Optical linear encoder

Abstract

To provide an optical linear encoder capable of identifying the cause of a defect.SOLUTION: An optical linear encoder includes: a scale unit having a built-in scale; a slider unit that moves linearly along the scale and outputs an A-phase signal and a B-phase signal based on light transmitted through or reflected by the scale; and an information processing unit that receives the A-phase signal and the B-phase signal and generates a square root of the sum of the squares of the A-phase signal and the B-phase signal as amplitude data. The information processing unit generates a first data set DS1 which is a collection of normal amplitude data C1(x) and a second data set DS2 which is a collection of second amplitude data C2(x) after use (S203), and determines whether there is a significant difference between the statistical values of the first data set DS1 and the statistical values of the second data set DS2 (S204 to S220).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to the configuration of an optical linear encoder, and more particularly to the configuration of an optical linear encoder capable of identifying the cause of a defect. [Background technology]

[0002] An optical linear encoder is an encoder that detects the amount of movement, and is composed of a scale unit and a slider unit. When an abnormality occurs in an optical linear encoder, it is necessary to remove the cause of the abnormality and return it to a normal state. As a method for detecting abnormalities in the slider and scale, Patent Document 1 discloses a method in which, in an abnormality determination signal, if the signal amplitude of the abnormality determination signal fluctuates steadily, it is determined that an abnormality has occurred on the encoder side, and if the signal amplitude fluctuates temporarily, it is determined that an abnormality has occurred on the scale side.

[0003] Furthermore, Patent Document 2 discloses a method for detecting the presence or absence of an abnormality in a rotary encoder by calculating the difference between the amplitude of a current detection signal and the amplitude of a past detection signal, and judging the presence or absence of an abnormality based on the difference. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7066264 specification [Patent Document 2] JP 2020-134183 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 may result in an erroneous determination if there are abnormalities in both the scale unit and the slider unit. Also, if the presence or absence of an abnormality is determined only by calculating the difference between the current detection signal amplitude and the past detection signal amplitude, as in the method described in Patent Document 2, there is a problem in that it is not possible to grasp the range in which the abnormality occurs within the measurement length.

[0006] Therefore, an object of the present disclosure is to provide an optical linear encoder capable of identifying the cause of a defect. [Means for solving the problem]

[0007] The optical linear encoder disclosed herein is a linear encoder comprising: a scale unit having a built-in scale; a slider unit that moves linearly along the scale and outputs an A-phase signal and a B-phase signal based on light transmitted through or reflected by the scale; and an information processing unit that receives the A-phase signal and the B-phase signal and generates, as amplitude data for the absolute position of the scale, a sum of squares of the A-phase signal and the B-phase signal with respect to the absolute position of the scale, or a square root of the sum of squares of the A-phase signal and the B-phase signal with respect to the absolute position of the scale, wherein the information processing unit generates a first data set which is a collection of amplitude data under normal conditions with respect to the absolute position of the scale and a second data set which is a collection of amplitude data after use with respect to the absolute position of the scale, statistically processes the first data set and the second data set, and determines an abnormality of the scale unit or the slider unit based on the presence or absence of a significant difference between a statistical value of the first data set and a statistical value of the second data set.

[0008] This makes it possible to determine whether the abnormality has occurred in the scale unit or the slider unit, and to identify the cause of the malfunction in the optical linear encoder.

[0009] In the optical linear encoder of the present disclosure, the information processing unit may determine that the scale unit is abnormal when there is a significant difference between the variance of the first data set and the variance of the second data set, and may determine that the scale unit is normal when there is no significant difference between the variance of the first data set and the variance of the second data set.

[0010] If an anomaly is present anywhere in the scale unit, a significant difference will occur between the variance of the first data set and the variance of the second data set. Therefore, by determining whether there is a significant difference between the variance of the first data set and the variance of the second data set, it is possible to easily determine whether the scale unit is abnormal or normal as a whole.

[0011] In the optical linear encoder of the present disclosure, the information processing unit may determine whether or not there is a significant difference between the variance of the first data set and the variance of the second data set by an F-test.

[0012] In this way, a statistical method is used to determine whether there is a significant difference between the variance of the first data set and the variance of the second data set, thereby making it possible to reduce the occurrence of erroneous determinations.

