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

Position detection system, actuator, and position detection method

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

[0002] The actuator includes a servo motor and a reducer that are 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 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 memory.

[0003] Furthermore, Japanese Patent Application Laid-Open No. 2006-300596 proposes a method in which the reduction ratio of the reducer is set to 1 / n (n is a non-integer), a "criterion" value is calculated from the position of the secondary encoder, and the value of the criterion and the result of determining whether the position of the primary encoder is positive or negative determine ±1 rotation of the secondary encoder.

[0004] JP 2007-113932 A JP 2006-300596 A

[0005] However, the method of JP 2006-300596 A cannot be used as a battery-less absolute encoder when the output shaft rotates two or more times.

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

[0007] According to a first aspect of the present disclosure, there is provided a position detection system including a primary encoder that detects a position of a motor shaft of a motor, a secondary encoder that detects a position of an output shaft of a reducer coupled to the motor, and a calculation unit, wherein a 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 an absolute position of the rotor within one rotation in the primary encoder based on an absolute position within one rotation of the secondary encoder, and the calculation unit calculates a total number of rotations of the secondary encoder based on an actual position value related to the absolute position of the rotor within one rotation detected by the primary encoder and the plurality of position calculation values.

[0008] According to another aspect of the present disclosure, there is provided a position detection system including a primary encoder that detects a position of a motor shaft of a motor, a secondary encoder that detects a position of an output shaft of a reducer coupled to the motor, and a calculation and determination unit, wherein the calculation and determination unit calculates a position calculation value relating to the absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft 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 when the absolute value of the deviation between the position calculation value and an actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder is equal to or greater than a predetermined value.

[0009] The objects, features, and advantages of the present disclosure will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings.

[0010] 1 is a schematic side view of a position detection system according to a first embodiment of the present disclosure; FIG. 2 is a first flowchart showing the operation of the position detection system shown in FIG. 1; FIG. 3 is a diagram showing the relationship between the position of an output shaft and the position of an input shaft; FIG. 4 is another diagram showing the relationship between the position of an output shaft and the position of an input shaft; and FIG. 5 is a second flowchart showing the operation of a position detection system according to a second embodiment.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Corresponding components are designated by common reference numerals throughout the drawings. FIG. 1 is a schematic side view of a position detection system according to a first embodiment of the present disclosure. The position detection system 5 is incorporated into a machine 3 having a shaft, for example, a robot 3. Below, a case in which the position detection system 5 is incorporated into a robot 3 will be described, but the same applies to a case in which the position detection system 5 is incorporated into another machine 3 having a shaft, for example, a machine tool.

[0012] 1 , actuator 6 disposed on link 1 includes a motor 10, for example a servo motor, which are connected to each other, and a reducer 20 coupled to a motor shaft 13 of motor 10. Motor 10 includes a rotor 12 that rotates integrally with motor shaft 13, and a stator 11 that is arranged to surround rotor 12. The tip of an output shaft 23 of reducer 20 is connected to link 2. Therefore, actuator 6 consisting of motor 10 and reducer 20 rotates link 2 relatively to link 1 within a predetermined operating range, thereby controlling its positioning. The reduction ratio n of reducer 20 is a positive non-integer, for example, n = α + 1 / β (α and β are positive numbers greater than 1).

[0013] The motor shaft 13 is, for example, a hollow shaft, and has a primary encoder 15 equipped with a rotary disk 15A 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 detector 16, which uses a known method to detect the absolute position θp within one rotation of the motor shaft 13 and the total number of rotations. The detected information is stored in a memory 7, for example, a volatile memory.

[0014] The output shaft 23 passes through the hollow motor shaft 13 and extends toward the motor 10, and a secondary encoder 25 equipped with a rotary 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 a detector 26, which uses a known method to detect the absolute position θs within one rotation of the output shaft 23 and the total number of rotations i. The detected information is stored in a memory 7, for example, a volatile memory.

[0015] The information stored in the memory 7 is maintained for a certain period of time by a battery 8, for example, a button battery or a capacitor. The position detection system 5 shown in Fig. 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 a separate memory and battery.

[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 controls the drive of the motor 10 and performs a positioning operation to position the link 2 at a target position relative to the link 1. Furthermore, the built-in brake 50 provided on the outer surface of the motor shaft 13 is activated in response to an instruction from the controller 9 to brake the motor shaft 13. Furthermore, the controller 9 also serves to energize the primary encoder 15 and the secondary encoder 25 when the machine 3 is operating.

