JP7281778B1 - absolute position encoder - Google Patents

Abstract

An absolute position encoder detects an absolute position over a wide detection area with a compact and inexpensive configuration. A main scale detector detects sine waves and cosine waves from the main scale. The subscale detector detects sine waves and cosine waves from subscales having a period different from that of the main scale. The R/D converter R/D converts the sine wave and cosine wave detected by the main scale detector and the sine and cosine wave detected by the subscale detector to obtain position data of the main scale and subscale position data. Output position data. The calculation unit calculates the number of rotation data indicating which rotation of the main scale the data is based on the relationship between the position data of the main scale and the position data of the subscale. Further, the calculation unit calculates the absolute position based on the position data of the main scale and the frequency data of the main scale. [Selection drawing] Fig. 1

Description

The present invention relates to an absolute position encoder for detecting an absolute position in a positioning device, a position detecting device, or the like.

Incremental systems are often used for positioning devices and position detection devices. In the case of this increment type, an origin search operation is required when the power is turned on, and there is a problem that the operation rate of the apparatus is lowered. Therefore, an absolute encoder is required, but the conventional type is considerably complicated and expensive.

Japanese Patent Application Laid-Open No. 2010-217160 Japanese Patent Application Laid-Open No. 2001-194185

Since Patent Document 1 uses a CMOS linear array as a detector to perform calculations, a considerably high initial investment is required for creation, and an arbitrary encoder cannot be created easily.

Patent Document 2 requires a light shielding plate having a complicated slit array and a light receiving cell array provided with slits, and cannot easily produce an encoder.

As described above, the absolute position encoder needs to detect the absolute position over a wide detection area with a compact and inexpensive configuration.

The present invention has been devised in view of the above-mentioned conventional problems, and one aspect of the present invention is a main scale detector that detects sine waves and cosine waves from a main scale, and a subscale that has a period different from that of the main scale. A sub-scale detection section for detecting sine waves and cosine waves, a sine wave and cosine wave detected by the main scale detection section, and a sine wave and cosine wave detected by the sub-scale detection section are subjected to R/D conversion. an R/D converter for outputting the position data of the main scale and the position data of the sub-scale; and a computing unit that calculates the absolute position based on the position data of the main scale and the frequency data of the main scale.

Further, as one aspect thereof, the calculation unit calculates an X value by the following formula (1) or (2), and divides the X value by the length of the half cycle of the subscale to obtain the main scale. is calculated, and the absolute position is calculated by the following equation (3).

When Y0≧Y1, X=Y0-(Y1×L/M) (1)
When Y1>Y0, X=Y0-(Y1-Pm) L/M (2)
P=Y0+Pm×n (3)
P: Absolute position X: X value Y0: Position data of main scale Y1: Position data of sub-scale Pm: Maximum value of position data of main scale and sub-scale M: Length of N pole and S pole of main scale L: Length n of north and south poles of subscale: frequency data of main scale.

Further, as another aspect, a plurality of sub-scales having different cycles are provided, and the calculating section calculates the frequency data of the main scale based on the relationship between the position data of the main scale and the position data of the plurality of sub-scales. is calculated, and the absolute position is calculated based on the position data of the main scale and the frequency data of the main scale.

Further, as one aspect thereof, the calculation unit calculates the X value based on each sub-scale by the following formula (1) or (2) based on the position data of the main scale and the position data of each of the sub-scales. is calculated, and the X value based on each subscale is divided by the length of the half cycle of each subscale to calculate the frequency data based on each subscale, and j is 0, 1, 2, 3, 4, . . . are added one by one to repeat up to the maximum value of the frequency data. (3) is used to calculate the absolute position.

When Y0≧Y1, X=Y0-(Y1×L/M) (1)
When Y1>Y0, X=Y0-(Y1-Pm) L/M (2)
P=Y0+Pm×n (3)
P: Absolute position X: X value Y0: Position data of main scale Y1: Position data of sub-scale Pm: Maximum value of position data of main scale and sub-scale M: Length of N pole and S pole of main scale L: Length n of north and south poles of subscale: frequency data of main scale.

In one aspect, the absolute position encoder is a linear encoder.

In another aspect, the absolute position encoder is a rotating system, and is characterized in that the position data obtained by dividing one rotation into a plurality of parts is converted into an absolute position by specifying the angle of one rotation.

According to the present invention, an absolute position encoder can detect an absolute position over a wide detection area with a compact and inexpensive configuration.

