JP3449795B2 - Absolute encoder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial code represented by binary codes of 0 and 1 (hereinafter, simply referred to as a binary serial code). It relates to the absolute encoder used. 2. Description of the Related Art Conventionally, as an absolute value encoder, an absolute value encoder using an M-sequence random number code and having a code plate in which a binary serial code is arranged on a single track has been proposed. This type of absolute encoder engraves a binary serial code having a division number of 2 ⁿ corresponding to a desired resolution on a code plate in the form of a slit or the like, and reads the code string with n detection elements. Since the absolute position data is obtained, a reading error occurs in a detection value in a boundary region (unstable region) of the divided value (minimum reading unit) of the binary serial code. [0003] In order to solve this problem, two sets of n detecting elements are prepared for group A and group B, and the detecting elements of group A and the detecting elements of group B are arranged with a phase difference, or , A binary serial code track is divided into an A track and a B track and two sets are prepared on a code plate without giving a phase difference between the detection elements of the A group and the B group, and a phase difference is provided between slits of the A track and the B track. At the same time, an incremental code track that is twice as large as this binary serial code, that is, divided into 2 × 2 ⁿ pieces, is separately provided on a code plate for the purpose of discriminating a boundary area (unstable area). There is known a configuration in which the detection value is detected by the detection element and the stable region of the detection value by the detection element of the group A or the group B is selected using the detection result to obtain a detection value without reading error. As described above, in a conventional absolute value encoder provided with a code plate on which a binary serial code is arranged, in order to obtain absolute position data without reading errors, A The detection values of the detection elements of the group and the group B were obtained by the same sign having a phase difference. [0005] It is an object of the present invention to ensure that absolute value data is read by using an incremental code in addition to a binary serial code. The sign of the binary serial code has an inverted logic relationship, and the absolute position data can be obtained even if the detected values of the detection elements of the group A and the group B have a phase difference. . A feature of the present invention for solving the above-mentioned problem is that in an absolute value encoder using a binary serial code, an N-divided binary serial code and a continuous K + 1 (Where K is an integer value of 2 or more that satisfies 2 ^{K -1} <N ≦ 2 ^K ), all of which have different absolute value data, and the sum of any two read binary values is 2 ^{K + 1} − A first track on which a binary serial code created under the condition that it does not become 1, a second track on which a logically inverted serial code of the binary serial code is formed, and a 2N-divided incremental code And a code plate provided with a third track on which is formed a first track having K + 1 detection elements for reading absolute position information from the first track.
A second detector having K + 1 detection elements for reading absolute position information from the second track, a third detector having detection elements for reading an incremental code from the third track, and a third detector. Selecting means for extracting either the first detector output or the second detector output as output data according to the logic of the output from the detector. The binary serial code to be formed on the first track is an N-divided serial code, and is K + 1 consecutive codes (K is an integer value of 2 or more satisfying 2 ^{K -1} <N ≦ 2 ^K ). In addition to using the absolute position data which are read under the condition that all the read absolute position data are different and the sum of any two read binary values does not become 2 ^{K + 1} −1, the binary serial code logic Combinations with inverted binary serial codes can be used. [0008] This combination is a 2N divisional arrangement in which every other position is alternately arranged so that the detection value at an arbitrary position and the detection value before or after this arbitrary position always have an inverted logic relationship at all positions. Is required to be a binary serial code. On the second track, a logically inverted binary serial code of the above-described 2N-divided binary serial code is formed, and a third track is formed.
