JPH03285114A - Code plate for 1 track absolute encoder - Google Patents

Abstract

PURPOSE:To improve the resolution of an absolute pattern without restraints of limits of the sensor pitch by arranging the n-bit code detected by (n) sensors to be a specific array of codes different at every absolute position. CONSTITUTION:When two kinds of minimum reading units with different physi cal properties are represented by codes 0. 1, and supposing that (lambda) is the length of the minimum reading unit and (m) is an integer not smaller than 3 in a code plate A of an absolute encoder wherein a predetermined array of codes 0,1 is arranged in a longitudinal direction of a track T, the n-bit code detected by (n) sensors each placed in the longitudinal direction of the track T and having an array of codes arranged opposite to the track T with the pitch corre sponding to mlambda is made a specific array of codes different at any absolute position. The code plate A detects a plurality of minimum reading units with alternate two or more tracks T, thereby obtaining a code signal. Therefore, it is enough for the sensor S to be provided with a predetermined number of bits separated 3lambda or more in a sensor head SH, and the requirement for the sensor pitch is eased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a code plate used in a one-track type absolute encoder. A method is provided that facilitates the production of absolute encoders.

[Prior art] An encoder detects the amount of B movement and the movement angle and speed obtained based on this, and consists of two types: ■Absolute encoder that can detect the absolute position within the movement range; It is also classified as an incremental encoder that can only detect the angle of movement.

In any case, the encoder has the following configuration: (1) The minimum reading unit of the Zfi class, which has different physical properties such as reflectance, transmittance, polarization state, magnetic properties, and direction of magnetization, is a number of 0.1. A code plate formed by forming a predetermined code sequence consisting of a sequence of 0.1 on a track when expressed as a binary code;
(2) A sensor head that distinguishes and detects 0.1.

In addition, a mechanical drive mechanism is actually required to move the code plate and the sensor head relative to each other in parallel.

The code board is a long plate (with tracks along a straight line).
...linear encoder), disc-shaped (with tracks along the circumference...rotary encoder), cylindrical shape (with tracks along the outer circumferential surface of the cylinder...rotary encoder), etc.

Recently, a one-track absolute encoder that can determine the absolute position with just one track has been proposed (Japanese Patent Laid-Open No. 57
-175211, Japanese Utility Model Application Publication No. 80-152916, and Japanese Patent Application Publication No. 1-152314).

In the code plate of this one-track absolute encoder, the code string consisting of the Oll number sequence has a special arrangement. For example, in the case of n=4 bits, the total number of codes p(
= 2°''4 = 16) code strings are as follows (see Figure 2).

000010011110101 ↑111 - Movement Here, the arrow ↑ indicates the position of the sensor installed in the sensor head to detect this code string, and the position of the sensor is
It moves in the direction of the arrow as the code plate and sensor head move relative to each other.

In other words, the sensor head has a minimum reading unit length of λ
, n sensors are arranged at a pitch corresponding to λ in the longitudinal direction of the track, and these n sensors simultaneously detect n consecutive minimum reading units in parallel to determine the absolute position of the sensor head with respect to the code plate. We are assembling a code signal representing .

Therefore, in the above example, the first absolute position indicated by the arrow ttX is the coat signal oooo, and the absolute position 'j82, which is moved by approximately λ in one direction of the arrow, is the coat signal 0001.
If the sensor heads are sent sequentially in this manner, the relationship between each absolute position and its code signal will be as follows. However, it is assumed that this code string is compatible with a rotary encoder, with its right end connected to its left end.

First absolute position: ooo.

Second absolute position: 0001 Third absolute position: 0010 Fourth absolute position: 0100 Fifth absolute position + 1001 Sixth absolute position + 0011 Seventh absolute position: 0111 Eighth absolute position: 1111 9 absolute position + 1110 10th absolute position: 1101 'tS11 absolute position: 1010 12th absolute position: 0101 13th absolute position 1011 14th absolute position 011O 15th absolute position 1100 ! F: Absolute position of J16 1000 First absolute position 0000 As described above, the n=4-bit coat signal detected by the n=4 sensors is different at each absolute position, and conversely, The absolute position of the sensor head relative to the code plate can be determined from the detected coat signal. Further, for example, by using a comparison table (memory) that converts the detected code signal one-to-one into a binary ordinal number signal, it is possible to obtain this address signal in a numerical value that is easier to understand.