[0017] The controller 9 also functions as a calculator that calculates a plurality of position calculation values ​​relating to the absolute position of the motor shaft 13 within one rotation in the primary encoder 13 based on the absolute position of the secondary encoder 25 within one rotation, and calculates the total number of rotations of the secondary encoder 25 based on the actual position value relating to the absolute position of the motor shaft 13 within one rotation detected by the primary encoder 15 and the plurality of position calculation values.

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

[0019] Fig. 2 is a first flowchart showing the operation of the position detection system shown in Fig. 1. The contents of the program shown in Fig. 2 are stored in a storage unit (not shown) in the controller 9 or in the memory 7. The contents shown in Fig. 2 are executed as appropriate 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) related to the absolute position within one rotation of the primary encoder 15 based on the following equation (1) (i is a positive number equal to or less than β): θp*(i)=MOD[{(θs×(α+1 / β)+(360 / β)×(i−1))}÷360]×360 Equation (1) Note that "MOD[ ]" refers to a function that calculates the remainder of division.

[0021] 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 reducer 20, and the vertical axis indicates the position of the input shaft. The "position of the input shaft" refers to the position of the input shaft that inputs to the secondary encoder 25. In this specification, since the secondary encoder 25 is connected downstream of the primary encoder 15, the "position of the input shaft" can also be rephrased as the position of the rotating disk 15A of the primary encoder 15 or the position of the motor shaft 13. Note that in FIG. 3, both the horizontal and vertical axes are expressed in degrees. As mentioned above, the reduction ratio n of the reducer 20 is n = α + 1 / β (α and β are positive numbers greater than 1), and in the example shown in FIG. 3, α = 2 and β = 3.

[0022] 3 shows three lines L1, L2, and L3. 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 is making its first rotation. The dashed line L2 indicates the position of the input shaft when the output shaft 23 is making its second rotation. The dashed line L3 indicates the position of the input shaft when the output shaft 23 is making its third rotation.

[0023] 3, the position detection system 5 in the first embodiment can detect up to β rotations of the output shaft 23. Furthermore, the position of the output shaft 23 differs between the first rotation and the second rotation. In the first embodiment, the total number of rotations of the output shaft 23 is obtained by utilizing the difference between the position of the first rotation and the position of the second rotation.

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

[0025] In step S13, the controller 9 acquires the detected position value θp relating to the absolute position within one rotation of the motor shaft 13 detected by the primary encoder 15. The controller 9 then calculates the absolute values ​​θd(i) (=|θp-θp*(i)|) of the deviations between the detected position value θp and the plurality of calculated position values ​​θp*(i). In FIG. 3, the absolute values ​​θd(1) (=|θp-θp*(1)|), θd(2) (=|θp-θp*(2)|), and θd(3) (=|θp-θp*(3)|) of the deviations are indicated by arrows.

[0026] Next, in step S14, the controller 9 selects the minimum value Minθd(i) from the plurality of absolute values, θd(1), θd(2), and θd(3) in Fig. 3. In the example shown in Fig. 3, θd(2)<θd(1)<θd(3), so 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 determination value θj1. The first error determination value θj1 is calculated in advance based on the following equation (2): θj1=360 / β-n·θsa_max-θpa_max-θnois_max Equation (2) Here, θsa indicates 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 indicates 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 indicates the width of the disturbance of the position detection system 5, and θnois_max is its maximum value.

[0028] If it is determined in step S15 that the minimum value Minθd(i) is not greater than the first error determination value θj1, it is determined that there is no problem, and the process proceeds to step S19. Then, in step S19, the minimum value Minθd(i) is compared with the second error determination value θj2. The second error determination 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 determination value θj2 is smaller than the first error determination value θj1.

[0029] 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 the position of at least one of the primary encoder 15 and the secondary encoder 25. The controller 9 then determines this to be a detection error and stops the operation of the motor 10. At this time, a display unit (not shown), for example, a screen of a teaching control panel, may display this information.

[0030] On the other hand, if it is determined in step S19 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 Fig. 3, θd(2) is the minimum value Minθd(i), so it is clear that the total number of rotations i is 2.

[0031] As described above, the process of obtaining the total number of rotations of the secondary encoder 25 in the first embodiment of the present disclosure does not require an additional battery. Therefore, in the first embodiment of the present disclosure, the position detection system 5 can be used without requiring an additional battery even when the output shaft 23 rotates two or more times. In other words, even if the encoders 15, 25 are operated in a situation where the controller 9 does not supply power to the encoders 15, 25, the position detection system 5 in the first embodiment can obtain the total number of rotations of the output shaft 23.