[0013] In the optical linear encoder of the present disclosure, the information processing unit may determine that the slider unit is abnormal if there is a significant difference between the average of the first data set and the average of the second data set, and may determine that the slider unit is normal if there is no significant difference between the average of the first data set and the average of the second data set.

[0014] If there is an abnormality anywhere in the slider unit, a difference will occur between the normal signal and the signal during use over almost the entire full stroke of the scale. Therefore, by determining whether there is a significant difference between the average of the first data set and the average of the second data set, it is possible to easily determine whether the slider unit is normal or abnormal.

[0015] In the optical linear encoder of the present disclosure, the information processing unit may determine whether there is a significant difference between the variance of the first data set and the variance of the second data set using an F-test, and if it is determined by the F-test that there is no significant difference between the variance of the first data set and the variance of the second data set, determine whether there is a significant difference between an average of the first data set and an average of the second data set using a Student's t-test, and if it is determined by the F-test that there is a significant difference between the variance of the first data set and the variance of the second data set, determine whether there is a significant difference between the average of the first data set and the average of the second data set using a Welch's t-test, and determine that there is an abnormality in the slider unit if it is determined that there is a significant difference between the average of the first data set and the average of the second data set.

[0016] In this way, the testing method for determining the mean of the first data set and the mean of the second data set is changed depending on the result of the F-test determining whether there is a significant difference between the variance of the first data set and the variance of the second data set, so that it is possible to reliably determine the significant difference between the two means.

[0017] In the optical linear encoder of the present disclosure, the information processing unit may divide the full stroke of the scale into a plurality of sections, extract a collection of normal amplitude data for the absolute position of the scale in each section as a first section data set for each section, extract a collection of after-use amplitude data for the absolute position of the scale in each section as a second section data set for each section, perform an F-test for each section, and if there is a section where it is determined that there is a significant difference between the variance of the first section data set and the variance of the second section data set, determine that there is an abnormality in the scale unit in that section.

[0018] This makes it possible to judge whether there is an abnormality in the scale unit for each section, and to identify the abnormal part of the scale unit.

[0019] In the optical linear encoder of the present disclosure, the information processing unit may determine, for a section determined to have no significant difference between the variance of the first section data set and the variance of the second section data set, whether there is a significant difference between the average of the first data set and the average of the second data set using a Student's t-test, and determine, for a section determined to have a significant difference between the variance of the first section data set and the variance of the second section data set, whether there is a significant difference between the average of the first data set and the average of the second data set using a Welch's t-test, and may determine that there is an abnormality in the slider unit if the ratio of the number of sections determined to have a significant difference between the average of the first section data set and the average of the second section data set to the total number of sections is equal to or greater than a predetermined threshold.

[0020] In this way, a slider unit abnormality is judged for each section, and if the ratio of the number of sections in which it is judged that there is a significant difference between the average of the first data set and the average of the second data set to the total number of sections is equal to or greater than a predetermined threshold, it is judged that there is an abnormality in the slider unit. This prevents erroneous judgments and makes it possible to more accurately judge whether the slider unit is abnormal.

[0021] In the optical linear encoder of the present disclosure, the Student's t-test and the Welch's t-test may be one-sided tests.

[0022] This makes it easy to determine whether there is a significant difference between two means.

[0023] The linear encoder of the present disclosure may further include a display device connected to the information processing unit, and the information processing unit may display the presence or absence of an abnormality in the scale unit or the slider unit on the display device. The information processing unit may also display, on the display device, a section in which it is determined that there is a significant difference between the variance of the first section data set and the variance of the second section data set, as an abnormal section of the scale.

