Encoder system, encoder calibration method and encoder

Abstract

To provide an encoder system, an encoder calibration method and an encoder, capable of eliminating an error similarly to when a plurality of measurement units are used without providing the plurality of measurement units when detecting a state of a measurement object on actual measurement.SOLUTION: An encoder system includes an encoder 110, a reference encoder 120 and an arithmetic unit 140. On adjustment, the encoder 110 measures a state of a measurement object 10 to generate a measurement value, the reference encoder 120 measures a state of the measurement object 10 to generate a reference measurement value, the arithmetic unit 140 calculates a correction value for correcting the measurement value on actual measurement from the measurement value and the reference measurement value, and the encoder 110 is made to store the correction value. On actual measurement, the encoder 110 measures a state of the measurement object 10 to generate the measurement value, and uses the stored correction value to correct the measurement value to output the corrected measurement value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an encoder system, an encoder calibration method, and an encoder, and more particularly to a technique for correcting an error component using a single encoder. [Background technology]

[0002] In optical encoders that detect the angle of a rotating body, the detected angle may contain a first-order rotational component error due to eccentricity of the rotating plate that has a reading pattern. To eliminate this type of first-order rotational component error due to eccentricity, there is a method for correcting it by arranging multiple measuring units in the encoder. An example of this type of encoder calibration system is described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-161644 Summary of the Invention [Problem to be solved by the invention]

[0004] The encoder calibration system disclosed in Patent Document 1 is configured to reduce error components during measurement by, for example, averaging detection signals from multiple detection heads.

[0005] When multiple measuring units are used in an encoder, various problems arise, such as an increase in the number of parts, wiring, occupied area (volume), cost, and signal processing load. These types of problems occur not only with optical encoders but also with magnetic encoders.

[0006] For this reason, there has been a demand for an encoder and a calibration method therefor that can eliminate errors equivalent to those that would occur if multiple measurement units were used, without providing multiple measurement units, when detecting the state of a measurement object. The present invention has been made to solve the above-mentioned problems, and aims to provide an encoder system, an encoder calibration method, and an encoder that, when detecting the state of an object to be measured during actual measurement, can eliminate errors in the same way as when multiple measurement units are used, without providing multiple measurement units. [Means for solving the problem]

[0007] The encoder system according to the present invention comprises an encoder, a reference encoder, and a calculation unit; during adjustment, the encoder measures the state of the object to be measured and generates a measurement value; the reference encoder measures the state of the object to be measured and generates a reference measurement value; the calculation unit calculates a correction value from the measurement value and the reference measurement value to correct the measurement value during actual measurement and stores the correction value in the encoder; during actual measurement, the encoder measures the state of the object to be measured and generates a measurement value; corrects the measurement value using the stored correction value; and outputs the corrected measurement value.

[0008] In the above encoder system, the calculation unit may further include an appropriate measurement value estimation unit that estimates an appropriate measurement value from the measurement value and the reference measurement value, and a correction value calculation unit that calculates a correction value from the difference between the appropriate measurement value and the measurement value.

[0009] In the above encoder system, the calculation unit may further include a correction tolerance range storage unit that stores information on the tolerance range of the correction value in advance, an abnormality detection unit that refers to the tolerance range and detects that the correction value is abnormal if the calculated correction value exceeds the tolerance range, and an alarm unit that alerts the detected abnormality.

[0010] The encoder calibration method according to the present invention is an encoder calibration method for an encoder system comprising an encoder, a reference encoder, and a calculation unit, wherein during adjustment, the encoder measures the state of the object to be measured to generate a measurement value, the reference encoder measures the state of the object to be measured to generate a reference measurement value, the calculation unit calculates a correction value from the measurement value and the reference measurement value to correct the measurement value during actual measurement, stores the correction value in the encoder, and during actual measurement, the encoder measures the state of the object to be measured to generate a measurement value, corrects the measurement value using the stored correction value, and outputs the corrected measurement value.

[0011] In the encoder calibration method, the calculation unit may estimate an appropriate measurement value from the measurement value and the reference measurement value, and calculate a correction value from a difference between the appropriate measurement value and the measurement value.

[0012] In the encoder calibration method, the calculation unit may store information on an allowable range of the correction value in advance, and may notify an abnormality in the correction value if the calculated correction value exceeds the allowable range.

