Robot System

Abstract

This robot system comprises a robot with one or more joints (J1), and a determination unit connected to the robot. The joints (J1) are provided with: a motor (9); a speed reduction mechanism (10) for reducing the speed of revolution of the motor (9); and a torque sensor (11) capable of measuring output torque of the speed reduction mechanism (10). The speed reduction mechanism (10) comprises a plurality of speed reduction elements for reducing the speed of revolution of the motor (9) at a predetermined reduction ratio. The determination unit calculates time-series data about input torque to the speed reduction mechanism (10), and determines a speed reduction mechanism having a problem, on the basis of time-series data about the number of revolutions of the motor (9), the calculated time-series data about the input torque, time-series data about the output torque measured by the torque sensor (11), and the reduction ratio of the respective speed reduction elements.

Description

[Technical Field]

[0001] The present disclosure relates to robotic systems. [Background technology]

[0002] There is known a method for detecting an abnormality in a motor and a reducer from the torque generated by the drive current of the motor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5927440 Summary of the Invention [Problem to be solved by the invention]

[0004] When diagnosing a failure in a reduction gear mechanism, it is important to be able to identify the faulty part. If a failure is diagnosed, the reduction gear mechanism must be further investigated in detail, or if there is no time for an investigation, the entire reduction gear mechanism must be replaced. Since a detailed investigation takes time and replacing the entire reduction gear mechanism is costly, it is desirable to be able to easily identify the cause of the failure within the reduction gear mechanism. [Means for solving the problem]

[0005] One aspect of the present disclosure is a robot system comprising: a robot having one or more joints; and a determination unit connected to the robot; wherein the joints comprise a motor, a reduction mechanism that reduces the rotation of the motor, and a torque sensor capable of measuring the output torque of the reduction mechanism; the reduction mechanism comprises a plurality of reduction elements that reduce the rotation of the motor at a predetermined reduction ratio; and the determination unit calculates time series data of input torque to the reduction mechanism, and determines which reduction element is malfunctioning based on the time series data of the rotation speed of the motor, the time series data of the calculated input torque, the time series data of the output torque measured by the torque sensor, and the reduction ratios of each of the reduction elements. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is an overall configuration diagram showing a robot system according to a first embodiment of the present disclosure. [Figure 2] 2 is a diagram showing a first rotary joint and a control device of the robot in the robot system of FIG. 1. FIG. [Figure 3] 3 is a schematic diagram showing an example of a speed reduction mechanism in the first rotary joint portion of FIG. 2. FIG. [Figure 4] FIG. 2 is a block diagram illustrating a control device of the robot system of FIG. [Figure 5] 5 is a diagram illustrating a reduction ratio stored in a determination unit in FIG. 4. FIG. [Figure 6] 2 is a flowchart illustrating a diagnostic method for the robot system of FIG. 1. [Figure 7] 7 is a flowchart following the flowchart of FIG. 6. [Figure 8] 7 is a time chart illustrating time series data of motor rotation speed and torque used in the diagnostic method of FIG. 6. [Figure 9] FIG. 10 is a block diagram illustrating a control device of a robot system according to a second embodiment of the present disclosure. [Figure 10] 10 is a flowchart illustrating a diagnostic method for the robot system of FIG. 9. [Figure 11]11 is a time chart illustrating time series data of torque used in the diagnostic method of FIG. 10. [Figure 12] 10 is a flowchart illustrating a diagnostic method in a robot system according to a third embodiment of the present disclosure. [Figure 13] FIG. 13 is a schematic diagram illustrating the configuration of a robot in the robot system of FIG. 12. [Figure 14] 13 is a diagram showing an example of a speed reduction mechanism in the robot system of FIG. 12, illustrating an example of a mechanical part from which a load is calculated and the position of the load. FIG. [Figure 15] 1. FIG. 4 is a schematic diagram illustrating a modification of the position of the torque sensor in the robot system of FIG. [Figure 16] 1. FIG. 4 is a schematic diagram illustrating another modified example of the position of the torque sensor in the robot system of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] A robot system 1 according to a first embodiment of the present disclosure will be described below with reference to the drawings. As shown in FIG. 1, a robot system 1 according to this embodiment includes a robot 2 and a control device (determination unit) 3 connected to the robot 2.

