Position detection system, actuator, and position detection method

Abstract

A position detection system (5) comprises a primary encoder (15) that detects the position of a motor shaft, a secondary encoder (25) that detects the position of an output shaft of a reducer, and a calculation unit (9). The reduction ratio of the reducer is 1 / n, where n is a non-integer. The calculation unit calculates a plurality of position calculation values related to the position within one rotation of the motor shaft on the basis of the position within one rotation of the secondary encoder, and calculates the total number of rotations of the secondary encoder on the basis of the actual position value related to the position within one rotation of a rotor and the plurality of position calculation values.

Description

Technical Field

[0001] The present disclosure relates to a position detection system, an actuator, and a position detection method.

Background Art

[0002] An actuator includes a servo motor and a speed reducer connected to each other. A primary encoder is connected to the motor shaft of the servo motor, and detects the absolute position within one rotation of the motor shaft and the total number of rotations of the motor shaft. Similarly, a secondary encoder is connected to the output shaft of the speed reducer, and detects the absolute position within one rotation of the output shaft and the total number of rotations of the output shaft (see, for example, Japanese Patent Application Laid-Open No. 2007-113932). Information detected by each encoder is stored in a memory.

[0003] Furthermore, Japanese Patent Application Laid-Open No. 2006-300596 proposes a method of calculating a value of a “determination criterion” from the position of a secondary encoder with the reduction ratio of the speed reducer being 1 / n (n is a non-integer), and determining ±1 rotation of the secondary encoder from the positive / negative discrimination result between the value of the determination criterion and the position of the primary encoder.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method of Japanese Patent Application Laid-Open No. 2006-300596, when the output shaft rotates two or more times, it cannot be a battery-less absolute encoder.

[0006] Therefore, there is a need for a position detection system that can be used without requiring an additional battery, even when the output axis rotates more than two times. [Means for solving the problem]

[0007] According to a first aspect of the present disclosure, a position detection system is provided comprising: a primary encoder for detecting the position of the motor shaft of a motor; a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor; and a calculation unit, wherein the reduction ratio of the reduction gear is 1 / n, where n is a non-integer; the calculation unit calculates a plurality of position calculation values ​​relating to the absolute position of the rotor in the primary encoder within one revolution based on the absolute position of the secondary encoder within one revolution; and the calculation unit calculates the total number of revolutions of the secondary encoder based on the actual position value relating to the absolute position of the rotor within one revolution detected by the primary encoder and the plurality of position calculation values.

[0008] According to another aspect of the present disclosure, a position detection system is provided comprising: a primary encoder for detecting the position of the motor shaft of a motor; a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor; and a calculation and determination unit, the calculation and determination unit calculates a position calculation value for the absolute position of the motor shaft within one revolution based on the absolute position of the output shaft within one revolution detected by the secondary encoder; and the calculation and determination unit further determines that there is an abnormality in the position of at least one of the primary encoder and the secondary encoder if the absolute value of the deviation between the actual position value for the absolute position of the motor shaft within one revolution detected by the primary encoder and the position calculation value is greater than or equal to a predetermined value.

[0009] The purposes, features, and advantages of this disclosure will become even clearer from the following description of embodiments related to the accompanying drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic side view of a position detection system based on the first embodiment of the present disclosure. [Figure 2] Figure 1 is the first flowchart illustrating the operation of the position detection system. [Figure 3] This diagram shows the relationship between the position of the output axis and the position of the input axis. [Figure 4] This is another diagram showing the relationship between the position of the output axis and the position of the input axis. [Figure 5] This is a second flowchart illustrating the operation of the position detection system based on the second embodiment. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described below with reference to the attached drawings. Throughout all drawings, corresponding components are denoted by the same reference numerals. Figure 1 is a schematic side view of a position detection system based on a first embodiment of the present disclosure. The position detection system 5 is incorporated into a machine 3 having a shaft, such as a robot 3. The following description will focus on the case where the position detection system 5 is incorporated into a robot 3, but the same applies to the case where the position detection system 5 is incorporated into another machine 3 having a shaft, such as a machine tool.