It is necessary to form 4N-divided incremental codes on tracks. The N-ary binary serial code is described as follows: "Absolute position data read by the detector all have different contents, and the sum of any two read binary values is 2 ^{K + 1} -1. If addition to creating, resolution of N = 2 ^K pieces to the original condition that become not "in the portion where the sign is the K series of prepared 2 ^K -1 pieces of M-sequence code" 1 "and" The symbol “1” may be added. Further, the absolute position data read by the detector described above has different contents, and the sum of any two read binary values is 2 ^{K + 1} −
2 divided into N created under the condition that it does not become 1
Hex serial code or 2 ^K -1 M-sequence code "1"
Code can be created by obtaining the exclusive OR of the K pieces continuously to portions are "1" the same division number of the incremental code and binary serial code with a code added to 2 ^K divided created by in. In the former configuration, the first and second detectors output N-position absolute position data, respectively, and either one of them is output in accordance with the logic of the incremental code detected by the third detector. Is output from the selection means. Thus, code detection without reading errors can be realized. In addition, by considering the readout result of the incremental code in the detected absolute position data, 2N
The data becomes the absolute position data of the division, and the incremental code has two functions of preventing a reading error and doubling the number of divisions. When the latter code plate configuration is adopted, 4N-divided absolute position data can be obtained in the same manner. In this case, the code to be formed on the first track can be easily created based on the N-ary binary serial code. An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the configuration of a rotary type absolute value encoder 1 according to the present invention. The absolute value encoder 1 includes a code plate 2 fixed to a rotating shaft of a detection object (not shown), a light source 3 disposed on one side of the code plate 2, and an absolute position data read by the code plate 2. The code plate 2 receives light from the light source 3 through a slit representing a binary serial code formed as described later.
Detection elements SA1 to S for optically reading the sign of
A4, a reading device 4 having SB1 to SB4, and SC1. As shown in FIG. 2, in the present embodiment, a first track T1, a second track T
2. A third track T3 is provided, and each of the divided segments of the track is optically represented by a binary serial code with white portions (light-transmitting portions) being "1" and black portions (light-shielding portions) being "0". It is configured to display. Further, in this embodiment, since the binary serial code of the first track T1 and the second track T2 is a rotary absolute encoder, a cyclic element is required (hereinafter, in this embodiment, a binary cyclic serial code is used). ). The first track T1 and the second track T2 are each divided into eight, and provided with a binary cyclic serial code created as described below.
On the other hand, the third track T3 is provided with a 16-fold incremental code that is twice as large. To read a code from the first track T1, detection elements SA1 to SA4 constituting the first detector SA are used.
Are arranged along the direction as shown. On the other hand, the second
To read the code from the track T2, the second detector SB
Are arranged along the detection elements SB1 to SB4 as shown in FIG. The detection element SC1 constitutes a third detector for reading an incremental code formed on the third track T3. Next, the relationship between the number N of divisions of the code plate 2 and the number Q of detection elements required at that time will be described. When the absolute position data read by the K detectors is represented by a K-bit binary value, the number of binary serial codes for obtaining absolute position data in which the binary values do not overlap is 2 ^K It is as follows. In this case, N (2 ^K-1 <N ≦
2 ^K ) binary serial codes and a logically inverted binary serial code obtained by logically inverting the binary serial code, in order to prevent all the binary values of the absolute position data read by the detector from overlapping, all 2 The number of binary serial codes is 2N (2 ^K <2N ≦ 2
^{K + 1} ), and the number Q of the detection elements requires K + 1. Therefore, in the present embodiment, as described above, the division into eight is performed. Since 2 ^3-1 <8 ≦ 2 ^{3 and} K = 3, the number Q of the detection elements is from K + 1 to 4, so that the reading device 4 Has four detection elements SA1 to SA4 and SB1 to SB
4 are prepared. On the other hand, the eight-divided binary cyclic serial code attached to the first track T1 of the code plate 2 states that the absolute position data read by the four detectors all have different contents, and that The sum of the two read binary values of
^It does not become ^{3 + 1} -1. Created under the condition " In this embodiment, it is [11110100], and this binary serial code is the first code of the code plate 2 of the absolute value encoder 1.
A slit is formed in the track T1 with a white portion (light-transmitting portion) being “1” and a black portion (light-shielding portion) being “0” (see FIG. 2). In this binary cyclic serial code, no matter where the four consecutive codes are detected, the detected values are all different, and the sum of the binary numbers of any two detected values is not 2 ^{K + 1} -1. It is determined as follows. As a result, the eight values obtained by reading the four consecutive codes of the binary cyclic serial code are all different from the values obtained by logically inverting the eight values. On the second track T2, a logically inverted binary cyclic serial code [00001011] is formed as shown in FIG. 2 so as to correspond to each bit. FIG. 3A shows each detection position (address) 1.
