KR20220123761A - Absolute Encoder - Google Patents

Abstract

The absolute encoder 1X receives the light from the first position of the disk-shaped scale 20 on which the absolute value sign pattern is disposed, and the scale 20 and the image sensor 3X for outputting a first analog signal; An image sensor 4X that receives light from a second position of the scale 20 and outputs a second analog signal, an AD converter 5A that converts the first analog signal into a first digital signal, and a second analog signal An AD converter 5B for converting a signal into a second digital signal, and an absolute position calculating unit 6X for calculating a first absolute position on the scale 20 based on the first and second digital signals are provided. .

Description

Absolute Encoder

The present disclosure relates to an absolute encoder for measuring an angular position of a measurement object.

An absolute encoder for measuring the mechanical angular position of a measurement object such as a shaft is a disk scale in which a plurality of marks are arranged, and by irradiating light to the disk scale, a signal corresponding to the angular position of the measurement object is obtained from the disk scale An optical sensor module is provided.

In the absolute encoder described in Patent Document 1, marks in which an ABS (ABSolute) pattern and an INC (INCremental) pattern are combined are arranged on the original scale. This absolute encoder acquires the position information obtained from the disc scale with two detectors, decomposes it into position information of the ABS pattern and the position information of the INC pattern, and by averaging these position information, the resolution of the position information is improved, have.

Patent Document 1: Japanese Patent No. 5787513

However, in the technique of Patent Document 1, the light received from the original scale is received from one area of the original scale, and the position information of the ABS pattern and the position information of the INC pattern are obtained based on the light received from the one area. Calculated and averaged. For this reason, in the technique of the said patent document 1, there existed a problem that the reliability of position information was impaired when a foreign material adhered etc. to either of the two detectors.

The present disclosure has been made in view of the above, and an object of the present disclosure is to obtain an absolute encoder capable of calculating position data with high reliability and high resolution.

In order to solve the above-mentioned problem and achieve the objective, the absolute encoder of this indication is equipped with the disk-shaped scale on which the absolute value code pattern is arrange|positioned, and the light emitting element which irradiates light to the scale. In addition, the absolute encoder of the present disclosure includes a first image sensor that receives a first light from a first position separated by a first distance from the center of the scale and outputs a first analog signal corresponding to the first light; and a second image sensor that receives a second light from a second position separated by a second distance from the center and outputs a second analog signal corresponding to the second light. In addition, the absolute encoder of the present disclosure includes a first signal converter for converting a first analog signal into a first digital signal, a second signal converter for converting a second analog signal into a second digital signal, and a first digital An absolute position calculating unit for calculating a first absolute position on the scale based on the signal and the second digital signal is provided.

The absolute encoder according to the present disclosure achieves the effect that position data with high reliability and high resolution can be calculated.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the absolute encoder which concerns on Embodiment 1. As shown in FIG.
2 is a diagram illustrating a signal input to a light amount correcting unit of the absolute encoder according to the first embodiment.
3 is a diagram illustrating a signal output by a light amount correcting unit of the absolute encoder according to the first embodiment.
FIG. 4 is a diagram illustrating a signal of an edge region shown in FIG. 3 .
5 is a diagram for explaining a rising edge and a falling edge detected by the edge detection unit of the absolute encoder according to the first embodiment.
FIG. 6 is a diagram illustrating a bit string corresponding to edge information shown in FIG. 5 .
Fig. 7 is a diagram for explaining processing for specifying an approximate absolute position of a decode unit of the absolute encoder according to the first embodiment;
It is a figure for demonstrating the amount of phase deviation of the signal which the phase detection part of the absolute encoder which concerns on Embodiment 1 calculates.
9 is a diagram for explaining the characteristics of a signal obtained by the absolute encoder according to the first embodiment.
Fig. 10 is a diagram showing the configuration of the absolute encoder according to the second embodiment.
It is a figure for demonstrating the arrangement position of the image sensor in the absolute encoder which concerns on Embodiment 2. FIG.
12 is a diagram showing the configuration of the absolute encoder according to the third embodiment.
13 is a flowchart showing a process procedure for generating position data by the position data generating unit of the absolute encoder according to the third embodiment.
14 is a flowchart showing a processing procedure of a first example of abnormality determination processing by the position data generation unit of the absolute encoder according to the third embodiment.
15 is a flowchart showing a processing procedure of a second example of abnormality determination processing by the position data generation unit of the absolute encoder according to the third embodiment.
16 is a diagram for explaining face deflection occurring in the scale of the absolute encoder according to the third embodiment.
17 is a diagram showing a schematic configuration of an absolute encoder according to the fourth embodiment.
18 is a diagram showing a first configuration example of a module in which the image sensor of the absolute encoder according to the fourth embodiment is mounted.
19 is a diagram showing a second configuration example of a module in which the image sensor of the absolute encoder according to the fourth embodiment is mounted.
20 is a diagram showing a third configuration example of a module on which an image sensor of an absolute encoder according to the fourth embodiment is mounted.
Fig. 21 is a diagram showing the configuration of an absolute encoder when the module shown in Fig. 20 is applied to the absolute encoder of the third embodiment.
22 is a diagram showing an example of a hardware configuration for realizing an absolute position calculating unit included in the absolute encoder according to the first embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, the absolute encoder which concerns on embodiment of this indication is demonstrated in detail based on drawing.

Embodiment 1.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the absolute encoder which concerns on Embodiment 1. As shown in FIG. The absolute encoder 1X includes a light emitting element 2, an image sensor 3X, 4X, a scale 20, an AD (Analog to Digital) converter 5A, 5B, and an absolute position calculating unit 6X. are doing

The light emitting element 2 is an illumination unit that irradiates light to the scale 20 . For the light emitting element 2, for example, a point light source LED (Light Emitting Diode, light emitting diode) is used. The image sensors 3X and 4X are light detection units that receive light from the scale 20 . As the image sensors 3X and 4X, an imaging device such as a Charge Coupled Device (CCD) image sensor and a Complementary Metal Oxide Semiconductor (CMOS) image sensor is used. In Embodiment 1, the case where the image sensors 3X and 4X are one-dimensional image sensors will be described. However, the image sensors 3X and 4X may be two-dimensional image sensors.

The scale 20 is a disk-shaped scale. The scale 20 is connected to a rotating shaft 7 provided in a motor (not shown) or the like, and as the rotating shaft 7 rotates, the scale 20 rotates. The scale 20 has only one track having the absolute value sign pattern 30 which is an absolute position pattern in a direction along the circumference. In the absolute value sign pattern 30 , a plurality of reflective portions 31 and a plurality of non-reflecting portions 32 extending in the radial direction of the scale 20 are disposed.

The reflective part 31 is a part that reflects the light from the light emitting element 2, and the non-reflecting part 32 is a part which absorbs or transmits the light from the light emitting element 2 . The non-reflecting portion 32 may be a portion that reflects with a reflectance lower than the reflectance of the reflection portion 31 . The reflective portion 31 and the non-reflecting portion 32 function to modulate the light intensity distribution projected onto the image sensors 3X and 4X.

The absolute sign pattern 30 consists of a reflective portion 31 and a non-reflecting portion 32 to characterize the angular position of the scale 20 . For the arrangement of the absolute code pattern 30, for example, a code string obtained by Manchester-coding a pseudo-random code such as an M-series is used.

In Embodiment 1, the light emitting element 2 and the image sensors 3X, 4X are all exemplified by the reflective encoder arranged on the upper surface which is the surface on one side of the scale 20. As shown in FIG. Further, the absolute encoder 1X of the first embodiment is also applied to a transmissive encoder in which the light emitting element 2 and the image sensors 3X and 4X are disposed on the upper and lower surfaces opposite to each other with the scale 20 interposed therebetween. It is possible.

In the case of a transmissive encoder, the absolute value code pattern 30 may be composed of a transmissive part that transmits light and a non-transmissive part that does not transmit light. In either case of the reflective encoder and the transmissive encoder, the configuration of the absolute value code pattern 30 is not particularly limited as long as it is configured to modulate the light intensity distribution projected on the image sensors 3X and 4X.

Moreover, in Embodiment 1, along the radial direction from the center of the scale 20, the light emitting element 2 and the image sensors 3X, 4X are the light emitting element 2, the image sensor 3X, and the image sensor ( 4X), although the example is shown, the order of arrangement|positioning is not limited to this order. That is, the order of arrangement of the light emitting element 2 and the image sensors 3X and 4X is not limited as long as the reflection positions of the received light on the scale 20 are different.