[0024] This enables an operator or inspector to easily identify the abnormal portion. Effect of the Invention

[0025] The present disclosure can provide an optical linear encoder capable of identifying the cause of a defect. [Brief description of the drawings]

[0026] [Figure 1] 1 is a three-dimensional diagram showing a schematic configuration and a system configuration of an optical linear encoder according to an embodiment; [Diagram 2] 5 is a flowchart showing a preparation operation of the optical linear encoder according to the embodiment in a normal state. [Diagram 3] 5 is a flowchart showing a basic defect cause identifying operation of the optical linear encoder of the embodiment. [Figure 4] 10 is a flowchart showing a malfunction cause identifying operation of the optical linear encoder of the embodiment, specifically, a flowchart showing an operation of identifying an abnormality occurrence portion for each section of the full stroke of the scale. [Diagram 5] 5 is a continuation of the flowchart shown in FIG. 4. [Figure 6] 6 is a continuation of the flowchart shown in FIG. 5. [Figure 7] FIG. 11 is a diagram showing changes in first amplitude data C1(x) relative to the absolute position x of the scale in a normal or initial state. [Figure 8] FIG. 13 is a diagram showing changes in the second amplitude data C2(x) relative to the absolute position x of the scale when the scale is dirty after use. [Figure 9] 13 is a table showing the determination results for each section. [Figure 10] 13 is a table showing the determination results. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] An optical linear encoder 100 according to an embodiment will be described below with reference to the drawings. As shown in FIG.

[0028] A glass scale 11, which is a longitudinal member, is built into the scale unit 10. The scale 11 is provided with graduations consisting of a grid array aligned in the longitudinal direction, which is the measurement direction.

[0029] The slider unit 20 moves linearly in the x direction along the scale 11, as indicated by an arrow 91 in Fig. 1. The slider unit 20 has a light-emitting unit 22 and a light-receiving unit 23. The light-emitting unit 22 emits parallel light toward the scale 11. The light-receiving unit 23 receives the light emitted from the light-emitting unit 22 and transmitted through the scale 11, and outputs an A-phase signal that changes sinusoidally, and a B-phase signal that changes sinusoidally and is 90° out of phase with the A-phase signal.

[0030] The information processing unit 25 is a computer including a CPU 26, which is a processor that performs information processing, and a memory 27 that stores operation programs and data. In the optical linear encoder 100 of the embodiment, the information processing unit 25 is built into the slider unit 20. The operation of the information processing unit 25 is realized by the CPU 26 executing the program stored in the memory 27. The information processing unit 25 receives an A-phase signal and a B-phase signal from the light receiving unit 23. The information processing unit 25 detects an absolute position x of the slider unit 20 with respect to the scale 11 based on the A-phase signal and the B-phase signal. Here, the absolute position x is the position from the right end of the scale 11, as shown in FIG. 1.

[0031] Furthermore, the information processing unit 25 generates the square root of the sum of the squares of the voltages of the A-phase signal and the B-phase signal for the absolute position x of the scale 11 as amplitude data C(x) for the absolute position x of the scale 11 using the following equation 1.

number

[0032] In addition, the information processing unit 25 calculates the first amplitude data C1(x) in the normal state for the absolute position x of the scale 11 using the following equation 2, generates a first data set DS1 which is a collection of the first amplitude data C1(x), and stores it in the memory 27.

number

[0033] In addition, the information processing unit 25 calculates the second amplitude data C2(x) after use for the absolute position x of the scale 11 using the following equation 3, generates a second data set DS2 which is a collection of the second amplitude data C2(x), and stores it in the memory 27.

number

[0034] Then, the information processing unit 25 performs statistical processing on the first data set DS1 and the second data set DS2, and determines whether there is an abnormality in the scale unit 10 or the slider unit 20 based on the presence or absence of a significant difference between the statistical values ​​of the first data set DS1 and the statistical values ​​of the second data set DS2.

[0035] The display device 30 is connected to the information processing unit 25 and displays the determination result of an abnormality in the scale unit 10 or the slider unit 20. The display device 30 may be, for example, a display, a display device of an NC, or a mobile terminal such as a tablet or a smartphone. In addition, the communication method between the information processing unit 25 and the display device 30 may be wired communication or wireless communication as long as they are in a state where they can communicate with each other.

[0036] When the current absolute position x cannot be detected normally or when regular maintenance is to be performed, the optical linear encoder 100 executes a malfunction cause identifying operation as described below.