[0012] In Figure 1, the actuator 6 located on link 1 includes a motor 10, such as a servo motor, connected to each other, and a reduction gear 20 coupled to the motor shaft 13 of the motor 10. The motor 10 includes a rotor 12 that rotates integrally with the motor shaft 13 and a stator 11 arranged to surround the rotor 12. The tip of the output shaft 23 of the reduction gear 20 is connected to link 2. Therefore, the actuator 6, consisting of the motor 10 and the reduction gear 20, controls the position by rotating link 2 relative to link 1 within a predetermined operating range. The reduction ratio n of the reduction gear 20 is assumed to be a positive non-integer, for example, n = α + 1 / β (where α and β are positive numbers greater than 1).

[0013] The motor shaft 13 is, for example, a hollow shaft, and a primary encoder 15 equipped with a rotating disk 15A is attached to its rear end. The primary encoder 15 is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by a detection unit 16, and the absolute position θp and the total number of rotations within one revolution of the motor shaft 13 are detected by known methods. The detected information is stored in a memory 7, for example, a volatile memory.

[0014] The output shaft 23 extends towards the motor 10 through the hollow motor shaft 13, and a secondary encoder 25 equipped with a rotating disk 25A is attached to the rear end of the output shaft 23. The secondary encoder 25 is, for example, an incremental encoder and outputs A-phase, B-phase, and Z-phase signals. The output signals are detected by the detection unit 26, which uses known methods to detect the absolute position θs and the total number of rotations i within one revolution of the output shaft 23. The detected information is stored in memory 7, for example, volatile memory.

[0015] The information stored in memory 7 is retained for a certain period by a battery 8, such as a button cell or capacitor. The position detection system 5 shown in Figure 1 includes a common memory 7 and a common battery 8 for the primary encoder 15 and the secondary encoder 25. However, the primary encoder 15 and the secondary encoder 25 may each have separate memories and batteries.

[0016] The information stored in the memory 7 is supplied to the controller 9. The controller 9 may be a control device that controls the machine 3 or an LSI mounted on the encoders 15 and 25. Based on the supplied information, the controller 9 drives and controls the motor 10 to perform a positioning operation for positioning the link 2 to a target position with respect to the link 1. Further, the built-in brake 50 provided on the outer surface side of the motor shaft 13 is activated according to an instruction from the controller 9 to brake the motor shaft 13. Further, the controller 9 also serves to energize the primary encoder 15 and the secondary encoder 25 during the operation of the machine 3.

[0017] Also, the controller 9 calculates a plurality of position calculation values regarding the absolute position within one rotation of the motor shaft 13 in the primary encoder 13 based on the absolute position within one rotation of the secondary encoder 25, and based on the actual position value regarding the absolute position within one rotation of the motor shaft 13 detected by the primary encoder 15 and the plurality of position calculation values, it serves as a calculation unit for calculating the total number of rotations of the secondary encoder 25.

[0018] Furthermore, the controller 9 calculates a position calculation value regarding the absolute position within one rotation of the motor shaft 13 based on the absolute position within one rotation of the output shaft 23 detected by the secondary encoder 25, and when the absolute value of the deviation between the actual position value regarding the absolute position within one rotation of the motor shaft 13 detected by the primary encoder 15 and the position calculation value is greater than or equal to a predetermined value, it serves as a calculation and determination unit for determining that there is an abnormality in the position of at least one of the primary encoder 15 and the secondary encoder 25.

[0019] FIG. 2 is a first flowchart showing the operation of the position detection system shown in FIG. 1. The content of the program shown in FIG. 2 is assumed to be stored in a storage unit (not shown) in the controller 9 or in the memory 7. The content shown in FIG. 2 is assumed to be appropriately implemented when the motor 10 is driven.

[0020] First, in step S11, the secondary encoder 25 detects the absolute position θs within one rotation of the output shaft 23. Next, in step S12, the controller 9 uses the detected absolute position θs to calculate a position calculation value θp*(i) regarding the absolute position within one rotation of the primary encoder 15 based on the following formula (1) (i is a positive number not exceeding β). θp*(i)=MOD[{(θs×(α + 1 / β)+(360 / β)×(i - 1))}÷360]×360 Formula (1) Note that "MOD[]" means a function for calculating the remainder of a division.