The image sensors 3X and 4X and the light emitting element 2 are radial lines extending from the center of the scale 20 in the first radial direction of the scale 20 when viewed from the rotation axis direction, which is the upper surface side of the scale 20 . placed so as to overlap. In Embodiment 1, the center of the image sensor 3X, the center of the image sensor 4X, and the center of the light emitting element 2 overlap on this semi-rectangular line when viewed from the upper surface side of the scale 20, Image sensors 3X, 4X and a light emitting element 2 are arranged.

In Embodiment 1, the image sensor 3X is a first image sensor, and the image sensor 4X is a second image sensor. The image sensor 3X receives the first light from a first position separated by a first distance from the center of the scale 20 and outputs an analog signal corresponding to the first light. The image sensor 4X receives the second light from a second position separated by a second distance from the center of the scale 20 and outputs an analog signal corresponding to the second light. In Embodiment 1, the first distance and the second distance are different distances. The analog signal output from the image sensor 3X is the first analog signal, and the analog signal output from the image sensor 4X is the second analog signal.

The AD converter 5A is a first signal converter that converts the analog signal detected by the image sensor 3X into a digital signal. The AD converter 5B is a second signal converter that converts the analog signal detected by the image sensor 4X into a digital signal. The digital signal converted by the AD converter 5A is the first digital signal, and the digital signal converted by the AD converter 5B is the second digital signal.

The absolute position calculating part 6X is an calculating part which computes the absolute position of the scale 20 based on the output from AD converter 5A, 5B. The absolute position calculating part 6X calculates the absolute position on the scale 20 based on a 1st digital signal and a 2nd digital signal, and outputs it as position data 40X. In the first embodiment, the position data 40X is the first absolute position.

The absolute position calculating unit 6X includes the light quantity correction units 10A and 10B, the edge detection units 11A and 11B, the decode unit 12A, the rough detection unit 13A, the phase detection unit 14B, and the high-precision detection unit. (15X).

The light amount correction unit 10A equalizes the signal intensity of the digital signal sent from the AD converter 5A, and sends it to the edge detection unit 11A. The light amount correcting unit 10B equalizes the signal intensity of the digital signal sent from the AD converter 5B, and sends it to the edge detecting unit 11B.

The edge detection unit 11A corresponds to a signal whose signal intensity is equalized by the light quantity correcting unit 10A, and the edge position on the image sensor 3X (hereinafter referred to as an edge pixel position) coincides with a preset threshold level. ) to find In addition, the edge detection unit 11A discriminates whether the edge pixel position is a rising edge indicating a rising edge or a falling edge indicating a falling edge.

The edge detection unit 11B obtains an edge pixel position on the image sensor 4X that coincides with a preset threshold level for the signal whose signal intensity is equalized by the light amount correcting unit 10B. In addition, the edge detection unit 11B determines whether the edge pixel position is a rising edge indicating a rising edge or a falling edge indicating a falling edge.

The decoding unit 12A converts the signal into a bit string composed of a bit value "1" and a bit value "0" based on the rising edge and the falling edge determined by the edge detection unit 11A.

The rough detection unit 13A detects a rough absolute position from the bit string converted by the decoding unit 12A. The rough detection unit 13A detects a rough absolute position, for example, by comparing a lookup table indicating the bit string of the absolute value code pattern 30 with the bit string converted by the decoding unit 12A. In Embodiment 1, the rough absolute position detected by the rough detection part 13A is a 2nd absolute position.

The phase detection unit 14B calculates an amount of phase deviation with respect to a pixel position serving as a reference (a reference pixel position 150 to be described later) based on the rising edge and the falling edge determined by the edge detection unit 11B.

The high-precision detection unit 15X calculates the absolute position of the scale 20 by adding both the rough absolute position detected by the rough detection unit 13A and the amount of phase deviation calculated by the phase detection unit 14B. The high-precision detection unit 15X outputs the calculated absolute position as position data 40X.

In addition, the image sensors 3X, 4X and the light emitting element 2 may not be arrange|positioned so that they may overlap on a semi-linear line. In other words, the image sensors 3X and 4X do not overlap on a straight line extending from the center of the scale 20 in the first radial direction of the scale 20 when viewed from the rotation axis direction, which is the upper surface side of the scale 20 . you don't have to That is, the straight line connecting the image sensor 3X and the center of the scale 20 and the straight line connecting the image sensor 4X and the center of the scale 20 may be straight lines in different directions.

When the image sensors 3X, 4X and the light emitting element 2 do not overlap on a ray, the absolute position calculating unit 6X uses the pre-calculated phase difference between the image sensors 3X and 4X, and the image sensors 3X and 4X ), at least one of the absolute positions obtained from For example, the rough detection unit 13A may determine the absolute position obtained from the image sensor 3X, the absolute position obtained from the image sensor 3X when the image sensors 3X and 4X and the light emitting element 2 are arranged on a semi-linear line. correct the position. In addition, the phase detection unit 14B calculates the phase deviation amount obtained from the image sensor 4X, the phase shift obtained from the image sensor 4X when the image sensors 3X and 4X and the light emitting element 2 are arranged on a semi-linear line. It can be corrected by vehicle.

When the image sensors 3X, 4X and the light-emitting element 2 do not overlap on a semi-linear line, the two light-emitting elements 2 are arranged in the absolute encoder 1X. The image sensor 3X receives light from one light emitting element 2 of the two light emitting elements 2 , and the image sensor 4X receives light from the other light emitting element 2 of the two light emitting elements 2 . receive light

Next, the operation of each component of the absolute position calculating unit 6X will be described. When the AD converter 5A converts the analog signal detected by the image sensor 3X into a digital signal and sends it to the light amount correcting unit 10A, the light level correcting unit 10A equalizes the signal strength of the digital signal, and the edge detecting unit ( 11A).

When the AD converter 5B converts the analog signal detected by the image sensor 4X into a digital signal and sends it to the light amount correcting unit 10B, the light level correcting unit 10B equalizes the signal intensity of the digital signal, and the edge detection unit ( 11B).

2 is a diagram illustrating a signal input to a light amount correcting unit of the absolute encoder according to the first embodiment. The horizontal axis of FIG. 2 is the pixel position, and the vertical axis is the signal intensity. The signals input to the light amount correcting units 10A and 10B have the same distribution as the light intensity distribution 70 .

The signal input to the light amount correcting unit 10A and the signal input to the light amount correcting unit 10B are different signals by the difference in the arrangement positions of the image sensors 3X and 4X. Since the image sensors 3X and 4X execute the same processing, the light amount correcting units 10A and 10B execute the same processing, and the edge detection units 11A and 11B execute the same processing, In 5, the process by the image sensor 3X, the light amount correction part 10A, and the edge detection part 11A is demonstrated.

The high bit 8 shown in FIG. 2 represents the pattern in the reflective part 31 of the scale 20, and the low bit 9 shows the pattern in the non-reflecting part 32 of the scale 20. As shown in FIG. As shown in FIG. 2 , the signal corresponding to the absolute value sign pattern 30 of the scale 20 projected on the image sensor 3X has a light intensity distribution in which the High bit 8 and the Low bit 9 are non-uniform. becomes (70). That is, the signal by the absolute value sign pattern 30 has a non-uniform light intensity distribution ( 70) becomes. Accordingly, the light amount correcting unit 10A corrects the light amount for each pixel based on the light amount correction value previously measured so that the non-uniform light intensity distribution 70 becomes a uniform light intensity distribution.

3 is a diagram illustrating a signal output by a light amount correcting unit of the absolute encoder according to the first embodiment. 3 , the horizontal axis indicates pixel positions, and the vertical axis indicates signal strength. In FIG. 3 , the light intensity distribution 71 of the signal after the light amount correcting unit 10A corrects the light amount of the signal shown in FIG. 2 is shown. As shown in Fig. 3, after the light amount correction, the signal corresponding to the absolute value sign pattern 30 has a light intensity distribution 71 in which the high bit 8 and the low bit 9 are uniform. The light amount correcting unit 10A sends the light intensity distribution 71 to the edge detecting unit 11A. Further, the light amount correcting unit 10B sends the light intensity distribution in which the light amount has been corrected to the edge detecting unit 11B.

The edge detection unit 11A corresponds to the signal of the light intensity distribution 71 at an edge pixel position on the image sensor 3X that coincides with a preset threshold level 105 (edge pixel position 110 to be described later). save In FIG. 3 , an edge region 75 is shown as an example of an edge region that is a region including an edge pixel position.

