JP2005221429A - Position correction method, position correction apparatus, and feeder using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position correction method which enables a position measurement with few errors. <P>SOLUTION: The position correction method determines a position P<SB>2</SB>with a corrected position error generated from in-phase phase changes of nearly sinusoidal signals (A<SB>3</SB>, ..., X<SB>3</SB>) by a velocity of V<SB>1</SB>. The method comprises a position acquisition process (S10) which determines a position P<SB>1</SB>of a move section 22 on the basis of the signals (A<SB>3</SB>, ..., X<SB>3</SB>) obtained from a circuit 12 when the move section 22 relatively moves with respect to a base section 20, a velocity acquisition process (S12) which determines the velocity V<SB>1</SB>of the move section 22 on the basis of the signals (A<SB>3</SB>, ..., X<SB>3</SB>), and a position compensation process (S14) which corrects the position P<SB>1</SB>determined in the position acquisition process (S10) with a correction amount which can correct the position error generated from the in-phase phase changes of nearly sinusoidal signals (A<SB>3</SB>, ..., X<SB>3</SB>) by the velocity of V<SB>1</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a position correction method, a position correction device, and a feed device using the position correction method, and more particularly to an improvement in an error reduction technique for obtaining a position based on a substantially sinusoidal signal having two or more phases.

Conventionally, in many precision machines such as precision measuring instruments and precision processing apparatuses, a feeding device is provided to perform relative movement between a base and a moving part. In this type of field, precise feed is required compared to general machines.
The accuracy of feeding depends largely on the accuracy of position detection of the moving unit relative to the base. For this reason, in the position detection of a precision machine, interpolation is performed using a two-phase sine wave signal when the position is obtained based on the sine wave signal.
By the way, although the interpolation can detect a movement amount finer than the pitch of the scale, an error due to the interpolation also occurs. In order to reduce the error due to such interpolation, the relative phase change of the two-phase sinusoidal signal is conventionally corrected (for example, Patent Document 1).
JP 2003-222534 A

By the way, in this type of field, as the precision machine becomes more highly accurate, the position error is required to be further reduced. Also in the above-mentioned Patent Document 1, although further improvement is required for the position error, conventionally, there has been no appropriate technique that can solve this.
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a position correction method, a position correction apparatus, and a feeding apparatus using the position correction method that can perform position measurement with less error.

As a result of extensive investigations by the present inventor on the reduction of the position error, the inventors first succeeded in identifying a characteristic error factor in the precision machine.
That is, in the precision machine, the moving part is coarsely moved, finely moved, accelerated / decelerated, and the like with respect to the base part. When used at such various different speeds, the influence of the position error due to the speed is large. The reason for this is that the influence of the in-phase phase change of the sinusoidal signal due to the so-called speed, in which all the sine wave signals of two or more phases have the same phase change depending on the magnitude of the speed, has been found. .
In addition, the present inventor estimates the in-phase phase change of the sinusoidal signal due to the speed as described above from the frequency phase characteristics of the circuit, and corrects the position measurement result with an optimum correction amount according to the speed. Thus, it has been found that the position error can be further reduced, which has been extremely difficult in the past when the position of the moving part is obtained based on a sinusoidal signal of two or more phases, and the present invention has been completed.

That is, in order to achieve the above object, the position correction method according to the present invention determines the position of the moving unit based on a substantially sinusoidal signal of two or more phases obtained from the circuit by moving the moving unit relative to the base. A position correction method for obtaining a position of a moving part, which is used in obtaining the position error generated from the in-phase phase change of a substantially sinusoidal signal due to the speed of the moving part, the position obtaining step and the speed obtaining step And a position compensation step.
Here, the position acquisition step obtains the position of the moving part with respect to the base part based on a substantially sinusoidal signal having two or more phases obtained from the circuit when the moving part is moved relative to the base part. .

In the speed acquisition step, the speed of the moving part relative to the base is obtained based on a substantially sinusoidal signal having two or more phases obtained from the circuit when the moving part is moved relative to the base.
The position compensation step is a correction amount capable of correcting a position error generated from the in-phase phase change of the substantially sinusoidal signal at the speed obtained in the speed acquisition step, and the position obtained in the position acquisition step. to correct.
The substantially sine wave signal of the present invention includes not only a sine wave shape but also a signal similar to a sine wave shape (square wave, sawtooth wave, etc.).

  In the position correction method, the speed acquisition step differentiates the position obtained in the position acquisition step to obtain the speed of the moving unit. The position compensation step is a position generated from the in-phase phase change of the substantially sinusoidal signal at the speed of the moving part obtained in the speed acquisition step, obtained based on the frequency phase characteristics of the circuit obtained in advance. It is preferable to correct the position obtained in the position acquisition step with a correction amount that can correct the error.