[0037] Before performing the malfunction factor identification operation, the optical linear encoder 100 performs a preparatory operation as shown in FIG. 2. In the preparatory operation, as shown in step S101 in FIG. 2, the information processing unit 25 moves the slider unit 20 at an arbitrary constant speed during normal operation or at the beginning of operation until the absolute position x becomes the full stroke of the scale 11 from 0, and acquires the voltage of the A-phase signal and the voltage of the B-phase signal for the absolute position x. Then, the information processing unit 25 calculates the first amplitude data C1(x) during normal operation for the absolute position x by the above-described formula 2. An example of the first amplitude data C1(x) during normal operation is shown in FIG. 7. Then, a set of the calculated first amplitude data C1(x) is stored in the memory 27 as the first data set DS1. The number of data in the first data set DS1 may be equal to or greater than the number that does not cause any trouble in performing the F-test, Student's t-test, and Welch's t-test, which will be described later.

[0038] Next, a basic malfunction identification operation of the optical linear encoder 100 will be described with reference to Fig. 3. In step S201 of Fig. 3, the information processing unit 25 checks whether communication with the display device 30 is possible. If communication with the display device 30 is not possible, the information processing unit 25 judges NO in step S201 of Fig. 3 and proceeds to step S202 of Fig. 3, where it is determined that there is an abnormality in the slider unit 20. On the other hand, if the information processing unit 25 judges YES in step S201 of Fig. 3, it proceeds to step S203 of Fig. 3.

[0039] In step S203 in FIG. 3, the information processing unit 25 moves the slider unit 20 at an arbitrary constant speed until the absolute position x is from 0 to the full stroke of the scale 11, and acquires the voltage of the A-phase signal and the voltage of the B-phase signal for the absolute position x. Then, the information processing unit 25 calculates the second amplitude data C2(x) after use for the absolute position x of the scale 11 by Equation 3, generates a second data set DS2 which is a collection of the second amplitude data C2(x), and stores it in the memory 27. FIG. 8 shows an example of the second amplitude data C2(x) after use. In the example shown in FIG. 8, there is partial dirt in sections 1 to 3 of the scale 11 due to use, and the light entering the light receiving unit 23 is blocked in the corresponding parts, and the magnitude of the second amplitude data C2(x) is reduced in the corresponding parts. The number of data in the second data set DS2 may be any number greater than or equal to a number that does not cause any trouble in performing the F-test, Student's t-test, and Welch's t-test, which will be described later. After generating the second data set DS2 and storing it in the memory 27, the information processing unit 25 proceeds to step S204 in FIG.

[0040] In step S204 in Fig. 3, the information processing unit 25 determines whether there is a significant difference between the variance of the first data set DS1 and the variance of the second data set DS2 by an F-test. Here, the F-test is a two-sided test. If the information processing unit 25 determines that there is a significant difference between the two variances, it determines YES in step S205 in Fig. 3 and proceeds to step S206 in Fig. 3, determining that there is an abnormality in the scale unit 10. The information processing unit 25 then proceeds to step S207 in Fig. 3.

[0041] In step S207 of Fig. 3, the information processing unit 25 determines whether there is a significant difference between the average of the first data set DS1 and the average of the second data set DS2 by Welch's t-test. Here, the Welch's t-test is a one-sided test. If there is a significant difference between the two averages, the information processing unit 25 determines YES in step S208 of Fig. 3 and proceeds to step S209 of Fig. 3 to determine that there is an abnormality in the slider unit 20. Then, the information processing unit 25 proceeds to step S210 of Fig. 3 to output a determination result that there is an abnormality in both the scale unit 10 and the slider unit 20 to the display device 30. The display device 30 displays the determination result in step S220 of Fig. 3.

[0042] Moreover, if there is no significant difference between the two averages, the information processing unit 25 judges NO in step S208 in Fig. 3 and proceeds to step S211 in Fig. 3, where it is determined that the slider unit 20 is normal. Then, the information processing unit 25 proceeds to step S212 in Fig. 3, where it outputs a determination result that there is an abnormality in the scale unit 10 and that the slider unit 20 is normal to the display device 30. The display device 30 displays the determination result in step S220 in Fig. 3.

[0043] On the other hand, if the information processing unit 25 determines that there is no significant difference between the two variances, it makes a NO determination in step S205 in Fig. 3, proceeds to step S213 in Fig. 3, and determines that the scale unit 10 is normal. Then, the information processing unit 25 proceeds to step S214 in Fig. 3.