[0021] Here, FIG. 3 is a diagram showing the relationship between the position of the output shaft and the position of the input shaft. In FIG. 3, the horizontal axis indicates the position of the output shaft 23 of the speed reducer 20, and the vertical axis indicates the position of the input shaft. The "position of the input shaft" means the position of the input shaft input to the secondary encoder 25. In the present specification, since the secondary encoder 25 is connected downstream of the primary encoder 15, the "position of the input shaft" can also be described as the position of the rotation disk 15A of the primary encoder 15 or the position of the motor shaft 13. In FIG. 3, both the horizontal axis and the vertical axis are shown in degrees. Also, as described above, the reduction ratio n of the speed reducer 20 is n = α + 1 / β (α and β are positive numbers greater than 1), and in the example shown in FIG. 3, it is assumed that α = 2 and β = 3.

[0022] In FIG. 3, three lines L1, L2, and L3 are shown. The number of these lines L1, L2, and L3 is equal to the value of β described above. The solid line L1 indicates the position of the input shaft when the output shaft 23 makes the first rotation. The dashed line L2 indicates the position of the input shaft when the output shaft 23 makes the second rotation. The dash-dotted line L3 indicates the position of the input shaft when the output shaft 23 makes the third rotation.

[0023] As can be seen from Figure 3, the position detection system 5 in the first embodiment can detect the output shaft 23 up to the βth rotation point. Furthermore, the position of the output shaft 23 differs between the first and second rotations. In the first embodiment, the difference between the position of the first rotation and the position of the second rotation is used to obtain the total number of rotations of the output shaft 23.

[0024] In the example shown in Figure 3, β=3, so the vertical axis in Figure 3 shows θp*(1), θp*(2), and θp*(3). These θp*(i) are the values ​​on the vertical axis that correspond to the intersection point between the absolute position θs of the output axis 23 and the three lines L1, L2, and L3.

[0025] In step S13, the controller 9 obtains a position detection value θp related to the absolute position of the motor shaft 13 within one revolution detected by the primary encoder 15. The controller 9 then calculates the absolute values ​​θd(i) (=|θp-θp*(i)|) of multiple deviations between the position detection value θp and multiple position calculation values ​​θp*(i). In Figure 3, the absolute values ​​of the deviations θd(1) (=|θp-θp*(1)|), θd(2) (=|θp-θp*(2)|), and θd(3) (=|θp-θp*(3)|) are indicated by arrows.

[0026] Next, in step S14, the controller 9 selects the minimum value Minθd(i) from a plurality of absolute values, θd(1), θd(2), and θd(3) in Figure 3. In the example shown in Figure 3, since θd(2) < θd(1) < θd(3), θd(2) corresponds to the minimum value Minθd(i).

[0027] Then, in step S15, the controller 9 compares the selected minimum value Minθd(i) with the first error judgment value θj1. The first error judgment value θj1 is assumed to be calculated in advance based on the following equation (2). θj1=360 / β-n·θsa_max-θpa_max-θnois_max Equation (2) Here, θsa represents the detection accuracy determined according to the characteristics of the secondary encoder 25, and θsa_max is the value at which the detection accuracy is lowest. θpa represents the detection accuracy determined according to the characteristics of the primary encoder 15, and θpa_max is the value at which the detection accuracy is lowest. Furthermore, θnois represents the width of the disturbance in the position detection system 5, and θnois_max is its maximum value.

[0028] In step S15, if it is determined that the minimum value Minθd(i) is not greater than the first error judgment value θj1, it is determined that there is no problem and the process proceeds to step S19. In step S19, the minimum value Minθd(i) is compared with the second error judgment value θj2. The second error judgment value θj2 is calculated in advance based on the following equation (3). θj2≧θj1-360=n·θsa_max+θpa_max+θnois_max Equation (3) As can be seen from equation (3), the second error threshold θj2 is smaller than the first error threshold θj1.

[0029] Then, if it is determined that the minimum value Minθd(i) is not smaller than the second error determination value θj2, the process proceeds to step S21. In step S21, it is determined that there is an abnormality in at least one of the primary encoder 15 and the secondary encoder 25. The controller 9 then stops the operation of the motor 10, treating it as a detection error. At this time, a message to that effect may also be displayed on a display unit (not shown), such as the screen of a teaching control panel.