[0008] The robot 2 is, for example, a vertical six-axis articulated robot equipped with six rotary joints (joints) J1, J2, J3, J4, J5, and J6. The robot 2 includes a base 4 placed on the floor and a rotating body 5 supported rotatably relative to the base 4 about a vertical first axis A. The robot 2 also includes a first arm 6 supported rotatably relative to the rotating body 5 about a horizontal second axis B, and a second arm 7 supported rotatably relative to the first arm 6 about a third axis C parallel to the second axis B. The robot 2 also includes a three-axis wrist unit 8 attached to the tip of the second arm 7.

[0009] The wrist unit 8 includes a first wrist element 30 rotatably supported relative to the second arm 7 about a fourth axis D perpendicular to the third axis C, a second wrist element 31 rotatably supported relative to the first wrist element 30 about a fifth axis E perpendicular to the fourth axis D, and a third wrist element 32 rotatably supported relative to the second wrist element 31 about a sixth axis F perpendicular to the fourth axis D and the fifth axis E.

[0010] As shown in Fig. 2, the first rotary joint J1 includes a pair of joint members made up of a base 4 and a rotating body 5 that are supported rotatably about a first axis A. The first rotary joint J1 also includes a servo motor (motor) 9 fixed to the base 4, which is one of the joint members, and a speed reduction mechanism 10 that is disposed between the pair of joint members. The first rotary joint J1 also includes a torque sensor 11 that is disposed between the speed reduction mechanism 10 and the rotating body 5, which is the other joint member, and that is capable of detecting the torque acting between them.

[0011] The servo motor 9 includes a motor shaft 12 that is driven to rotate, and an encoder 13 that detects the rotation angle of the motor shaft 12 . The reduction gear mechanism 10 is a mechanism that reduces the speed of rotation of the motor shaft 12 and transmits it to the other joint member, and includes a plurality of reduction gear elements 14, 15, and 16 connected in series or in parallel. The reduction gear mechanism 10 may have any configuration, but will be described as including three reduction gear elements 14, 15, and 16 connected in series, as shown in Fig. 3, for example.

[0012] The first reduction element (reduction element) 14 includes a first gear 17 fixed to the motor shaft 12 of the servo motor 9, a second gear 18 meshing with the first gear 17, and a first bearing (bearing) 20 supporting the first shaft 19 to which the second gear 18 is fixed so as to be rotatable around its longitudinal axis. The second reduction element (reduction element) 15 includes a third gear 21 fixed to the first shaft 19, a fourth gear 22 meshing with the third gear 21, and a second bearing (bearing) 24 supporting the second shaft 23 to which the fourth gear 22 is fixed so as to be rotatable around its longitudinal axis.

[0013] The third reduction element (reduction element) 16 includes a fifth gear 25 fixed to the second shaft 23, a sixth gear 26 meshing with the fifth gear 25, and a third bearing (bearing) 28 that supports a third shaft 27 to which the sixth gear 26 is fixed so as to be rotatable about its longitudinal axis. The third shaft 27 is fixed to an output flange 29 of the reduction mechanism 10, and the torque sensor 11 is fixed to a flange surface 29a of the output flange 29. The reduction ratio between the first gear 17 and the second gear 18 is reduction ratio R1, the reduction ratio between the third gear 21 and the fourth gear 22 is reduction ratio R2, and the reduction ratio between the fifth gear 25 and the sixth gear 26 is reduction ratio R3.

[0014] The rotation speed N of the motor shaft 12 of the servo motor 9 is reduced to N / R1 by the first reduction element 14, reduced to N / (R1·R2) by the second reduction element 15, and reduced to N / (R1·R2·R3) by the third reduction element 16. That is, the reduction ratio of the first reduction element 14 as viewed from the servo motor 9 side is R1, the reduction ratio of the second reduction element 15 as viewed from the servo motor 9 side is R1·R2, and the reduction ratio of the third reduction element 16 as viewed from the servo motor 9 side is R1·R2·R3.

[0015] The second rotary joint J2 has the same structure as the first rotary joint J1, except that the pair of joint members is a rotating body 5 and a first arm 6. The third rotary joint J3 has the same structure as the first rotary joint J1, except that the pair of joint members is a first arm 6 and a second arm 7.