[0013] The encoder of the present invention comprises a memory unit that stores the correction value calculated by the calculation unit, a measurement unit that measures the state of the object to be measured and generates a measurement value, and a correction unit that corrects the measurement value using the correction value stored in the memory unit and outputs the corrected measurement value. The encoder may further include a calculation unit therein. [Effects of the Invention]

[0014] This invention includes an encoder, a reference encoder, and a calculation unit, and during adjustment, the encoder measures the state of the measurement object to generate a measurement value, the reference encoder measures the state of the measurement object to generate a reference measurement value, the calculation unit calculates a correction value for correcting the measurement value during actual measurement from the measurement value and the reference measurement value and stores the correction value in the encoder, and during actual measurement, the encoder measures the state of the measurement object to generate a measurement value, corrects the measurement value using the stored correction value, and outputs the corrected measurement value. This makes it possible to correct using the correction value calculated during adjustment when detecting the state of the measurement object during actual measurement, and makes it possible to eliminate errors equivalent to using multiple measurement units without providing multiple measurement units. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a configuration diagram showing the configuration of an encoder system and an encoder according to a first embodiment. [Figure 2] 4 is a flowchart showing a processing procedure of the encoder system and the encoder according to the first embodiment. [Figure 3] FIG. 10 is a configuration diagram showing the configuration of an encoder system according to a second embodiment. [Figure 4] 10 is a flowchart showing a processing procedure of an encoder system and an encoder according to a second embodiment. [Figure 5] FIG. 10 is a configuration diagram showing the configuration of an encoder system and an encoder according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of an encoder system, an encoder calibration method, and an encoder according to the present invention will be described with reference to the drawings. In each drawing, the same components are designated by the same reference numerals.

[0017] Embodiment 1 First, the configuration of the encoder system 100 and the encoder 110 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a configuration diagram showing the configuration of the encoder system 100 and the encoder 110 according to the first embodiment. (a) of Fig. 1 shows the configuration of the encoder system 100 during adjustment together with the measurement target 10. (b) of Fig. 1 shows the configuration of the encoder 110 during actual measurement together with the measurement target 10. Here, the adjustment period refers to a period during which correction values ​​for the encoder 110 are calculated. On the other hand, the actual measurement period refers to a period during which the state of the measurement target 10 is measured by the encoder 110 while the measurement target 10 is actually operating.

[0018] [composition] The encoder system 100 mainly comprises an encoder 110, a reference encoder 120, and a calculation unit 140. The encoder 110 and the reference encoder 120 are attached to a movable part 11 of a measurement object 10. The measurement object 10 is a movable body such as a motor or an actuator. The movable part 11 is the rotating shaft of a motor or the drive shaft of an actuator, etc.

[0019] 1(a), the encoder 110 is installed on the movable part 11 as part of the encoder system 100 together with the reference encoder 120. During the adjustment, the measurement values ​​generated by the encoder 110 are supplied to the calculation part 140. On the other hand, during actual measurement shown in Fig. 1(b), the encoder 110 is installed on the movable part 11 in a standalone state without the reference encoder 120. During actual measurement, the measurement value generated by the encoder 110 is supplied to a drive device or a control device of the measurement object 10, etc.

[0020] The encoder 110 is a measuring device that measures angle, speed, or position by optical, magnetic, or other methods. The encoder 110 is provided with a measuring unit 111, a correcting unit 112, and a storage unit 113. The measurement unit 111 measures the movement of the movable unit 11 during adjustment and during actual measurement to generate measurement values, and supplies the generated measurement values ​​to one input of the correction unit 112. During adjustment, when no correction values ​​are stored in the memory unit 113, the correction unit 112 outputs the measurement values ​​generated by the measurement unit 111 without correcting them. During actual measurement, the correction unit 112 corrects the measurement values ​​generated by the measurement unit 111 with the correction values ​​stored in the memory unit 113, and outputs the corrected measurement values. The memory unit 113 stores the correction values ​​calculated by the calculation unit 140, and supplies the stored correction values ​​to the other input of the correction unit 112.