FIG. 2 shows an example of a rotary absolute encoder using an absolute track of this code string.

In Figure 2, code plate A has white parts as O1 and hatched parts as 1
An absolute track T is formed by arranging the minimum reading units of length λ, each represented by , clockwise along the circumference from the mark M to form the above-mentioned code string, and the sensor head S
Four sensors S are arranged along this track T at a pitch λ.

Therefore, in the rotary absolute encoder of FIG. 2, the minimum reading unit length and the sensor pitch are equal to λ.

By the way, in the rotary absolute encoder shown in FIG. 2, one of the sensors S is of a different type.
If you turn on the power to the encoder and start detecting the absolute position from a stopped state in which the sensor straddles two minimum reading units, it is uncertain which of the two minimum reading units the sensor will read, and the output There is a possibility that an error may occur in the code signal that is sent. For example, if a code signal of 1001 should normally be output at a position approximately halfway between the fifth absolute position and the sixth absolute position, but the leftmost sensor detects the neighboring O, the output code The signal becomes 0001. Since this is a code signal representing the second absolute position, it can be said to be a serious reading error.

In order to solve the misreading of the coat signal caused by the sensor detecting the minimum reading unit boundary, especially the instability of the coat signal when the power is turned on, n sensors (referred to as a sensor group) are used. A technique of arranging 2M, shifted by about 1/2λ, and outputting a code signal by selecting the set in which the minimum reading unit center is detected among these two sets (for example, Japanese Patent Laid-Open No. 79619/1983) Figure 7 of the publication) was developed.

With this technology, 1/
An incremental track with a pitch of 1λ and a phase difference of 4λ is provided, and an incremental sensor for detecting this track is also provided. Then, if the output of the incremental sensor is high level (1) when the power is turned on, one set of sensors does not include the sensor on the minimum reading unit boundary, so select it and read the absolute position correctly. If it is low level (0), the other set of sensors does not include the sensor on the boundary, so it can be selected to read the absolute position correctly.

Therefore, in such an absolute encoder, the minimum reading unit length of the absolute pattern is λ, whereas the sensor head has two sensor groups of I/2
Since they are arranged with a shift of λ, the actual sensor pitch is 1/
2λ roars.

[Problem to be solved by the invention] When actually designing and producing a rotary absolute encoder as shown in Fig. 2, the sensor head SH has
As a sensor group arranged at a sensor pitch, a sensor array formed by continuously adjoining a large number of short photosensors is generally adopted, but with current technology, the dimensions of the photosensors that make up the sensor array However, this is the limit for miniaturization and high resolution of encoders.

In other words, in the case of the rotary absolute encoder shown in Fig. 2, a simple transparent or opaque pattern can be used as the track T, for example, using photolithography technology.
Although it is easy to obtain a λ of about 1 μm, due to reasons such as: - Decrease in S/N ratio due to reduction in sensor light receiving area, - Mutual interference, - Problems with insulation, - Effect of diffracted light from adjacent minimum reading units, etc. The sensor pitch in the sensor head is limited to 20 .mu.m, and as a result, the minimum reading unit length on the code plate side has to be 20 .mu.m even though a shorter length can be obtained.

Furthermore, as mentioned above, "Two sets of sensor groups are provided, and the coat signal is output by the set that detects the minimum reading unit central part."
In the case of an absolute encoder, if the sensor pitch of the sensor array is set to the limit of 20 μm, and each sensor group is composed of every other sensor, ^ = 40 μm.
We had no choice but to accept a large-diameter code plate with considerably low resolution and a minimum reading unit length of 40 μm for the absolute pattern, even though it could produce more minute details.

Therefore, in order to achieve further miniaturization and higher resolution in these types of one-track absolute encoders that use sensor arrays, that is, to reduce the minimum reading unit length λ of the absolute pattern, it is necessary to increase the sensor pitch. Solving problems was considered important.

SUMMARY OF THE INVENTION An object of the present invention is to provide a code plate that is not limited by the sensor pitch limit as in the past and is capable of increasing the resolution of an absolute pattern.

