaneous value detector 10 are converted into an instantaneous value comparator 41 composed of a comparator and the like, and an instantaneous value holding circuit composed of a memory element and the like. 42, and is input to the instantaneous value storage unit 40. The instantaneous value comparator 41 always detects the instantaneous values of the two-phase sine wave signals x and y, and the three conditions or above, ie, x = 0, y = 0 and | x |
The control signal CS is generated at the timing when | = | y |.
When the control signal CS is input to the instantaneous value holding circuit 42, the instantaneous values of the two-phase sine wave signals x and y input at that timing are captured and held. The instantaneous values of the two-phase sine wave signals x and y held by this operation are represented by y ₁ , y ₂ , x ₁ , x ₂ , x ₃ , and y ₃ in the waveform of FIG.
It is a value indicated by x _4. An algorithm for simultaneously calculating the error amounts A, K, C, and d from the values of y ₁ , y ₂ , x ₁ , x ₂ , x ₃ , and x ₄ thus held and stored will be described below. . This calculation is performed in the error calculation unit 50 in FIG. First condition number 19, that is, substituting y = _{y 1} and _{y 3} when x = 0, we obtain the following two formulas number 20 and number 21.

(Equation 20)

[Mathematical formula-see original document] Then, by subtracting both sides of the equations (20) and (21),

The following is obtained. Similarly, substituting x = x ₁ , x ₂ for the condition in Equation 19, ie, when y = 0,

(Equation 23)

24 is obtained. Similarly, subtract both sides of Expression 23 and Expression 24,

Equation 25 is obtained. Further, the following Expression 26 is obtained by using Expression 20 and Expression 23.

(Equation 26)

Then, on both sides of Equation 26, Equations 22 and 25
Can be substituted, and as a result, the following Expression 27 is obtained.

[Equation 27] By transforming this equation 27,

-Y ₁ y ₂ = A ² (-x ₁ x ₂ )

Equation 29] ^{_{A 2 = y 1 y 2 /}} x 1 x 2 is obtained. Although the amplitude error A can be obtained from Expression 28, a square root operation is required for that. Considering the use of a general microprocessor, a simpler operation is desirable. Therefore, the following approximate calculation is performed by utilizing that the amplitude error A is extremely close to 1 in a general magnetic sensor. That is, the following equation is obtained

A = 1 + α where

(Equation 31) It is. Substituting Equation 30 into Equation 29 gives

[Number 32] _{^{(1 + α) 2 = y}} 1 y 2 / x 1 x 2

Equation 33] _{^{1 + 2α + α 2 = y}} 1 y 2 / x 1 x 2 is obtained. And because equation 31 holds

(Equation 34) And the result is

Α = (y ₁ y ₂ −x ₁ x ₂ ) / 2 × ₁ x ₂ Here, by returning to A = 1 + α again,

A = 1 + α = (x ₁ x ₂ + y ₁ y ₂ ) / 2x ₁ x ₂

Next, the above condition, that is, x ₃ =
y ₃ and x ₄ = −y ₄ are substituted, but before that, for simplification of the following description, Equation 18 is obtained based on Equation 21 and Equation 24.
Review of. That is, Equation 19 can be transformed into the following equation.

Equation 37] ^{A 2 {x 2 -2 (C} + Kd / A) x} + y 2 -2 (d + AKC) y + 2AKxy + (d 2 + A 2 C 2 + 2AKCd-1) = 0 and the number 22 and number this number 37 Substituting 25 gives

Equation 38] A ² becomes ^{(y 1 + y 2) y} + 2AKxy + (d 2 + A 2 C 2 + 2AKCd-1) = 0 - {x 2 - (x 1 + x 2) x} + y 2. By substituting the condition x ₃ = y ₃ for the equation 38 obtained in this way instead of the equation 19,

[Equation 39] Is obtained, and by the transformation of Expression 39,

(Equation 40) Is obtained. Similarly, by substituting x ₄ = −y ₄ into Equation 38,

[Equation 41] Is obtained, and by the transformation of Expression 41,

(Equation 42) Becomes

Then, by adding both sides of Expression 40 and Expression 42,

[Equation 43] Therefore, the coefficient 2AK on the left side is considered. Taking advantage of the fact that A is extremely close to 1, A =
1 + α (however, Equation 31)

[Equation 44] Can be approximated. Therefore, this equation 44 is replaced by
Substituting into

[Equation 45] Is obtained, and further, A ² obtained by Expression 29 is substituted,

[Equation 46] Is obtained.