[0016] The fourth rotary joint J4 has the same structure as the first rotary joint J1, except that the pair of joint members is the second arm 7 and the first wrist element 30. The fifth rotary joint J5 has the same structure as the first rotary joint J1, except that the pair of joint members are a first wrist element 30 and a second wrist element 31. The sixth rotary joint J6 has the same structure as the first rotary joint J1, except that the pair of joint members are a second wrist element 31 and a third wrist element 32.

[0017] The control device 3 includes at least one processor and at least one memory. As shown in Fig. 4, the control device 3 includes a robot control unit 33 that supplies command currents to the servo motors 9 by receiving rotation angle values ​​fed back from encoders 13 provided in the servo motors 9 of the rotary joints J1, J2, J3, J4, J5, and J6, a determination unit 34, and a notification unit 35.

[0018] The determination unit 34 receives as input a command current value output from the robot control unit 33, a rotation angle value output from the encoder 13 of the servo motor 9, and an actual torque Ts, which is the output torque detected by the torque sensor 11. The determination unit 34 stores the reduction ratios R1, R2, and R3 of the reduction elements 14, 15, and 16, as shown in Fig. 5. The determination unit 34 calculates the input torque input from the servo motor 9 to the reduction mechanism 10 based on the command current value input from the robot control unit 33, and also calculates an ideal torque Ti, which is the ideal output torque of the reduction mechanism 10, from the input torque and the reduction ratios R1, R2, and R3.

[0019] The determination unit 34 also calculates the differential torque TD1 by subtracting the measured torque Ts from the calculated ideal torque Ti. Furthermore, the determination unit 34 performs frequency analysis on the differential torque TD1 using a known method such as FFT to calculate the frequency f of the periodic component contained in the differential torque TD1.

[0020] The determination unit 34 compares the value N / f obtained by dividing the rotation speed N of the motor shaft 12, which is based on the amount of change in the rotation angle value detected by the encoder 13, by the calculated frequency f with the reduction ratios 1, R1, R1·R2, R1·R2·R3. If the difference between the value N / f and any of the reduction ratios 1, R1, R1·R2, R1·R2·R3 is within a predetermined threshold value as a result of the comparison, the determination unit 34 determines that there is a possibility that a malfunction has occurred in the corresponding reduction element 14, 15, 16.

[0021] If the value N / f is close to a reduction ratio of 1, there is a possibility that there is a problem with the servo motor 9 or the first gear 17 of the first reduction element 14 fixed to the motor shaft 12. If the value N / f is close to the reduction ratio R1, there is a possibility that the second gear 18 or the third gear 21 fixed to the first shaft 19 of the first reduction element 14 has a problem.

[0022] If the value N / f is close to the reduction ratio R1·R2, there may be a problem with the fourth gear 22 or the fifth gear 25 fixed to the second shaft 23 of the second reduction element 15. If the value N / f is close to the reduction ratios R1·R2·R3, there is a possibility that the sixth gear 26 fixed to the third shaft 27 of the third reduction element 16 has a problem.

[0023] The notification unit 35 then notifies the outside of the determination result by the determination unit 34. Any method of notification by the notification unit 35 may be used, and the possible location of a malfunction can be notified to the outside by displaying on the monitor of the control device 3, displaying with a lamp, or displaying with a buzzer.

[0024] Next, a method for diagnosing whether or not a malfunction has occurred in the reduction mechanism 10 in the robot system 1 according to this embodiment will be described. The operator operates the control device 3 to operate the robot 2. The operation of the robot 2 may be any operation that simultaneously or multiplely operates the six rotary joints J1, J2, J3, J4, J5, and J6, but it is preferable to execute a diagnostic program that operates the six rotary joints J1, J2, J3, J4, J5, and J6 one by one. Since the diagnostic method for each of the rotary joints J1, J2, J3, J4, J5, and J6 is the same, the diagnostic method for the first rotary joint J1 will be described here as an example.

[0025] 6, the operator executes the diagnostic program to start constant-speed operation of only the first rotary joint J1 of the robot 2 (step S1). As a result, the servo motor 9 is operated by a command current value output from the robot control unit 33, and the rotating body 5 is rotated about the first axis A relative to the base 4. In this state, the rotation angle value detected by the encoder 13 of the servo motor 9 is input to the determination unit 34, which then obtains the rotation speed N of the servo motor 9 from the change in the rotation angle value over time (step S2).

