JP7560355B2 - Encoder signal conditioning method - Google Patents

Description

The present invention relates to an encoder that detects position, displacement, angle, angular velocity, etc. Specifically, the present invention relates to an encoder signal adjustment method that converts n-phase detection signals output from a detection head unit of an encoder into two-phase signals with a phase difference of 90°.

The encoder has a scale and a detection head portion that is provided so as to move relatively to the scale.
The scale has a periodic pattern with a constant pitch in the positioning direction.
The detection head is provided with a detection pattern so as to read n-phase detection signals having different phases within one period of the periodic pattern. A Lissajous figure is drawn from the n-phase detection signals, and the deviation angle is used to perform interpolation with a resolution of one pitch or less of the periodic pattern, thereby enabling high-resolution position (displacement) detection.

Patent 4713123 JP2003-279382A Patent Publication No. 2006-3307 Patent 6517540 Patent 5964162 Patent 4768248

In order to plot a Lissajous figure from an n-phase detection signal output from the detection head unit, it is necessary to perform n-phase to 2-phase conversion on the n-phase detection signal to obtain 2-phase signals (phase A and phase B) having a phase difference of 90° from the n-phase detection signal. For example, if the detection signal is a 3-phase signal (S1, S2, S3) having a phase difference of 120°, the 3-phase to 2-phase conversion is expressed as follows:
The intensity of the detection signal S1 is I1,
The intensity of the detection signal S2 is I2,
The intensity of the detection signal S3 is I3.

This three-phase to two-phase conversion is based on the premise that the phase difference between the three-phase detection signals is 120°.
However, in reality, the detection pattern of the detection head has processing errors, and three-phase detection signals with a phase difference of 120° are not obtained as designed. Furthermore, the strength (amplitude) of the detection signals may vary within the axis for each signal, reflecting waviness of the scale, etc.
If the above-mentioned n-phase to two-phase conversion is performed on such an n-phase (e.g., three-phase) detection signal that deviates from the design value, an error due to the deviation from the design value will occur in the two-phase signal, which will cause a deterioration in accuracy.

To address this issue, a method may be used in which n-phase (e.g., 3-phase) detection signals are corrected so that they correspond to the design values, and then n-phase to 2-phase conversion is performed.

However, a correction matrix that corrects both signal strength (amplitude) and phase (phase difference) has many elements, and calculating such a correction matrix in real time imposes a significant computational load. Furthermore, when correcting both signal strength (amplitude) and phase (phase difference) to achieve the relationship according to the design values, it is, in principle, extremely difficult to correct both with a high degree of accuracy.

The encoder signal adjustment method of the present invention includes the steps of:
An encoder signal adjustment method for converting an n-phase (n is an integer equal to or greater than 2) detection signal output from a detection head unit of an encoder into a two-phase signal having A phase and B phase having a phase difference of 90° from each other, comprising:
The encoder is
A scale having a periodic pattern with a constant pitch in the positioning direction;
a detection head portion that moves relative to the scale and has a detection pattern disposed thereon so as to read detection signals of n phases having different phases within one period of the periodic pattern,
The phase relationship between the n-phase detection signals is expressed as φ1, ..., φn (0 ≤ φ1, ..., φn < 360°) using the phase within one period,
When the values of the n-phase detection signals output from the detection head unit are represented as I1, I2, . . . , In,
The encoder signal adjustment method includes:
When the sine curve that best fits a set of n-phase detection signals, each of which has values I1, I2, . . . In when the phases are φ1, . . . φn, is defined as a regression sine curve,
The sine component of the regression sine curve is defined as phase A,
The cosine component of the regression sine curve is set to be a B phase.

In one embodiment of the present invention,
The sine regression curve is preferably obtained as a solution of the n-phase detection signals by a least squares method.

In one embodiment of the present invention,
The calculation for converting the n-phase detection signals into the two-phase signals preferably includes a conversion matrix T for converting n phases into two phases, which is expressed by the following equation:

In one embodiment of the present invention,
The calculation for converting the n-phase detection signals into the two-phase signals includes an amplitude correction matrix D for correcting amplitudes of the n-phase detection signals,
The amplitude correction matrix D is preferably a diagonal matrix.

