JPH041522A - Absolute encoder capable of detecting abnormal state - Google Patents

Abstract

PURPOSE:To detect the occurrence of a read error of a detector immediately by arranging plural detectors and providing a means which compares absolute position relations obtained by the respective detectors and outputs an alarm signal unless they do not match each other. CONSTITUTION:The absolute encoder consists of a code plate A where a multi- track or one-track type absolute pattern is formed and a detection part B which is equipped with detectors (b) for detecting absolute positions on the pattern and can move relatively to the code plate A; and a detector b1 reads a binary sequence starting with 0000, a detector b2 reads a binary sequence starting with 0100, and the output difference between the both is always 0100. Therefore, when the detector b1 generates a read error and wrong numeral codes are outputted as outputs d1-d4, a comparator R detects a difference in output be tween a computing element C and an output device F to output the alarm signal to an output terminal (r), thereby securing the safe operation of the whole device.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is an absolute encoder that reads a pattern on a code plate with a detector of a detection unit and assembles a numerical code corresponding to the positional relationship between the code plate and the detection unit. In detail, we introduce a mechanism for constantly checking the accuracy/inaccuracy of assembled numerical codes.

[Prior Art] Various absolute encoders are known as one type of measuring instrument that detects angular position coordinate values associated with the rotation of a rotating body and position coordinate values associated with the movement of an a-line moving body. - Numerically speaking, an absolute encoder consists of a code plate that forms an absolute track and a detection section that is movable relative to this track, one of which is fixed to the object to be measured. move with This causes a relative movement between the two, but the detector installed in the detection unit detects the absolute track at the momentary relative position of the two, and the position coordinate value that corresponds one-to-one to the relative position of the two is detected. A numerical code is assembled.

Here, the unit increments section on the absolute track detected by the detector is called the minimum reading unit, and is given various physical properties representing numerical values. Therefore, in other words, an absolute track is a special sequence of numbers expressed by this arrangement of physical properties, and includes positional coordinate information at each relative position, and is a combination of numerical values detected at one time on the sequence. is a numerical code representing the absolute position.

A commonly known type of absolute encoder is a J-type encoder that detects multiple absolute tracks in parallel and assembles a numerical code in a binary ordinal sequence. Track: 0000000011111111...(4)↑ ■...-Moving direction 0000111100001111...(3)↑ ■...-Moving direction 0011001100110011...(2)■
...-Moving direction 0101010101010101...(1) ■
...-For the moving direction (1) to (4), the detection unit has a 4-biased sensor ■~
A detector consisting of ■ is installed, and when the sensors ■ to ■ read numerical values one by one from absolute tracks (1) to (4), the detection part moves in one direction of the arrow, with the current position as the first absolute position. The numerical code assembled with ■■■■ is the first absolute position: ooo.

Second absolute position: ooo Third absolute position: 0O10 Fourth absolute position ・0011 Fifth absolute position +0100 Sixth absolute position: 0101 Seventh absolute position: 0110 Eighth absolute position: 0111 Absolute position of 9: 1000 Absolute position of 1st O: 100f @ Absolute position of 11 +1010 's12(7) M pair position +1011 Absolute position of 13th: 1100 Absolute position of 14th: 1101 Absolute position of 15th +1110 16th There are 16 different absolute positions of +1111, and each absolute position is 1
Distinguish on a 1-to-1 basis.

Here, each of the absolute tracks (1) to (4) is, for example, a transparent minimum reading unit and an opaque minimum reading unit arranged according to the Oll of each numerical sequence, and
Each of the sensors described in (2) can be configured by a combination of a light source and a photosensor that distinguish between light blocking and light transmission, but it is also possible to express the numerical distinction by another physical property such as the direction of magnetization, and use a magnetic head etc. as the sensor. Yes.