Further, in the position correction method, the substantially sinusoidal signal obtained from the circuit by moving the moving part relative to the base is a two-phase sinusoidal signal α, β, and the two-phase sinusoidal signals α, β are: When the in-phase phase change f (V), which is a function of the velocity V of the moving part, is included and can be expressed by the following formula 2, the position compensation step is performed by using the velocity V of the moving unit obtained in the velocity acquisition step. phase sinusoidal signals alpha, the correction amount ΔP which can correct the position error generated from the in-phase phase variation f (V) of beta (V), and corrects the position P ₁ obtained by the position obtaining step, correction It is preferable to obtain the subsequent position data P ₂ (= P ₁ −ΔP (V)).

(Equation 2)
Sinusoidal signal α = Sin (2 · π · (P / λ) + f (V))
Sinusoidal signal β = Cos (2 · π · (P / λ) + f (V))
Where P: position of the moving part
λ: Wavelength of the substantially sinusoidal signal Here, since the phase is basically delayed, the position P ₁ obtained in the position acquisition process is shifted in the direction of delay with respect to the actual position P of the moving unit. If the moving direction is positive, the error ΔP (V) is a negative value.

In order to achieve the above object, the position correction apparatus according to the present invention obtains the position of the moving unit based on a substantially sinusoidal signal having two or more phases obtained from the circuit by moving the moving unit relative to the base. A position correction device for determining a position of a moving unit in which a position error generated from an in-phase phase change of a substantially sinusoidal signal due to the speed of the moving unit is corrected, the circuit, a position acquisition unit, a speed An acquisition means and a position compensation means are provided.
Here, when the moving unit is relatively moved with respect to the base, the circuit generates a substantially sinusoidal signal having two or more phases according to the position of the moving unit with respect to the base.

The position acquisition means obtains the position of the moving part with respect to the base part based on a substantially sinusoidal signal having two or more phases obtained from the circuit when the moving part is moved relative to the base part.
The speed acquisition means obtains the speed of the moving part relative to the base based on a substantially sinusoidal signal of two or more phases obtained from the circuit when the moving part is moved relative to the base.
The position compensation means is a correction amount capable of correcting a position error generated from the in-phase phase change of the substantially sinusoidal signal at the speed obtained by the speed acquisition means, and the position obtained by the position acquisition means. to correct.
The position correction device includes a memory. The position compensation means acquires a correction amount corresponding to the speed obtained by the speed detection means from the correction information of the memory, and uses the obtained correction amount to determine the position of the moving unit obtained in the position obtaining step. It is preferable to correct.

Here, the memory can correct the position error generated from the in-phase phase change of the speed of the moving unit and the substantially sinusoidal signal at the speed obtained based on the frequency phase characteristics of the circuit. Correction information representing the relationship with the correction amount is stored.
In order to achieve the above object, a feeding device according to the present invention is a feeding device including the position correction device, a drive unit, and a scale, and the position compensation means is obtained from the scale. The position data of the moving unit is corrected.
Here, the drive unit is for performing relative movement between the base and the moving unit.
The scale is for obtaining the position of the moving part with respect to the base part.
Examples of the scale of the present invention include a linear scale, a linear encoder, a rotary encoder, a position acquisition device using a Michelson interferometer, and the like.

As described above, according to the position correction method and apparatus according to the present invention, the position compensation step (in which the position error due to the in-phase phase change of the substantially sinusoidal signal of two or more phases is corrected with the optimum correction amount according to the speed ( Therefore, it is possible to further reduce the position error, which has been extremely difficult in the past when obtaining the position of the moving part based on the substantially sinusoidal signal of two or more phases.
Further, according to the feeding device according to the present invention, since the position correcting device is used, feeding with higher accuracy can be performed.

(Example 1)
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a phase correction apparatus for performing a position correction method according to an embodiment of the present invention. In the present embodiment, an example will be described in which the phase correction device is connected to the linear scale (scale) of the feeding device, and the position from the scale is corrected.
The position correction apparatus 10 shown in the figure includes a sinusoidal signal circuit (circuit) 12 and a position calculator (position acquisition means) 14 for performing the position acquisition step (S10) of the present invention, and a speed acquisition step ( A speed calculator (speed acquisition means) 16 for performing S12) and a position compensator (position compensation means) 18 for performing the position compensation step (S14) of the present invention are provided.