In one embodiment of the present invention,
The detection signal has three or more phases,
The phases of any three of the detection signals having adjacent phases are
φi-1, φi, φi+1 (i is an integer from 2 to n-1)
Expressed as
moreover,
The phase difference between φi-1 and φi is Δφ(i-1, i).
The phase difference between φi and φi+1 is Δφ(i, i+1)
When expressed as
It is preferable that Δφ(i−1, i) and Δφ(i, i+1) differ by 1° or more.

For example, the difference between Δφ(i−1, i) and Δφ(i, i+1) is set to 1° or more and less than 20°.
For example, the difference between Δφ(i−1, i) and Δφ(i, i+1) is set to 3° or more and less than 15°. More preferably,
For example, the difference between Δφ(i−1, i) and Δφ(i, i+1) is set to 10°.

Furthermore, even if there is a manufacturing tolerance in the encoder's light receiving element array, a manufacturing error equivalent to 1° will not occur, and if there is a deviation of 1°, it can be considered that the design is intentionally slightly shifted.
Furthermore, it is not necessary that the phase differences between detection signals having adjacent phases are all different for all i, and it is sufficient that the above condition is satisfied for at least one i.

In one embodiment of the present invention,
The detection signal has two or more phases,
The phases of any two of the detection signals having adjacent phases are
φi, φi+1 (i is an integer from 1 to n-1)
Expressed as
The phase difference between φi and φi+1 is Δφ(i, i+1)
When we express it as
For Δφ(i, i+1),
It is preferable that 89°<Δφ(i, i+1)<91° is not satisfied.

FIG. 1 is a diagram showing the external appearance of an encoder 100. 2 is a diagram illustrating an example of an internal configuration of a detection head unit 300. FIG. 3 is a diagram illustrating an example of an arrangement of light receiving elements 340. FIG. 13 is a diagram illustrating an example of the phase relationship of a group of light receiving elements 340 that are not equally spaced. FIG. 1 is a diagram illustrating a Lissajous figure. FIG. 4 is a functional block diagram of a calculation processing unit 400. FIG. 1 is a diagram illustrating a schematic representation of how a detection signal is corrected in the prior art. 5A and 5B are diagrams illustrating a schematic representation of how a detection signal is corrected in the present embodiment. FIG. 1 is a diagram illustrating a process of determining a sine regression curve. 1 is a diagram illustrating a fundamental wave, a third harmonic, and a fifth harmonic.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be illustrated and described with reference to the reference numerals given to the various elements in the drawings.
Before describing specific embodiments of the encoder signal adjustment method of the present invention, a general configuration of an encoder (displacement measuring device) will first be described.
FIG. 1 is a diagram showing the external appearance of an encoder 100. As shown in FIG.
The encoder 100 has a scale 200 and a detection head unit 300 that is provided so as to be movable relative to the scale 200 .
The encoder 100 is used to control the movement of a mechanical device having elements that move relative to one another. For example, if the mechanical device is a moving stage, the scale 200 is attached to a base (one element) and the detection head unit 300 is attached to the stage (the other element).

The scale 200 has a periodic pattern 210 with a constant pitch in the length measurement direction (position measurement direction). In the case of the photoelectric encoder 100, the periodic pattern 210 is a light reflecting portion or a light transmitting portion formed with a predetermined pitch, and is a so-called diffraction grating.

The detection head unit 300 has a detection pattern 310 that pairs with the periodic pattern 210 of the scale 200 , and reads a detection signal from the periodic pattern 210 of the scale 200 .
A light source 320 and a light receiving section 330 as shown in FIG. 2 are disposed within the detection head section 300 .
The light receiving section 330 includes light receiving elements 340 arranged parallel to the periodic pattern 210 of the scale 200 .
The light receiving elements 340 are arranged so as to emit light receiving signals corresponding to different phases of the interference fringes 220 caused by the periodic pattern 210 of the scale 200, as shown in FIG.