On the other hand, in recent years, one-track absolute encoders have been actively developed and reported in which the number sequence of the absolute track has been devised so that a numerical code is assembled by reading multiple minimum reading units on one track. . In this one-track absolute encoder, a special sequence such as a full period sequence or an M sequence is adopted as the absolute track sequence, and the numerical code assembled from this is used to mutually change the absolute positions of the code plate and the detection section. It is only for distinguishing between the above 4-track type absolute and
It does not have a regular, easy-to-understand order like an encoder. However, since the L-track type absolute encoder only requires one absolute track, it has various advantages in terms of sensor arrangement and code plate production.

As an example of such a one-track absolute encoder, Japanese Patent Application Laid-open No. 1-152314 discloses "n
An absolute track is formed on the code plate, representing the complete periodic series of bits in an optical light-dark pattern;
A method has been introduced in which a numerical code is assembled by detecting n consecutive minimum reading units on the track in parallel with a detector consisting of n photosensors.

The absolute track used here represents a binary number sequence called a total periodic sequence.
For example, for an absolute track with a minimum reading unit of 16 periods, the total period series is: 1111...-According to the moving direction ■■■■, the transparent part is O5 and the opaque part is 1, and the minimum reading unit is are arranged. However, after 01 at the right end, it returns to the first OO... On the other hand, the detection unit is equipped with a detector consisting of sensors ↑ to ↑ that determine whether the minimum reading unit is transparent or opaque, and reads the four consecutive minimum reading units indicated by the arrows ↑ in parallel to obtain a 4-bit numerical value. Assemble the code. That is, when the detection unit moves in one direction of the arrow with the absolute position where 0000 is detected as the first absolute position, the first absolute position, the second absolute position, the third absolute position, the fourth absolute position 345. Absolute position Sixth absolute position 1iS7 absolute position: ooo.

:0OO1 :0O11 +0110 +1101 +1010 +0101 8th absolute position ・1011 9th absolute position ・0111 io's absolute position = 111 11th absolute position. 1110 12th absolute position: 1100 13th absolute position ・1001 14th absolute position: 0O10 15th absolute position +0100 16th absolute position: 1000 1st absolute position: 0OOO, and so on, each of the 16 different numerical codes,
The signals are sequentially read and each absolute position of the detection unit with respect to the code plate is determined on a one-to-one basis.

[Problem to be solved by the invention] By the way, regardless of whether it is a multi-track type or a one-track type,
If even one sensor misreads the minimum reading unit, there is a problem that the correspondence between the numerical code and the absolute position will be lost.

For example, in the 4-track type absolute encoder mentioned above, when the actual positional relationship between the code plate and the detection section is at the 6th absolute position: 0101 ■■■■, a reading error may occur in the sensor ■ of the detector. Then,
The obtained numerical code becomes 0111, and at this time, the absolute encoder determines that the positional relationship between the code plate and the detection section is at the eighth absolute position: 0111 ■■■■.

In addition, in the above-mentioned one-track type absolute encoder, when the actual positional relationship between the code plate and the detection section is at the sixth absolute position: 1010 ■■■■, if a reading error occurs in the sensor ■ of the detector,
The obtained numerical code ends up being 1000, and at this time, the absolute encoder determines that the positional relationship between the code plate and the detection section is at the 16th absolute position ・1000 ■■■■.

Such reading errors in absolute encoders are not only simple errors in data processing, but also cause malfunctions and runaways in machines that incorporate absolute encoders, so it is necessary to reduce the possibility of reading errors (0 ) is an important design issue. Also, in the unlikely event that a -1 reading error occurs, immediately press #! It is desirable to have a warning signal to stop the machine, etc.

The present invention is an absolute encoder that can constantly monitor whether the numerical code assembled by reading the minimum reading unit is accurate or inaccurate, and can detect an abnormal situation by immediately issuing a warning signal if a reading error occurs. The purpose is to provide

[Means for Solving Problem H] The invention of claim 1 provides a code plate (A) on which a multi-track or one-track absolute pattern is formed.
and a detection section (B) which is provided with a detector (b) that detects an absolute position on the pattern and is movable relative to the code plate (A). ) are arranged so that each detects a different absolute position, and the arrangement relationship of each is compared with the on-the-spot absolute position relationship obtained from each detector during driving, and if the two do not match, , a warning means for outputting a warning signal.