The position correction device 10 is configured to move the moving portion 22 relative to the base portion 20 of the feeding device 19 in the direction of the arrow in the figure and obtain an N-phase sinusoidal signal (approximately two or more sine signals) obtained from the sinusoidal signal circuit 12. This is used when determining the position of the moving unit 22 based on the wavy signal.
Here, the sine wave signal circuit 12 has an N-phase signal according to the position of the moving unit 22 with respect to the base 20 when the moving unit 22 moves relative to the base 20 of the feeding device 19 in the direction of the arrow in the figure. A sinusoidal signal (A ₃ ... X ₃ ) is generated.
The position calculator 14 moves based on the N-phase sine wave signal (A ₃ ... X ₃ ) obtained from the sine wave signal circuit 12 when the moving unit 22 is moved relative to the base 20. determining the position _{P 1} of the pre-correction parts 22.

What is characteristic in the present invention is that the position error due to the in-phase phase change in which all of the N-phase sinusoidal signals (A ₃ ... X ₃ ) have the same phase change is corrected by the speed V ₁ of the moving unit 22. That is.
Therefore, in this embodiment, when the speed calculator 16 moves the moving unit 22 relative to the base 20, an N-phase sine wave signal (A ₃ ... X) obtained from the sine wave signal circuit 12. from the position _{P 1} obtained based on _3), determining the velocity _{V 1} of the moving part 22.
The position compensator 18 is capable of correcting a position error ΔP that can correct a position error generated from a change in phase of the N-phase sinusoidal signal (A ₃ ... X ₃ ) at the speed V ₁ obtained by the speed calculator 16. ₁ (V), the position P ₁ before correction obtained by the position calculator 14 is corrected.

In the present embodiment, the position correction device 10 is connected to a linear scale (scale) 32 of the feeding device 19.
The linear scale 32 includes a main scale 34, an index scale 36, a light source 38, and detection means 40.
The main scale 34 and the index scale 36 are arranged to face each other, and the main scale 34 is provided in the moving unit 22 of the feeding device 19. The index scale 36 is provided on the base 20 of the feeding device 19. The main scale 34 is provided by the drive unit 42 so as to be movable relative to the index scale 36 in the direction of the arrow in the figure. A light source 38 and a detection means 40 are arranged to face each other with the main scale 34 and the index scale 36 interposed therebetween.

For this reason, in this embodiment, based on the corrected position P ₂ obtained by the position compensator 18, the coordinate value of the moving unit 22 from the position of the index scale 36 relative to the main scale 34 in the direction of the arrow in the figure, for example, tertiary Since the original measuring machine or the like can obtain the coordinate value or the like of the probe or the like, the dimension information and shape information of the object to be measured can be obtained. The returns the position compensator 18 corrected position P ₂ determined by the input side of the driving unit 42, by comparing a command value, it is accurate positioning of the movable portion 22 by the feedback control.
Next, a more specific configuration of the position correction apparatus 10 according to the present embodiment will be described.
In the phase correction apparatus 10 shown in the figure, the sine wave signal circuit 12 includes a detection means 40, an amplification / filter means 44, and an AD converter means 46.

The detection means 40 includes N-phase detectors 40a to 40x, the amplification / filter means 44 includes N-phase amplification / filters 44a to 44x, and the AD converter means 46 includes an N-phase AD converter 46a. With ~ 46x.
Here, the N-phase detectors 40 a to 40 x are arranged at predetermined intervals along the relative movement direction of the moving unit 22.
Further, an amplification / filter unit 44 and an AD converter unit 46 are provided at the subsequent stage of the detection unit 40, respectively. The position calculator 14 is provided at the subsequent stage of the AD converter means 46. A speed calculation device 16 and a position compensator 18 are provided following the position calculator 14.

Here, the detectors 40 a to 40 x output an N-phase sinusoidal signal (A ₁ ... X ₁ ) according to the position of the main scale 34 with respect to the index scale 36.
The amplifying / filters 44a to 44x amplify and filter the sine wave signal (A ₁ ... X ₁ ) from the detectors 40a to 40x to obtain a sine wave signal (A ₂ ... X ₂ ).
The AD converters 46a to 46x sample (AD-convert) the sine wave signal (A ₂ ... X ₂ ) from the amplification / filters 44a to 44x at a sampling period T, and sine wave (digital) signal (A ₃ ... X ₃ ) is obtained.
The position calculator 14 is a position in the relative movement direction of the main scale 34 with respect to the index scale 36 based on the N-phase sinusoidal signal (A ₃ ... X ₃ ) obtained from the AD converters 46 a to 46 x in the same manner. determine the P _1.

The speed calculator 16 numerically differentiates the position P ₁ obtained by the position calculator 14 to obtain the speed V ₁ of the moving unit 22.
The position compensator 18 is an N-phase sine wave signal (A ₃ ... X) at the speed V ₁ obtained by the speed calculator 16, which is obtained based on the frequency phase characteristics of the sine wave signal circuit 12 obtained in advance. ₃ ) The correction amount ΔP (V ₁ ) that can correct the position error caused by the in-phase phase change of ₃ ) is corrected for the pre-correction position P ₁ obtained by the position calculator 14, and the corrected position P ₂ (= P ₁ −ΔP (V ₁ )) is obtained.
The phase correction apparatus 10 according to the present embodiment is configured as described above, and the operation thereof will be described below.