8 show the values of the first absolute position data P1 from the first track T1 in the first to third tracks. FIG. 3B shows the second absolute position data P1 from the second track T2 in each of the detection positions (addresses) 1 to 8. The value of the absolute position data P2 is shown. FIG. 3 shows that two pieces of absolute position data having different contents are assigned to the same address, and that 1
It can be seen that the contents of the six types of absolute position data do not overlap at all. The minimum reading unit of the first and second tracks is λ
, The detection elements SA1 to SA4 and SB1 to SB4 of the first and second detectors SA and SB have a pitch λ, respectively.
And the first detector SA and the second detector SB are arranged with a phase difference θp1 (0 <θp1 <λ) so as not to read the unstable region at the same time. In the present embodiment, θp1 = λ / 2 is set. Note that this phase difference θp1 is different from the first track T1 and the second track T1.
The second slit may be provided. The detecting element SC1 includes the first and second detectors S
A phase difference mλ / 2 + θp2 (m is an integer and 0 <0) with respect to the first detector SA so that the detection stable regions of A and SB can be determined.
θp2 <θp1). In the illustrated embodiment, m = 0 and θp2 = λ / 4. Each detection element SA1 to SA4, SB1 to SB
4. The output from SC1 is waveform-shaped by a waveform shaping circuit 5, and the detection output signals DA1 to DA4, DB1 to DB
4. Output as DC1 (FIG. 1). FIG. 4 shows signal waveforms at various points in FIG. 1 when the code plate 2 is rotated once in the configuration shown in FIG. Returning to FIG. 1, the detection output signals DA1 to DA
A secretor 6 is provided for selecting one of DB4 and DB1 to DB4 at the level of the detection output signal DC1 of the incremental code. The secretor 6 comprises a first group of input terminals A1 to A
4 and a second group of input terminals B1 to B4, and the respective detection output signals are input to these input terminals as shown in FIG. The secretor 6 takes out, as an output Yn, an input An of the two inputs An and Bn shown in the figure, when the level of the detection output signal DC1 applied to the terminal G is "H". , "L", four sets of selection circuits for taking out the input Bn as the output Yn are provided. From the above description, when the level of the detection output signal DC1 is "H", in each selection circuit, the detection output signal D1 input to the first group of input terminals A1 to A4 is output.
A1, DA2, DA3, and DA4 are output terminals Y1, Y2,
From Y3, Y4, absolute position data DO1, DO2, DO
3, output as DO4. On the other hand, the detection output signal DC
1 is "L", the detection output signals DB1, DB2, DB3, DB4 input to the second group of input terminals B1 to B4 in each selection circuit are output terminals Y1, Y4.
2, Y3, Y4 to absolute position data DO1, DO2, D
Output as O3 and DO4. Here, since the relationship between the detection output signals DA1 to DA4 and DB1 to DB4 and DC1 is as shown in FIG. 4, it can be seen that each detection output can be read in the stable region. As a result, as shown in FIG. 5, absolute position data of 16 divisions composed of output data DO1 to DO4 is obtained. FIG. 6 shows another configuration of the code plate and the arrangement of the corresponding detection elements. The code plate 2 'shown in FIG. 6 includes a first track T1 and a second track T2.