[0044] In step S214 of Fig. 3, the information processing unit 25 determines whether there is a significant difference between the average of the first data set DS1 and the average of the second data set DS2 by Student's t-test. Here, the Student's t-test is a one-sided test. If there is a significant difference between the two averages, the information processing unit 25 determines YES in step S215 of Fig. 3 and proceeds to step S216 of Fig. 3 to determine that there is an abnormality in the slider unit 20. Then, the information processing unit 25 proceeds to step S217 of Fig. 3 to output a determination result that the scale unit 10 is normal and that there is an abnormality in the slider unit 20 to the display device 30. The display device 30 displays the determination result in step S220 of Fig. 3.

[0045] Moreover, if there is no significant difference between the two averages, the information processing unit 25 judges NO in step S215 of Fig. 3 and proceeds to step S218 of Fig. 3, where it is determined that the slider unit 20 is normal. Then, the information processing unit 25 proceeds to step S219 of Fig. 3, and outputs the determination result that both the scale unit 10 and the slider unit 20 are normal to the display device 30. The display device 30 displays the determination result in step S220 of Fig. 3.

[0046] As described above, the optical linear encoder 100 of the embodiment can determine whether an abnormality has occurred in the scale unit 10 or the slider unit 20, and can identify the cause of the malfunction of the optical linear encoder 100.

[0047] Next, a malfunction cause identifying operation for identifying an abnormality occurrence location for each section of the full stroke of the scale 11 will be described with reference to Figures 4 to 6. The same steps as those in the malfunction cause identifying operation previously described with reference to Figure 3 will be assigned the same step numbers and will not be described again.

[0048] The information processing section 25 executes steps S201 to S203 in Fig. 4, similarly to the malfunction cause identifying operation previously described with reference to Fig. 3. After that, the information processing section 25 proceeds to step S301 in Fig. 4.

[0049] In step S301 of Fig. 4, the information processing unit 25 divides the full stroke of the scale 11 into N sections. For example, as shown in Figs. 7 and 8, if the full stroke of the scale 11 is from 0 mm to 80 mm, the full stroke is divided into eight sections, section 1 to section 8, each having a length of 10 mm, from section 1 of 0-10 mm to section 8 of 70-80 mm.

[0050] 4, the information processing unit 25 extracts a set of first amplitude data C1(x) included in section N from the first data set DS1 stored in the memory 27 as a first section data set DS1(N) for section N, and stores it in the memory 27. Also, in step S303 in Fig. 4, the information processing unit 25 extracts a set of second amplitude data C2(x) included in section N from the second data set DS2 stored in the memory 27 as a second section data set DS2(N) for section N, and stores it in the memory 27. Note that the number of data in the first section data set DS1(N) and the second section data set DS2 may be equal to or greater than a number that does not cause any hindrance in performing an F-test, a Student's t-test, and a Welch's t-test, which will be described later.

[0051] Next, in step S305 of Fig. 5, the information processing unit 25 sets a counter K to an initial value of 1. Then, in step S306 of Fig. 5, the information processing unit 25 determines whether there is a significant difference between the variance of the first section data set DS1(K) and the variance of the second section data set DS2(K) by an F-test in section K. Then, when the information processing unit 25 determines that there is a significant difference between the two variances, it determines YES in step S307 of Fig. 5 and proceeds to step S308 of Fig. 5, where it determines that there is an abnormality in the scale 11 of the section K. Then, the information processing unit 25 proceeds to step S309 of Fig. 5, where it determines whether there is a significant difference between the average of the first section data set DS1(K) and the average of the second section data set DS2(K) in section K by a Welch's t-test. Then, if there is a significant difference between the two averages, the information processing unit 25 determines YES in step S310 of Fig. 5, and determines in step S311 of Fig. 5 that there is an abnormality in the slider unit 20 in section K. On the other hand, if there is no significant difference between the two averages, the information processing unit 25 determines NO in step S310 of Fig. 5, and determines in step S312 of Fig. 5 that the slider unit 20 is normal in section K.