The invention of claim 2 is the invention of claim 1, which comprises:
The warning means includes: a storage means that stores the difference in absolute position of the plurality of detectors (b); and a calculation means that calculates the difference in absolute position obtained from each detector at the time of driving. and a comparator that compares the difference calculated by the calculation means with the difference stored in the storage means and outputs a warning signal if the two do not match.

The invention of claim 3 is the invention of claim 1, which comprises:
The warning means includes: a storage means storing the difference in absolute positions of the plurality of detectors (b); and a storage means storing the difference in absolute positions of the plurality of detectors (b); A prediction means that adds or subtracts the difference stored in the means to predict the absolute position detected by another detector (b2) at that time; It consists of a comparator that compares the absolute position detected by the detector (b2) and outputs a warning signal if the two do not match.

The invention of claim 4 is the invention of claim 1, which comprises:
The warning means is a reference in which the relationship between the absolute position detected by one (b2) of the detectors (b) at each absolute position and the absolute position detected by the other detector (b2) at that time is stored. Table and detector (b2
) detects a certain absolute position, the predicted absolute position of the other detector (b2) obtained from the comparison table and the absolute position actually output from the other detector (b2) at this time are calculated. It consists of a comparator that compares the two and outputs warning No. 12 if the two do not match.

[Operation] According to the invention of claim 1, two or more detectors are arranged in the pressure detection section, and numerical codes at moved positions on the absolute track are compared with each other to detect an abnormal situation.

In other words, a plurality of detectors with a fixed mutual positional relationship are arranged in the detection section, and each detector is placed at a different position on the absolute track corresponding to the positional relationship, and the required number of minimum reading units are set. Read and assemble a numerical code for each. Here, if the reading and assembly are performed normally, the relationship between each numerical code will be a constant one corresponding to the arrangement relationship of the pressure detector. Therefore, the warning means determines whether the relationship between each numerical code is a constant relationship corresponding to the arrangement relationship, and issues a warning signal if they do not match.

For example, in the above 4-track type absolute encoder, the 4-tree absolute track 00000000 1 1 1 1 1 1 1 1
...(4)1 ↑ ■＊＊＊＊■ ...-Moving direction oooozzooooiiz ... (3) Dingr ■＊＊＊＊■ ...-Moving direction 0011001100110011 ... (2)
1↑ ■＊＊＊＊■ ...-Moving direction 0101010101010101 ... (1)
1 piece ■＊＊＊＊■ ...-For the moving directions (1) to (4), the detection unit has five detectors consisting of sensors ■ to ■ and sensors ■ to ■. When arranged at intervals corresponding to the length of the minimum reading unit, the relationship between the numerical code assembled as ■■■■ and the numerical code assembled as O■■■ as the detection part moves in one direction of the arrow is as follows. ■■■■ -■■■■ First absolute position: 0O00-0101 Second absolute position: 0OO1-0110 Third absolute position: 0O10→
0111 Fourth absolute position: 0O1f -1000
5th absolute position ・0100 → 1001 6th absolute position ・0101 → 1010 7th absolute position: Q
l 10 → 1011 8th absolute position Ko0111
→ 1100, and the numerical code of ■■■■ represents the absolute position shifted by the minimum reading unit of 5 layers starting from the 6th absolute position, as stated in the numerical code of ■■■■. Become.