FIG. 10 is a diagram showing half-cycle lengths, position data, X values, and absolute positions of the main scale and subscale; FIG. 3 is a diagram in which N poles and S poles are alternately arranged at regular intervals, and sensor A is arranged at a position where a sine wave output and sensor B a cosine wave output can be obtained. The figure which shows the relationship between a sine wave, a cosine wave, and position data. The figure which shows the combination of one main scale and two subscales. FIG. 10 is a diagram showing processing of the second embodiment;

Embodiments 1 and 2 of the absolute position encoder according to the present invention will be described in detail below with reference to FIGS. 1 to 4. FIG.

[Embodiment 1]
FIG. 1 is a diagram showing the length of the main scale and sub-scales, position data, X value, and absolute position of the absolute position encoder of the first embodiment. FIG. 1(a) shows the length (pitch) of the half period of the main scale and the subscale.

As shown in FIG. 1(a), the first embodiment has one main scale and one sub-scale. The main scale and subscale have N and S poles, respectively. Here, the N pole and the S pole each constitute a half cycle, and the N pole+S pole constitutes one cycle. The length (pitch) of the N pole and S pole (half cycle) of the main scale and the sub scale are different.

Each length of the N pole and S pole (half period) of the main scale is M=10 mm. The length of one cycle of the main scale is 20 mm (N pole + S pole). Each length of the N pole and S pole (half period) of the subscale is L=12.5 mm. The length of one cycle of the subscale is 25 mm for N pole + S pole.

The absolute position encoder of the first embodiment is an example in which N=100 mm and one cycle. That is, 5 cycles of the main scale (20 mm (N pole + S pole) x 5 (cycle)) and 4 cycles of the sub scale (25 mm (N pole + S pole) x 4 (cycle)) are the absolute position encoder of the first embodiment. for one period (detection area).

FIG. 2 is a diagram in which the N pole and S pole of the main scale are alternately arranged at a constant cycle, and the sensor A of the main scale detection section is arranged at a position where an output of a sin θ wave and a sensor B of a cos θ wave can be obtained. The sub-scale and the sub-scale detector also have the same configuration, although the pitches are different. For example, the main scale detector and the subscale detector are hall elements.

The main scale detection section and the subscale detection section can detect sine waves and cosine waves by using an optical type with a slit or by a magnetoresistive effect element. FIG. 2 shows an example in which the main scale and sub-scale are fixed to the moving body, and the main-scale detection section and sub-scale detection section (sensor A and sensor B) are fixed. A configuration in which the main scale detection section and the sub-scale detection section (sensor A, sensor B) are moved may be used.

FIG. 3 is a diagram showing position data obtained by R/D converting sin θ waves and cos θ waves in an R/D (resolver/digital) converter. A sin θ wave and a cos θ wave become sawtooth-shaped position data in one cycle.

FIG. 1(b) shows position data when each cycle of the main scale and subscale is R/D converted. Y0 is the position data of the main scale, and Y1 is the position data of the sub-scale.

When the maximum value of each of the position data Y0 and Y1 is 50, the coordinates of each point a to m are a=20, b=25, c=30, d=37.5, e=6.75, f = 45.4, g = -4.6, h = 37.5, i = 20, j = 46, k = 20, l = 37.5, m = 10. Note that g is a value based on f-50. The configuration of the first embodiment can detect the absolute position for five cycles of the main scale. That is, the absolute position P is P=50×5=250, which is 250 detection areas.

At the same absolute position, L/M=1.25. For example, point a and point b at the same absolute position are a=20 (M) and b=25 (L), and L/M=25/20=1.25.

FIG. 1(c) shows a time chart of X values calculated from the position data Y0 and Y1. The X value is given by the following formula (1) when Y0≧Y1, and given by the following formula (2) when Y1>Y0.

X=Y0-Y1×(L/M) (1)
X=Y0-(Y1-50)×(L/M) (2)
At Y0=point b and Y1=point a, X=25−20×1.25=0. At Y0=d point and Y1=c point, X=37.5−30×1.25=0. Therefore, as shown in FIG. 1(c), all values are 0 in the A section.

At Y0=e point and Y1=f point (g point), X=6.75-(f-50)×1.25=12.5. At Y0=h point and Y1=i point, X=37.5−20×1.25=12.5. Therefore, as shown in FIG. 1(c), all B sections are 12.5.

Similarly, X=25 for the C section, X=37.5 for the D section, and X=50 for the E section, and it is possible to identify the data of what round of the main scale.