Is divided into 16, and the third track T3 is provided with a 32-part incremental code, which is different from the configuration in FIG. The serial code provided on the first track T1 alternates between the code [11110100] of the first track T1 in the configuration shown in FIG. 2 and the code [00001011] of the second track T2 obtained by logically inverting the code. A composite serial code [1010101011001]
01]. As is clear from the description above,
Since this composite serial code is obtained by alternately arranging two codes of two sets of binary cyclic serial codes, if every four of the composite serial codes provided on the first track T1 are sequentially read out, the readout becomes The 16 sets of data output all have different values. That is, if every other four of the combined serial codes are read out, they become a 16-part binary cyclic serial code. On the second track T2 of the code plate 2 ', a logically inverted composite serial code [010
1010110011010] is formed as shown in FIG. 6 so as to correspond to each code of the first track T1. As can be seen from the above description, the first detector S
The detection elements of A and the second detector SB are arranged at an interval of 2λ, which is twice the minimum reading unit λ of each track T1, T2 in FIG. The arrangement phase difference between the first detector SA to the third detector SC is the same as that in the configuration of FIG. 2 as shown in detail in FIG. When the code plate 2 'is rotated once by the configuration shown in FIG. 6, the signal waveforms of the respective parts in FIG. 1 are as shown in FIG. 7, and at that time DO1, DO2, DO3, DO4,
The absolute position data obtained from DC1 is shown in FIG. In the above embodiment, an optical rotary encoder having a circular code plate has been described as an example. However, a linear encoder having a linear code plate, a magnetic encoder that magnetically detects a code, or the like is used. Needless to say, the present invention can be similarly applied. According to the present invention, 2 having special conditions can be used.
Since the code plate is formed by using the binary serial code, the binary serial code can be reliably read without errors by reading the signal from the incremental code track. By creating an N-divided binary serial code, a 2N-divided absolute value encoder can be obtained, and the code creation cost can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a main part of a configuration of an embodiment of an absolute value encoder according to the present invention. FIG. 2 is an explanatory diagram for explaining a configuration of a code plate and an arrangement of detection elements of the absolute value encoder of FIG. 1; FIG. 3 is a view showing contents of absolute position data obtained by reading a binary cyclic serial code formed on a track of the code plate shown in FIG. 2; FIG. 4 is a time chart showing waveforms of signals of respective parts in FIG. 1 when the code plate is rotated once in the case of the configuration of the code plate and the detection element shown in FIG. 2; FIG. 5 is a diagram showing contents of absolute position data obtained from the output of the absolute value encoder shown in FIG. FIG. 6 is an explanatory diagram for explaining a configuration of a code plate different from the code plate shown in FIG. 2 and an arrangement of detection elements according to the configuration. 7 is a time chart showing waveforms of signals of respective parts in FIG. 1 when the code plate is rotated once in the case of the configuration of the code plate and the detection element shown in FIG. 6; 8 is a diagram showing contents of absolute position data obtained from the output of the absolute value encoder shown in FIG. 1 when the configuration of the code plate shown in FIG. 6 and the arrangement of detection elements according to the configuration are used. [Description of Codes] 1 Absolute value encoder 2, 2 'code plate 4 Reading device 6 Selectors SA1 to SA4, SB1 to SB4, SC1 Detecting element SA (SA1 to SA4) First detector SB (SB1 to SB4) Second detection Detector SC (SC1) Third detector T1 First track T2 Second track T3 Third track λ Minimum reading unit

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Claims (1)

(57) [Claims 1] In an absolute value encoder using a binary serial code, in the case of 2N division, an N-divided binary serial code and continuous K + 1 (K is 2 ^{K -1} <N ≦ 2 2 or more integer values that satisfy the ^K) to read said with absolute position data are all different content absolute position data and said binary logic inversion comprising the respective codes of serial symbol logically inverts A first track on which a binary serial code is formed such that the absolute position data read by K + 1 consecutive binary serial codes have different contents, and a logical inversion 2 of the binary serial code. A code plate provided with a second track on which a binary serial code is formed and a third track on which a 2N-divided incremental code is formed; and, in the case of a 4N-divided, N-divided binary serial code. The logical inversion binary direct The code is a 2N-divided 2N code that is alternately arranged every other so that the code at a given position and the code before or after the given position are always in an inverted logic relationship at all positions. A first track on which a binary serial code is formed; a second track on which a logically inverted binary serial code of the 2N-divided binary serial code is formed;
A code plate provided with a third track on which an N-divided incremental code is formed; and K + 1 for reading absolute position information from the first track
A first detector having a plurality of detecting elements, and K + 1 for reading absolute position information from a second track.
A second detector having a plurality of detection elements, a third detector having a detection element for reading an incremental code from the third track, and a first detector output or a second detector output based on a logic of a detection value from the third detector. Selecting means for extracting one of the two detector outputs as absolute position data.