[0030] In contrast, if in step S19 it is determined that the minimum value Minθd(i) is smaller than the second error determination value θj2, the process proceeds to step S20. In step S20, the controller 9 calculates the total number of rotations of the secondary encoder 25 based on the minimum value Minθd(i). In the example shown in Figure 3, since θd(2) is the minimum value Minθd(i), it can be seen that the total number of rotations i is 2.

[0031] Thus, the process for obtaining the total number of rotations of the secondary encoder 25 in the first embodiment of this disclosure does not require an additional battery. Therefore, in the first embodiment of this disclosure, the position detection system 5 can be used without requiring an additional battery even when the output shaft 23 rotates more than two times. In other words, even if the encoders 15 and 25 are moved while the controller 9 is not supplying power to them, the position detection system 5 in the first embodiment can obtain the total number of rotations of the output shaft 23.

[0032] By the way, if in step S15 the minimum value Minθd(i) is determined to be greater than the first error judgment value θj1, the process proceeds to step S16. Figure 4 is another diagram similar to Figure 3, showing the relationship between the position of the output axis and the position of the input axis. The case in which the minimum value Minθd(i) is determined to be greater than the first error judgment value θj1, as in step S15, is a situation like the example shown in Figure 4.

[0033] In Figure 4, the absolute position θs within one rotation of the output shaft 23 is in a different position than in Figure 3. Comparing the absolute values ​​of the deviations θd(1) (=|θp-θp*(1)|), θd(2) (=|θp-θp*(2)|), and θd(3) (=|θp-θp*(3)|) in the example shown in Figure 4, we find that θd(3) < θd(2) < θd(1).

[0034] In Figure 4, the minimum value Minθd(i) should be θd(1), and setting θd(3) as the minimum value Minθd(i) is clearly incorrect. However, since the position of the motor shaft 13 with respect to the primary encoder 15 is near 0° (near 360°), it is difficult to make the above determination. For this reason, assuming that the position of the motor shaft 13 with respect to the primary encoder 15 is near 0°, in step S16, the controller 9 corrects the absolute value of the deviation θd(i) obtained in step S13 for positional jump.

[0035] The formula (4) used for positional jump correction is as follows: θd(i)=|θp-θp*(i)|=360-360(i-1) / β-nθsa-θpa-θnois Equation (4)

[0036] As a result, θd(1), θd(2), and θd(3) are corrected as shown in equations (5) to (7) below. θd(1)=|θp-θp*(1)|=360-nθsa-θpa-θnois

[0037] Formula (5) θd(2)=|θp-θp*(2)|=240-nθsa-θpa-θnois

[0038] Formula (6) θd(3)=|θp-θp*(3)|=120-nθsa-θpa-θnois

[0039] Formula (7) In equations (4) to (7), θsa and θpa are approximately 0.01 degrees, and θnois is approximately a few degrees.

[0040] Then, in step S17, the controller 9 selects the minimum value Minθd(i) from the multiple absolute values ​​θd(i) that have been corrected in this way. In the example shown in Figure 4, the minimum value Minθd(i) is the corrected absolute value θd(1). Through this position jump correction, the correct minimum value Minθd(i) (the corrected absolute value θd(1) in Figure 4) is selected.

[0041] Subsequently, in step S18, the correct minimum value Minθd(i) after correction is set again as the minimum value Minθd(i). Then, proceeding to step S20, the total number of rotations of the secondary encoder 25 is calculated according to the new minimum value Minθd(i), as described above. In the example shown in Figure 4, since θd(1) is the minimum value Minθd(i), it can be seen that the total number of rotations i is 1.

[0042] With this configuration, even when the position of the motor shaft 13 relative to the primary encoder 15 is near 0°, the total number of rotations of the secondary encoder 25 can be accurately determined.

[0043] Incidentally, Figure 5 is a second flowchart showing the operation of the position detection system based on the second embodiment. The contents of the program shown in Figure 5 are assumed to be stored in the storage unit (not shown) or memory 7 within the controller 9. The contents shown in Figure 5 are assumed to be executed as appropriate when the motor 10 is driven.