[0026] Furthermore, the command current value output from the robot control unit 33 is input to the determination unit 34, which calculates the ideal torque Ti based on the input torque of the servo motor 9 (step S3). The ideal torque Ti is calculated by multiplying the input torque by the reduction ratios R1·R2·R3 of the entire reduction mechanism 10 and the transmission efficiency.

[0027] At the same time, the actual torque Ts detected by the torque sensor 11 is input to the determination unit 34 (step S4). The acquired rotation speed N, the calculated ideal torque Ti, and the detected actual torque Ts are stored in association with the rotation angle value, the command current value, and the time of input of the actual torque Ts to the determination unit 34 (step S5).

[0028] Then, it is determined whether the operation of the robot 2 has ended (step S6), and if not, the process from step S2 is repeated. In step S6, when it is determined that the operation of the robot 2 for diagnosis has ended, time series data of the rotation speed N of the servo motor 9, the ideal torque Ti, and the measured torque Ts within a predetermined time range is obtained, as shown in Fig. 8. Furthermore, as shown in Fig. 7, the time series data of the measured torque Ts is subtracted from the time series data of the ideal torque Ti to obtain time series data of the differential torque (first differential torque) TD1 shown in Fig. 8 (step S7).

[0029] It is determined whether or not a differential torque TD1 exceeding a predetermined threshold value Th1 occurs in the acquired time-series data of the differential torque TD1 (step S8). If there is a time when a differential torque TD1 exceeding the threshold value Th1 occurs, the frequency f of the periodic component included in the time-series data of the differential torque TD1 is extracted (step S9), as shown in Fig. 7.

[0030] Then, the determination unit 34 calculates the value N / f by dividing the rotation speed N of the servo motor 9 by the extracted frequency f (step S10). The calculated value N / f is compared with the reduction ratios 1, R1, R1·R2, R1·R2·R3 in order (steps S11 to S14).

[0031] If it is determined in step S11 that the value N / f is equal to 1 (the difference between the value N / f and 1 is smaller than the predetermined threshold value Th2), there is a possibility that there is a malfunction in the servo motor 9 and the first gear 17 rotating at the rotation speed N (step S15). If there is some kind of malfunction in the rotor of the servo motor 9 or if the first gear 17 is missing a tooth, the output torque will fluctuate at the same frequency as the rotation speed N. If it is determined that there is a possibility of a malfunction, the notification unit 35 notifies the outside (step S19).

[0032] If it is determined in step S11 that the value N / f is different from 1, it is determined whether or not the value N / f is equal to R1 (the difference between the values ​​N / f and R1 is smaller than a predetermined threshold value Th2) (step S12). If it is determined in step S12 that the value N / f is equal to R1, there is a possibility that there is a malfunction in the second gear 18 and the third gear 21 fixed to the first shaft 19 rotating at the rotation speed N / R1 (step S16). In this case, too, the notification unit 35 notifies the outside to that effect (step S19).

[0033] Furthermore, if it is determined in step S12 that the value N / f is different from R1, it is determined whether or not the value N / f is equal to R1·R2 (i.e., whether the difference between the values ​​N / f and R1·R2 is smaller than a predetermined threshold value Th2) (step S13). If it is determined in step S13 that the value N / f is equal to R1·R2, there is a possibility that a malfunction exists in fourth gear 22 and fifth gear 25 fixed to second shaft 23, which rotates at rotation speed N / (R1·R2) (step S17). In this case, too, the notification unit 35 notifies the outside (step S19).

[0034] Furthermore, if it is determined in step S13 that the value N / f is different from R1·R2, it is determined whether or not the value N / f is equal to R1·R2·R3 (i.e., whether the difference between the values ​​N / f and R1·R2·R3 is smaller than a predetermined threshold value Th2) (step S14). If it is determined in step S14 that the value N / f is equal to R1·R2·R3, there is a possibility that there is a malfunction in the sixth gear 26 fixed to the third shaft 27 rotating at the rotation speed N / (R1·R2·R3) (step S18). In this case, too, the notification unit 35 notifies the outside (step S19).

[0035] The threshold value Th2 in steps S11 to S14 may be the same or different. After the diagnosis of the first rotary joint J1 is completed, the diagnosis of the second rotary joint J2 to the sixth rotary joint J6 may be carried out in sequence.