For example, where the pitch P of the interference fringes 220 caused by the periodic pattern 210 of the scale 200 is equal to, the light receiving elements 340 are arranged at a pitch of (1/n)P.
Here, as a first example, it is assumed that the light receiving elements 340 are arranged at a pitch of (1/3)P.
In this case, for one wavelength of the interference fringes 220 from the periodic pattern 210 of the scale 200, the light receiving element 340 emits phase signals shifted by 120°.
For the purpose of explanation, the light receiving elements 340 are classified into three groups, and the group of light receiving elements 340 corresponding to a certain phase is designated as a first phase (α).
The group of light receiving elements 340 having a phase difference of 120° with respect to the first phase (α) is defined as a second phase (β), and the group of light receiving elements 340 having a phase difference of 120° with respect to the second phase (β) is defined as a third phase (γ).

In this embodiment, the light receiving elements 340 may be arranged at equal intervals with a pitch of (1/n)P, as in the conventional technology.
However, in order to effectively utilize the advantages of the present invention, unlike the prior art, the arrangement of the light receiving elements 340 may be intentionally designed to be slightly shifted from the equal intervals.
For example, suppose that the light receiving elements 340 are arranged in three phases, and a first phase (α) light receiving element 340 (group) is arranged to correspond to a certain phase of the interference fringes 220. Then, a group of light receiving elements 340 is arranged to have a phase difference of 110° with respect to the first phase (α), which is defined as a second phase (β). Furthermore, a group of light receiving elements 340 is arranged to have a phase difference of 130° with respect to the second phase (β), which is defined as a third phase (γ).

If the phase of the first phase (α) is 0°, the phase relationship between the detection signals is such that the phase of the second phase (β) is 110°, and the phase of the third phase (γ) is 240° (−120°).
in this case,
The phase difference between the first phase (α) and the second phase (β) is 110°.
The phase difference between the second phase (β) and the third phase (γ) is 130°.
The phase difference between the third phase (γ) and the first phase (α) is 120°.
FIG. 4 is an example of the phase relationship of a group of light receiving elements 340 that are not equally spaced.

In both the conventional technology and the present embodiment, even if the layout design of the light receiving element 340 is ideally created, there may be deviations from the design values in the actual product, and there may also be variations between products. Therefore, a reference signal is actually input to the light receiving section 330 in which the light receiving element 340 is patterned, and the phases (phase differences) of the 1st phase to the nth phase are obtained.
For example, the phase of the first phase (α) is 0°, the phase of the second phase (β) is 109°, the phase of the third phase (γ) is 241° (−119°), and so on.
In the conventional technology, the phase (phase shift) of the detection signal obtained in advance is used to correct the detection signal before two-phase conversion, but in this embodiment, it is used during two-phase conversion.
Details will be provided later.

Detection signals of the first phase (α), second phase (β), third phase (γ), etc. are output from the detection head portion 300, and by processing these signals, the relative displacement amount L between the scale 200 and the detection head portion 300 can be obtained.
The details of this calculation process will be described later as the operation of the calculation processing unit 400 in FIG. 6, but an outline will be given here.
First, as shown in the example of FIG. 5, two-phase signals (phase A and phase B) having a phase difference of 90° from each other are obtained from the detection signals of the first phase (α), second phase (β), third phase (γ), etc., and the total rotation angle θT of the Lissajous figure drawn by these two-phase signals is calculated.
The total rotation angle θT is the sum of the number of rotations and the argument θ within one rotation as shown in Fig. 5. Once the total rotation angle θT is obtained, the relative displacement L between the scale 200 and the detection head unit 300 is given by the following equation in relation to the grating pitch PS:

L=(θT/360°)×PS

By accurately determining the argument θ within one rotation of the Lissajous figure, it is possible to interpolate with a resolution of less than one pitch (PS).