[0021] During adjustment, the reference encoder 120 is installed on the movable part 11 together with the encoder 110. It is desirable to install the reference encoder 120 in a position where errors appear in the reference measurement values ​​in a pattern different from the pattern of errors occurring in the measurement values ​​of the encoder 110. During adjustment, the reference measurement values ​​generated by the reference encoder 120 are supplied to the calculation unit 140. On the other hand, the reference encoder 120 is detached from the movable unit 11 during actual measurement. The reference encoder 120 is provided with a reference measurement unit 121. The reference measurement unit 121 measures the movement of the movable part 11 and generates a reference measurement value. In (a) of Fig. 1, a plurality of reference encoders 120 are installed on the movable part 11, but the number of reference encoders 120 may be one or more.

[0022] During adjustment, the calculation unit 140 calculates a correction value for correcting the measurement value of the encoder 110 at the time of actual measurement, from the measurement value of the encoder 110 and the reference measurement value of the reference encoder 120. The calculation unit 140 stores the calculated correction value in the memory unit 113 in the encoder 110. The calculation unit 140 is provided with an appropriate measurement value estimation unit 141 and a correction value calculation unit 142. During adjustment, the appropriate measurement value estimation unit 141 removes error components by, for example, averaging the measurement value of the encoder 110 and the reference measurement value of the reference encoder 120, and estimates an appropriate measurement value. An appropriate measurement value is a measurement value that is estimated to be appropriate by removing the error components. The correction value calculation unit 142 calculates the difference between the measurement value of the encoder 110 and the appropriate measurement value estimated by the appropriate measurement value estimation unit 141 as a correction value.

[0023] [process] The processing of encoder system 100 during adjustment and the processing of encoder 110 during actual measurement will be described below with reference to the flowchart of Fig. 2. Fig. 2 is a flowchart showing the processing procedures of encoder system 100 and encoder 110 according to the first embodiment. In FIG. 2, steps S101 to S106 are processes during adjustment, and step S107 is a process during actual measurement.

[0024] In step S101, the encoder 110 and the reference encoder 120 are attached to the moving part 11 of the measurement object 10. At this time, it is desirable to attach the encoder 110 in a position where it will be used as is for actual measurement, and to attach the reference encoder 120 in a position where it can be removed when adjustment is completed. After this, the process proceeds to step S102.

[0025] In step S102, the encoder 110 and the reference encoder 120 measure the state of the measurement object 10. In the encoder 110, the measurement unit 111 measures the movement of the movable unit 11 to generate a measurement value, and supplies the generated measurement value to one input of the correction unit 112. Since no correction value is stored in the memory unit 113 during adjustment, the correction unit 112 outputs the measurement value generated by the measurement unit 111 without correcting it. The measurement value generated by the encoder 110 is supplied to the calculation unit 140. In the reference encoder 120, the reference measurement unit 121 measures the movement of the movable part 11 to generate a reference measurement value. The reference measurement value generated by the reference encoder 120 is supplied to the calculation unit 140. After that, the process proceeds to step S103.

[0026] In step S103, the proper measurement value estimation unit 141 in the calculation unit 140 removes the error component by, for example, averaging the measurement value of the encoder 110 and the reference measurement value of the reference encoder 120, and estimates the proper measurement value, which is a measurement value that is estimated to be proper and does not contain the error component. After this, the process proceeds to step S104.

[0027] In step S104, the correction value calculation unit 142 in the calculation unit 140 calculates a correction value for correcting the measurement value of the encoder 110 at the time of actual measurement by finding the difference between the measurement value of the encoder 110 and the appropriate measurement value estimated by the appropriate measurement value estimation unit 141. After this, the process proceeds to step S105. If the encoder 110 is an optical encoder that detects the rotation angle, the correction value corresponds to a first-order rotation error component caused by eccentricity of the rotating plate or the read pattern. If the encoder 110 is another type of encoder, the correction value corresponds to a similar error component.

[0028] In step S105, the calculation unit 140 stores the calculated correction value in the storage unit 113 in the encoder 110. After that, the process proceeds to step S106.

[0029] In step S106, the encoder 110 is left on the movable part 11 of the measurement object 10, and the reference encoder 120 is removed from the movable part 11 of the measurement object 10. The above steps up to step S106 are the processing during adjustment, and thereafter the processing proceeds to step S107 for actual measurement.