FIG. 4 is a diagram illustrating a signal of an edge region shown in FIG. 3 . 4 , the horizontal axis indicates pixel positions, and the vertical axis indicates signal strength. 4 shows an enlarged view of the edge region 75 shown in FIG. 3 . A pixel position coincident with the threshold level 105 among the signals of the light intensity distribution 71 is the edge pixel position 110 .

The edge detection unit 11A has one signal strength lower than the threshold level 105 among the signal strength of the i (i is a natural number)-th pixel and the signal strength of the i+1-th pixel adjacent to each other, and the other Two pixels whose signal strength is higher than the threshold level 105 are detected. Specifically, the edge detection unit 11A is an edge between two pixels in which the signal strength of the i-th pixel is lower than the threshold level 105 and the signal strength of the i+1-th pixel is higher than the threshold level 105 . It is determined that the pixel position 110 exists. Further, the edge detection unit 11A is positioned at an edge pixel position between two pixels in which the signal intensity of the i-th pixel is higher than the threshold level 105 and the signal intensity of the i+1-th pixel is lower than the threshold level 105 . It is determined that (110) exists.

Further, the edge detection unit 11A linearly interpolates the i-th pixel and the i+1-th pixel so as to exceed the threshold level 105 with respect to the i-th pixel and the i+1-th pixel determined to have the edge pixel position 110 . do. The edge detection unit 11A detects a point of coincidence between the linear interpolated signal and the threshold level 105 as the edge pixel position 110 . As described above, the edge pixel position 110 is a rising or falling position of the digital signal. In other words, the edge pixel position 110 is a boundary of the presence or absence of a digital signal.

Further, the edge detection unit 11A detects a rising edge and a falling edge by determining whether the detected edge pixel position 110 is a rising edge or a falling edge.

5 is a diagram for explaining a rising edge and a falling edge detected by the edge detection unit of the absolute encoder according to the first embodiment. The horizontal direction in FIG. 5 corresponds to the pixel position.

The edge detection unit 11A detects, as the rising edge 51 , an edge pixel position 110 in which the signal intensity of the i-th pixel is lower than the signal intensity of the i+1-th pixel among the detected edge pixel positions 110 .

In addition, the edge detection unit 11A detects, as the falling edge 52 , an edge pixel position 110 in which the signal intensity of the i-th pixel is higher than the signal intensity of the i+1-th pixel among the detected edge pixel positions 110 . .

Accordingly, the edge detection unit 11A transmits edge direction information 50 indicating whether the edge pixel position 110 is the rising edge 51 or the falling edge 52 to each edge pixel position 110 . set for The edge detection unit 11A sends the edge direction information 50 and the edge pixel position 110 to the decoding unit 12A.

The edge detection unit 11B also detects the edge direction information 50 and the edge pixel position 110 by the same processing as the edge detection unit 11A. The edge detection unit 11B sends the edge direction information 50 and the edge pixel position 110 to the phase detection unit 14B.

The decoding unit 12A converts the high bit 8 and the low bit 9 into bit values of “1” or “0” based on the edge direction information 50 and the edge pixel position 110, Converts a signal to a bit string.

FIG. 6 is a diagram illustrating a bit string corresponding to edge information shown in FIG. 5 . In Fig. 6, the decoding unit 12A converts the high bit 8 and the low bit 9 into "1" or "0" based on the edge direction information 50 and the edge pixel position 110. A bit string 120 is shown.

The decoding unit 12A sets, for example, the bit value "1" between the rising edge 51 and the falling edge 52, and the bit value between the falling edge 52 and the rising edge 51, for example. The bit string 120 is generated by setting it to the value "0". Thereby, the high bit 8 is expressed as a bit value "1", and the low bit 9 is expressed as a bit value "0".

In addition, the decoding unit 12A generates the bit string 120 so that the width of pixels per bit is equal to the basic period width. The basic period width is the minimum line width of the absolute value sign pattern 30 composed of the reflective part 31 and the non-reflective part 32 . However, since the absolute value sign pattern 30 is radially formed from the center of the scale 20 , the basic period width changes depending on the radial direction of the scale 20 .

The decoding unit 12A may convert the signal into the bit string 120 by converting the high bit 8 and the low bit 9 into bit values of “1” or “0” by binarization processing. The decoding unit 12A may convert the signal into the bit string 120 by any method as long as it can convert the signal into the bit string 120 composed of "1" and "0". The decoding unit 12A sends the bit string 120 to the coarse detection unit 13A.

The rough detection unit 13A detects a rough absolute position from the bit string 120 converted by the decode unit 12A. In the rough detection unit 13A, for example, a bit string constituting the absolute value code pattern 30 is stored in advance in a lookup table. The rough detection unit 13A specifies the approximate absolute position by comparing the bit string 120 detected by the decoding unit 12A with the bit string in the lookup table. The rough detection unit 13A specifies the rough absolute position based on which bit string in the lookup table the bit string 120 corresponds to.

Fig. 7 is a diagram for explaining processing for specifying a schematic absolute position of a decode unit of the absolute encoder according to the first embodiment. The coarse detection unit 13A refers to the lookup table 130 and searches for the bit string 140 that matches the bit string 120 . The rough detection unit 13A specifies the approximate absolute position corresponding to the bit string 120 by finding the absolute position corresponding to the bit string 140 . The coarse detection unit 13A detects a position corresponding to the position of the bit string 140 coincident with the bit string 120 as a rough absolute position. The rough detection unit 13A sends a specific absolute position to the high-precision detection unit 15X.

In addition, when the rough detection unit 13A specifies a rough absolute position based on the pixel position corresponding to the center bit of the bit string 140, the specific absolute position is the central pixel position obtained by the image sensor 3X. It corresponds to the absolute position in

When the phase detection unit 14B receives the edge direction information 50 and the edge pixel position 110 from the edge detection unit 11B, the phase detection unit 14B calculates the amount of phase deviation between the reference pixel position, which is the reference pixel position, and the signal.

It is a figure for demonstrating the amount of phase deviation of the signal which the phase detection part of the absolute encoder which concerns on Embodiment 1 calculates. The phase detection unit 14B calculates the amount of phase deviation θ with respect to the reference pixel position 150 of the image sensor 4X. Assuming that the center position of the reference pixel position 150 is P and the edge pixel position 110 closest to P is ZC(i), ZC(i) is the amount of phase deviation θ from the reference pixel position 150 . It can be expressed by the following formula (1) using

ZC(i)=P+θ...(1)

θ has a minus sign if it is to the left of the reference pixel position 150 , and a plus sign if it is to the right of the reference pixel position 150 . In other words, θ has a negative sign when it is in front of the reference pixel position 150 in the rotational direction, and has a positive sign when it is located inside the reference pixel position 150 in the rotational direction. The phase detection unit 14B searches for ZC(i) closest to P among the edge pixel positions 110 detected by the edge detection unit 11B, and obtains the phase deviation amount θ by taking the difference between ZC(i) and P Calculate.

Moreover, in Embodiment 1, although the phase detection part 14B calculates the phase deviation amount θ using only ZC(i) and P, the phase detection part 14B uses all the edge pixel positions 110 and uses the least squares. You may calculate the phase deviation amount (theta) by a method. Further, the reference pixel position 150 may be a central pixel of the image sensor 4X, or a pixel at the left or right end, and the position of the reference pixel position 150 is not particularly limited. The phase detection unit 14B sends the phase deviation amount θ to the high-precision detection unit 15X.

The high-precision detection unit 15X calculates the absolute position of the scale 20 by adding both the rough absolute position calculated by the rough detection unit 13A and the phase deviation amount θ calculated by the phase detection unit 14B. The high-precision detection unit 15X matches the pixel position corresponding to the bit used for specifying the rough absolute position with the reference pixel position 150 used for calculating the phase deviation amount θ, and then the absolute position of the scale 20 to calculate The high-precision detection unit 15X outputs the calculated absolute position as position data 40X.

In this way, the absolute encoder 1X can detect the absolute position with high precision from only the absolute value code pattern 30 as the pattern for signal detection. Accordingly, the absolute encoder 1X can detect an absolute position with high reliability and high resolution without complicating the pattern for signal detection.

Moreover, since the absolute encoder 1X uses the two image sensors 3X and 4X arrange|positioned along the radial direction of the scale 20, the detection precision of an absolute position can be improved. Here, the reason why the absolute encoder 1X can improve the detection accuracy of the absolute position by using the two image sensors 3X and 4X will be described.