Also, for example, in the above-mentioned one-track type absolute encoder, one absolute track: ↑1↑↑ ↑↑↑↑ ...-Moving direction ■■■■ ■■
For ■■, the detection unit includes a detector consisting of sensors ■～■,
When a detector consisting of sensors ■ to ■ is arranged at intervals corresponding to the length of the five minimum reading units, as the detection part moves in one direction of the arrow, the numerical code assembled as ■■■■, The relationship between ■■■■ and the assembled numerical code is: ■■■■ -■■■■ First absolute position: 0O001010 Second absolute position 0001 0101 Third absolute position: OO111,011 Fourth absolute position Position ・01
10 0111'ts 5 (D absolute position: 11
01 titi 6th absolute position: 1010
1110 7th absolute position +0101 1100
8th absolute position: 1011 1001, and the numerical code of ■■■■ is shifted by the minimum reading unit of 5 starting from the 6th absolute position, in terms of the numerical code of ■■■■ It represents the absolute position.

Therefore, in these two examples, the warning means determines whether the two numerical codes obtained separately from the two detectors have a positional relationship that is shifted by five minimum reading units, In the unlikely event that this relationship deviates, a warning signal will be sent immediately.

By the way, in this example, a numerical code that combines the outputs of each sensor was used to represent the absolute position, but instead of using this directly, it is also possible to use a value converted to an appropriate numerical value using a memory element etc. be. In particular, when comparing two numerical codes using the one-track type absolute encoder, calculation processing is facilitated by converting the numerical codes into binary ordinal numbers. Therefore, in the following claims, the combined numerical code itself and its converted numerical value are collectively referred to as absolute position.

In the invention as claimed in claim 2, the warning means is composed of a storage means, an arithmetic means, and a comparator. In other words, the storage means stores the difference that two absolute positions obtained from the two detectors should have, considering their arrangement on the detection unit, which corresponds to the distance between the two detectors on the absolute track. is stored in advance. Further, the calculation means calculates the difference between the two absolute positions actually obtained from the two detectors by subtraction.

In the invention of claim 3, the comparator compares this difference with the difference that should be stored in the storage means and issues a warning signal when the two do not match. It consists of a prediction means and a comparator. In other words, the storage means stores the difference between the two absolute positions obtained from the two detectors, which corresponds to the distance between the two detectors on the absolute track, considering their arrangement on the detection unit. is stored in advance. Further, the prediction means adds or subtracts the difference between the two absolute positions stored in the storage means to the absolute position actually obtained from one detector, and calculates the difference obtained from the other detector. I'm looking for absolute position. In the invention according to claim 4, the comparator compares this absolute position with the absolute position actually obtained from the other detector and issues a warning signal when the two do not match. It consists of a comparison table and a comparator. In other words, the comparison table stores the absolute position obtained from one detector and the absolute position that should be obtained from the other detector, and it is necessary to input the absolute position obtained from one detector. As a result, the absolute position to be obtained from the other detector is output.

The comparator compares the absolute position that should be obtained from the other detector obtained from the comparison table with the absolute position actually obtained from the other detector, and issues a warning signal if the two do not match. Output.

[Embodiments of the Invention] First to "i43 embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows the multi-track absolute type of the first embodiment.
The structure of the encoder is shown. In this embodiment, the answer obtained by adding the 4-bit binary number read by detector b1 and the constant 0100 is compared with the 4-bit binary number read by detector b1, and if they do not match, a warning signal is output. do.

In Figure 1, code plate A contains a 4-digit binary ordinal number,
0 is the white part and 1 is the shaded part, respectively 221.22.2
Four tracks T1, T2, T3, and T4 are formed to which 3 are allocated. On the other hand, the detection section B includes detectors b1 and b.
2 are provided at intervals of four minimum reading units, and the values read by detectors b1 and b2 from tracks T1, T2, T3, and T4 are 23 to T4.22 to T3.21 to T2.2.
It is assembled into a 4-digit numerical code with ° as T1 and stored in output devices E and F. Among these, the output terminal d of the output WE
1~d4 or 2°~2 of this absolute encoder
Gives an output of 3.

The calculation section adds the 4-digit numerical code stored in the output device E and the constant 0100 stored in the memory M,
The answer is output to adder C.