FIG. 1(d) shows a state in which the small periods (periods of the main scale) are concatenated and converted into an absolute value. The frequency data n of the main scale is calculated from the X value. The X value is X=0 for the A section, X=12.5 for the B section, X=25 for the C section, X=37.5 for the D section, and X=50 for the E section. When this X value is divided by the half period of the subscale = 12.5, the frequency data n of each section is A section: n = 0/12.5 = 0, B section: n = 12.5/12.5 = 1, C section: n = 25/12.5 = 2, D section: n = 37.5/12.5 = 3, E section: n = 50/12.5 = 4.

Let Pm be the position data for one cycle of the main scale (50 in the first embodiment). The absolute position P can be represented by the following equation (3).

P=Y0+Pm×n (3)
For example, the absolute position P of point l is P=37.5+50×2=137.5.

As described above, according to the first embodiment, high-accuracy position data that repeats in a short period obtained by R/D conversion from a sine wave and cosine wave of a constant period, and the number of times of the data An absolute position encoder with a wide detection area can be realized at a low cost with a simple configuration by calculating the absolute position based on the number of rotation data indicating .

[Embodiment 2]
The second embodiment is an example in which a plurality of subscales are provided to increase the upper limit of the main scale frequency data n. FIG. 4 shows an example with two subscales. The upper limit of the main scale frequency data n varies depending on the length M of the main scale, the length L of the first subscale, and the length R of the second subscale.

For example, when there are two sub-scales, the X value based on the first sub-scale is calculated using the equations (1) and (2) as in the first embodiment based on the position data of the main scale and the first sub-scale. . Also, based on the position data of the main scale and the second sub-scale, the X value based on the second sub-scale is calculated using the equations (1) and (2) as in the first embodiment.

By dividing the X value based on the first subscale by the half period of the first subscale=25, the frequency data n1 of each section based on the first subscale can be calculated. The frequency data n1 based on the first subscale is n1=0 to 4 as shown in FIG.

Similarly, by dividing the X value based on the second subscale by the half period of the second subscale=30, the frequency data n2 of each section based on the second subscale can be calculated. The frequency data n2 based on the second subscale is n2=0 to 1 as shown in FIG.

where N1max is the number of n1 values. In FIG. 4, n1 has five values of 0, 1, 2, 3, and 4, so N1max=5. Also, N2max is the number of values of n2. In FIG. 4, n2 has two values of 0 and 1, so N2max=2.

j is a value that is repeated up to the maximum value of the frequency data by adding 1 to 0, 1, 2, 3, 4, . . . j%N1max is the remainder of j divided by N1max. j%N2max is the remainder of j divided by N2max. In the case of FIG. 4, since N1max=5 and N2max=2, j%N1max=j%5 and j%N2max=j%2.

j%5 is j%5=0 when j=0 and j%5=1 when j=1. j%2 is j%2=0 when j=0 and j%2=1 when j=1, that is, j%2 is 0,1.

Table 1 below shows n1, n2, j (=j+1), j%5, j%2, n (=j) in the case of FIG.

Here, processing of the second embodiment will be described based on FIG. Here, n1x=j%5 and n2x=j%2. j repeats up to a preset value. In FIGS. 4 and 5, j<=9 (or j<10), where j is less than 10 (that is, j repeats from 0 to 9). In S1, if j is smaller than 10, the process proceeds to S3.

In S3, the value of j when n1x=n1 and n2x=n2 is taken in as the frequency data n at j to which +1 is successively added.

In S4, 1 is added to j and the process returns to S1. When it is determined in S1 that j has reached 10, the process proceeds to S2 and sets j=0.

After that, the same processing is repeated from S1. When the frequency data n1 based on the first subscale and the frequency data n2 based on the second subscale are the same as before, the frequency data n is also the same value as before. If the position has moved from the previous state, the value of j where n1x=n1 and n2x=n2 is read as the number of rotation data n. In this manner, if the frequency data n1 based on the first sub-scale and the frequency data n2 based on the second sub-scale do not change, the frequency data n is held, and if they do change, the frequency data n is corresponded. change by

The absolute position P is calculated in the same manner as the formula (3) of the first embodiment using the number of rotation data n.

That is, in the second embodiment, based on the position data of the main scale and the position data of each subscale, the X value based on each subscale is calculated by the formula (1) or (2). Cycle number data based on each subscale is calculated by dividing the X value based on each subscale by the length of the half cycle of each subscale. j is a value that is repeated up to the maximum value of the frequency data by incrementing 0, 1, 2, 3, 4, . . . If the frequency data based on each subscale changes, j is held as the frequency data and 1 is added to j. Then, the absolute position is calculated by the formula (3).