[0030] During actual measurement in step S107, the encoder 110 measures the state of the measurement object 10 to generate a measurement value, corrects the measurement value using the stored correction value, and outputs the corrected measurement value. A measurement unit 111 in the encoder 110 measures the movement of the movable unit 11 to generate a measurement value, and supplies the generated measurement value to one input of a correction unit 112. A memory unit 113 stores a correction value calculated by the calculation unit 140, and supplies the stored correction value to the other input of the correction unit 112. The correction unit 112 corrects the measurement value generated by the measurement unit 111 with the correction value stored in the memory unit 113, and outputs the corrected measurement value.

[0031] [Effects obtained by the first embodiment] The encoder system 100, the encoder calibration method, and the encoder 110 according to the first embodiment provide the following advantages.

[0032] Encoder system 100 according to the first embodiment includes encoder 110, reference encoder 120, and calculation unit 140. During adjustment, encoder 110 measures the state of measurement object 10 and generates a measurement value, reference encoder 120 measures the state of measurement object 10 and generates a reference measurement value, and calculation unit 140 calculates a correction value for correcting the measurement value from the measurement value and the reference measurement value and stores the correction value in encoder 110. During actual measurement, encoder 110 measures the state of measurement object 10 and generates a measurement value, corrects the measurement value using the stored correction value, and outputs the corrected measurement value. As a result, when detecting the state of the measurement target 10 during actual measurement, the encoder 110 can make corrections using the correction values ​​obtained during adjustment. This makes it possible for the encoder 110 to eliminate errors in the same way as when multiple measurement units are used, without providing multiple measurement units.

[0033] In the encoder system 100 of the first embodiment, the calculation unit 140 further includes an appropriate measurement value estimation unit 141 that estimates an appropriate measurement value from a measurement value and a reference measurement value, and a correction value calculation unit 142 that calculates a correction value from the difference between the appropriate measurement value and the measurement value. This allows the encoder system 100 to estimate an appropriate measurement value from the measurement value of the encoder 110 and the reference measurement value of the reference encoder 120, and to calculate a correction value for correcting the measurement value of the encoder 110 during actual measurement based on the difference between the appropriate measurement value and the measurement value of the encoder 110.

[0034] In the encoder calibration method according to the first embodiment, during adjustment, the state of the object to be measured 10 is measured by the encoder 110 to generate a measurement value, the state of the object to be measured 10 is measured by the reference encoder 120 to generate a reference measurement value, and the calculation unit 140 calculates a correction value for correcting the measurement value from the measurement value and the reference measurement value and stores the correction value in the encoder 110. Then, during actual measurement, the state of the object to be measured 10 is measured by the encoder 110 to generate a measurement value, the measurement value is corrected using the stored correction value, and the corrected measurement value is output. This allows correction to be made using the correction value obtained during adjustment when detecting the state of the measurement object 10 during actual measurement, making it possible to eliminate errors in the same way as if multiple measurement units were used, without having to set up multiple measurement units.

[0035] In the encoder calibration method of the first embodiment, the calculation unit 140 estimates an appropriate measurement value from the measurement value and the reference measurement value, and calculates a correction value from the difference between the appropriate measurement value and the measurement value. This makes it possible to estimate an appropriate measurement value from the measurement value of the encoder 110 and the reference measurement value of the reference encoder 120, and to calculate a correction value for correcting the measurement value of the encoder 110 during actual measurement based on the difference between the appropriate measurement value and the measurement value of the encoder 110.

[0036] Encoder 110 according to the first embodiment includes storage unit 113 that stores correction values ​​calculated by calculation unit 140, measurement unit 111 that measures the state of measurement object 10 and generates measurement values, and correction unit 112 that corrects the measurement values ​​using the correction values ​​stored in storage unit 113 and outputs the corrected measurement values. As a result, when encoder 110 detects the state of measurement object 10 during actual measurement, it can correct the measurement values ​​of measurement unit 111 using the correction values ​​calculated during adjustment and stored in storage unit 113. This makes it possible to eliminate errors in the same way as when multiple measurement units are used, without providing multiple measurement units.

[0037] Embodiment 2 The configuration of encoder system 100 according to the second embodiment will be described with reference to Fig. 3. Fig. 3 is a configuration diagram showing the configuration of encoder system 100 according to the second embodiment. Fig. 3 shows the configuration of encoder system 100 during adjustment together with measurement target 10. In Fig. 3, the same components as those in Fig. 1 are given the same reference numerals, and redundant explanations will be omitted, with the explanation focusing on the different parts.