From the above, according to equations 36 and 46, 2
From the instantaneous values of the phase sine wave signals x and y, A and K of the error components of the two-phase sine wave could be solved. Next, when solving for the remaining C and d using Equations 22 and 25,

Equation 47] Since _{d = (y 1 + y 2} ) / 2-AKC is obtained by substituting this into Equation 25,

[Equation 48] And by the transformation of the expression 48,

C + K (y ₁ + y ₂ ) / 2A−K ² C = (x
₁ + x ₂ ) / 2. here,

[Equation 50] Approximate

The following equation is obtained: C = (x ₁ + x ₂ ) / 2−K (y ₁ + y ₂ ) / 2A Then, substituting equation 51 into equation 47

D = (y ₁ + y ₂ ) / 2−AK ｛(x ₁ + x
₂ ) / 2−K (y ₁ + y ₂ ) / 2A｝, and by approximating again to Equation 50,

The following equation is obtained: d = (y ₁ + y ₂ ) / 2−AK (x ₁ + x ₂ ) / 2

As described above, the error components A, K, C, and
d is the instantaneous value (x ₁ , x _{1) of} the two-phase sinusoidal signals x and y
₂ , y ₁ , y ₂ , x ₃ , x ₄ ), and
3, Equation 47 and Equation 49 could be calculated simultaneously . That is, the arithmetic processing in the error arithmetic unit 50 in FIG. 1 embodies the above equations 33, 43, 47 and 49, and these operations are easily realized by an arithmetic element such as a microprocessor. You can do it.

Using the error components A, K, C, and d calculated by the error calculation unit 50 in this manner, the error correction unit 60 in FIG. The ideal two-phase sine waves x ′ and y ′ having a phase difference of 90 ° and no DC offset are calculated.
That is, the operations shown in the above equations 11 and 12 are performed.
Since the two-phase sine wave signals x 'and y' thus obtained are ideal two-phase sine waves having no error, the position detector 30 uses the divider 31 in the position detector 30.

Y ′ / x ′ = sin θ / cos θ is obtained, and by using the tan ⁻¹ data table 32,

[Mathematical formula-see original document] θ = tan ⁻¹ (y ′ / x ′) = tan ⁻¹
By converting as (sin θ / cos θ), the rotation angle θ of the rotating body 1 can be accurately detected. Although not shown in FIG. 1, as shown in FIG. 5, by providing the upper digit detection unit 20 and adding the upper digit detection unit 20 to the rotation angle θ, the position detection over the entire circumference of the rotating body 1 can be performed.

Incidentally, the above-described error calculation processing, error correction processing, and the like are generally performed by digitizing a two-phase sine wave with an A / D converter and using numerical data. . When the A / D conversion is performed as described above, the digital-valued two-phase sine wave may take a continuous value due to the limitation of the conversion speed of the A / D converter and the limitation of the processing time of the operation. Can not. As a result, FIG.
As shown in, for example, the timing at which x = 0 under the above conditions cannot be accurately detected, and therefore, the instantaneous value y of y
A situation arises in which the correct value of ₁ (or y ₂ ) cannot be obtained. This state will be described with reference to FIG. It is in the section A or B in the figure that it is possible to detect that the digitized data x has become 0 at the timing when Vx becomes 0 in the figure. Y ₁ , y ₂ in FIG. 3 include △ y ₁ , 中 y
It will contain only _two errors. In order to avoid such a situation, as shown in FIG. 4, only when the period of Vx and Vy is larger than the sampling period T, that is, when the rotation speed of the rotating body 1 is low, the instantaneous value holding circuit 42 The instantaneous values of the phase sine wave signals x and y are fetched and held, so that the error Δy ₁ is so small that it can be ignored in accuracy. That is, when the rotation speed of the rotating body 1 is high, the instantaneous value holding circuit 42 does not update the instantaneous values of the two-phase sine wave signals x and y, but holds the instantaneous value captured when the rotation speed is low. I try to keep going. As a result, when the rotation speed is high, each error included in the two-phase sine wave cannot be detected in real time, and correction is performed using the value detected when the rotation speed is low. However,
Generally, position detection accuracy is required at very low speeds in many cases, so that there is no practical problem.