[0032] However, if it is determined in step S15 that the minimum value Minθd(i) is greater than the first error determination value θj1, the process proceeds to step S16. Fig. 4 is another diagram similar to Fig. 3, showing the relationship between the position of the output shaft and the position of the input shaft. The case in which it is determined in step S15 that the minimum value Minθd(i) is greater than the first error determination value θj1 is, for example, a situation such as the example shown in Fig. 4.

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

[0034] 4, the minimum value Minθd(i) should be θd(1), and it is clearly incorrect to set θd(3) as the minimum value Minθd(i). However, because the position of the motor shaft 13 relative to the primary encoder 15 is near 0° (near 360°), it is difficult to make the above-mentioned determination. For this reason, assuming that the position of the motor shaft 13 relative to the primary encoder 15 is near 0°, in step S16, the controller 9 performs position jump correction on the absolute value of the deviation θd(i) acquired in step S13.

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

[0036] As a result, θd(1), θd(2), and θd(3) are corrected according to the following equations (5) to (7): θd(1)=|θp-θp*(1)|=360-nθsa-θpa-θnois

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

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

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

[0040] Then, in step S17, the controller 9 selects the minimum value Minθd(i) from the plurality of absolute values ​​θd(i) corrected in this manner. In the example shown in Fig. 4, the minimum value Minθd(i) is the corrected absolute value θd(1). By such position jump correction, the correct minimum value Minθd(i) (the corrected absolute value θd(1) in Fig. 4) is selected.

[0041] Thereafter, in step S18, the correct minimum value Minθd(i) after correction is reset as the minimum value Minθd(i). Then, the process proceeds to step S20, where the total number of rotations of the secondary encoder 25 is calculated in the same manner as described above, based on the new minimum value Minθd(i). In the example shown in FIG. 4, θd(1) is the minimum value Minθd(i), so 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] 5 is a second flowchart showing the operation of the position detection system according to the second embodiment. The contents of the program shown in FIG. 5 are stored in a storage unit (not shown) in the controller 9 or in the memory 7. The contents shown in FIG. 5 are 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 the one described above. That is, the reduction ratio n in this case may be 1 / α (α is a positive number greater than 1). The second embodiment also includes a case where an additional reducer (not shown) is disposed 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' (α' is a positive number greater than 1).

[0045] First, in step S31, similarly to the above, the secondary encoder 25 detects a position detection value θs relating to the absolute position within one rotation of the output shaft 23. Then, in step S32, similarly to the description with reference to FIG. 3, the controller 9 serving as a calculation determination unit uses the position detection value θs of the detected absolute position to calculate a position calculation value θp* relating 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 of the primary encoder 15 and the position calculation value θp* based on the following equation (9): θpd=|θp*−θp|

[0047] Then, in step S34, the controller 9 determines whether the absolute value θpd of the deviation is greater than a third error determination value θj3. Here, the absolute value θpd of the deviation indicates the deviation in the detected positions between the primary encoder 15 and the secondary encoder 25. In an ideal state where there is no backlash of the reducer 20 or any detection errors, the absolute value θpd of the deviation is 0. Therefore, the third error determination value θj3 is a value greater than zero that is predetermined by the operator.

[0048] If it is determined in step S34 that the absolute value of the deviation θpd is 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, it is determined that there is an abnormality in the set position of the primary encoder 15 and / or the secondary encoder 25, and the controller 9 stops the operation of the motor 10. At this time, a display unit (not shown), for example, a screen of a teaching control panel, may display a message to that effect.

[0049] On the other hand, if it is determined in step S34 that the absolute value of the deviation θpd is not 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 normal (step S36), and the processing is terminated.

[0050] In this way, no additional battery is required for the process of determining whether or not there is an abnormality in the relative position between the primary encoder 15 and the secondary encoder 25 in the second embodiment of the present disclosure. 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] In addition, the computer program for executing the processing of the controller 9 as the calculation unit and the calculation determination unit may be provided in a form recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium.