[Means for solving the problem] One-track absolute type according to claim 1 of the present invention
[The code plate for an encoder is formed by forming a predetermined code string of 0.1 in the longitudinal direction of the track when two types of minimum reading units with different physical properties are represented by the code O11] In the code plate for a track-type absolute encoder. , λ: Length of the minimum reading unit m: When an integer of 3 or more, the code string is defined as "n sensors facing the track and arranged in the longitudinal direction of the track at a pitch corresponding to mλ. '' is a special code string in which the n-bit code detected at any absolute position is different.

One-track absolute type according to claim 2 of the present invention.
The code plate for an encoder is a code plate for a one-track absolute encoder according to claim 1, in which the n-bit code detected by "n sensors arranged in the longitudinal direction of the track at a pitch corresponding to λ" is A code string that differs also in absolute position is referred to as a reference code string A (where 1
≦i≦p, p is the total number of codes in the track), the special code string Bt (where 1≦j≦p, p is the total number of codes in the track) is a fraction m/p or irreducible. The reference code string A1 is rearranged according to the following formula under the condition that .

[Function] One-track absolute type according to claim 1 of the present invention.
The encoder code plate has an absolute track that detects a plurality of consecutive minimum reading units to obtain a code signal, rather than the conventional one that detects a plurality of minimum reading units separated by 2 m or more. A coat signal is obtained by detecting this. Therefore, the sensor for detecting this track only needs to have a predetermined number of bits arranged at least 3λ apart on the sensor head, and the requirements for the sensor pitch are relaxed compared to the conventional case where they are arranged at intervals of λ. . In other words, ■ increasing the length along the sensor track or the spacing between sensors, or ■ increasing the minimum reading unit length λ or smaller for a sensor array with the same sensor pitch as in the past, i.e., creating a code with high resolution. It is now possible to use the board.

In addition, when this code plate is applied to the above-mentioned absolute encoder in which two sets of sensor groups are provided and the code signal is output by the set that detects the minimum reading unit central part, The distance between the two sensor groups is 1/2λ
■The distance between the first sensor group and the second sensor group is 3/
Various selections such as 2λ are possible, and the degree of freedom in design is increased, but in both cases, including (1) and (2), the requirements for the sensor pitch are similarly relaxed. In particular, when the sensors of the first sensor group and the sensors of the second sensor group are arranged alternately and at equal intervals, for example, when the sensor pitch of the first sensor group is 3λ, the interval between the first sensor group and the second sensor group is 3/2λ
In this case, the requirement for sensor pitch is naturally
It will be the minimum.

Now, as the code string (called a special code string) that makes up this absolute track, it is not possible to use the conventional code string as it is. or ■ mechanically rearrange a known code string (referred to as a reference code string) from which a code signal can be obtained from n consecutive minimum reading units to create a special replacement type code string. It is necessary to separately define the value by converting it into a code string.

One-track absolute type according to claim 2 of the present invention.
In the encoder code plate, this special code string is a replacement type of ■, and one method of mechanically rearranging a known reference code string is introduced. If this method fails, ■
A special code string can be obtained with less time and effort than the above method. This procedure will be explained in detail below.

In this method, first, a conventionally known one-track type absolute pattern is prepared as a reference code string. In this reference code string, the n-bit code read by "n sensors arranged in the longitudinal direction of the track at a pitch corresponding to λ" differs at any absolute position. This is now expressed as A, (1≦i≦p). Here, p is the total number of codes in the track and is usually 2°. Further, the target special code string is represented by B, (1≦j≦p). In this case, Ai to B under the condition that the fraction m/p is irreducible.
The sorting to is expressed by the following formula: %expression%).

That is, B ll
+a low 11 = A H...1st B l++mf
2-11 = A 2 - m + 1st B l++
+++3-11=A, -2m + 1st and so on until A2 is replaced, and the code string B to be obtained is obtained.
(1≦j≦p) is obtained.

Let me explain in more detail. Considering the reference code string of n=4 bits listed earlier: 0000100111101011, each code of this code string is now written as the symbol abcde.
It is shown as fghijklmnop. A special code string for assembling a coat signal with m=3, that is, four codes divided by two, is formed by rearranging the codes a, b, c, . . . three times as follows.

Standard code 0000100111101011 number sequence
abcdefghijk1mnop 1st lap a**
b**c**d**e**f 2nd lap **g**h*
*3rd lap on *i**j** *1 **m**n*
*o**p**mouth↓↓↓↓↓↓↓↓↓↓1↓↓↓ Special code algbmhcnidojepkfSpecial code string obtained in this way: algbmhcnidojepkf oooool 100101 1 1 1 10 1 1
↑ ↑ - From the movement direction, the following coat signal is assembled using every second code indicated by arrow 1.