In the absolute encoder 1X, as shown in FIG. 1, when viewed from the rotation axis direction of the scale 20, the center of the light emitting element 2 and the center of the image sensor 3X with respect to the radial direction of the scale 20 , and the light emitting element 2 and the image sensors 3X and 4X are arranged so that the center of the image sensor 4X is on a straight line. In addition, the image sensor 3X is arranged at a position closer to the center of the scale 20 than the image sensor 4X. Here, the image sensors 3X and 4X have the same specifications.

Here, the characteristics of the signal obtained by processing the light received by the image sensors 3X and 4X by the AD converters 5A and 5B and the absolute position calculating unit 6X will be described.

9 is a diagram for explaining the characteristics of a signal obtained by the absolute encoder according to the first embodiment. In a part of the scale 20 shown on the left of FIG. 9 , a reflection point 160 on the scale 20 of the light received by the image sensor 3X and the scale 20 of the light received by the image sensor 4X A reflection point 170 of is shown. Moreover, on the right side of FIG. 9, the light intensity distributions 72 and 73 after the light quantity correction of the light projected by the image sensors 3X, 4X are shown. The light intensity distribution 72 is the light intensity distribution at the reflection point 160 , and the light intensity distribution 73 is the light intensity distribution at the reflection point 170 .

The reflection point 160 of the light received by the image sensor 3X includes more absolute value sign patterns 30 than the reflection point 170 of the light received by the image sensor 4X. For this reason, when the edge detection unit 11B executes edge detection processing on the light intensity distribution 72 of the light projected on the image sensor 3X, the light intensity distribution 73 of the light projected on the image sensor 4X is More edge pixel positions 110 than edge detection are detected.

In addition, when paying attention to the line width of the same reflective part 31 or the same non-reflective part 32 included in the reflection points 160 and 170, the line width at the reflection point 160 is the reflection point ( 170), which is narrower than the line width. For this reason, the basic periodic width in the light intensity distribution 72 is narrower than the basic periodic width in the light intensity distribution 73 . This means that the bit string 18 generated by the decoding unit 12A for the light intensity distribution 72 has fewer pixels per bit than the bit string 19 generated for the light intensity distribution 73, It means that the number (bit length) is large. That is, since the light received by the image sensor 4X has more pixels per bit than the light received by the image sensor 3X, the resolution is higher than that of the light received by the image sensor 3X. On the other hand, since the number of bits of the light received by the image sensor 3X is larger than that of the light received by the image sensor 4X, the reliability is higher than that of the light received by the image sensor 4X.

The absolute encoder 1X of the first embodiment separately processes the signals obtained by the image sensors 3X and 4X within the absolute position calculation unit 6X, and the high-precision detection unit 15X collects all the separately obtained position information. are adding

In the absolute encoder 1X, the AD converter 5A converts the analog signal from the image sensor 3X into a digital signal, and inputs it to the absolute position calculating part 6X. The absolute position calculating unit 6X executes light amount correction processing, edge detection processing, and decoding processing on the digital signal from this AD converter 5A, and the rough detection unit 13A calculates a rough absolute position.

The rough detection unit 13A specifies the rough absolute position by comparing the bit string 18 generated from the signal acquired by the image sensor 3X with the bit string stored in the lookup table 130 . Since the bit string 18 has a larger number of bits than the bit string 19, the coarse detection unit 13A can compare more bits than the case where the bit string 19 is used, thereby increasing the reliability of the calculated absolute position. can For example, even when light to the scale 20 is blocked by the adhesion of foreign matter to the scale 20 and an error occurs in some bits of the bit string 18, if the number of bits to be compared is large, the The detection unit 13A can specify the absolute position without being affected by the adhesion of the foreign object.

Moreover, in the absolute encoder 1X, the AD converter 5B converts the analog signal from the image sensor 4X into a digital signal, and inputs it to the absolute position calculating part 6X. The absolute position calculating unit 6X executes light amount correction processing and edge detection processing on the digital signal from the AD converter 5B, and the edge detection unit 11B calculates the phase deviation amount θ.

The unit of the phase deviation amount θ calculated by the phase detection unit 14B is the number of pixels. The number of pixels per bit of the bit string 19 acquired by the image sensor 4X is larger than the number of pixels per bit of the bit string 18 . Accordingly, as for the number of pixels corresponding to the phase deviation amount θ, the number of pixels in the bit string 19 is larger than the number of pixels in the bit string 18 . Since the phase detection unit 14B calculates the phase deviation amount θ using the bit string 19, it is possible to calculate the phase deviation amount θ with higher resolution than when calculating the phase deviation amount θ using the bit string 18. can

The high-precision detection unit 15X adds both the highly reliable rough absolute position calculated by the rough detection unit 13A and the high-resolution phase deviation amount θ calculated by the phase detection unit 14B. In this way, the absolute encoder 1X separately processes the signals obtained from the image sensors 3X and 4X and adds them all to obtain an absolute position with high reliability and high resolution.

In this way, since the absolute encoder 1X calculates the position data 40X based on two signals measured at two points in the absolute value sign pattern 30, an absolute position with high reliability and high resolution can be obtained. .

Further, since the absolute encoder 1X can obtain an absolute position with high reliability and high resolution, it is not necessary to improve the resolution of the AD converters 5A, 5B, nor to increase the number of detections.

In addition, the scale 20 of the absolute encoder 1X has only one track having the absolute value sign pattern 30 in the circumferential direction, so an absolute position with high reliability and high resolution can be obtained with a simple configuration. have.

In the first embodiment, the case of using the image sensors 3X and 4X of the same specification has been described, but if the condition that the number of bits in the bit string 18 is larger than the number of bits in the bit string 19 is satisfied , an image sensor 3X smaller in size than the image sensor 4X may be used. Thereby, the mounting volume of the absolute encoder 1X can be reduced. Moreover, the absolute encoder 1X may detect an absolute position using three or more image sensors.

Thus, in the absolute encoder 1X of Embodiment 1, the image sensors 3X, 4X are arrange|positioned so that they may overlap on the radial line extending from the center of the scale 20 in the radial direction. Further, the absolute position calculating unit 6X calculates the approximate absolute position on the scale 20 based on the signal from the image sensor 3X, and the reference pixel position based on the signal from the image sensor 4X. The amount of phase deviation θ from (150) is calculated. Then, the absolute position calculating unit 6X calculates the position data 40X by adding both the rough absolute position and the phase deviation amount θ. Thereby, the absolute position calculating unit 6X can add both the absolute position calculated based on the highly reliable rough information and the phase deviation amount θ calculated based on the high-resolution information, so that the reliability is high and the resolution is high. High position data 40X can be calculated.

Embodiment 2.

Next, Embodiment 2 is demonstrated using FIG.10 and FIG.11. In the second embodiment, the absolute position calculating unit generates a bit string in which a bit string calculated using a signal obtained from one image sensor and a bit string calculated using a signal obtained from the other image sensor are connected to each other, to calculate the absolute position.

Fig. 10 is a diagram showing the configuration of the absolute encoder according to the second embodiment. It is a figure for demonstrating the arrangement position of the image sensor in the absolute encoder which concerns on Embodiment 2. FIG. The same code|symbol is attached|subjected about the component which achieves the same function as the absolute encoder 1X of Embodiment 1 shown in FIG. 1 among each component of FIG. 10, and overlapping description is abbreviate|omitted.

The absolute encoder 1Y is provided with the light emitting element 2, image sensors 3Y, 4Y, the scale 20, AD converters 5A, 5B, and the absolute position calculating part 6Y. The image sensors 3Y and 4Y are the same image sensors as the image sensors 3X and 4X, and their arrangement positions in the direction along the circumference of the scale 20 are different from those of the image sensors 3X and 4X.

The absolute position calculating unit 6Y includes the light quantity correcting units 10A and 10B, the edge detecting units 11A and 11B, the decoding units 12A and 12B, the coarse detecting unit 13Y, and the phase detecting units 14A and 14B. , it has high-precision detection units 15A and 15B, and an arithmetic unit 45 .