[0052] According to a first aspect of the present disclosure, there is provided a position detection system including a primary encoder that detects the position of a motor shaft of a motor, a secondary encoder that detects the position of an output shaft of a reducer coupled to the motor, and a calculation unit, wherein the reduction ratio of the reducer is 1 / n, where n is a non-integer, the calculation unit calculates multiple position calculation values ​​related to the absolute position of the motor shaft within one rotation in the primary encoder based on the absolute position of the secondary encoder within one rotation, and the calculation unit calculates a total number of rotations of the secondary encoder based on the multiple position calculation values ​​and an actual position value related to the absolute position of the motor shaft within one rotation detected by the primary encoder. According to a second aspect, according to the first aspect, the calculation unit calculates the total number of rotations of the secondary encoder based on an absolute value of a deviation between the actual position value and the multiple position calculations. According to a third aspect, according to the first or second aspect, if the minimum of the absolute values ​​of the deviations between the actual position value and the multiple position calculations is greater than a predetermined first error determination value, the calculation unit corrects the multiple position calculations before calculating the minimum value. According to a fourth aspect, in any of the first to third aspects, if the minimum value of the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is not smaller than a predetermined second error judgment value that is smaller than the first error judgment value, the calculation unit calculates the total number of rotations of the secondary encoder.According to a fifth aspect, there is provided an actuator including a motor, a reducer coupled to the motor, a primary encoder that detects a position of a motor shaft of the motor, a secondary encoder that detects a position of an output shaft of the reducer, and a calculation unit, wherein a 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 an absolute position of the motor shaft within one rotation in the primary encoder based on an absolute position within one rotation of the secondary encoder, and the calculation unit calculates a total number of rotations of the secondary encoder based on an actual position value related to the absolute position of the motor shaft within one rotation detected by the primary encoder. According to a sixth aspect, there is provided an actuator according to the fifth aspect, wherein the calculation unit calculates the total number of rotations of the secondary encoder based on an absolute value of a deviation between the actual position value and the plurality of position calculation values. According to a seventh aspect, in the fifth or sixth aspect, if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is greater than a predetermined first error determination value, the calculation unit corrects the plurality of position calculation values ​​and then calculates the minimum value. According to an eighth aspect, in any of the fifth to seventh aspects, if the minimum of the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is not smaller than a predetermined second error determination value that is smaller than the first error determination value, the calculation unit calculates the total number of rotations of the secondary encoder.According to a ninth aspect, there is provided a position detection method for a position detection system including a primary encoder that detects the position of a motor shaft of a motor and a secondary encoder that detects the position of an output shaft of a reducer coupled to the motor, wherein the reduction ratio of the reducer is 1 / n, where n is a non-integer, and the method calculates multiple position calculation values ​​related to the absolute position of the motor shaft within one rotation in the primary encoder based on the absolute position within one rotation of the secondary encoder, and calculates a total number of rotations of the secondary encoder based on the multiple position calculation values ​​and an actual position value related to the absolute position within one rotation of the motor shaft detected by the primary encoder. According to a tenth aspect, the method of the ninth aspect further includes calculating the total number of rotations of the secondary encoder based on an absolute value of a deviation between the actual position value and the multiple position calculation values. According to an eleventh aspect, according to the ninth or tenth aspect, if the minimum of the absolute values ​​of the deviations between the actual position value and the multiple position calculation values ​​is greater than a predetermined first error determination value, the calculation unit corrects the multiple position calculation values ​​before calculating the minimum value. According to a twelfth aspect, in any of the ninth to eleventh aspects, the total number of rotations of the secondary encoder is calculated when the minimum value of the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is smaller than the first error judgment value and not smaller than a predetermined second error judgment value.According to a thirteenth aspect, there is provided a position detection system comprising: a primary encoder that detects the position of a motor shaft of a motor; a secondary encoder that detects the position of an output shaft of a reducer coupled to the motor; and a calculation and determination unit, wherein the calculation and determination unit calculates a position calculation value relating to the absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft 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 when the absolute value of the deviation between the position calculation value and an actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder is equal to or greater than a predetermined value. According to a fourteenth aspect, there is provided an actuator comprising: a motor; a reducer coupled to the motor; a primary encoder that detects a position of a motor shaft of the motor; a secondary encoder that detects a position of an output shaft of the reducer; and a calculation and determination unit, wherein the calculation and determination unit calculates a position calculation value relating to the absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft 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 when the absolute value of the deviation between the position calculation value and an actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder is equal to or greater than a predetermined value.According to a fifteenth aspect, there is provided a position detection method for a position detection system including a primary encoder that detects the position of a motor shaft of a motor, and a secondary encoder that detects the position of an output shaft of a reducer coupled to the motor, the position detection method calculating a position calculation value relating to the absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft detected by the secondary encoder, and determining 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 position calculation value and an actual position value relating to the absolute position within one rotation of the motor shaft detected by the primary encoder is equal to or greater than a predetermined value.

[0053] Although the embodiments of the present disclosure have been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the invention or the idea and spirit of the present disclosure derived from the content described in the claims and their equivalents. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments. Furthermore, appropriate combinations of several of the above-described embodiments are within the scope of the present disclosure.