[0036] As described above, the robot system 1 according to this embodiment has the advantage of being able to identify the cause of a failure within the reduction mechanism 10, that is, a malfunction of each of the reduction elements 14, 15, and 16 provided within the reduction mechanism 10, rather than a malfunction of the entire reduction mechanism 10. This makes it possible to replace the reduction elements 14, 15, and 16 for which a malfunction has been identified, without having to remove the entire reduction mechanism 10 and re-examine it, or replace the entire reduction mechanism 10, thereby minimizing the number of replacement parts and significantly reducing the man-hours and costs required for maintenance.

[0037] In this embodiment, it is determined whether or not there is a malfunction in the servo motor 9 or the first to sixth gears 17, 18, 21, 22, 25, 26 provided in each of the reduction gear elements 14, 15, 16, but a malfunction in any other mechanical element can also be determined in a similar manner. For example, if there is a malfunction in the first bearing 20 supporting the first shaft 19, it is conceivable that the output torque will vibrate at a frequency that is the same as or close to the rotation speed N / R1, and therefore a malfunction may be determined in a similar manner.

[0038] Furthermore, if there is a problem with the second bearing 24 that supports the second shaft 23, it is conceivable that the output torque will vibrate at a frequency that is the same as or close to the rotational speed N / R1·R2, so it is also possible to determine whether there is a problem in the same way. Furthermore, if there is a problem with the third bearing 28 that supports the third shaft 27, it is conceivable that the output torque will vibrate at a frequency that is the same as or close to the rotational speed N / R1·R2·R3, so it is also possible to determine whether there is a problem in the same way.

[0039] Next, a robot system according to a second embodiment of the present invention will be described below with reference to the drawings. In the description of this embodiment, parts having the same configuration as the robot system 1 according to the first embodiment described above will be denoted by the same reference numerals, and the description thereof will be omitted.

[0040] In the robot system according to this embodiment, as shown in Fig. 9, the control device 3 includes a storage unit 36 ​​that stores time-series data of the reference torque TR. The reference torque TR is the differential torque between the ideal torque Ti when the robot 2 is in a normal state and the measured torque Ts, which is obtained at the time of shipping the robot 2, etc. For example, the time-series data of the differential torque TD1 obtained by executing steps up to step S7 in Fig. 6 at the time of shipping the robot 2, may be stored in the storage unit 36.

[0041] In the robot system according to this embodiment, the determination unit 34 subtracts the time series data of the reference torque TR read from the storage unit 36 ​​from the time series data of the calculated differential torque TD1. As a result, time series data of the differential value (second differential torque) TD2 is calculated (step S21), as shown in Fig. 10. The relationship between the differential torque TD1, the reference torque TR, and the differential value TD2 is, for example, as shown in Fig. 11.

[0042] Then, the determination unit 34 determines whether the absolute value of the average value of the difference values ​​TD2 exceeds a predetermined threshold value Th3 (step S22). If the absolute value of the average value of the difference values ​​TD2 exceeds the threshold value Th3, it determines that there is a problem with any of the bearings 20, 24, 28 or the lubricant inside the speed reduction mechanism 10, and notifies the fact via the notification unit 35 (step S23).

[0043] The differential torque TD1 is a resistance component within the reduction gear mechanism 10 obtained by subtracting the measured torque Ts from the ideal torque Ti, and varies depending on the amount of preload on the bearings 20, 24, and 28 and the state of the lubricant. The differential value TD2 indicates how much the current differential torque TD1 has changed with respect to the normal state of the robot 2, by subtracting the reference torque TR from the differential torque TD1.

[0044] By subtracting the reference torque TR from the differential torque TD1, even if the differential torque TD1 contains offsets or vibrations specific to each of the rotary joints J1, J2, J3, J4, J5, and J6, these can be eliminated if they are normal. This has the advantage that it is possible to accurately extract the amount of change from the normal state and accurately determine whether there is a possibility of a malfunction.

[0045] If the average value of the difference value TD2 is negative, there may be a malfunction such as a decrease in the preload of the bearings 20, 24, 28 due to wear, softening due to deterioration of the lubricant grease, or a decrease in belt tension if the reduction mechanism 10 includes a belt. On the other hand, if the average value of the difference value TD2 is positive, the following possibilities are considered: The deterioration of the lubricant grease has caused wear particles from mechanical parts such as the bearings 20, 24, and 28 to clog the bearings 20, 24, and 28, or debris from mechanical parts such as the gears 17, 18, 21, 22, 25, and 26 to clog the bearings 20, 24, and 28, or the wear particles have hardened the grease, or other problems may have occurred.