In the absolute encoder 1Y, the center Ca of the image sensor 3Y and the center Cb of the image sensor 4Y are at different positions with respect to the direction along the circumference of the scale 20 . In other words, in the absolute encoder 1Y, when the scale 20 is viewed from the upper surface side, at least one of a position other than the center Ca of the image sensor 3Y and a position other than the center Cb of the image sensor 4Y is The image sensors 3Y and 4Y are arranged so as to overlap on a ray 22 extending in the first radial direction of the scale 20 from the center C1 of the scale 20 . That is, a part of the image sensor 3Y and a part of the image sensor 4Y overlap on the ray 22 , and at least one of the center Ca of the image sensor 3Y and the center Cb of the image sensor 4Y is a ray Image sensors 3Y and 4Y are arranged so as not to overlap on 22 . The light emitting element 2 is arrange|positioned so that the center C2 of the light emitting element 2 may overlap on this ray 22. The shortest distance from the center Ca to the ray 22 is equal to the shortest distance from the center Cb to the ray 22 .

Moreover, in the absolute encoder 1Y, the ray 22 connecting the center C2 of the light emitting element 2 and the center C1 of the scale 20 is the light receiving surface 21A of the image sensor 3Y and the image sensor 4Y ), the image sensors 3Y and 4Y are disposed so as to pass through the light receiving surface 21B. In addition, in the absolute encoder 1Y, the center line 41 extending in the longitudinal direction of the image sensor 3Y and the center line 42 extending in the longitudinal direction of the image sensor 4Y do not overlap, so that the image sensor 3Y, 4Y) is placed. The longitudinal direction of the image sensors 3Y and 4Y is a direction perpendicular to the ray 22 . In Embodiment 2, the image sensor 3Y is a first image sensor, and the image sensor 4Y is a second image sensor.

In this way, in the absolute encoder 1Y, the position along the circumference and the position in the radial direction of the image sensors 3Y and 4Y are different, and the ray 22 passes through the light receiving surfaces 21A and 21B, Image sensors 3Y and 4Y are disposed.

Due to the arrangement of the image sensors 3Y and 4Y, the common absolute value sign pattern is partially included in the light received by the light receiving surfaces 21A and 21B. Thereby, the absolute encoder 1Y can obtain the bit string 23 which mutually connected the bit string obtained by decoding the signal of the image sensors 3Y, 4Y.

In the absolute position calculating unit 6Y, the light quantity correcting unit 10A, the edge detecting unit 11A, the decoding unit 12A, the phase detecting unit 14A, and the high-precision detecting unit 15A, respectively, the light quantity correcting unit 10B, Processes similar to those of the edge detection unit 11B, the decode unit 12B, the phase detection unit 14B, and the high-precision detection unit 15B are executed. Therefore, here, the processing performed by the light amount correction part 10A, the edge detection part 11A, the decoding part 12A, the phase detection part 14A, and the high precision detection part 15A is demonstrated. Moreover, the process performed by the outline detection part 13Y and the calculating part 45 is demonstrated.

The light amount correction unit 10A, the edge detection unit 11A, the decode unit 12A, the rough detection unit 13Y, the phase detection unit 14A, and the high-precision detection unit 15A of the absolute position calculating unit 6Y are, respectively, absolute The same processing as that of the light amount correction unit 10A, the edge detection unit 11A, the decode unit 12A, the rough detection unit 13A, the phase detection unit 14B, and the high-precision detection unit 15X of the position calculating unit 6X is executed do.

That is, the light amount correcting unit 10A equalizes the signal intensity of the digital signal sent from the AD converter 5A, and sends it to the edge detecting unit 11A. The edge detection unit 11A obtains an edge pixel position 110 that coincides with a threshold level 105 for a signal having a uniform signal intensity. In addition, the edge detection unit 11A sets edge direction information 50 indicating the rise or fall of the edge at each edge pixel position 110 . The edge detecting unit 11A of the absolute position calculating unit 6Y sends the edge direction information 50 and the edge pixel position 110 to the decoding unit 12A and the phase detecting unit 14A.

Based on the edge direction information 50 and the edge pixel position 110, the decoding unit 12A converts the signal into a bit string composed of a bit value "1" and a bit value "0". The decoding unit 12A sends the bit string to the coarse detection unit 13Y.

In addition, the decoding unit 12B executes the same processing as that of the decoding unit 12A. That is, the decoding unit 12B generates a signal based on the edge direction information 50 and the edge pixel position 110 received from the edge detection unit 11B, the signal having a bit value of “1” and a bit value of “0”. Convert to bit string. The decoding unit 12B sends the bit string to the coarse detection unit 13Y.

The rough detection unit 13Y generates the bit string 23 by connecting the bit string converted by the decoding unit 12A and the bit string converted by the decoding unit 12B to each other. The coarse detection unit 13Y detects the coarse absolute position by comparing the bit string 23 with the lookup table 130 . At this time, the rough detection unit 13Y detects the rough absolute position after adjusting the rough absolute position so that the specified rough absolute position becomes the scale angular position on the ray 22 . In Embodiment 2, the rough absolute position detected by the rough detection part 13Y is a 2nd absolute position. The rough detection unit 13Y sends the rough absolute position after adjustment to the high-precision detection units 15A and 15B.

The phase detection unit 14A calculates the phase deviation amount θ with respect to the reference pixel position 24 based on the rising edge 51 and the falling edge 52 determined by the edge detection unit 11A. At this time, the phase detection unit 14A adjusts the phase deviation amount θ so that the reference pixel position of the image sensor 3Y becomes the reference pixel position 24 on the ray 22 , and then calculates the phase deviation amount θ. The phase detection unit 14A sends the phase deviation amount θ to the high-precision detection unit 15A.

Further, the phase detection unit 14B calculates the phase deviation amount θ with respect to the reference pixel position 25 based on the rising edge 51 and the falling edge 52 determined by the edge detection unit 11B. At this time, the phase detection unit 14B adjusts the phase deviation amount θ so that the reference pixel position of the image sensor 4Y becomes the reference pixel position 25 on the ray 22 , and then calculates the phase deviation amount θ. The phase detection unit 14B sends the phase deviation amount θ to the high-precision detection unit 15B.

In Embodiment 2, the reference pixel position 24 is the first reference pixel position, and the phase deviation amount θ calculated by the phase detection unit 14A is the first phase deviation amount. Moreover, in Embodiment 2, the reference pixel position 25 is a 2nd reference pixel position, and the phase deviation amount (theta) calculated by the phase detection part 14B is a 2nd phase deviation amount.

The high-precision detection unit 15A calculates the absolute position of the scale 20 by adding both the rough absolute position detected by the rough detection unit 13Y and the phase deviation amount θ calculated by the phase detection unit 14A. The high-precision detection unit 15A sends the calculated absolute position to the calculation unit 45 .

In addition, the high-precision detection unit 15B, similarly to the high-precision detection unit 15A, adds both the approximate absolute position detected by the rough detection unit 13Y and the amount of phase deviation θ calculated by the phase detection unit 14B to scale. Calculate the absolute position of (20). The high-precision detection unit 15B sends the calculated absolute position to the calculation unit 45 .

In Embodiment 2, the absolute position calculated by the high-precision detection part 15A is a 3rd absolute position, and the absolute position calculated by the high-precision detection part 15B is a 4th absolute position.

In this way, the signal acquired by the image sensor 3Y is calculated as the absolute position of the scale 20 by processing from the light amount correcting unit 10A to the high-precision detection unit 15A, and the signal acquired by the image sensor 4Y is calculated as the absolute position of the scale 20 by processing from the light amount correcting unit 10B to the high-precision detection unit 15B.

The calculating part 45 calculates the average position of the absolute position calculated by the high-precision detection part 15A, and the absolute position computed by the high-precision detection part 15B, and outputs the calculated average position as position data 40Y. In Embodiment 2, the positional data 40Y is the first absolute position.

As described above, in the absolute position calculating unit 6Y of the second embodiment, the rough detection unit 13Y connects the bit string converted by the decoding unit 12A and the bit string converted by the decoding unit 12B to each other, the bit string 23 ) to calculate the absolute position, a highly reliable absolute position can be obtained.

Embodiment 3.

Next, Embodiment 3 will be described with reference to FIGS. 12 to 16 . In the absolute encoder of the third embodiment, two image sensors are disposed at opposing positions with the center of the scale 20 interposed therebetween. The absolute encoder of the third embodiment outputs an absolute position obtained from a normal image sensor when one of the two image sensors has abnormal angle detection functions, and when both of the angle detection functions are normal, the average position of the absolute positions print out

12 is a diagram showing the configuration of the absolute encoder according to the third embodiment. Among the components in Fig. 12, the same reference numerals are assigned to components that achieve the same function as the absolute encoder 1X of the first embodiment shown in Fig. 1 or the absolute encoder 1Y of the second embodiment shown in Fig. 10, A duplicate description is omitted.