Furthermore, the comparator R compares the output of the adder C and the 4-digit code signal stored in the output device F for each digit, and if the two do not match, sends a warning signal to the output terminal r. Output.

In the multi-track absolute encoder configured in this way, when the code plate A rotates in the direction of the arrow,
Detector b1 sequentially reads a binary number sequence starting from 0000h), while detector b2 sequentially reads a binary number sequence starting from oiooo, and the output difference between the two is always 010.
It becomes 0. Therefore, when the detector b1 generates a reading error and an incorrect numerical code is output to the outputs d1 to d4,
Comparator R immediately detects the difference between the outputs of arithmetic unit C and output unit F, and outputs a warning signal to output terminal r.

FIG. 2 shows the one-track absolute type of the second embodiment.
The structure of the encoder is shown. In this example, three detectors b
Regarding the outputs of 1, b2, and b3, 1, K are stored in the comparison table memory.
2 to check for misreading.

In Fig. 2, the code plate A contains a 4-bit full-period sequence: An absolute number with 0 represented by white areas and 1 represented by diagonal lines.
A track T is formed. On the other hand, in the detection part B,
For detector b1, each minimum reading unit is 5 pieces, 9
Detectors b2 and b3 are provided at an interval of one detector. The numerical code read from the track T by the detector b1 is stored in the output device E, and the output terminals d1 to d4 of the output device E are
gives the output of this absolute encoder. In addition, the numerical codes read from the track T by detectors b2 and b3 are entered into the comparison table memory as 1, and manually entered in K2. Output to R. Here, the relationship between the address and data in K2 with 1 in the comparison table memory is as follows: 1 in the comparison table memory → data iiti ttot... Earthenware b1 1st absolute position 2nd absolute position 343 absolute position 4th Absolute position 't Absolute position of S5 6th absolute position 7th absolute position 1001 1011 8th absolute position comparison table memory 2 near address → data...Detector b1111
1 0000 First absolute position 1110
0001 Second absolute position 1100 0011
3rd absolute position 1000 CLIIO 4th
Absolute position 0000 1101 Fifth absolute position 0001 1010 Absolute position 001 of $6
1 0101 Seventh absolute position 0110
1011 At the 8th absolute position, output the numerical code that is reversed by 5 minimum reading units and 9 minimum reading units, that is, the numerical code that should be output by the detector b1.

On the other hand, the comparator R first compares the output of the output device E with the output of 1 in the comparison table memory, then compares it with the output of 2 in the comparison table memory, and the output of the output device E is stored in the comparison table memory. 1, K2
If neither of these matches, a warning signal is output to the output terminal r.

In the one-track absolute encoder configured in this way, when the code plate A moves in the direction of the arrow,
The numerical code read by the detector bt is output to the output terminals d1 to d4 of the output device E. On the other hand, detectors b2, b
The numerical code read by 3 is stored in the reference table memory as 1, converted by K2 into the numerical code to be read by detector b1 at that time, inputted to comparator R, and compared with the numerical code actually read by detector b1. and if they do not match, a warning signal is generated at the output terminal r. The comparator R of this embodiment is
When the detector bl reads correctly and a reading error occurs in either of the detectors b2 and b3, a warning signal is not erroneously output.

FIG. 3 shows the multi-track absolute type of the third embodiment.
The structure of the encoder is shown, with (a) being a plan view and (b) being a front view. In this embodiment, a code plate 1 with a Gray code absolute track is used, and the Gray code is read at two locations on the code plate 1, and this is converted into a binary ordinal number and arithmetic processing (subtraction) is performed. , to determine whether there is a reading error.

In FIGS. 3(a) and (b), a gray code pattern consisting of seven tracks is formed on the code plate 1, with 0 being a white part (transparent) and 1 being a black part (opaque). There is. On the other hand, as a detection section, detectors 10 and 11 are provided at a distance of 16 minimum reading units. Further, a light source 3.4 is provided so as to face the detectors 10 and 11 with the code plate 1 in between. A code plate 1 is held by a shaft 2.