Next, the arithmetic processing (encoder 100 signal adjustment method) by the arithmetic processing unit (encoder signal adjustment device) 400 will be described.
FIG. 6 is a functional block diagram of the arithmetic processing unit 400.
The calculation process converts the n-phase detection signal into a two-phase signal, and further calculates the amount of relative displacement between the scale 200 and the detection head portion 300 based on the two-phase signal.

Although a functional block diagram is shown in FIG. 6 for convenience of explanation, the program for executing this arithmetic processing may be stored in a computer (CPU, ROM, RAM) 120 and the program may be executed by a central processing unit (CPU) to realize the processing.
In FIG. 1, the calculation processing unit 400 is provided in a computer (PC) 120 connected to the detection head unit 300 via a wired cable 110 or wireless communication, but the detection head unit 300 itself may have a built-in microcomputer, and the calculation processing may be performed by this microcomputer.

The calculation processing unit 400 has a receiving interface 410, an adjustment calculation unit 420, a Lissajous transform unit 450, and a displacement amount calculation unit 460.

The receiving interface 410 receives the n-phase detection signals output from the light receiving unit 330 and sends them to the adjustment calculation unit 420 at the next stage.
The adjustment calculation unit 420 converts the n-phase detection signal into a two-phase signal. The adjustment calculation unit 420 includes an amplitude correction unit 430 and a two-phase conversion unit 440.

First, the amplitude correction unit 430 adjusts the amplitudes of the detection signals of n phases so that they are all the same.
When n-phase detection signals are denoted by S1, ..., Sn, the amplitude correction unit 430 multiplies each of the detection signals S1, S2, ..., Sn by a coefficient, for example, based on the amplitude of S1 so that the amplitudes of S2, ..., Sn become the same as that of S1. The amplitude correction coefficient matrix D is a diagonal matrix, and is expressed, for example, as follows:

The amplitude correction unit 430 may, for example, compare the magnitudes of the detection signals S1...Sn input from the receiving interface 410 in real time and calculate the coefficient D to be multiplied by each detection signal in real time. Alternatively, the detection head unit 300 may be moved on the scale 200 in an actual product to determine in advance the difference in magnitude between the detection signals S1...Sn for each location (section) on the scale 200, and a coefficient for correcting this difference may be prepared in a correction coefficient table.

One of the key points of the first embodiment is that the amplitude correction unit 430 corrects only the amplitude (magnitude) of the detection signals S1...Sn, and does not adjust, for example, the phase (shift) of the detection signals S1...Sn. For example, in the prior art, if the detection signals were designed to be acquired with a phase difference of 120°, it was previously necessary to correct both the amplitude and the phase (phase difference).

To illustrate this, if the detection signal is three-phase, the relationship between the three detection signals is adjusted to signals of equal magnitude with a phase difference of 120°, as shown in Figure 7. For this reason, the correction matrix C is expressed, for example, as follows:

This is because in the conventional technology, calculations were performed under the assumption that the phase difference of the detection signals in the next stage of three-phase to two-phase conversion (or n-phase to two-phase conversion) was 120° (or 360°/n).
Correction matrix C, which corrects both amplitude and phase (phase difference), has many elements, and if such a correction matrix is to be calculated in real time, it is a heavy load to recalculate all the elements of matrix C. Even if only the amplitude of the detection signal fluctuates due to a change in the relative position between the scale 200 and the detection head unit 300, all the elements of matrix C must be recalculated. And multiplying the detection signals S1...Sn by the correction matrix requires a large amount of calculation. Conventionally, because this amount of calculation is large, it sometimes took some time to display the displacement of the detection head unit 300.
If the responsiveness of the displacement display is considered important, complete correction of the detection signals S1 to Sn could be omitted. However, this would distort the Lissajous figure, making it necessary to either include an error in the measurement value or to add another correction calculation.

In this embodiment, the amplitude correction coefficient matrix D has only diagonal elements, so the amount of calculation is significantly reduced.
Furthermore, as a characteristic of the encoder 100, the amplitude of the detection signal is sensitive to undulations of the scale 200 and has relatively large intra-axial fluctuations. On the other hand, the phase of the detection signal is determined by a mechanical structure such as the arrangement of the light receiving elements 340 and has relatively small intra-axial fluctuations. Therefore, by using an amplitude correction coefficient matrix D consisting only of diagonal elements as in this embodiment, it is possible to reduce the labor and power required for calculations, as well as to increase the speed, while also improving accuracy.