The precision machines that require high accuracy and high speed as described above require highly accurate position measurement, and it is important to always keep track of fluctuations in the accuracy of the linear scale. The reduction in accuracy of the linear scale has various error factors, but the influence of errors due to interpolation is also great. In the past, in order to reduce errors due to interpolation, changes in the amplitude of the two-phase sinusoidal signal and changes in the relative phase of the two-phase sinusoidal signal were corrected. However, it is difficult to further reduce the error. there were.
That is, in a precision machine that requires high accuracy and high speed, the moving unit is often subjected to acceleration / deceleration and coarse movement at high speed during normal movement or positioning to a target position. On the other hand, there are many fine movements at a low speed during precise positioning before the target position or during scanning measurement. For this reason, since the precision machine has a larger speed change than a general machine, the influence of the in-phase phase change of the sinusoidal signal due to the speed of the moving part becomes serious.

For example, in the case of the photoelectric encoder shown in FIG. 1, when the light spot from the light source 38 scans the slit Retsujo pitch L at the speed V _1, the light frequency (V / L) reaches the detector 40. This becomes an input signal of the sine wave signal circuit 12. For this reason, the change of the moving speed V ₁ of the moving part 22 causes the frequency change of the N-phase sinusoidal signal (A ₃ ... X ₃ ). The frequency change of such N-phase sinusoidal signals (A 3 _... X _3), in-phase phase change due to frequency change of the N-phase sinusoidal signals (A 3 _... X ₃₎ occurs. This is the main error factor of position error in precision machines that require high accuracy and high speed.

What is characteristic in the present embodiment is that the in-phase phase change accompanying the frequency change of the N-phase sinusoidal signal (A ₃ ... X ₃ ), which was not considered in the conventional method, was corrected. Based on the frequency phase characteristics of the sinusoidal signal circuit 12, the position measurement result is corrected with an optimal correction amount ΔP ₁ (V ₁ ) corresponding to each speed V ₁ .
First, an ideal case with no error due to the interpolation is shown in FIG.
In this case, the output signal of the sine wave signal circuit 12 is assumed to be two-phase sine wave signals A ₃ and B ₃ (see FIG. 4A).
At this time, even if the speed V of the moving unit is increased, for example, the in-phase phase change does not occur in the sine wave signals A ₃ and B ₃ from the sine wave signal circuit 12. Therefore, when the position P _{1 of the} moving part with respect to the reference position P ₀ is obtained based on the sine wave signals A ₃ and B ₃ from the sine wave signal circuit 12, the actual position P of the moving part with respect to the reference position P ₀ is obtained. The same result (P ₁ = P) is obtained.

Next, the case where the in-phase phase change occurs is shown in FIG.
In this case, the output signal of the sine wave signal circuit 12 is set to two-phase sine wave signals A ₃ and B ₃ (see FIG. 4B).
As shown in FIG. 5B, the in-phase phase change f (V) in which the two-phase sinusoidal signals A ₃ and B ₃ (α, β) from the sinusoidal signal circuit 12 are a function of the velocity V of the moving part. including. At this time, in a certain speed (frequency) range, as the speed V increases, the phase change f (V) also increases.
As a result, the sinusoidal signals A ₃ and B ₃ from the sinusoidal signal circuit 12 increase the in-phase phase change f (V) of the output signal with respect to the input signal as the speed V increases.

Here, since the phase is basically delayed, even if the position P _{1 of the} moving part with respect to the reference position P ₀ is obtained based on the sine wave signals A ₃ and B ₃ from the sine wave signal circuit 12, the obtained position P ₁ is than the actual position P to be determined originally, (in the figure, an arrow to the left) delayed direction position shifted result sought. An error (= ΔP (V)) is obtained by a difference between the position P ₁ obtained based on the sine wave signals A ₃ and B ₃ from the sine wave signal circuit 12 and the actual position P to be originally obtained. End up. This error ΔP (V) also increases in the direction of delay as the speed V increases.

As described above, since the position error ΔP (V) is related to the velocity V, in this embodiment, it is necessary that the position detection accuracy is always constant even for various magnitudes of the velocity V. . For this reason, in this embodiment, the measurement result is corrected with the optimum correction amount ΔP (V) corresponding to the speed V based on the frequency phase characteristic of the sine wave signal circuit 12 obtained in advance.
In this embodiment, the position compensator corrects a position error generated from the in-phase phase change f (V) of the two-phase sinusoidal signals α and β at the speed V obtained by the speed calculator. The position P obtained by the position calculator with the correction amount ΔP (V) that can be obtained, that is, the optimum correction amount according to the speed, which is obtained based on the frequency phase characteristic of the sine wave signal circuit obtained in advance. ₁ is corrected. That is, the position compensator obtains the corrected position P ₂ (= P ₁ −ΔP (V)). Here, the error ΔP (V) becomes a negative value when the moving direction of the moving unit is positive.