[0046] This embodiment has the advantage of being able to notify of a malfunction in any of the bearings 20, 24, 28 or lubricant inside the reduction gear mechanism 10, in addition to malfunctions in the gears 17, 18, 21, 22, 25, 26 of the reduction gear elements 14, 15, 16 in the first embodiment. It also has the advantage of being able to improve the rigidity and rotation accuracy of the rotary joints J1, J2, J3, J4, J5, J6 by adjusting the preload of the bearings 20, 24, 28. Furthermore, if a malfunction in the lubricant is suspected, the malfunction can be repaired by simply replacing the lubricant without replacing other mechanical parts, significantly reducing the man-hours and costs required for maintenance work.

[0047] In this embodiment, the possibility of a problem with the bearings 20, 24, 28 or the lubricant is notified based on whether the absolute value of the average value of the difference values ​​TD2 is greater than a predetermined threshold value Th3. Alternatively, the type of problem may be further classified and notified based on the sign of the average value of the difference values ​​TD2.

[0048] Furthermore, in this embodiment, the determination unit 34 determines the possibility of a malfunction based on the absolute value of the average value of the difference values ​​TD2. Alternatively, time series data of the difference values ​​TD2 during the time periods when the rotary joints J1, J2, J3, J4, J5, and J6 start to move and the time periods when the rotary joints J1, J2, J3, J4, J5, and J6 are operating at a constant speed may be extracted based on the time series data of the difference values ​​TD2 calculated in step S21 and the time series data of the rotation angle values ​​that have been stored.

[0049] The possibility of a malfunction may then be determined based on the difference value TD2 in the extracted time period. Specifically, the maximum value of the difference value TD2 in the time period when the rotary joints J1, J2, J3, J4, J5, and J6 start to move is a non-periodic component that corresponds to the resistance component due to static friction of the mechanical parts. If the absolute value of the maximum value of the difference value TD2 in the time period when the rotary joints J1, J2, J3, J4, J5, and J6 start to move exceeds a predetermined threshold value Th3, it is determined that the preload of the bearings 20, 24, and 28 is too large.

[0050] Furthermore, the average value of the difference value TD2 during the time period when the rotary joints J1, J2, J3, J4, J5, and J6 are operating at a constant speed is also a non-periodic component, and corresponds to the resistance component due to dynamic friction of the mechanical parts. If the absolute value of the average value of the difference value TD2 during the time period when the rotary joints J1, J2, J3, J4, J5, and J6 are operating at a constant speed exceeds a predetermined threshold value Th3, it can be determined that the lubricant has softened or hardened due to deterioration.

[0051] Furthermore, time series data of the differential value TD2 during the time period when the rotary joints J1, J2, J3, J4, J5, and J6 are operating at a constant speed may be used to extract the frequency in step S9. This allows the frequency of the periodic component contained in the differential torque TD1 to be determined more accurately than if time series data of the differential torque TD1 during the entire time period when the rotary joints J1, J2, J3, J4, J5, and J6 are operating was used.

[0052] In this embodiment, the differential value TD2 is calculated by subtracting the time series data of the reference torque TR from the time series data of the differential torque TD1. The reference torque TR is the differential torque TD1 measured by executing a diagnostic program under predetermined conditions, for example, at the time of shipping the robot 2. Therefore, it is preferable that the diagnosis at the site is also performed under the same conditions as at the time of shipping.

[0053] However, for example, it is difficult to make the temperature of the reduction mechanism 10 when the diagnosis is performed the same as when it was shipped. Therefore, it is preferable that a temperature sensor capable of detecting the temperature of the reduction mechanism 10 is provided, and the determination unit 34 is provided with a correction unit that corrects the time-series data of the reference torque TR based on the temperature detected by the temperature sensor. Also, instead of a temperature sensor that directly detects the temperature of the reduction mechanism 10, for example, the temperature detected by a temperature sensor provided in the torque sensor 11 may be used.

[0054] Furthermore, when performing a diagnosis on-site, it is not realistic to have the robot 2 perform the same diagnostic operations as those performed at the time of shipment. Therefore, time-series data of the reference torque TR and time-series data of the rotation angle values ​​when the reference torque TR is measured may be stored in the storage unit 36. Then, during diagnosis, the reference torque TR may be corrected using the speed and acceleration of each of the rotary joints J1, J2, J3, J4, J5, and J6 calculated from the rotation angle values ​​detected at each moment by the encoders 13 provided at each of the rotary joints J1, J2, J3, J4, J5, and J6, to generate time-series data of the reference torque TR for the operation during diagnosis.