Next, the two-phase conversion unit 440 will be described.
The two-phase conversion unit 440 finds a sine curve that best fits the set of n-phase detection signals after correction, and finds two-phase signals (A phase, B phase) with a phase difference of 90°, with the sine component of the sine curve as phase A and the cosine component as phase B.
Here, the sine curve that best fits the set of n-phase detection signals is referred to as a regression sine curve.

In this embodiment, we will explain the case where the least squares method is used to fit the sine curve (curve fitting), but there are other ways to find the optimal sine curve. All that is needed is to minimize the cumulative difference Σf(Δ) between the regression sine curve to be found and the set of n-phase detection signals. The shape of f(Δ) is not limited to a square.

When the detection signal has n phases, the transformation matrix T of the n-phase to 2-phase transformation in this embodiment is expressed by the following equation.

The above formula can be visually represented as shown in FIG.
If the detection signal has three phases S1, S2, and S3,
It is assumed that, relative to the phase φ1 of the detection signal S1, the phase φ2 of the detection signal S2 is 109° and the phase φ3 of the detection signal S3 is 241°.
and,
The intensity of the detection signal S1 is I1,
The intensity of the detection signal S2 is I2,
The intensity of the detection signal S3 is I3.
At this time, the sine curve that best fits these three points is a regression sine curve, the sine component of this regression sine curve is the A-phase component, and the cosine component is the B-phase component.

When expressed using a sine function, it can be interpreted, for example, as follows.
Now, let the signal intensities I1, I2, I3 of the detection signals S1, S2, S3 be expressed as follows:
(The amplitudes have already been adjusted, so they are omitted here.)
I1=sin(θ+φ1)
I2=sin(θ+φ2)
I3=sin(θ+φ3)

The calculated sine regression curve y is expressed as y=sin(φ+θ).
And then,
y=cosθ・sinφ+sinθ・cosφ
Therefore, the sine component of the regression sine curve y is the A-phase component, and the cosine component is the B-phase component.

It should be noted that the above transformation matrix T includes an expression of an inverse matrix.
Here, since the rotation angle of the Lissajous figure can be calculated correctly if the ratio of the two-phase signals is maintained, only the cofactor matrix needs to be used in the calculation, and the coefficient (the inverse of the determinant) can be ignored. (Alternatively, it can be interpreted as multiplying the determinant as a coefficient to set the coefficient to 1.)

Therefore, the transformation matrix T can be expressed as follows:

The calculations performed by the adjustment calculation unit 420 can be expressed as a set as follows:
The intensity I of the n-phase detection signal (S1 . . . Sn) is defined as [I] = (I1, . . . , In).
A set of two-phase signals of phases A and B is represented as [R] = (A, B).

[R] = [T]・[D]・[I]

The n-phase to 2-phase conversion in this embodiment does not assume that the phases of the detection signals are equally spaced (360°/n), nor does it assume that the phases of the detection signals are as designed (phase difference).
The n-phase to 2-phase conversion in this embodiment involves calculating the sine component (A phase) and cosine component (B phase) of a regression sine curve based on the actual phases (φ1, . . . φn) of the detection signal.
This makes it possible to reduce the amount of calculation labor and increase the speed while also improving accuracy.

(Harmonic separation as an additional effect)
It has been explained that it is a good idea to intentionally shift the phase difference between the detection signals from the equal intervals by intentionally designing the arrangement of the light receiving elements 340 to be slightly shifted from the equal intervals. This makes it easier to distinguish the harmonics mixed in with the main fundamental wave.

The detection signal output from the encoder 100 is a periodic signal, e.g. a sine wave, but harmonic distortion inevitably gets mixed in with periodic signals, which becomes a cause of error in the position (displacement) detection accuracy of the encoder 100. However, theoretically, if it is possible to determine which harmonics are mixed in and to what extent, correction is possible.