As described above, in this embodiment, the correction amount ΔP (V) with respect to the position before correction obtained by the position calculator is adjusted to an optimum magnitude according to the magnitude of the velocity V of the moving unit. Even at various different speeds, the position error caused by the in-phase phase change in which all of the N-phase sinusoidal signals change in the same phase is corrected more appropriately.
As a result, in this embodiment, even in a precision machine that uses a large change in the moving speed of the moving unit, by correcting the in-phase change of the N-phase sinusoidal signal due to the speed, the error due to further interpolation can be reduced. Since reduction is achieved, more accurate position measurement can be performed.
Hereinafter, the position correction method according to the present invention will be described more specifically.
A transfer function generated according to the principle and configuration of the detection means 40 is represented by G _X0 . The transfer function of the amplification / filter means 44 is G _X1 , and the transfer function of the AD converter means 46 is G _X2 . The N-phase detector 40x (x = a, b, c...), The amplification / filter 44x, and the AD converter 46x have the same characteristics and configuration.

As an example, assuming that the transfer function G _{X0 of} the detector 40x and the transfer function G _X1 of the amplification / filter 44x have first-order high-cut filter characteristics, they can be expressed by the following equations 1 and 2, respectively. The transfer function _{G X2} of the AD converter 46x, assuming to have a zero-order hold characteristics, expressed by the following equation 3. The transfer function _{G X3} from the detector 40x to AD converter 44x is expressed by the following equation 4. These transfer functions G _{X0 to} G _X3 are represented by Laplace transform notation.
G _X0 = 1 / (1 + T _X1 · s) Equation 1
G _X1 = 1 / (1 + T _X2 · s) Equation 2
G _X2 = (1−exp (T _X3 · s)) / (T _X3 · s)...
G _X3 = G _X0 · G _X1 · G _X2 Equation 4
However, x = a, b, c.
FIG. 3 shows gain characteristics of the respective frequencies of the transfer functions G _{X0 to} G _{X3 under} the following conditions 1a to 1c, and FIG.
T _X1 = 1 / (2 · π · 1000) ... Condition 1a
T _X2 = 1 / (2 · π · 100) ... Condition 1b
T _X3 = 1/1000 ... Condition 1c

In the present embodiment, the conditions 1a to 1c are assumed for ease of explanation. Generally, the transfer characteristic from the detection means 40 to the AD converter means 46 has the analog filter characteristic as described above and the zeroth order. In many cases, it can be expressed by the product of the hold characteristics. However, since the conversion time cannot be ignored in the pipeline type AD converter, a dead time transmission characteristic (group delay characteristic) may be added.
Here, if Patent Document 1 is used, the relative phase change and amplitude change of a two-phase sine wave can be corrected, but if the two-phase sine wave changes in the same phase, the error is detected. The error cannot be corrected.

That is, in the conventional method such as Patent Document 1, two phases having a phase difference of 90 degrees are obtained from the N-phase sinusoidal signal X ₃ (X = A, B, C) as shown in the following equations 5 and 6. A sine wave signal α and a two-phase sine wave signal β are generated, and various errors such as relative phase difference and amplitude are corrected so that the Lissajous waveform draws a circle centered on the origin as shown in FIG. ing.
However, in the conventional method, when all of the measured N-phase sinusoidal signals have the same phase change, the Lissajous curve remains a perfect circle, and the error appears as a phase error generated on the circumference. Therefore, this in-phase error cannot be corrected.

α = g (V) · Sin (2 · π · (P / λ) + f (V)) Equation 5
β = g (V) · Cos (2 · π · (P / λ) + f (V)) Equation 6
Where P: position of the moving part
λ: wavelength of the sinusoidal signal
g (V): Frequency gain characteristic (Amplitude change: Correctable)
f (V): frequency phase characteristic (phase change: uncorrected)
Similarly, while maintaining an N-phase sinusoidal signal X ₃ (X = A, B... X) with a specific phase difference, for example, a phase difference between the detectors that is often determined by the physical arrangement of the detectors, It is also possible to correct various errors such as relative phase difference and amplitude, considering a data group moving on the circumference. However, even in this case, since the in-phase phase change becomes a phase error on the circumference, the in-phase phase error cannot be corrected.