Although the embodiment of the present invention has been described above with reference to a magnetic rotary position detecting device, the principle of the present invention is not limited to a rotary type position detecting device, and can be applied to a linear moving type position detecting device in the same manner. . The present invention is not limited to the magnetic type using a gear, but may be applied to any type using a two-phase sine wave signal such as a detector using a magnetized drum or an optical type detector.

[0020]

As described above, according to the position detecting device with an error correcting function according to the present invention, the amplitude error, the phase error and the DC offset included in the two-phase sine wave signal detected according to the moving distance of the moving body. By automatically detecting and correcting the errors at the same time , it is possible to realize a high-accuracy position detection device that does not include the effects of these errors. The arithmetic processing for detecting and correcting the error can be realized by an inexpensive microprocessor or the like without requiring a special processing circuit. Furthermore, even if the two-phase sine wave signal contains the above error component, it can be automatically corrected to realize high-accuracy position detection. A great amount of time and man-hours can be reduced, and a highly reliable position detection device can be realized without the influence of artificial adjustment failure in the adjustment work.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic rotational position detecting device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a two-phase sine wave signal for explaining the principle of the present invention.

FIG. 3 is a diagram for explaining the operation of the present invention, in which a two-phase sine wave signal detected by a magnetic sensor and this signal is represented by A
FIG. 4 is a waveform diagram showing data converted into digital numerical values by a / D converter.

FIG. 4 is a waveform diagram similar to FIG. 3, showing a case where the rotation speed of a rotating body is low.

FIG. 5 is a configuration diagram of a magnetic rotational position detecting device according to the related art.

FIG. 6 is a flowchart when a conventional detection device is realized by software processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating body 2 Gear 10 Instantaneous value detection part 30 Position detection part 40 Instantaneous value storage part 41 Instantaneous value comparator 42 Instantaneous value holding circuit 50 Error calculation part

Claims (2)

(57) [Claims] A detecting unit that outputs first and second two-phase sine wave signals x and y having different phases according to a moving distance θ of a moving object; 1 / A ・
(Cos θ−K · sin θ) + C, when the second sine wave signal is expressed as y = sin θ + d, instantaneous values y ₁ and y ₂ of y at the time of x = 0 and at the time of y = 0 the instantaneous value _{x 1} and _{x 2} of x, | x | = | y |
Become instantaneous value of x or y at time _{x 3} and _{x 4,} or _{y 3} and _{y 4} and storage means for storing a; _y 1 stored in the storage _{means, y 2, x 1, x} 2, x ₃ or y
_3, with x ₄ or y _4, determined by calculation the number 1 of the A representative of the difference in amplitude of the two-phase sine wave signals x and y, the
K representing the phase difference between the two-phase sinusoidal signals x and y is expressed by
It is obtained by an operation, and the DC output of the two-phase sine wave signals x and y is obtained.
C and d representing the offset are calculated by the operations of Equations 3 and 4.
Calculating means ; and using C, d, A, and K simultaneously obtained by the error calculating means, the two-phase sine wave signals x and y have phases different from each other by 90 ° and equal amplitudes, Error correction means for obtaining third and fourth two-phase sinusoidal signals x '= cos θ and y' = sin θ without a DC offset component; and the third and fourth two-phase sinusoidal signals x 'and y' And a position detecting unit for calculating the moving distance θ of the moving body based on the calculation of θ = tan ⁻¹ (y ′ / x ′). (Equation 1) (Equation 2) (Equation 3) (Equation 4) Wherein said storage means, the moving speed of the moving body in the case of more than the predetermined value _{y 1, y 2, x 1} , x 2, x
_3, x ₄ holds without updating the said when the moving speed of the moving body is equal to or less than the predetermined value is the y _1,
y ₂ , x ₁ , x ₂ , x ₃ , and x ₄ are sequentially updated and stored at a time when x = 0, a time when y = 0, and a time when | x | = | y | Claim 1
4. The position detecting device with an error correction function according to 1.