Here, when n-phase detection signals are acquired using the conventional method, it can be difficult to distinguish and grasp to what extent each harmonic is mixed with the fundamental wave.
For example, Fig. 10 shows an example of a fundamental wave, a third harmonic, and a fifth harmonic, but the harmonics (third, fifth, seventh, ... harmonics) are waves with cycles that are integer multiples of the fundamental wave. When n-phase detection signals are acquired, for example, when the fundamental wave is mixed with the third harmonic and when the fifth harmonic is mixed with it, the fluctuation period of the detected wave may be the same, and in such a case, it is impossible to distinguish whether the distortion is caused by the third harmonic or the fifth harmonic.

For example, if a four-phase detection signal is obtained with a phase difference of 90°, the Lissajous distortion is λ/4 whether the third harmonic or the fifth harmonic is mixed in.

In this regard, if the phase difference between the detection signals can be intentionally shifted from an equal interval,
Since it becomes possible to establish a one-to-one correspondence between the order of the mixed harmonic and the resulting Lissajous distortion, it becomes possible to detect the degree to which the harmonic is mixed in from the information on the Lissajous distortion.

For example, consider an encoder that obtains a six-phase detection signal.
If the phases of the six-phase detection signals are equally spaced, Δφ=60°.
Now, if we make the spacing unequal for the purpose of harmonic separation,
Δφ(1,2)=50°
Δφ(2,3)=70°
Δφ(3,4)=60°
Δφ(4,5)=60°
Δφ(5,6)=60°
Δφ(6,1)=60°
It may be combined as follows.
Although Δφ(3,4)=Δφ(4,5)=Δφ(5,6)=Δφ(6,1), the harmonics can be distinguished without any problem.
In other words, it is sufficient that the above requirement is satisfied for at least one i.

Also, although it is not the same as "shifting from equal intervals," if we expand on the above idea, we can think of it as follows.
For example, when the detection signal is two-phase and one detection signal has a phase difference of 90° with respect to the other detection signal, as described above, when a third harmonic or a fifth harmonic is mixed in, the Lissajous distortion becomes λ/4 and cannot be distinguished.
On the other hand, if the phase of one detection signal is other than 90° with respect to the phase of the other detection signal, it becomes possible to distinguish harmonics. Therefore, it is sufficient that the phase of one detection signal is other than 90° with respect to the phase of the other detection signal. In other words, Δφ(i, i+1) does not satisfy 89°<Δφ(i, i+1)<91°. (Alternatively, Δφ(i, i+1) satisfies 1°≦Δφ(i, i+1)≦89° or 91°≦Δφ(i, i+1)≦179°.)
For example, it is sufficient that the phase of one detection signal is 89° or 91° with respect to the phase of the other detection signal, and if a more significant shift is required, it may be set to, for example, 100°.
(Note that two or more phases are sufficient, and the above requirement needs to be met for at least one of the i.)

As explained above, even if the phase difference between the detection signals is not equally spaced, or even if the phase difference is an odd number such as 89°, 91°, or 100° that cannot be handled (or is difficult to handle) by conventional methods, in this embodiment, a two-phase signal (phase A, phase B) with a phase difference of 90° can be obtained from n-phase detection signals. Therefore, by obtaining a two-phase signal (phase A, phase B) that separates the harmonics that cause distortion, the accuracy of the encoder 100 can be further improved.

The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit and scope of the present invention.
The encoder may be a capacitive encoder or a magnetic encoder.
In the case of a capacitive encoder, the periodic pattern is a conductive electrode arranged at a predetermined pitch, and in the case of a magnetic encoder, the periodic pattern is a coil arranged at a predetermined pitch.
The detection head portion is provided with electrodes and coils (transmitting/receiving electrodes, transmitting/receiving coils) that are coupled with the electrodes and coils of the scale.

In the above explanation, sine waves (and sine curves) are used, but this invention should be construed to include mathematically equivalent transformations such as cosine waves (cosine curves), changes to or fine-tuning of mathematically self-evident formulas, rotation or movement of coordinate axes, and advance or delay of the overall phase.