The absolute encoder 1Z includes light emitting elements 2A and 2B, image sensors 3Z and 4Z, a scale 20, AD converters 5A and 5B, and an absolute position calculating unit 6Z. The image sensors 3Z and 4Z are the same image sensors as the image sensors 3X and 4X, and have different arrangement positions from the image sensors 3X and 4X.

In the third embodiment, the image sensors 3Z and 4Z are disposed at positions symmetrically shifted by 180° from the rotation axis of the rotation shaft 7 . In other words, the image sensors 3Z and 4Z are arranged to face each other with the center position of the scale 20 interposed therebetween.

In addition, the light emitting elements 2A and 2B are illumination parts which irradiate light to the scale 20 similarly to the light emitting element 2 of Embodiment 1. FIG. The image sensor 3Z receives the light irradiated by the light emitting element 2A and reflected from the scale 20, and outputs an analog signal corresponding to the received light to the AD converter 5A. The image sensor 4Z receives the light irradiated by the light emitting element 2B and reflected from the scale 20, and outputs an analog signal corresponding to the received light to the AD converter 5B.

In Embodiment 3, the light emitting element 2A is a first light emitting element that irradiates light to a first position of the scale 20 , and the light emitting element 2B is a second light emitting element that irradiates light to a second position of the scale 20 . 2 is a light emitting device. Moreover, in Embodiment 3, the image sensor 3Z is a 1st image sensor, and the image sensor 4Z is a 2nd image sensor. The image sensor 3Z receives the first light from a first position separated by a first distance from the center of the scale 20 and outputs an analog signal corresponding to the first light. The image sensor 4Z receives the second light from the second position separated by a second distance from the center of the scale 20 and outputs an analog signal corresponding to the second light. In the third embodiment, the first distance and the second distance may be different distances or the same distance. The analog signal output from the image sensor 3Z is the first analog signal, and the analog signal output from the image sensor 4Z is the second analog signal.

The absolute position calculating unit 6Z includes the light quantity correcting units 10A and 10B, the edge detecting units 11A and 11B, the decoding units 12A and 12B, the coarse detecting units 13A and 13B, and the phase detecting units 14A and 14B. ), high-precision detection units 15A and 15B, and a position data generation unit 16 .

The coarse detection unit 13A detects the approximate absolute position by comparing the bit string converted by the decoding unit 12A with the lookup table 130 . The rough detection unit 13A sends the rough absolute position after adjustment to the high-precision detection unit 15A.

The coarse detection unit 13B detects the approximate absolute position by comparing the bit string converted by the decoding unit 12B with the lookup table 130 . The rough detection unit 13B sends the rough absolute position after adjustment to the high-precision detection unit 15B.

The high-precision detection unit 15A calculates the absolute position of the scale 20 by adding both the rough absolute position detected by the rough detection unit 13A and the phase deviation amount θ calculated by the phase detection unit 14A. The high-precision detection unit 15A sends the calculated absolute position to the position data generation unit 16 .

The high-precision detection unit 15B calculates the absolute position of the scale 20 by adding both the rough absolute position detected by the rough detection unit 13B and the phase deviation amount θ calculated by the phase detection unit 14B. The high-precision detection unit 15B sends the calculated absolute position to the position data generation unit 16 .

In this way, the absolute position calculating unit 6Z separately processes the signal acquired by the image sensor 3Z and the signal acquired by the image sensor 4Z, and calculates the absolute position from each signal. That is, the absolute position calculating unit 6Z calculates the absolute position from the signal acquired by the image sensor 3Z by processing from the light amount correcting unit 10A to the high-precision detection unit 15A. Moreover, the absolute position calculating part 6Z calculates an absolute position from the signal acquired by the image sensor 4Z by the process from the light amount correction part 10B to the high-precision detection part 15B.

The position data generating unit 16 calculates and outputs the average position of the absolute position of the image sensor 3Z and the absolute position of the image sensor 4Z as position data 40Z. In Embodiment 3, the absolute position of the image sensor 3Z is the second absolute position, and the absolute position of the image sensor 4Z is the third absolute position. Moreover, in Embodiment 3, the positional data 40Z is a 1st absolute position.

13 is a flowchart showing a process procedure for generating position data by the position data generating unit of the absolute encoder according to the third embodiment. The position data generation unit 16 corrects the phase difference between the absolute position calculated by the high-precision detection unit 15A and the absolute position calculated by the high-precision detection unit 15B (step S10). The absolute position calculated by the high-precision detection unit 15A is an absolute position obtained from the image sensor 3Z, and the absolute position calculated by the high-precision detection unit 15B is an absolute position obtained from the image sensor 4Z. The position data generating unit 16 corrects at least one of the absolute positions obtained from the image sensors 3Z and 4Z by using the previously calculated phase difference between the image sensors 3Z and 4Z.

The position data generation unit 16 determines whether or not the absolute encoder 1Z is abnormal (step S20). The abnormality of the absolute encoder 1Z is an abnormality of at least one of the angle detection function of the image sensor 3Z and the angle detection function of the image sensor 4Z. When the position data generating unit 16 detects an abnormality, the operation of the absolute encoder 1Z is urgently stopped, or the operation is continued by correcting the absolute position so as to obtain a normal absolute position.

14 is a flowchart showing a processing procedure of a first example of abnormality determination processing by the position data generation unit of the absolute encoder according to the third embodiment. After correcting the phase difference, the position data generating unit 16 determines whether the absolute position difference obtained from the image sensors 3Z and 4Z is equal to or greater than a reference value of the difference (step S110).

When the absolute position difference is equal to or greater than the reference value of the difference (step S110, Yes), the position data generation unit 16 determines that the absolute encoder 1Z is abnormal. That is, the position data generation unit 16 determines that at least one of the angle detection function of the image sensor 3Z and the angle detection function of the image sensor 4Z is abnormal. In this case, the position data generating unit 16 urgently stops the rotation of the scale 20 by urgently stopping the motor that rotates the rotating shaft 7 (step S120). Specifically, when the absolute position difference is equal to or greater than the reference value of the difference, the position data generation unit 16 transmits a command for emergency stop of the motor to the motor control device that controls the motor. Thereby, the motor control device stops the motor.

On the other hand, when the absolute position difference is less than the reference value of the difference (step S110, No), the position data generation unit 16 determines that the absolute encoder 1Z is normal. In this case, the position data generating unit 16 outputs the average position of the absolute positions after phase difference correction obtained from the image sensors 3Z and 4Z as position data 40Z (step S130). Thereby, the absolute encoder 1Z can obtain a highly reliable absolute position by simple calculation.

15 is a flowchart showing a processing procedure of a second example of abnormality determination processing by the position data generation unit of the absolute encoder according to the third embodiment. The position data generation unit 16 determines whether the angle detection function of the image sensor 3Z is abnormal (step S210). The position data generation unit 16 determines, for example, to be abnormal when the number of edge pixel positions 110 detected by the edge detection unit 11A is equal to or less than a reference value of the number of edges. Further, the position data generation unit 16 may determine that it is abnormal when the number of bits difference between the bit string 120 calculated by the rough detection unit 13A and the bit string 140 in the lookup table 130 is equal to or greater than a threshold value. .

When the angle detection function of the image sensor 3Z is abnormal (step S210, Yes), the position data generation unit 16 determines whether the angle detection function of the image sensor 4Z is abnormal (step S220). The position data generation unit 16 determines that it is abnormal, for example, when the number of edge pixel positions 110 detected by the edge detection unit 11B is equal to or less than a reference value of the number of edges. The edge pixel position 110 in the image sensor 3Z is the first edge position, and the edge pixel position 110 in the image sensor 4Z is the second edge position.

In addition, the position data generation unit 16 may determine that it is abnormal when the number of bits difference between the bit string 120 calculated by the rough detection unit 13B and the bit string 140 in the lookup table 130 is equal to or greater than a threshold value. In Embodiment 3, the bit string 120 calculated|required by the rough detection part 13A is a 1st bit string, and the bit string 120 calculated|required by the rough detection part 13B is a 2nd bit string. Also, the bit string 140 in the lookup table 130 is the third bit string. Moreover, in Embodiment 3, the angle detection function of the image sensor 3Z is a 1st angle detection function, and the angle detection function of the image sensor 4Z is a 2nd angle detection function.

When the angle detection function of the image sensor 4Z is abnormal (step S220, Yes), the position data generation unit 16 makes an emergency stop of the motor (step S230).