[0052] On the other hand, if the information processing unit 25 determines that there is no significant difference between the two variances, it determines NO in step S307 in FIG. 5 and proceeds to step S313 in FIG. 5, and determines that the scale 11 in the section K is normal. Then, the information processing unit 25 proceeds to step S314 in FIG. 5 and determines whether there is a significant difference between the average of the first section data set DS1(K) and the average of the second section data set DS2(K) in the section K by Student's t-test. Then, if there is a significant difference between the two averages, the information processing unit 25 determines YES in step S315 in FIG. 5, and determines that there is an abnormality in the slider unit 20 in the section K in step S316 in FIG. 5. Also, if there is no significant difference between the two averages, the information processing unit 25 determines NO in step S315 in FIG. 5, and determines that the slider unit 20 is normal in the section K in step S317 in FIG. 5.

[0053] After performing any one of steps S311, S312, S316, and S317 in Fig. 5, the information processing unit 25 proceeds to step S318 in Fig. 5 to determine whether the counter K has reached the total number of sections, that is, N. If the determination is NO in step S318 in Fig. 5, the information processing unit 25 proceeds to step S319 in Fig. 5 to increment the counter K by 1, and returns to step S306 in Fig. 5.

[0054] In this manner, the information processing section 25 repeatedly executes steps S306 to S319 in FIG. 5 until the counter K reaches N, which is the total number of sections.

[0055] If the information processing unit 25 judges YES in step S318 of Fig. 5, it proceeds to step S320 of Fig. 6. Then, it is determined whether there is a section in which it is determined that there is an abnormality in the scale 11 in step S320 of Fig. 6, and if it judges YES in step S320 of Fig. 6, it proceeds to step S321 of Fig. 6 and judges that there is an abnormality in the scale unit 10. In this case, the information processing unit 25 displays on the display device 30 the section in which it is determined that there is an abnormality in the scale 11 in step S322 of Fig. 6.

[0056] Then, the information processing unit 25 proceeds to step S323 in Fig. 6 to determine whether the ratio of the number of sections in which it is determined that the slider unit 20 has an abnormality to the total number of sections is equal to or greater than a threshold value. Here, the number of sections in which it is determined that the slider unit 20 has an abnormality is the number of sections in which it is determined that there is a significant difference between the two average values ​​in step S310 in Fig. 5. Then, if the information processing unit 25 determines that there is an abnormality in the slider unit 20 in step S324 in Fig. 6, when it determines that there is an abnormality in step S323 in Fig. 6, the information processing unit 25 proceeds to step S324 in Fig. 6 to determine that there is an abnormality in the slider unit 20. Then, in step S326 in Fig. 6, the information processing unit 25 outputs the determination result that there is an abnormality in both the scale unit 10 and the slider unit 20 to the display device 30. The display device 30 displays the determination result in step S334 in Fig. 6.

[0057] Moreover, if the information processing unit 25 judges NO in step S323 of Fig. 6, the process proceeds to step S325 of Fig. 6 and judges that the slider unit 20 is normal. Then, in step S327 of Fig. 6, the information processing unit 25 outputs a judgment result that there is an abnormality in the scale unit 10 and that the slider unit 20 is normal to the display device 30. The display device 30 displays the judgment result in step S334 of Fig. 6.

[0058] On the other hand, if the information processing unit 25 determines NO in step S320 in FIG. 6, it proceeds to step S328 in FIG. 6 and determines that the scale unit 10 is normal.

[0059] Then, the information processing unit 25 proceeds to step S329 in Fig. 6 to determine whether the ratio of the number of sections in which it is determined that the slider unit 20 has an abnormality to the total number of sections is equal to or greater than a threshold value. Here, the number of sections in which it is determined that the slider unit 20 has an abnormality is the number of sections in which it is determined that there is a significant difference between the two average values ​​in step S315 in Fig. 5. Then, if the information processing unit 25 determines that there is an abnormality in the slider unit 20 in step S329 in Fig. 6, it proceeds to step S330 in Fig. 6 to determine that there is an abnormality in the slider unit 20. Then, in step S331 in Fig. 6, the information processing unit 25 outputs the determination result that the scale unit 10 is normal and that there is an abnormality in the slider unit 20 to the display device 30. The display device 30 displays the determination result in step S334 in Fig. 6.

[0060] Moreover, if the information processing unit 25 determines NO in step S329 in Fig. 6, it proceeds to step S332 in Fig. 6 and determines that the slider unit 20 is normal. Then, in step S333 in Fig. 6, the information processing unit 25 outputs a determination result that both the scale unit 10 and the slider unit 20 are normal to the display device 30. In step S334 in Fig. 6, the display device 30 displays the determination result.