The encoder signal adjustment program may be installed in the memory so that it can function as a computer, and the installed program may be used to operate the CPU and other components to realize the functions of the various functional units described in the above embodiment. The encoder signal adjustment program may be distributed by recording it on a non-volatile recording medium (CD-ROM, memory card, etc.), or by downloading it via an internet line, etc.

Reference Signs List 100 Encoder 200 Scale 210 Periodic pattern 220 Interference fringes 300 Detection head section 310 Detection pattern 320 Light source 330 Light receiving section 340 Light receiving element 400 Calculation processing section 410 Reception interface 420 Adjustment calculation section 430 Amplitude correction section 440 Two-phase conversion section 450 Lissajous conversion section 460 Displacement amount calculation section

Claims (9)

An encoder signal adjustment method for converting an n-phase (n is an integer of 2 or more) detection signal output from a detection head unit of an encoder into a sine curve , comprising the steps of:
The encoder is
A scale having a periodic pattern with a constant pitch in the positioning direction;
a detection head portion that moves relative to the scale and has a detection pattern disposed thereon so as to read detection signals of n phases having different phases within one period of the periodic pattern,
The phase relationship between the n-phase detection signals is expressed as φ1, ..., φn (0 ≤ φ1, ..., φn < 360°) using the phase within one period,
When the values of the n-phase detection signals output from the detection head unit are represented as I1, I2, . . . , In,
The encoder signal adjustment method includes:
The regression sine curve that best fits the set of n-phase detection signals whose values are I1, I2, . . . In when the phases are φ1, . . . φn is defined as the sine curve .
13. An encoder signal conditioning method comprising : 2. The method of adjusting an encoder signal according to claim 1,
The encoder signal conditioning method according to claim 1, wherein the regression sine curve is obtained as a solution of the n-phase detection signals by a least squares method . 2. The method of adjusting an encoder signal according to claim 1,
The sine component of the regression sine curve is defined as phase A, and the cosine component of the regression sine curve is defined as phase B,
The detection signal output from the detection head of the encoder is a two-phase signal having phases A and B with a phase difference of 90°.
13. An encoder signal conditioning method comprising: 4. The method for adjusting an encoder signal according to claim 3 ,
the calculation for converting the n-phase detection signal into the two-phase signal includes a conversion matrix T for converting n-phase into two-phase, the conversion matrix T being expressed by the following equation:
The encoder signal adjustment method according to claim 3 or 4 ,
The calculation for converting the n-phase detection signals into the two-phase signals includes an amplitude correction matrix D for correcting amplitudes of the n-phase detection signals,
The method for adjusting an encoder signal, wherein the amplitude correction matrix D is a diagonal matrix. 6. The encoder signal adjustment method according to claim 1,
The detection signal has three or more phases,
The phases of any three of the detection signals having adjacent phases are
φi-1, φi, φi+1 (i is an integer from 2 to n-1)
Expressed as
moreover,
The phase difference between φi-1 and φi is Δφ(i-1, i).
The phase difference between φi and φi+1 is Δφ(i, i+1)
When expressed as
A method for adjusting an encoder signal, wherein Δφ(i−1, i) and Δφ(i, i+1) differ from each other by 1° or more. 6. The encoder signal adjustment method according to claim 1,
The detection signal has two or more phases,
The phases of any two of the detection signals having adjacent phases are
φi, φi+1 (i is an integer from 1 to n-1)
Expressed as
The phase difference between φi and φi+1 is Δφ(i, i+1)
When expressed as
For Δφ(i, i+1),
The encoder signal adjusting method according to claim 1, wherein 89°<Δφ(i, i+1)<91° is not satisfied. An encoder signal adjustment program that causes a computer to execute the encoder signal adjustment method according to any one of claims 1 to 7 . 9. An encoder comprising: a scale; a detection head portion provided so as to be movable relatively to the scale; and a computer having stored therein the encoder signal adjustment program according to claim 8 .

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