For example, as shown in FIG. 4, when M=20, L=25, and R=30, the combination of only the main scale M and the sub-scale L makes one cycle in five periods of the main scale. It can be seen that the combination of the length M, the length L of the first sub-scale, and the length R of the second sub-scale makes it possible to set a wide range of absolute positions, one cycle in 10 cycles of the main scale.

As described above, in addition to the effects of the first embodiment, the second embodiment can detect a wider range of absolute positions by using a plurality of sub-scales.

Note that the encoder is not limited to a linear encoder, but is a rotary system, and it is also possible to identify the angle of one rotation from the position data obtained by dividing one rotation into a plurality of parts, and convert the position data into an absolute position.

Although the present invention has been described in detail only with respect to the specific examples described above, it is obvious to those skilled in the art that various modifications and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are, of course, covered by the claims.

M: Length of half cycle of main scale L: Length of half cycle of (first) subscale R: Length of half cycle of second subscale n: Frequency data P: Absolute position Y0: Main scale Position data Y1: Sub-scale position data

Claims (4)

a main scale detector that detects sine waves and cosine waves from the main scale;
a subscale detection unit that detects sine waves and cosine waves from subscales having a period different from that of the main scale;
The sine wave and cosine wave detected by the main scale detection unit and the sine wave and cosine wave detected by the subscale detection unit are R/D converted to obtain the position data of the main scale and the position data of the subscale. an output R/D converter;
Circulation number data indicating the number of laps of the main scale data is calculated from the relationship between the position data of the main scale and the position data of the sub-scales, and the position data of the main scale and the lap number data of the main scale are calculated. a calculation unit that calculates an absolute position based on
with
The calculation unit is
Calculate the X value by the following formula (1) or (2),
calculating the frequency data of the main scale by dividing the X value by the length of the half cycle of the subscale;
An absolute position encoder, wherein the absolute position is calculated by the following equation (3).
When Y0≧Y1, X=Y0-(Y1×L/M) (1)
When Y1>Y0, X=Y0-(Y1-Pm) L/M (2)
P=Y0+Pm×n (3)
P: Absolute position X: X value Y0: Position data of main scale Y1: Position data of sub-scale Pm: Maximum value of position data of main scale and sub-scale M: Length of N pole and S pole of main scale L: Length of north pole and south pole of sub scale n: frequency data of main scale a main scale detector that detects sine waves and cosine waves from the main scale;
a subscale detection unit that detects sine waves and cosine waves from subscales having a period different from that of the main scale;
The sine wave and cosine wave detected by the main scale detection unit and the sine wave and cosine wave detected by the subscale detection unit are R/D converted to obtain the position data of the main scale and the position data of the subscale. an output R/D converter;
Circulation number data indicating the number of laps of the main scale data is calculated from the relationship between the position data of the main scale and the position data of the sub-scales, and the position data of the main scale and the lap number data of the main scale are calculated. a calculation unit that calculates an absolute position based on
with
having a plurality of subscales with different periods,
The calculation unit calculates the frequency data of the main scale from the relationship between the position data of the main scale and the position data of the plurality of sub-scales, and calculates the position data of the main scale and the frequency data of the main scale. calculating the absolute position based on
The calculation unit is
calculating an X value based on each subscale by the following formula (1) or (2) based on the position data of the main scale and the position data of each of the subscales;
calculating frequency data based on each subscale by dividing the X value based on each subscale by the length of the half cycle of each subscale;
j is 0, 1, 2, 3, 4, . and add 1 to j,
An absolute position encoder, wherein the absolute position is calculated by the following equation (3).
When Y0≧Y1, X=Y0-(Y1×L/M) (1)
When Y1>Y0, X=Y0-(Y1-Pm) L/M (2)
P=Y0+Pm×n (3)
P: Absolute position X: X value Y0: Position data of main scale Y1: Position data of sub-scale Pm: Maximum value of position data of main scale and sub-scale M: Length of N pole and S pole of main scale L: Length of north pole and south pole of sub scale n: frequency data of main scale 3. The absolute position encoder according to claim 1, wherein said absolute position encoder is a linear encoder. 3. The absolute position encoder according to claim 1, wherein said absolute position encoder is of a rotary system, and the position data obtained by dividing one rotation into a plurality of parts is converted into an absolute position by specifying an angle of one rotation.

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