[0061] Here, when the second amplitude data C2(x) stored in memory 27 is as shown in Fig. 8, the information processing unit 25 determines in step S307 of Fig. 5 that there is a significant difference between the two variances in sections 1, 2, and 3. The information processing unit 25 also determines in step S307 of Fig. 5 that there is no significant difference between the two variances in sections 4 to 8. The results of the determination for each section are shown in Fig. 9. Therefore, in step S322 of Fig. 6, the information processing unit 25 outputs to the display device 30 the determination result that there is an abnormality in sections 1 to 3 of the scale unit 10, as shown in Fig. 10.

[0062] Moreover, the information processing unit 25 determines in step S310 of Fig. 5 that there is a significant difference between the two averages in intervals 1, 2, and 3. Moreover, the information processing unit 25 determines in step S315 of Fig. 5 that there is no significant difference between the two averages in intervals 4 to 8. The results of the determination for each interval are shown in Fig. 9.

[0063] As a result, as shown in Fig. 10, the number of sections determined to have a significant difference by the t-test = 3, and the total number of sections = 8, so the ratio of the number of sections determined to have a significant difference by the t-test to the total number of sections is 37.5%. For example, if the predetermined threshold is 95%, this ratio, 37.5%, is smaller than 95%. Therefore, the information processing unit 25 judges NO in step S323 in Fig. 6, and judges the slider unit 20 to be normal in step S325 in Fig. 6.

[0064] As described above, the optical linear encoder 100 of the embodiment can judge whether or not there is an abnormality in the scale unit 10 for each section, and can identify and display the abnormal part of the scale unit 10. This makes it possible to identify the cause of the malfunction of the scale unit 10 in more detail. Also, because the optical linear encoder 100 judges whether or not there is an abnormality in the slider unit 20 for each section, and judges that there is an abnormality in the slider unit 20 when the ratio of the number of sections determined to have a significant difference by the t-test to the total number of sections is equal to or greater than a predetermined threshold value, it is possible to suppress erroneous judgments and more accurately judge whether or not there is an abnormality in the slider unit 20.

[0065] In the above description, the scale 11 is made of glass and transmits the light emitted from the light-emitting unit 22, and the light-receiving unit 23 receives the light transmitted through the scale 11 and outputs an A-phase signal and a B-phase signal, but this is not limiting. For example, the scale 11 may be configured to reflect the light emitted from the light-emitting unit 22, and the light-receiving unit 23 may be configured to receive the light reflected by the scale 11 and output an A-phase signal and a B-phase signal.

[0066] In the above description, the amplitude data C(x), the first amplitude data C1(x), and the second amplitude data C2(x) are calculated by the square root of the sum of the squares of the voltages of the A-phase signal and the B-phase signal for the absolute position x of the scale 11 as shown in Equation 1 to Equation 3, but this is not limiting. For example, they may be calculated as the sum of the squares of the voltages of the A-phase signal and the B-phase signal for the absolute position x of the scale 11 as shown in Equation 4 to Equation 6 below.

number

number

number

[0067] In the above explanation, the F-test is performed as a two-sided test, and the Student's t-test and the Welch's t-test are performed as one-sided tests, but this is not limited to the above. For example, all tests may be performed as two-sided tests, or all tests may be performed as one-sided tests. Also, the F-test may be performed as a one-sided test, and the Student's t-test and the Welch's t-test may be performed as two-sided tests.

[0068] In the above description, the information processing unit 25 is described as being built into the slider unit 20, but this is not limiting, and the information processing unit 25 may be configured as a device separate from the slider unit 20. In this case, the information processing unit 25 and the slider unit 20 may be connected by a communication line such as wireless or wired. [Explanation of symbols]

[0069] 10 scale unit, 11 scale, 20 slider unit, 22 light emitting unit, 23 light receiving unit, 25 information processing section, 26 CPU, 27 memory, 30 display device, 100 optical linear encoder.