However, in many cases, the actual sinusoidal signal X ₃ (X = A, B... X) has a transfer characteristic that can be expressed by the transfer function G _X3 . Has the same phase error as shown.
In order to solve this problem, the conventional method employs the following method, and suppresses the in-phase error to a target value (accuracy) or less.
(1) A time constant (T _X1 , T _X2 , T _X3 ) of a transfer function of a device generally constituted by an electric circuit is reduced.
(2) In order to reduce the upper limit of the frequency of the sinusoidal signal, the upper limit of the speed is limited to a lower value.

However, a device having a high frequency characteristic (small time constant) is expensive, and an electric circuit noise (electric noise) tends to be large. Further, the inventor has shown that the frequency phase characteristic of the sine wave signal circuit 12 shown in FIG. 4 is greatly affected by the frequency lower than the frequency gain characteristic of the sine wave signal circuit 12 shown in FIG. From this, it can be seen that the correction of the position error by the frequency phase characteristic is very important in this embodiment.
For this reason, high precision and high speed are also required in precision machines, but for the reasons described above, it has been difficult to achieve high precision and high speed.

Therefore, in this embodiment, in order to achieve high accuracy and high speed at the same time, for example, the two-phase sinusoidal signals α and β include an in-phase phase change f (V) that is a function of the velocity V, 6, the position compensation step corrects a position error generated from the in-phase phase change f (V) of the two-phase sinusoidal signals α and β based on the velocity data V obtained in the velocity acquisition step. in the correction amount ΔP that can (V), and corrects the position data _{P 1} obtained by the position obtaining step, it is preferable for obtaining the corrected position data _{P 2 (= P 1 -ΔP (} V)).

More specifically, the sinusoidal signal _{(A 3, B 3, ...} X 3) was obtained by the AD converter 46A～46x, numerically differentiating the position _{P 1} obtained from data acquired from the AD converter 46A～46x obtain the moving speed _{V 1} Te. Based on the detection means 40 which had been obtained in advance in the frequency-phase characteristic of the sinusoidal signal circuit 12 to the AD converter unit 46, seeking optimum correction amount [Delta] P ₁ corresponding to the moving speed V _1, the position P ₁ Is corrected. Thus, in this embodiment, the transfer characteristic of the sinusoidal signal circuit 12 (transfer function G _X3 ) from the detection means 40 to the AD converter means 46, for example, the frequency phase characteristic as shown in FIG. 4 is corrected. It becomes.

As a result, in this embodiment, the sinusoidal signal circuit 12 has various moving speeds compared to the conventional one without increasing the frequency characteristics of the sinusoidal signal circuit 12 or limiting the upper limit of the speed of the moving unit 22 to be low. Since the position error caused by the in-phase phase change of the signal can be greatly reduced, more accurate position measurement can be performed.
As a result, in this embodiment, position measurement with less error can be performed using a sine wave signal circuit such as a detector, an amplifier / filter, etc., which is relatively inexpensive and has low electrical noise and lower frequency characteristics. In the present embodiment, the upper limit of the speed can be increased compared to the conventional case, so that the speed of the moving unit can be increased even if a detector and an amplification / filter having the same frequency characteristics as the conventional one are used. Even in position measurement during high-speed movement, position measurement with little error can be performed.

Here the frequency phase characteristics, in the present embodiment, required for obtaining an optimum correction amount for the speed, the frequency-phase characteristic of the circuit 12, in advance measures the transfer function G _X3 sinusoidal signal circuit 12 The phase characteristic can be obtained.
However, the method of obtaining the frequency phase characteristics of the sinusoidal signal circuit 12 is not limited to this, and the same effects as in the above embodiment can be obtained also by the following methods 1 to 3, for example.
(Method 1) The transfer function G _X3 is measured in advance, the frequency phase characteristic is obtained, and then the transfer function G _X3a approximating the frequency phase characteristic is used.
(Method 2) The phase characteristic is calculated directly from the transfer functions G _X3 and G _X3a .
(Method 3) The phase characteristics are corrected by using a linear interpolation using a table or an approximate curve such as a spline function as a function f (v).

Here, a general method can be used as a method of obtaining the phase characteristics in the methods 1 and 2. One example will be described below.
For example, the input signal u (t) and the output signal y (t) of the sine wave signal circuit 12 are Laplace transformed, and the transfer function of the sine wave signal circuit 12 is determined from the relationship between the input signal u (s) and the output signal y (s). G (s) (= y (s) / u (s)) is obtained.
Here, the transfer function G _X3 which is the transfer function G (s) of the sinusoidal signal circuit 12 is the transfer function G _X3 if there is no reaction due to the coupling of the detection means 40, the amplification / filter means 44, and the AD converter means 46. It can be expressed as a product (G _X3 = G _X0 · G _X1 · G _X2 ).
In this transfer function G (s), the complex operator s is a pure imaginary number jw (s = jw), and a frequency transfer function G (jw) that can be expressed by a gain characteristic and a phase characteristic can be obtained.