[0055] In this embodiment, the resistance components due to static and dynamic friction are used to determine malfunctions by extracting time-series data of the difference value TD2 during the period when the rotary joints J1, J2, J3, J4, J5, and J6 begin to move and during the period when the rotary joints J1, J2, J3, J4, J5, and J6 are operating at a constant speed. Alternatively, this data may be used to measure the smoothness of rotation of the reduction gear mechanism 10. Since changes in the internal resistance of the reduction gear mechanism 10 can be determined, it is also possible to estimate the lubrication state and the runout of the shaft center due to wear of the gears 17, 18, 21, 22, 25, and 26 and the bearings 20, 24, and 28. Furthermore, if a belt is present in the reduction gear mechanism 10, the tension of the belt can also be estimated.

[0056] Furthermore, in this embodiment, time series data of difference values ​​TD2 during the time periods when the rotary joints J1, J2, J3, J4, J5, J6 start to move and the time periods when the rotary joints J1, J2, J3, J4, J5, J6 are operating at a constant speed is extracted from the time series data of difference values ​​TD2 calculated using the torque Ts actually measured by the torque sensor 11. Alternatively, other encoders may be attached to the output positions of the respective reduction gear mechanisms 10 to determine the time periods when the rotary joints J1, J2, J3, J4, J5, J6 start to move and the time periods when the rotary joints J1, J2, J3, J4, J5, J6 are operating at a constant speed. Furthermore, instead of the torque sensors 11 attached to the output positions of the speed reduction mechanisms 10 of the rotary joints J1, J2, J3, J4, J5, and J6, force sensors may be used.

[0057] Next, a robot system according to a third embodiment of the present invention will be described below with reference to the drawings. In the description of this embodiment, parts having the same configuration as the robot system 1 according to the first and second embodiments described above will be denoted by the same reference numerals, and description thereof will be omitted.

[0058] The robot system of this embodiment not only performs the same diagnosis as the robot 2 of the first or second embodiment, but also notifies the presence or absence of a malfunction in any of the mechanical components provided in each reduction element 14, 15, 16 of each reduction mechanism 10. Figure 12 illustrates an example in which diagnosis by the robot system according to this embodiment is performed in the middle of diagnosis by the robot system 1 according to the first embodiment, but these may be performed in parallel or alternately.

[0059] In the robot system according to this embodiment, similar to the second embodiment shown in Fig. 9, the control device 3 includes a memory unit 36 ​​connected to a determination unit 34. The memory unit 36 ​​stores the main dimensions of each link member (the rotating body 5, the first arm 6, the second arm 7, and the wrist unit 8) that constitutes the robot 2, and the output position of each reduction mechanism 10 (the coordinates of the center position of the output flange 29). The memory unit 36 ​​also stores, for each mechanical component in each reduction mechanism 10, coefficients for calculating a third load from a second load (described below), thresholds for the force and moment at which the mechanical component begins to be affected, and a time limit for which the thresholds are allowed to be exceeded.

[0060] The coefficients, thresholds, and limit times are stored as values ​​corresponding to the forces Fx, Fy, and Fz in the three mutually orthogonal axes x, y, and z directions and the moments Mx, My, and Mz around each axis. All six axes or multiple forces and moments are hereinafter collectively referred to as the load. The three axes x, y, and z directions are set for each reduction mechanism 10.

[0061] 12, after calculating the differential torque TD1 (step S7), the determination unit 34 estimates (step S31) the first load acting on the tip of the wrist unit 8 of the robot 2 (the center position of the flange surface of the wrist flange). At this time, the first load is estimated from the differential torque TD1 for multiple axes of the robot 2. Next, the determination unit 34 estimates, from the first load, a second load applied to the output position (center position of the flange surface 29a of the output flange 29) of the reduction mechanism 10 of each of the rotary joints J1, J2, J3, J4, J5, and J6 (step S32). Next, the determination unit 34 estimates the third load applied to the mechanical components constituting each reduction gear mechanism 10 for each of the rotary joints J1, J2, J3, J4, J5, and J6 from the second load (step S33).