When the angle detection function of the image sensor 3Z is abnormal, but the angle detection function of the image sensor 4Z is not abnormal (step S220, No), the position data generating unit 16 sets the absolute value obtained from the image sensor 4Z The position is output as position data 40Z (step S240). That is, the position data generation unit 16 outputs the absolute position sent from the high-precision detection unit 15B as position data 40Z.

When the angle detection function of the image sensor 3Z is not abnormal (step S210, No), the position data generation unit 16 determines whether the angle detection function of the image sensor 4Z is abnormal (step S250). Here, the position data generation unit 16 may determine that the number of edge pixel positions 110 detected by the edge detection unit 11B is equal to or smaller than a reference value of the number of edges, and may determine that the bit string 120 and the bit string are abnormal. When the number of difference bits of (140) is equal to or greater than the threshold value, it may be determined as abnormal.

Although the angle detection function of the image sensor 3Z is not abnormal, when the angle detection function of the image sensor 4Z is abnormal (step S250, Yes), the position data generating unit 16 determines the absolute position obtained from the image sensor 3Z. is output as the position data 40Z (step S260). That is, the position data generation unit 16 outputs the absolute position transmitted from the high-precision detection unit 15A as position data 40Z.

When the angle detection function of the image sensors 3Z and 4Z is not abnormal (step S250, No), the position data generating unit 16 converts the average position of the absolute positions obtained from the image sensors 3Z and 4Z into the position data 40Z ) as an output (step S270). That is, the position data generation unit 16 outputs the average position of the absolute positions sent from the high-precision detection units 15A and 15B as the position data 40Z.

In this way, the position data generating unit 16 determines whether the angle detection function of the image sensors 3Z and 4Z is abnormal, and if there is a normal angle detection function, the operation continues, so the absolute encoder 1Z is robust. You can get the absolute position.

Moreover, in the absolute encoder 1Z, the image sensors 3Z, 4Z are arrange|positioned with the phase difference of 180 degrees. Then, the absolute encoder 1Z is generating the average position of the absolute positions obtained by the image sensors 3Z and 4Z as the position data 40Z. Thereby, the absolute encoder 1Z can remove the error component of the absolute position due to the surface deviation of the rotating scale 20 .

16 is a diagram for explaining a plane deviation occurring in the scale of the absolute encoder according to the third embodiment. In the absolute encoder 1Z, the upper surface of the scale 20 and the upper surface of the control board 27 are disposed to face each other.

The light emitting elements 2A and 2B and the image sensors 3Z and 4Z are disposed on the upper surface of the control board 27 . 16 shows a case in which the scale 20 is inclined with respect to the control board 27 due to plane deviation. In addition, the control board 27 may incline with respect to the scale 20 .

As described above, in the absolute encoder 1Z of the third embodiment, since the image sensors 3Z and 4Z are arranged with a phase difference of 180°, the distance between the image sensor 3Z and the scale 20 and the image sensor 4Z The sum of the distances between and the scale 20 becomes constant regardless of the rotational position of the scale 20 . Accordingly, the absolute position calculating unit 6Z uses the average position of the absolute positions obtained from the image sensors 3Z and 4Z as the position data 40Z, so that it is possible to remove the error component of the absolute position due to the plane deviation.

In addition, the distance between the image sensor 3Z and the scale 20 and the distance between the image sensor 4Z and the scale 20 may be different. Also in this case, the absolute position calculating unit 6Z uses the average position of the absolute positions obtained from the image sensors 3Z and 4Z as the position data 40Z, so that it is possible to reduce the error component of the absolute position due to the plane deviation. .

Embodiment 4.

Next, Embodiment 4 will be described with reference to FIGS. 17 to 21 . In Embodiment 4, the light emitting element 2 and the image sensors 3X and 4X are mounted in one module.

17 is a diagram showing a schematic configuration of an absolute encoder according to the fourth embodiment. The same code|symbol is attached|subjected about the component which achieves the same function as the absolute encoder 1X of Embodiment 1 shown in FIG. 1 among each component of FIG. 17, and overlapping description is abbreviate|omitted.

The absolute encoder 1X of the fourth embodiment has the same components as the absolute encoder 1X of the first embodiment. In the absolute encoder 1X of the fourth embodiment, the light emitting element 2 and the image sensors 3X and 4X are integrated into one module 80a, and a control board constituting the hardware of the absolute encoder 1X ( 27) is installed. Specifically, the light emitting element 2 and the image sensors 3X and 4X are mounted on a small substrate 26 , and the small substrate 26 is mounted on the upper surface of the control substrate 27 .

Here, the configuration of the module 80a and the configuration of the modules 80b and 80c in which the light emitting element 2 or the image sensors 3X and 4X are disposed at different positions from the module 80a will be described.

18 is a diagram showing a first configuration example of a module in which the image sensor of the absolute encoder according to the fourth embodiment is mounted. 18 shows a top view of the module 80a as viewed from the mounting direction of the image sensors 3X and 4X.

19 is a diagram showing a second configuration example of a module in which the image sensor of the absolute encoder according to the fourth embodiment is mounted. 19 shows a top view of the module 80b as viewed from the mounting direction of the image sensors 3P and 4P. The module 80b is applicable to the absolute encoder 1X and the like described in the first embodiment.

20 is a diagram showing a third configuration example of a module in which the image sensor of the absolute encoder according to the fourth embodiment is mounted. Fig. 20 shows a top view of the module 80c when the module 80c is viewed from the mounting direction of the image sensor 3Z. The module 80c is applicable to the absolute encoder 1Z and the like described in the third embodiment.

In the module 80a, the light emitting element 2 and the image sensors 3X, 4X are arranged on the upper surface of the small substrate 26 . In the module 80a, the image sensor 4X is disposed at a position opposite to the light emitting element 2, and the image sensor 3X is disposed between the light emitting element 2 and the image sensor 4X.

In the module 80b , the light emitting element 2 and the image sensors 3P and 4P are arranged on the upper surface of the small substrate 26 . The image sensors 3P and 4P are the same image sensors as the image sensors 3X and 4X, and have different arrangement positions from the image sensors 3X and 4X. In the module 80b, the image sensors 3P and 4P are disposed so that the image sensor 3P and the image sensor 4P face each other, and the light emitting element 2 is disposed between the image sensor 3P and the image sensor 4P. is placed.

In the module 80c , the light emitting element 2A and the image sensor 3Z are disposed on the upper surface of the small substrate 26 . In the module 80c, an image sensor 3Z is disposed at a position opposite to the light emitting element 2A. In addition, the light emitting element 2B and the image sensor 4Z are arranged on the upper surface of the small substrate 26 different from the small substrate 26 shown in FIG. 20 .

Fig. 21 is a diagram showing the configuration of an absolute encoder when the module shown in Fig. 20 is applied to the absolute encoder of the third embodiment. In FIG. 21, the cross-sectional view of the control board 27 etc. with which the absolute encoder 1Z is equipped at the upper end is shown, and the top view of the control board 27 with which the absolute encoder 1Z is equipped at the lower end is shown.

On the upper surface of the control board 27 , modules 80c and 80c are disposed to face each other with the center of the scale 20 interposed therebetween. One module 80c is the module described with reference to Fig. 20, in which the light emitting element 2A and the image sensor 3Z are mounted. In the other module 80c, an image sensor 4Z is mounted at a position opposite to the light emitting element 2B.

In addition, the light emitting element 2 and image sensors 3Y, 4Y of the absolute encoder 1Y demonstrated in Embodiment 2 may be mounted in one module. As described above, in the absolute encoders 1X, 1Y, and 1Z, at least one light emitting element and at least one image sensor are mounted on one module.

As described above, according to the fourth embodiment, when any of the modules 80a, 80b, and 80c is used, it is possible to realize the integration of mounted components, and it is possible to suppress the pressure on the mounting area of the control board 27 . Moreover, since components can be mounted as a module, the mounting speed at the time of production is improved, and it becomes possible to reduce the mounting position error at the time of mounting.

Here, the hardware configuration of the absolute position calculating units 6X to 6Z will be described. In addition, since the absolute position calculating part 6X-6Z has the same hardware structure, here, the hardware structure of the absolute position calculating part 6X is demonstrated.

22 is a diagram showing an example of a hardware configuration for realizing an absolute position calculating unit included in the absolute encoder according to the first embodiment. The absolute position calculating unit 6X may be realized by the input device 300 , the processor 100 , the memory 200 , and the output device 400 . An example of the processor 100 is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, also called DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). Examples of the memory 200 are random access memory (RAM) and read only memory (ROM).