[0038] [composition] The encoder system 100 mainly includes an encoder 110, a reference encoder 120, and a calculation unit 140. The calculation unit 140 further includes an appropriate measurement value estimation unit 141, a correction value calculation unit 142, a correction tolerance range holding unit 143, an abnormality detection unit 144, and a notification unit 145.

[0039] The correction tolerance holding unit 143 holds information on the tolerance of the correction value in advance. The abnormality detection unit 144 refers to the tolerance held in the correction tolerance holding unit 143 and determines whether the correction value calculated by the correction value calculation unit 142 exceeds the tolerance. If the correction value calculated by the correction value calculation unit 142 exceeds the tolerance, the abnormality detection unit 144 detects that the correction value is abnormal. The notification unit 145 notifies the abnormality detected by the abnormality detection unit 144 by an alarm sound, an alarm display, abnormality detection message data via communication, etc.

[0040] [process] The processing of the encoder system 100 during adjustment in the second embodiment will be described below with reference to the flowchart in Fig. 4, focusing on the differences from the first embodiment. Fig. 4 is a flowchart showing the processing procedure of the encoder system 100 and the encoder 110 according to the fourth embodiment.

[0041] Steps S101 to S103 and steps S105 to S107 are the same processes as those in embodiment 1. Therefore, duplicated explanations will be omitted. In step S104a, the correction value calculation unit 142 in the calculation unit 140 calculates a correction value for correcting the measurement value of the encoder 110 at the time of actual measurement by finding the difference between the measurement value of the encoder 110 and the appropriate measurement value estimated by the appropriate measurement value estimation unit 141. After this, the process proceeds to step S104b.

[0042] In step S104b, the abnormality detection unit 144 determines whether the correction value calculated by the correction value calculation unit 142 exceeds the allowable range held in the correction allowable range holding unit 143. If the abnormality detection unit 144 determines that the correction value calculated by the correction value calculation unit 142 falls within the allowable range held in the correction allowable range holding unit 143, the correction value is normal, and the process proceeds to step S105. On the other hand, if the abnormality detection unit 144 determines that the correction value calculated by the correction value calculation unit 142 exceeds the allowable range stored in the correction allowable range storage unit 143, the correction value is abnormal and the processing proceeds to step S108.

[0043] In step S108, the notification unit 145 uses various methods to notify of the abnormality in the calculated correction value detected by the abnormality detection unit 144. Then, the encoder system 100 ends the series of processes.

[0044] [Effects obtained by the second embodiment] According to the encoder system 100 and the encoder calibration method of the second embodiment, the following effects can be obtained.

[0045] In the encoder system 100 of the second embodiment, the calculation unit 140 further includes a correction tolerance storage unit 143 that stores information on the tolerance range of the correction value in advance, an abnormality detection unit 144 that refers to the tolerance range and detects that the correction value is abnormal if the calculated correction value exceeds the tolerance range, and a notification unit 145 that notifies of the detected abnormality. This allows the encoder system 100 to find and exclude abnormal correction values ​​when calculating correction values ​​for correcting the measurement values ​​of the measurement object 10. Then, the encoder 110 can perform correction using normal correction values.

[0046] Embodiment 3 The configurations of encoder system 100 and encoder 110 according to the third embodiment will be described with reference to Fig. 5. Fig. 5 is a configuration diagram showing the configurations of encoder system 100 and encoder 110 according to the third embodiment. (a) of Fig. 5 shows the configuration of encoder system 100 during adjustment together with the measurement target 10. (b) of Fig. 5 shows the configuration of encoder 110 during actual measurement together with the measurement target 10. In Fig. 5, the same components as in Fig. 1 are given the same reference numerals, so that duplicated explanations will be omitted and the explanation will focus on the different parts.

[0047] The encoder system 100 mainly includes an encoder 110 and a reference encoder 120. The encoder 110 includes a measurement unit 111, a correction unit 112, a storage unit 113, and a calculation unit 140. That is, the calculation unit 140, which existed independently in the first and second embodiments, is provided inside the encoder 110 in the third embodiment. During the adjustment shown in (a) of Fig. 5, the measurement values ​​generated by the encoder 110 and the reference measurement values ​​generated by the reference encoder 120 are supplied to the calculation unit 140 in the encoder 110 via the wiring bundle 105. The processing in the calculation unit 140 is as described in the first and second embodiments. When the adjustment is completed, as shown in (b) of Fig. 5, the encoder 110 is left on the movable part 11 of the measurement object 10, and the reference encoder 120 and the wiring bundle 105 are removed.