[0044] The reduction ratio n of the reducer 20 in the second embodiment is not limited to those described above. In other words, the reduction ratio n in this case may be 1 / α (where α is a positive number greater than 1). Furthermore, the second embodiment also includes the case where an additional reducer (not shown) is placed between the output shaft 23 and the secondary encoder 25, and the overall reduction ratio of the reducer 20 and the additional reducer is 1 / α' (where α' is a positive number greater than 1).

[0045] First, in step S31, as described above, the secondary encoder 25 detects a position detection value θs related to the absolute position within one rotation of the output shaft 23. Then, in step S32, as explained with reference to Figure 3, the controller 9, acting as a calculation and determination unit, uses the detected absolute position detection value θs to calculate a position calculation value θp* related to the absolute position within one rotation of the primary encoder 15 based on the following equation (8). θp*=MOD[{(θs×α×β))}÷360]×360 Equation (8)

[0046] Next, in step S33, the controller 9 calculates the absolute value θpd of the deviation between the position detection value θs and the position calculation value θp* of the primary encoder 15 based on the following equation (9). θpd = |θp* - θp| Equation (9)

[0047] Subsequently, in step S34, the controller 9 determines whether the absolute value of the deviation θpd is greater than the third error judgment value θj3. Here, the absolute value of the deviation θpd represents the difference in detection position between the primary encoder 15 and the secondary encoder 25. In an ideal state without backlash of the reduction gear 20 and various detection errors, the absolute value of the deviation θpd is 0. Therefore, the third error judgment value θj3 is a value greater than zero predetermined by the operator.

[0048] In step S34, if the absolute value of the deviation θpd is determined to be greater than the third error determination value θj3, it is determined that the relative position between the primary encoder 15 and the secondary encoder 25 is not normal (step S35). In this case, the controller 9 stops the operation of the motor 10, assuming that there is an abnormality in the set position of the primary encoder 15 and / or the secondary encoder 25. At this time, a display unit (not shown), such as the screen of a teaching control panel, may be displayed to that effect.

[0049] In contrast, if in step S34 it is determined that the absolute value of the deviation θpd is not greater than the third error determination value θj3, then it is determined that the relative position between the primary encoder 15 and the secondary encoder 25 is normal (step S36), and the process is terminated.

[0050] Thus, the process for determining whether there is an abnormality in the relative position between the primary encoder 15 and the secondary encoder 25 in the second embodiment of this disclosure does not require an additional battery. Therefore, in the second embodiment, an abnormality in the position of the primary encoder 15 and / or the secondary encoder 25 can be easily detected without requiring an additional battery.

[0051] Furthermore, the computer program for executing the processing of the controller 9, which acts as the calculation unit and calculation determination unit, may be provided in the form of a computer-readable recording medium, such as a semiconductor memory, magnetic recording medium, or optical recording medium.