Claims

1. a scale unit having a built-in scale; a slider unit that moves linearly along the scale and outputs an A-phase signal and a B-phase signal based on light that has passed through the scale or light that has been reflected by the scale; an information processing unit that receives the A-phase signal and the B-phase signal, and generates a sum of squares of the A-phase signal and the B-phase signal with respect to an absolute position of the scale, or a square root of the sum of squares of the A-phase signal and the B-phase signal with respect to the absolute position of the scale, as amplitude data with respect to the absolute position of the scale, The information processing unit includes: generating a first data set which is a set of amplitude data in a normal state relative to the absolute position of the scale, and a second data set which is a set of amplitude data after use relative to the absolute position of the scale; an optical linear encoder comprising: a first data set and a second data set; and determining whether or not there is an abnormality in the scale unit or the slider unit based on whether or not there is a significant difference between a statistical value of the first data set and a statistical value of the second data set.

2. 2. The optical linear encoder according to claim 1, The information processing unit includes: determining that the scale unit is abnormal when there is a significant difference between the variance of the first data set and the variance of the second data set; determining that the scale unit is normal if there is no significant difference between the variance of the first data set and the variance of the second data set; An optical linear encoder characterized by:

3. 3. The optical linear encoder according to claim 2, The information processing unit includes: determining whether there is a significant difference between the variance of the first data set and the variance of the second data set using an F-test; An optical linear encoder characterized by:

4. 4. An optical linear encoder according to claim 1, The information processing unit includes: determining that the slider unit is abnormal when there is a significant difference between the average of the first data set and the average of the second data set; determining that the slider unit is normal if there is no significant difference between the average of the first data set and the average of the second data set; An optical linear encoder characterized by:

5. 5. The optical linear encoder according to claim 4, The information processing unit includes: determining whether there is a significant difference between the variance of the first data set and the variance of the second data set using an F-test; When the F-test determines that there is no significant difference between the variance of the first data set and the variance of the second data set, a Student's t-test is used to determine whether there is a significant difference between the mean of the first data set and the mean of the second data set; When the F-test determines that there is a significant difference between the variance of the first data set and the variance of the second data set, a Welch's t-test is used to determine whether there is a significant difference between the average of the first data set and the average of the second data set; determining that the slider unit is abnormal when it is determined that there is a significant difference between the average of the first data set and the average of the second data set; An optical linear encoder characterized by:

6. 2. The optical linear encoder according to claim 1, The information processing unit includes: Dividing a full stroke of the scale into a plurality of sections; A set of amplitude data in a normal state with respect to the absolute position of the scale in each section is extracted as a first section data set for each section; A set of amplitude data after use relative to the absolute position of the scale in each section is extracted as a second section data set for each section; performing an F-test for each interval, and when there is an interval in which it is determined that there is a significant difference between the variance of the first interval data set and the variance of the second interval data set, determining that there is an abnormality in the scale unit in that interval; An optical linear encoder characterized by:

7. 7. An optical linear encoder according to claim 6, The information processing unit includes: For an interval in which it is determined that there is no significant difference between the variance of the first interval data set and the variance of the second interval data set, determining whether there is a significant difference between the average of the first dataset and the average of the second dataset by Student's t-test; For the intervals determined to have a significant difference between the variance of the first interval data set and the variance of the second interval data set, determining whether there is a significant difference between the average of the first dataset and the average of the second dataset by Welch's t-test; determining that the slider unit is abnormal when a ratio of the number of sections determined to have a significant difference between the average of the first section data set and the average of the second section data set to the total number of sections is equal to or greater than a predetermined threshold value; An optical linear encoder characterized by:

8. 8. An optical linear encoder according to claim 7, The Student's t-test and the Welch's t-test are one-tailed tests; An optical linear encoder characterized by:

9. 6. An optical linear encoder according to claim 5, A display device connected to the information processing unit, The information processing unit includes: displaying on the display device whether or not there is an abnormality in the scale unit or the slider unit; An optical linear encoder characterized by:

10. 8. An optical linear encoder according to claim 7, A display device connected to the information processing unit, The information processing unit includes: displaying on the display device whether or not there is an abnormality in the scale unit or the slider unit; An optical linear encoder characterized by:

11. 8. An optical linear encoder according to claim 7, A display device connected to the information processing unit, The information processing unit includes: displaying on the display device a section in which it is determined that the scale is abnormal; An optical linear encoder characterized by:

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