[0048] Therefore, the encoder system 100 of the third embodiment is composed only of the encoder 110, the reference encoder 120, and a wiring bundle 105 that supplies the measurement values ​​generated by the encoder 110 and the reference measurement values ​​generated by the reference encoder 120 to the calculation unit 140 in the encoder 110. This wiring bundle 105 only needs to connect the outputs of the encoder 110 and the reference encoder 120 to the input of the encoder 110. Therefore, the encoder system 100 enables reduction in wiring and device size.

[0049] [Effects obtained by the third embodiment] According to the encoder system 100 of the third embodiment, the following effects can be obtained. The encoder system 100 of the third embodiment includes a calculation unit 140 inside the encoder 110. Therefore, the encoder system 100 is composed of the encoder 110, a reference encoder 120, and a wiring bundle 105. Therefore, the encoder system 100 enables a reduction in the device scale and wire saving compared to the first and second embodiments. [Explanation of symbols]

[0050] 10 Measurement object, 11 Moving part, 100 Encoder system, 105 Wiring bundle, 110 Encoder, 111 Measurement unit, 112 Correction unit, 113 Memory unit, 120 Reference encoder, 121 Reference measurement unit, 140 Calculation unit, 141 Appropriate measurement value estimation unit, 142 Correction value calculation unit, 143 Correction tolerance range holding unit, 144 Abnormality detection unit, 145 Notification unit.

Claims

1. The system includes an encoder (110), a reference encoder (120), and a calculation unit (140), During adjustment, The encoder (110) measures the state of the measurement object (10) to generate a measurement value; The reference encoder (120) measures the state of the measurement object (10) to generate a reference measurement value; the calculation unit (140) calculates a correction value for correcting the measurement value at the time of actual measurement from the measurement value and the reference measurement value, and stores the correction value in the encoder (110); During actual measurement, The encoder (110) measures the state of the measurement object (10) to generate a measurement value, corrects the measurement value using the stored correction value, and outputs the corrected measurement value. Encoder system.

2. The calculation unit (140) an appropriate measurement value estimation unit (141) that estimates an appropriate measurement value from the measurement value and the reference measurement value; a correction value calculation unit (142) that calculates the correction value from the difference between the appropriate measurement value and the measurement value; and further comprising: The encoder system of claim 1 .

3. The calculation unit (140) a correction tolerance storage unit (143) that stores information on the tolerance range of the correction value in advance; an abnormality detection unit (144) that refers to the allowable range and detects that the calculated correction value is abnormal if the calculated correction value exceeds the allowable range; and a notification unit (145) that notifies the user of the detected abnormality.

3. The encoder system according to claim 1.

4. An encoder calibration method for an encoder system including an encoder (110), a reference encoder (120), and a calculation unit (140), comprising: During adjustment, The encoder (110) measures the state of the measurement object (10) to generate a measurement value; The reference encoder (120) measures the state of the measurement object (10) to generate a reference measurement value; the calculation unit (140) calculates a correction value for correcting the measurement value at the time of actual measurement from the measurement value and the reference measurement value, and stores the correction value in the encoder (110); During actual measurement, measuring the state of the measurement object (10) using the encoder (110) to generate a measurement value, correcting the measurement value using the stored correction value, and outputting the corrected measurement value; Encoder calibration methods.

5. The calculation unit (140) Estimating an appropriate measurement value from the measurement value and the reference measurement value; calculating a correction value from the difference between the appropriate measurement value and the measurement value; The encoder calibration method according to claim 4 .

6. The calculation unit (140) information on the tolerance range of the correction value is stored in advance, If the calculated correction value exceeds the allowable range, an abnormality in the correction value is reported. The encoder calibration method according to claim 4 or 5.

7. a storage unit (113) that stores the correction value calculated by the calculation unit (140) according to claim 1; a measurement unit (111) that measures the state of a measurement object (10) and generates a measurement value; a correction unit (112) that corrects the measurement value using the correction value stored in the storage unit (113) and outputs the corrected measurement value, Encoder.

8. The computing unit (140) is further provided. The encoder of claim 7.

Images