The absolute position calculating unit 6X is realized by the processor 100 reading and executing an absolute position calculating program executable in a computer for executing the operation of the absolute position calculating unit 6X stored in the memory 200 . . The absolute position calculation program, which is a program for executing the operation of the absolute position calculating unit 6X, can also be said to be a computer executing the procedure or method of the absolute position calculating unit 6X.

The absolute position calculation program executed by the absolute position calculation unit 6X includes the light quantity correction units 10A and 10B, the edge detection units 11A and 11B, the decode unit 12A, the coarse detection unit 13A, and the phase detection unit. It consists of a module structure including 14B and the high-precision detection part 15X, these are loaded on the main memory device, and these are created on the main memory device.

The input device 300 receives digital signals from the AD converters 5A and 5B and sends them to the processor 100 . The memory 200 is used as a temporary memory when the processor 100 executes various processes. In addition, the memory 200 stores a threshold level 105 , a lookup table 130 , and the like. The output device 400 outputs the position data 40X calculated by the processor 100 .

The absolute position calculation program may be stored in a computer-readable storage medium as a file in an installable format or an executable format, and may be provided as a computer program product. Moreover, the absolute position calculating program may be provided to the absolute position calculating part 6X via a network, such as the Internet. In addition, with respect to the function of the absolute position calculating part 6X, you may make it implement|achieve part with dedicated hardware, such as a dedicated circuit, and implement part with software or firmware.

The configuration shown in the above embodiment shows an example, it is possible to combine with other known techniques, it is also possible to combine the embodiments, and without departing from the gist, a part of the configuration is omitted or changed. It is also possible

1X, 1Y, 1Z: Absolute encoder 2, 2A, 2B: Light emitting element
3P, 3X, 3Y, 3Z, 4P, 4X, 4Y, 4Z: Image sensor
5A, 5B: AD converter 6X~6Z: Absolute position calculator
7: Rotating shaft 10A, 10B: Light quantity correction unit
11A, 11B: edge detection unit 12A, 12B: decode unit
13A, 13B, 13Y: rough detection unit 14A, 14B: phase detection unit
15A, 15B, 15X: High-precision detection unit 16: Position data generation unit
20: Scale 21A, 21B: light receiving surface
22: ray 24, 25: reference pixel position
30: absolute value sign pattern 31: reflector
32: Non-reflecting part 40X, 40Y, 40Z: Position data
45: calculation unit 70 to 73: light intensity distribution
80a, 80b, 80c: Module 100: Processor
105: threshold level 110: edge pixel position
130: lookup table 150: reference pixel position
160, 170: reflection point 200: memory
300: input device 400: output device

Claims (14)

A disk-shaped scale on which the absolute value sign pattern is placed,
a light emitting element irradiating light to the scale;
a first image sensor for receiving a first light from a first position separated by a first distance from the center of the scale and outputting a first analog signal corresponding to the first light;
a second image sensor for receiving a second light from a second position separated by a second distance from the center of the scale and outputting a second analog signal corresponding to the second light;
a first signal converter converting the first analog signal into a first digital signal;
a second signal converter converting the second analog signal into a second digital signal;
an absolute position calculating unit for calculating a first absolute position on the scale based on the first digital signal and the second digital signal;
Absolute encoder, characterized in that. The method according to claim 1,
The absolute position calculating unit,
A second absolute position on the scale is calculated based on the first digital signal, and an amount of phase deviation from a reference pixel position that is a reference pixel position is calculated based on the second digital signal, and the second absolute position is calculated based on the second digital signal. 2 calculating the first absolute position by adding both the absolute position and the phase deviation amount,
Absolute encoder, characterized in that. The method according to claim 1 or 2,
The first image sensor, the second image sensor, and the light emitting element are arranged to overlap on a semi-rectangular line extending from the center of the scale in the first radial direction of the scale when viewed in the direction of the rotation axis of the scale. there is,
Absolute encoder, characterized in that. 4. The method according to claim 3,
The first image sensor, the second image sensor, and the light emitting device may include a center of the first image sensor, a center of the second image sensor, and the Arranged so that the center of the light emitting element overlaps,
Absolute encoder, characterized in that. The method according to claim 1,
The first image sensor and the second image sensor are arranged to overlap on a radial line extending from the center of the scale in the first radial direction of the scale when viewed in the direction of the rotation axis of the scale, and The center of the image sensor and the center of the second image sensor are disposed so as not to overlap on the semi-rectangular line,
The absolute position calculating unit,
The second absolute position on the scale is calculated based on the first digital signal and the second digital signal, and the second absolute position is calculated from the first reference pixel position, which is a pixel position serving as a reference based on the first digital signal. Calculating one phase deviation amount, calculating a second phase deviation amount from a second reference pixel position that is a reference pixel position based on the second digital signal, and calculating the first phase deviation amount from the second absolute position A third absolute position is calculated by adding all of to calculate as the first absolute position,
Absolute encoder, characterized in that. 6. The method according to any one of claims 1 to 5,
At least one of the light emitting element and the first image sensor and the second image sensor is mounted on one module,
Absolute encoder, characterized in that. A disk-shaped scale on which the absolute value sign pattern is placed,
a first light emitting element irradiating light to a first position separated by a first distance from the center of the scale;
a second light emitting element irradiating light to a second position separated by a second distance from the center of the scale;
a first image sensor receiving the first light from the first position and outputting a first analog signal corresponding to the first light;
a second image sensor receiving the second light from the second position and outputting a second analog signal corresponding to the second light;
a first signal converter converting the first analog signal into a first digital signal;
a second signal converter converting the second analog signal into a second digital signal;
an absolute position calculating unit for calculating a first absolute position on the scale based on the first digital signal and the second digital signal;
The absolute position calculating unit,
Based on the first digital signal and the second digital signal, it is determined whether a first angle detection function of the first image sensor and a second angle detection function of the second image sensor are abnormal, and the first angle If the detection function and the second angle detection function are normal, the average position of the second absolute position on the scale corresponding to the first digital signal and the third absolute position on the scale corresponding to the second digital signal Calculated as the first absolute position,
Absolute encoder, characterized in that. 8. The method of claim 7,
The absolute position calculating unit,
If the first angle detection function is normal and the second angle detection function is abnormal, calculating the second absolute position as the first absolute position;
calculating the third absolute position as the first absolute position when the first angle detection function is abnormal and the second angle detection function is normal;
Absolute encoder, characterized in that. 8. The method of claim 7,
The absolute position calculating unit,
If the first angle detection function and the second angle detection function are abnormal, stopping the rotation of the scale,
Absolute encoder, characterized in that. 10. The method according to any one of claims 7 to 9,
The absolute position calculating unit,
When the difference between the first absolute position and the second absolute position is equal to or greater than a reference value, it is determined that at least one of the first angle detection function and the second angle detection function is abnormal, and the rotation of the scale is stopped;
Absolute encoder, characterized in that. 10. The method according to any one of claims 7 to 9,
The absolute position calculating unit,
Detects a first edge position that is a rising or falling position of the first digital signal and is a boundary of the presence or absence of the first digital signal, and when the number of first edge positions is less than or equal to a reference value, the first angle detection function is abnormal judge,
Detects a second edge position that is the rising or falling of the second digital signal and is a boundary of the presence or absence of the second digital signal, and determines that the second angle detection function is abnormal when the number of the second edge positions is less than or equal to the reference value doing,
Absolute encoder, characterized in that. 10. The method according to any one of claims 7 to 9,
The absolute position calculating unit,
generating a first bit string corresponding to the first digital signal and generating a second bit string corresponding to the second digital signal;
When the number of bits difference between the first bit string and a third bit string that is a bit string in a lookup table representing the bit string of the absolute value code pattern is equal to or greater than a threshold value, it is determined that the first angle detection function is abnormal;
determining that the second angle detection function is abnormal when the number of bits difference between the second bit string and the third bit string is equal to or greater than the threshold value;
Absolute encoder, characterized in that. 13. The method according to any one of claims 7 to 12,
The first image sensor and the second image sensor are disposed at opposing positions with the center of the scale interposed therebetween when viewed in the direction of the axis of rotation of the scale,
Absolute encoder, characterized in that. 14. The method according to any one of claims 7 to 13,
At least one of the first light emitting element and the second light emitting element and at least one of the first image sensor and the second image sensor are mounted in one module,
Absolute encoder, characterized in that.

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