From the thus obtained frequency transfer function G (jw) of the sinusoidal signal circuit 12, the phase advance and delay in the same phase between the input signal u (s) and the output signal y (s), etc. Can be obtained. The phase characteristic ∠G (jw) obtained in this way is equivalent to the frequency phase characteristic f (V) in the expressions 5 and 6.
Hereinafter, an example of how to obtain the phase characteristics by the method 3 will be described.
First, an input signal is given to the sine wave signal circuit 12 by changing the frequency, and their responses are measured.
For example, in the case of the photoelectric encoder shown in FIG. 1, when the light spot from the light source 38 scans the slit row with the pitch L at the speed V ₁ , the light having the frequency (V ₁ / L) reaches the detection means 40. This becomes an input signal of the sine wave signal circuit 12. Since the pitch L is constant, changing the speed V ₁ of the moving unit 22 changes the frequency (V ₁ / L) of the input signal of the sine wave signal circuit 12 while changing the output signal of the sine wave signal circuit 12 to the AD converter 46. The latter stage is monitored, that is, the phase difference between the input signal and the output signal is monitored.
The relationship between the frequency (V / L) of the input signal obtained based on the speed V of the moving unit 22 at this time and the phase difference f (V) between the input signal and the output signal is stored.

If the frequency (V / L) thus obtained is plotted on the horizontal axis and the phase difference f (V) is plotted on the vertical axis, linear interpolation using a table or an approximate curve such as a spline function is used, for example, FIG. The frequency phase characteristics of the sinusoidal signal circuit 12 as shown in FIG. Based on such frequency phase characteristics of the sinusoidal signal circuit 12, the optimum correction amount corresponding to the frequency (V / L) (the optimum correction amount ΔP (V) corresponding to the speed V) can be obtained.
If the frequency phase characteristics of the sinusoidal signal circuit 12 are modeled in this way, the optimum correction amount ΔP (V) corresponding to the speed V can be obtained easily and accurately, so that there are fewer errors. The position can be determined.

In the correction amount or in this embodiment, it is also preferable to add the following configuration in order to perform the error correction as described above more easily.
That is, as shown in FIG. 6, the present embodiment includes a memory 50.
Here, the memory 50 indicates the velocity V obtained based on the frequency phase characteristics of the sinusoidal signal circuit 12 as described above and a position error generated from the in-phase phase change of the substantially sinusoidal signal due to the velocity V. Correction information indicating the relationship with the correction amount ΔP (V) that can be corrected is stored.
The position compensator 18 obtains a correction amount ΔP (V) corresponding to the speed V obtained by the speed calculator 16 from the correction information in the memory 50. The position compensator 18 corrects the pre-correction position P ₁ of the moving part obtained by the position calculator 14 with the acquired correction amount ΔP (V), and the corrected position P ₂ (= P ₁ −ΔP ( V)) is preferably determined.

Here, in this embodiment, in order to obtain the correction information to be obtained in the memory 50, the optimum frequency phase characteristic for correcting the frequency phase characteristic is obtained from the frequency phase characteristic of the sine wave signal circuit 12 obtained in advance. It is also preferable to include a correction amount calculator 52 that calculates the correction amount with respect to the speed.
In the present embodiment, it is also preferable to include a phase characteristic acquisition unit 54 for obtaining the frequency phase characteristic of the sinusoidal signal circuit 12. For example, in the method 3, the frequency phase characteristic of the sine wave signal circuit 12 is obtained based on the sine wave signal (A ₃ ... X ₃ ) from the sine wave signal circuit 12 and the speed V obtained by the speed calculator 16. It is also suitable.
In this embodiment, in addition to the correction of the in-phase phase change accompanying the frequency change of the N-phase sinusoidal signal, other error factors can be corrected. For example, it is particularly preferable to combine the correction method based on the Lissajous curve of Patent Document 1 with more accurate position measurement.

In addition, as a field of application of the present invention, it is used for precision machines such as precision machine tools and precision measuring instruments that measure and calibrate positions based on two-phase sinusoidal signals or three-phase or more multiphase sinusoidal signals. be able to.
In addition, the detection method is not limited to the photoelectric method, and an arbitrary device such as a Michelson interferometer may be used.
In the above configuration, an example of a linear scale has been described. However, the present invention is not limited to this, and can also be applied to a rotary position detector such as a rotary encoder.
In the above-described configuration, the moving direction of the moving unit is assumed to be one axial direction in the direction of the arrow in the drawing, and the scale is provided in the one axial direction. However, when there are a plurality of moving axes of the moving unit, the scale is set for each axis. More preferably.