Absolute position of %s: abcd=ooo.

Second absolute position: 1mno=0101 Third absolute position ghij-0111 Fourth absolute position: bcd
e=ooo1 5th absolute position: mnop=1011
6th absolute position: hijk=1111 7th absolute position: cdef=oo10 8th absolute position: no
pa=0110 9th absolute position + 1jkl-111
0 10th absolute position: defg=0100 11th absolute position: opab=1010 12th absolute position:
Absolute position of jk1m=1101't%13: e
fgh=1001 14th absolute position: pabc=o
+o.

15th absolute position: k1mn=I010 16th absolute position: fghi=oo11 As above, n=4
The n=4-bit coat signal detected by the sensors is
Although the order is different, they are the same as each of the coat signal groups obtained from the original code string, and are different at each absolute position of the sensor head. Therefore, conversely, the absolute position of the sensor head relative to the code plate can be determined from the detected signal. Further, for example, by using a comparison table (memory) that converts the detected court signal one-to-one into a binary ordinal number signal, this address signal can be obtained in a numerical value that is easier to understand.

By the way, by using a code plate having this code string that detects the minimum reading unit for every three people, an absolute encoder of the above-mentioned "two sets of sensor groups are alternately switched" type is constructed, and the two sets of sensor groups are If they are arranged with a shift of 3/2λ or more, a problem arises in that the detection position moves backward due to switching of the sensor group. This means that the two sensor groups are divided by 1/2.
This is a problem that does not exist when the sensor heads are arranged with a shift of λ.
The problem is that code signals indicating different addresses separated by /2λ are output alternately. However, this problem can be solved by e.g.
This problem can be easily solved by providing a one-to-one code signal conversion memory in one sensor group and converting the code signal to one at an address shifted by one or two addresses.

[Embodiments of the invention] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a planar structure of a rotary encoder using a code plate for a one-track absolute encoder according to a first embodiment of the present invention.

In Figure 1, code plate A has a white part of O1 and a hatched part of O1.
An absolute track T is formed by arranging the minimum reading units of length λ, each represented by
Along this track T, four sensors S are arranged at a pitch λ. Furthermore, the memory element M converts the irregular code signals detected by the four sensors S into a BCD.
(binary ordinal) code.

The special code string B of this absolute track T is:
0000100111101011 is rearranged according to the following formula: 00001 100101 1 1 1 10↑ ↑
Form a code string of 16 minimum reading units in the direction of movement,
As shown by the arrow ↑, use every second code to assemble the following code signal. First absolute position: oooo → 0001 Second absolute position: 010i → 0010 Third absolute position + 01
11→0011 Fourth absolute position: 0001→010
0 5th absolute position 1011-0101 6th absolute position: 1iit-0110 7th absolute position: 00
10-0111 8th absolute position: 0110→100
0 9th absolute position: 1110 → 1001 10th absolute position + 0100 → 1010 11th absolute position:
1oto-toit 12th absolute position・1101→
1100 13th absolute position + 1001 → 1101 14th absolute position・0100 → 1110 15th absolute position: 1010 → 1111 16th absolute position: 0
011→0000 Immediately, each code signal is converted by the memory element M into a binary ordinal code signal indicated by an arrow, and is output to the output terminal C.

The columns are rearranged according to the following formula: i.e. 1+3X
(j-1) 10 as (Left, B, = A, ... 1st B4"A2 ... 3 + 1st B7 = A3 ... 6 + 1st B, o = A4 ・-9 + 1st B3 = A5 ...12+1-10th 6=A6
. . . The special code string B, (1≦j≦p) is obtained by sequentially purchasing AiO, such as 15th+1−10th.

FIG. 3 is for explaining a code plate for a one-track absolute encoder according to a second embodiment of the present invention.
The absolute track of the special code string formed on the code plate is shown. This is a standard code consisting of 10 minimum reading units of A1 to AiO. FIG. 4 illustrates the code plate for a one-track absolute encoder according to the third embodiment of the present invention, particularly the code string of its absolute track. (1) shows a reference code string having an M-sequence code arrangement, and (2) shows a special code string obtained by rearranging the reference code string.