[0054] REFERENCE SIGNS LIST 1, 2 Link 3 Machine (robot) 5 Position detection system 6 Actuator 7 Memory 8 Battery 9 Controller (calculation unit, calculation determination unit) 10 Motor 11 Stator 12 Rotor 13 Motor shaft 15 Primary encoder 16 Detection unit 20 Reducer 23 Output shaft 25 Secondary encoder 26 Detection unit 50 Built-in brake θj1 First error determination value θj2 Second error determination value θj3 Third error determination value

Claims

1. A primary encoder for detecting a position of a motor shaft of the motor; a secondary encoder for detecting a position of an output shaft of a reducer coupled to the motor; A calculation unit, 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 an absolute position within one rotation of the motor shaft in the primary encoder based on an absolute position within one rotation of the secondary encoder; The calculation unit calculates a total number of rotations of the secondary encoder based on an actual position value related to an absolute position within one rotation of the motor shaft detected by the primary encoder and the multiple position calculation values.

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

3. 3. The position detection system according to claim 1, wherein when a minimum value among the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is greater than a predetermined first error determination value, the calculation unit calculates the minimum value after correcting the plurality of position calculation values.

4. 3. The position detection system according to claim 1, wherein the calculation unit calculates a total number of rotations of the secondary encoder when a minimum value among the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is not smaller than a predetermined second error determination value which is smaller than the first error determination value.

5. A motor; A reducer coupled to the motor; a primary encoder for detecting a position of a motor shaft of the motor; A secondary encoder for detecting a position of an output shaft of the reducer; A calculation unit, 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 an absolute position within one rotation of the motor shaft in the primary encoder based on an absolute position within one rotation of the secondary encoder; The calculation unit calculates a total number of rotations of the secondary encoder based on an actual position value relating to an absolute position within one rotation of the motor shaft detected by the primary encoder and the multiple position calculation values.

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

7. 7. The actuator according to claim 5, wherein when a minimum value among the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is greater than a predetermined first error determination value, the calculation unit calculates the minimum value after correcting the plurality of position calculation values.

8. 7. The actuator according to claim 5, wherein the calculation unit calculates a total number of rotations of the secondary encoder when a minimum value among the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is not smaller than a predetermined second error determination value which is smaller than the first error determination value.

9. A primary encoder for detecting a position of a motor shaft of the motor; a secondary encoder for detecting a position of an output shaft of a reducer coupled to the motor, The reduction ratio of the reducer is 1 / n, where n is a non-integer; calculating a plurality of position calculation values ​​relating to an absolute position within one rotation of the motor shaft in the primary encoder based on the absolute position within one rotation of the secondary encoder; a total number of rotations of the secondary encoder based on an actual position value relating to an absolute position within one rotation of the motor shaft detected by the primary encoder and the plurality of position calculation values.

10. The position detection method according to claim 9 , further comprising the step of calculating a total number of rotations of the secondary encoder based on an absolute value of a deviation between the actual position value and the plurality of position calculation values.

11. 11. The position detection method according to claim 9, wherein when a minimum value among the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is greater than a predetermined first error determination value, the calculation unit calculates the minimum value after correcting the plurality of position calculation values.

12. 11. The position detection method according to claim 9 or 10, further comprising the step of calculating a total number of rotations of the secondary encoder when a minimum value among the absolute values ​​of the deviations between the actual position value and the plurality of position calculation values ​​is smaller than the first error determination value and is not smaller than a predetermined second error determination value.

13. A primary encoder for detecting a position of a motor shaft of the motor; a secondary encoder for detecting a position of an output shaft of a reducer coupled to the motor; A calculation determination unit, the calculation determination unit calculates a position calculation value relating to an absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft detected by the secondary encoder; 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 when an absolute value of a deviation between an actual position value relating to an absolute position within one rotation of the motor shaft detected by the primary encoder and the position calculation value is equal to or greater than a predetermined value.

14. A motor; A reducer coupled to the motor; a primary encoder for detecting a position of a motor shaft of the motor; A secondary encoder for detecting a position of an output shaft of the reducer; A calculation determination unit, the calculation determination unit calculates a position calculation value relating to an absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft detected by the secondary encoder; 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 when an absolute value of a deviation between an actual position value related to an absolute position within one rotation of the motor shaft detected by the primary encoder and the position calculation value is equal to or greater than a predetermined value.

15. A primary encoder for detecting a position of a motor shaft of the motor; a secondary encoder for detecting a position of an output shaft of a reducer coupled to the motor, calculating a position calculation value relating to an absolute position within one rotation of the motor shaft based on the absolute position within one rotation of the output shaft detected by the secondary encoder; a position detection method for detecting a position of the motor shaft when an absolute value of a deviation between an actual position value relating to an absolute position within one rotation of the motor shaft detected by the primary encoder and the calculated position value is equal to or greater than a predetermined value, the method determining that there is an abnormality in the position of at least one of the primary encoder and the secondary encoder.