It is explanatory drawing of schematic structure of the position correction apparatus for performing the position correction method concerning one Example of this invention. It is explanatory drawing of the in-phase phase change of the N phase sinusoidal signal by speed. It is an example of the frequency gain characteristic of the circuit shown in FIG. It is an example of the frequency phase characteristic of the circuit shown in FIG. It is explanatory drawing of the Lissajous curve obtained from the output signal of the circuit shown in FIG. It is explanatory drawing of schematic structure suitable for performing characteristic correction | amendment easily in the apparatus shown in FIG.

Explanation of symbols

10 position correction device 12 sinusoidal signal circuit (circuit)
14 Position calculator (position acquisition means)
16 Speed calculator (speed acquisition means)
18 Position compensator (position compensation means)
19 Feeder

Claims (6)

It is used to determine the position of the moving part based on two or more phase sine wave signals obtained from the circuit by moving the moving part relative to the base part. A position correction method for obtaining a position of a moving unit in which a position error generated from a phase change is corrected,
A position acquisition step of obtaining a position of the moving part relative to the base based on a substantially sinusoidal signal of two or more phases obtained from the circuit when the moving part is moved relative to the base;
A speed acquisition step of obtaining a speed of the moving part relative to the base based on a substantially sinusoidal signal of two or more phases obtained from the circuit when the moving part is moved relative to the base;
A position compensation step for correcting the position obtained in the position acquisition step with a correction amount capable of correcting a position error generated from the in-phase phase change of the substantially sinusoidal signal at the speed obtained in the velocity acquisition step; ,
A position correction method comprising: The position correction method according to claim 1, wherein the speed acquisition step differentiates the position obtained in the position acquisition step to obtain a speed of the moving unit,
The position compensation step corrects a position error caused by the in-phase phase change of the substantially sinusoidal signal at the speed obtained in the speed acquisition step, which is obtained based on the frequency phase characteristics of the circuit obtained in advance. A position correction method for correcting the position obtained in the position acquisition step with a correction amount that can be corrected. 3. The position correction method according to claim 1, wherein the substantially sinusoidal signal obtained from the circuit by moving the moving part relative to the base is a two-phase sinusoidal signal α, β, and the two-phase sinusoidal signal. When α and β include an in-phase phase change f (V) that is a function of the velocity V and can be expressed by the following equation 1, the position compensation step is performed at the velocity V obtained in the velocity acquisition step. phase sinusoidal signals alpha, the correction amount ΔP which can correct the position error generated from the in-phase phase variation f (V) of beta (V), and corrects the position P ₁ obtained by the position obtaining step, correction A position correction method characterized by obtaining a subsequent position P ₂ (= P ₁ −ΔP (V)).
(Equation 1)
Sinusoidal signal α = Sin (2 · π · (P / λ) + f (V))
Sinusoidal signal β = Cos (2 · π · (P / λ) + f (V))
Where P: position of the moving part
λ: wavelength of the substantially sinusoidal signal It is used to determine the position of the moving part based on two or more phase sine wave signals obtained from the circuit by moving the moving part relative to the base part. A position correction apparatus for obtaining a position of a moving unit in which a position error generated from a phase change is corrected,
A circuit that generates a substantially sinusoidal signal of two or more phases according to the position of the moving part relative to the base when the moving part is moved relative to the base;
A position acquisition means for obtaining a position of the moving part relative to the base based on a substantially sinusoidal signal of two or more phases obtained from the circuit when the moving part is moved relative to the base;
Based on a substantially sinusoidal signal of two or more phases obtained from the circuit when the moving unit is moved relative to the base, a speed acquisition unit that obtains the speed of the moving unit relative to the base;
Position compensation means for correcting the position obtained by the position obtaining means with a correction amount capable of correcting a position error generated from the in-phase phase change of the substantially sinusoidal signal at the speed obtained by the speed obtaining means; ,
A position correction apparatus comprising: 5. The position correction apparatus according to claim 4, wherein the position error generated from the speed of the moving unit and the in-phase phase change of the substantially sinusoidal signal at the speed obtained based on the frequency phase characteristic of the circuit is corrected. A memory storing correction information representing a relationship with a correction amount that can be
The position compensation means acquires a correction amount corresponding to the speed obtained by the speed detection means from the correction information in the memory, and uses the obtained correction amount to determine the position of the moving unit obtained by the position acquisition means. A position correction apparatus for correcting the position. A position correction device according to any one of claims 3 to 5,
A drive unit for performing relative movement between the base unit and the moving unit;
A scale for obtaining the position of the moving part relative to the base part;
A feeding device comprising:
The position compensation means corrects the position of the moving unit obtained by the scale.

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