The code string in FIG. 4 (1) is an M-sequence code string consisting of 1023 codes expressed by the following formula: Different at every position on the column.

The code string in FIG. 4(2) is the code string in FIG. 4(1) with m=
5, the code is rearranged according to the following formula: % Formula %), and the coat consisting of every fourth nine codes is different at every position on the code string.

FIG. 5 is a code plate for a one-track absolute encoder according to a fourth embodiment of the present invention, particularly for explaining the code string of its absolute track. (1) shows the code arrangement of the entire periodic sequence. (2) indicates a special code string obtained by rearranging the reference code string.

The code string in FIG. 5(1) is a full periodic code string consisting of I 000 codes, and the codes made up of 10 consecutive codes are different at any position on the code string.

The code string in FIG. 5(2) is the code string in FIG. 5(1) with m=
3, the codes are rearranged according to the following formula: % Formula %), and the coat composed of every second 10 codes is different at any position on the code string.

[Effect of the invention] The one-track absolute type according to claim 1 of the present invention
If an encoder code plate is adopted, compared to a conventional code plate, ■ the length along the sensor track and the spacing between sensors can be expanded, or ■ it is possible to increase the distance between sensors installed with the same sensor pitch as before. , it has become possible to reduce the minimum reading unit length on the absolute track, that is, to use a code plate with high resolution. Therefore, it is possible to easily downsize the absolute encoder and increase its resolution without impairing its reliability. In other words, even when the pitch of the absolute track becomes finer, the effective area of the sensor does not decrease with the optical type.
The magnetic type, which is easy to manufacture, can provide an easy-to-manufacture absolute encoder such as an MR sensor.

In particular, this code plate is used in an absolute encoder that has two sets of sensors and outputs a code signal by the set that detects the center of the minimum reading unit. If the encoder is placed in the
The resolution on the code plate side can be maximized without impairing the reliability of code detection and without being limited by the sensor pitch limit.

One track type absolute according to claim 2 of the present invention
The encoder code plate obtains its special code string by simple rearrangement from a known one-track absolute pattern code string, so it takes less time and effort than creating it from scratch by blind calculation. reduced. In addition, the special code string created in this way yields the same codes as those obtained from the original code string, although the order is different, so there are many commonalities in the electronic circuit configuration, and the parts It is advantageous for standardization and speeding up of design.

[Brief explanation of drawings]

FIG. 1 is a plan view of a rotary encoder using a code plate for a one-track absolute encoder according to a first embodiment of the present invention. FIG. 2 is a plan view of a conventional rotary absolute encoder. FIG. 3 is a diagram for explaining a code plate for a one-track absolute encoder according to a second embodiment of the present invention, and is a schematic diagram of absolute tracks formed on this code plate. FIG. 4 is a numerical sequence for explaining the code plate for a one-track absolute encoder according to the third embodiment of the present invention, particularly the code sequence of its absolute track, and (1) is a standard having an M-sequence code sequence. The number sequence (2) of the code string is a number sequence of the special code string obtained by rearranging the reference code string. FIG. 5 is a code plate for a one-track absolute encoder according to a fourth embodiment of the present invention, particularly for explaining the code string of its absolute track. (1) shows the code arrangement of the entire periodic sequence. The reference code sequence with (2
) is a sequence of special code sequences obtained by rearranging the standard code sequence. [Explanation of symbols of main parts]

Claims (2)

[Claims] (1) When two types of minimum reading units with different physical properties are represented by codes 0 and 1, in a code plate for a one-track absolute encoder in which a predetermined code string of 0 and 1 is formed in the longitudinal direction of the track, λ: Length of the minimum reading unit m: When an integer of 3 or more, the code string is "n sensors arranged in the longitudinal direction of the track facing the track at a pitch corresponding to mλ" A code plate characterized in that the n-bit code detected in the code is a special code string that differs at any absolute position. (2) Standard code string A is a code string in which the n-bit codes detected by "n sensors arranged in the longitudinal direction of the track at a pitch corresponding to λ" are different at any absolute position.
When _i (however, 1≦i≦p, p is the total number of codes in the track), the special code string B_j (however, 1≦j≦p, p is the total number of codes in the track) is a fraction m Under the condition that /p is irreducible, the reference code string A_i is expressed as follows: B_1_+_m_(_j_-_1_)=A_j(mod
．． 2. The code board according to claim 1, wherein the code board is arranged according to p).