[0052] The nature of this disclosure According to the first embodiment, a position detection system is provided comprising a primary encoder for detecting the position of the motor shaft of a motor, a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor, and a calculation unit, wherein the reduction ratio of the reduction gear is 1 / n, where n is a non-integer, and the calculation unit calculates a plurality of position calculation values ​​relating to the absolute position of the motor shaft in one rotation at the primary encoder based on the absolute position of the secondary encoder in one rotation, and the calculation unit calculates the total number of rotations of the secondary encoder based on the actual position value relating to the absolute position of the motor shaft in one rotation detected by the primary encoder and the plurality of position calculation values. According to the second embodiment, in the first embodiment, the calculation unit calculates the total number of rotations of the secondary encoder based on the absolute value of the deviation between the actual position value and the plurality of calculated position values. According to the third embodiment, in the first or second embodiment, if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of calculated position values ​​and then calculates the minimum value. According to the fourth embodiment, in any of the first to third embodiments, if the minimum absolute value of the deviation between the actual position value and the plurality of calculated position values ​​is not less than a predetermined second error determination value which is less than the first error determination value, the calculation unit calculates the total number of rotations of the secondary encoder. According to the fifth embodiment, an actuator is provided comprising a motor, a reduction gear coupled to the motor, a primary encoder for detecting the position of the motor shaft of the motor, a secondary encoder for detecting the position of the output shaft of the reduction gear, and a calculation unit, wherein the reduction ratio of the reduction gear is 1 / n, where n is a non-integer, and the calculation unit calculates a plurality of position calculation values ​​relating to the absolute position of the motor shaft in the primary encoder within one revolution based on the absolute position of the secondary encoder within one revolution, and the calculation unit calculates the total number of revolutions of the secondary encoder based on the actual position value relating to the absolute position of the motor shaft within one revolution detected by the primary encoder and the plurality of position calculation values. According to the sixth embodiment, in the fifth embodiment, the calculation unit calculates the total number of rotations of the secondary encoder based on the absolute value of the deviation between the actual position value and the plurality of calculated position values. According to the seventh embodiment, in the fifth or sixth embodiment, if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of calculated position values ​​and then calculates the minimum value. According to the eighth embodiment, in any of the fifth to seventh embodiments, if the minimum absolute value of the deviation between the actual position value and the plurality of calculated position values ​​is not less than a predetermined second error determination value which is less than the first error determination value, the calculation unit calculates the total number of rotations of the secondary encoder. According to the ninth embodiment, a position detection method is provided for a position detection system comprising a primary encoder for detecting the position of the motor shaft of a motor and a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor, wherein the reduction ratio of the reduction gear is 1 / n, where n is a non-integer, and a plurality of position calculation values ​​relating to the absolute position of the motor shaft within one rotation in the primary encoder are calculated based on the absolute position within one rotation of the secondary encoder, and the total number of rotations of the secondary encoder is calculated based on the actual position value relating to the absolute position of the motor shaft within one rotation detected by the primary encoder and the plurality of position calculation values. According to the tenth embodiment, in the ninth embodiment, the total number of rotations of the secondary encoder is calculated based on the absolute value of the deviation between the actual position value and the plurality of calculated position values. According to the eleventh embodiment, in the ninth or tenth embodiment, if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of calculated position values ​​and then calculates the minimum value. According to the twelfth embodiment, in any of the ninth to eleventh embodiments, the total number of rotations of the secondary encoder is calculated if the minimum absolute value of the deviation between the actual position value and the plurality of calculated position values ​​is not less than a predetermined second error determination value that is less than the first error determination value. According to the 13th embodiment, a position detection system is provided comprising a primary encoder for detecting the position of the motor shaft of a motor, a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor, and a calculation and determination unit, wherein the calculation and determination unit calculates a position calculation value for the absolute position of the motor shaft within one revolution based on the absolute position of the output shaft within one revolution detected by the secondary encoder, and the calculation and determination unit further determines that there is an abnormality in the position of at least one of the primary encoder and the secondary encoder if the absolute value of the deviation between the actual position value for the absolute position of the motor shaft within one revolution detected by the primary encoder and the position calculation value is greater than or equal to a predetermined value. According to the 14th embodiment, an actuator is provided comprising a motor, a reduction gear coupled to the motor, a primary encoder for detecting the position of the motor shaft of the motor, a secondary encoder for detecting the position of the output shaft of the reduction gear, and a calculation and determination unit, wherein the calculation and determination unit calculates a position calculation value for the absolute position of the motor shaft within one revolution based on the absolute position of the output shaft within one revolution detected by the secondary encoder, and the calculation and determination unit further determines that there is an abnormality in the position of at least one of the primary encoder and the secondary encoder if the absolute value of the deviation between the actual position value for the absolute position of the motor shaft within one revolution detected by the primary encoder and the position calculation value is greater than or equal to a predetermined value. According to the 15th embodiment, a position detection method is provided for a position detection system comprising a primary encoder for detecting the position of the motor shaft of a motor and a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor, wherein a calculated position value for the absolute position of the motor shaft within one revolution is calculated based on the absolute position of the output shaft within one revolution detected by the secondary encoder, and if the absolute value of the deviation between the actual position value for the absolute position of the motor shaft within one revolution detected by the primary encoder and the calculated position value is greater than or equal to a predetermined value, it is determined that there is an abnormality in the position of at least one of the primary encoder and the secondary encoder.