FIG. 4 shows the multi-track absolute type of the third embodiment.
The configuration of the encoder reading error detection circuit is shown. In this detection circuit, the numerical code (Gray code) read by the detectors 10 and 11 is converted into a binary ordinal number by a combination of simple exclusive OR circuits (converters 12 and 13).

In the 'tS4 diagram, converters 12.13 each convert the Gray code read by the detector 11.10 into a binary number. Further, the arithmetic unit 14 is connected to the converter 12 or the output terminal a6.
, a5, a4, a3, a2, al, aO, the converter 13 outputs the output terminals b6, b5, b4
, b3, b2, bl, and bo, and output the 7-digit answer to terminals q6, q5, q4, and q3.
, ql, 91, and qo.

A comparison circuit composed of a NOR gate 16 and an AND gate 17 has output terminals q6, q5, q4.93, ql, q
If the output output to l and qO is other than 16 (0010000), a warning signal (low level) is sent to output terminal 15.
Output.

In the multi-track absolute encoder configured in this way, when the code plate 1 moves, the detector 10
．． The numerical code read by 11 changes every moment, but if this reading is done correctly, the difference between the binary numbers output from converter 12 and 13 is always 16 (0010000).
Therefore, conversely, the output of the arithmetic unit 14 is 16 (001
0000), the occurrence of a reading error is detected by issuing a warning signal.

[Effects of the Invention] In the inventions of claims 1 to 4, if an abnormality occurs in the reading of the absolute track by the detector, a warning signal is immediately transmitted. By incorporating various safety compensation systems such as an emergency stop of the entire system, and by using the frequency of warning signals as a guideline for replacing the absolute enhancer, safe operation of the entire system is ensured and serious accidents can be prevented. Occurrence can also be prevented.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the structure of the absolute encoder of the 341 embodiment. 'M2 is a plan view showing the structure of the absolute encoder of the second embodiment. FIG. 3 shows the structure of the absolute encoder of the 'fS3 embodiment, where (a) is a plan view and (b) is a front view. FIG. 4 is a circuit diagram showing the configuration of the circuit section of the absolute encoder of the 's3 embodiment. [Explanation of symbols of main parts]

Claims (4)

[Claims] (1) A code plate (A) on which a multi-track type or one-track type absolute pattern is formed, and a detector (b) for detecting the absolute position on the pattern, with respect to the code plate (A). In an absolute encoder consisting of a relatively movable detection unit (B), a plurality of the detectors (b) are arranged so as to detect different absolute positions, and the relationship between each detector and the position of each detector during driving is as follows: 1. An encoder comprising a warning means for comparing the absolute positional relationship obtained from the above and outputting a warning signal if the two do not match. (2) The warning means includes a storage means that stores the difference in absolute position of the plurality of detectors (b), and a calculation means that calculates the difference in absolute position obtained from each detector at the time of driving. and a comparator that compares the difference calculated by the calculation means and the difference stored in the storage means and outputs a warning signal if the two do not match. Term encoder. (3) The warning means includes a storage means storing the difference in absolute positions of the plurality of detectors (b), and an absolute position obtained on the spot from one (b1) of the detectors (b). , a prediction means for adding or subtracting the difference stored in the storage means to predict the absolute position to be detected by another detector (b2) at that time; 2. The encoder according to claim 1, further comprising: a comparator that compares the absolute position detected by the other detector (b2) and outputs a warning signal if the two do not match. (4) The warning means stores the relationship between the absolute position detected by one (b1) of the detectors (b) at each absolute position and the absolute position detected by the other detector (b2) at that time. The comparison table and the detector (b1
) detects a certain absolute position, the predicted absolute position of the other detector (b2) obtained from the comparison table and the absolute position actually output from the other detector (b2) at this time are calculated. 2. The encoder according to claim 1, further comprising: a comparator that compares the two and outputs a warning signal if the two do not match.