[0053] While embodiments of this disclosure have been described in detail, this disclosure is not limited to the individual embodiments described above. These embodiments can be added, replaced, modified, or partially deleted in various ways, without departing from the spirit of the invention or the idea and intent of this disclosure derived from the claims and their equivalents. For example, the order of operations and processes in the embodiments described above are given as examples only and are not limited thereto. The same applies when numerical values ​​or mathematical formulas are used in the description of the embodiments described above. Furthermore, combining some of the embodiments described above as appropriate is within the scope of this disclosure. [Explanation of symbols]

[0054] 1, 2 links 3. Machines (Robots) 5. Position detection system 6 Actuators 7 memory 8 batteries 9. Controller (Calculation unit, Calculation determination unit) 10 motors 11 stata 12 rotors 13 Motor shaft 15 Primary Encoder 16 Detection unit 20 Reducer 23 Output shaft 25 Secondary Encoders 26 Detection unit 50 Built-in brakes θj1 First error judgment value θj2 Second error judgment value θj3 Third error judgment value

Claims

1. A primary encoder that detects the position of the motor shaft, A secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor, It comprises a calculation unit, The reduction ratio of the aforementioned gearbox is 1 / n, where n is a non-integer. The calculation unit calculates a plurality of position calculation values ​​relating to the absolute position of the motor shaft in the primary encoder within one rotation based on the absolute position within one rotation of the secondary encoder. The calculation unit is a position detection system that calculates the total number of rotations of the secondary encoder based on the actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder and the plurality of calculated position values.

2. The position detection system according to claim 1, wherein the calculation unit calculates the total number of rotations of the secondary encoder based on the absolute value of the deviation between the actual position value and the plurality of calculated position values.

3. If the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of calculated position values ​​and then calculates the minimum value, as described in claim 2.

4. The position detection system according to claim 2, wherein the calculation unit calculates the total number of rotations of the secondary encoder when the minimum absolute value of the deviation between the actual position value and the plurality of calculated position values ​​is not less than a predetermined second error determination value which is less than the first error determination value.

5. Motor and, A reduction gear coupled to the motor, A primary encoder for detecting the position of the motor shaft of the motor, A secondary encoder for detecting the position of the output shaft of the reduction gear, It comprises a calculation unit, The reduction ratio of the aforementioned gearbox is 1 / n, where n is a non-integer. The calculation unit calculates a plurality of position calculation values ​​relating to the absolute position of the motor shaft in the primary encoder within one rotation based on the absolute position within one rotation of the secondary encoder. The calculation unit calculates the total number of rotations of the secondary encoder based on the actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder and the plurality of calculated position values.

6. The actuator according to claim 5, wherein the calculation unit calculates the total number of rotations of the secondary encoder based on the absolute value of the deviation between the actual position value and the plurality of calculated position values.

7. The actuator according to claim 6, wherein if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of calculated position values ​​and then calculates the minimum value.

8. The actuator according to claim 6, wherein the calculation unit calculates the total number of rotations of the secondary encoder if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is not less than a predetermined second error determination value which is less than the first error determination value.

9. A primary encoder that detects the position of the motor shaft, A position detection method for a position detection system comprising a secondary encoder for detecting the position of the output shaft of a reduction gear coupled to the motor, and a calculation unit, The reduction ratio of the aforementioned gearbox is 1 / n, where n is a non-integer. Based on the absolute position within one revolution of the secondary encoder, a plurality of position calculation values ​​relating to the absolute position of the motor shaft within one revolution of the primary encoder are calculated. A position detection method that calculates the total number of rotations of the secondary encoder based on the actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder and the plurality of calculated position values.

10. The position detection method according to claim 9, wherein the total number of rotations of the secondary encoder is calculated based on the absolute value of the deviation between the actual position value and the plurality of calculated position values.

11. The position detection method according to claim 10, wherein if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of calculated position values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of calculated position values ​​and then calculates the minimum value.

12. The position detection method according to claim 10, wherein the total number of rotations of the secondary encoder is calculated when the minimum of the absolute values ​​of the deviation between the actual position value and the plurality of calculated position values ​​is not less than a predetermined second error determination value and is less than a first error determination value.

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