[0062] The first to third loads are estimated as time-series data. The determination unit 34 determines which mechanical component may be malfunctioning based on the time-series data of the third load of each mechanical component and the time-series data of the differential torque TD1 calculated in the first or second embodiment (step S34). If it is determined that any mechanical component is malfunctioning, the notification unit 35 notifies the fact (step S35).

[0063] The diagnostic method for the robot system according to this embodiment will be described below using as an example a case where the structure of the robot 2 is as shown in FIG. 13 and an external force X acts in the direction indicated by the arrow in FIG. 13. In this case, the first load is estimated based on the measured torques Ts detected by the three torque sensors 11 at the second rotary joint J2, the third rotary joint J3 and the fifth rotary joint J5 (step S31).

[0064] The determination unit 34 calculates the tip position of the wrist unit 8 using the rotation angle value from the encoder 13 and the main dimensions of each link member (the rotating body 5, the first arm 6, the second arm 7, and the wrist unit 8), and estimates the first load based on the calculated wrist tip position, the output position of each reduction mechanism 10, and the measured torque Ts. The first load is estimated as (Fx, Fy, Fz, Mx, My, Mz) by the forces in the three orthogonal axial directions and the moments around each axis. The same applies when other forces and moments act on the robot 2.

[0065] Next, the determination unit 34 calculates a coordinate transformation matrix for converting from the coordinate system of the tip of the wrist unit 8 to the coordinate system of the output position of each reduction mechanism 10, and calculates the second load applied to the output position of each reduction mechanism 10 using the calculated coordinate transformation matrix and the first load (step S32). Thereafter, the determination unit 34 calculates the third load acting on each mechanical component as time-series data by multiplying the second load by a coefficient stored in the storage unit 36 ​​(step S33). For example, as shown by reference characters P1 to P10 in Fig. 14, time-series data of the third load acting on the center positions P1 to P6 of the first gear 17 to the sixth gear 26 and the center positions P7 to P10 of the first bearing 20 to the third bearing 28 is calculated.

[0066] In step S34, the determination unit 34 compares the time series data of the third load applied to each mechanical component with the time series data of the differential torque TD1 calculated in step S7, aligning the time axes. This enables the determination unit 34 to determine that a malfunction may have occurred in a mechanical component that fluctuates at the same frequency f as the differential torque TD1.

[0067] Furthermore, in step S34, the determination unit (lifespan estimation unit) 34 accumulates the time during which the estimated third load exceeds the threshold value stored in the memory unit 36. Then, the determination unit 34 estimates the remaining lifespan of the mechanical component based on the accumulated time and the limit time stored in the memory unit 36. Then, the estimated remaining lifespan of the mechanical component is notified by the notification unit 35. This makes it possible to notify the outside of a mechanical component that is likely to develop a malfunction before a malfunction actually occurs.

[0068] In this embodiment, the time series data of the third load is compared with the time series data of the differential torque TD1 to determine the possibility of a malfunction. Alternatively, the time series data of the third load acquired for all mechanical parts may be frequency analyzed by FFT or the like to extract the frequency of the periodic component, and it may be determined that a mechanical part having a frequency matching the frequency of the periodic component of the differential torque TD1 has a malfunction.

[0069] Furthermore, for a mechanical component for which a possible malfunction is reported in the third embodiment, the report may be provided as additional information added to the malfunction report in the first or second embodiment. Furthermore, when it is determined that a mechanical component has a possible malfunction, the determination unit 34 may report this to the user, or the determination unit 34 may adjust the operating speed of the robot 2, so that the mechanical component is operated at a speed at which the malfunction of the mechanical component is more noticeable.

[0070] In this embodiment, the determination unit 34 compares the time-series data of the differential torque TD1 with the time-series data of the third load of each mechanical component to identify the mechanical component in which a malfunction has occurred. Alternatively, the determination unit 34 may be provided with a trained model that has trained the time-series data of the third load calculated when the reduction gear mechanism 10 is in a normal state, such as at the time of shipment. Then, when the robot 2 is in operation, the calculated time-series data of the third load of each mechanical component may be input to the trained model, and the deviation rate from the third load in a normal state may be calculated for each mechanical component, and the mechanical component in which a malfunction has occurred may be identified using a threshold value or the like.

[0071] Furthermore, in each of the above embodiments, a torque sensor 11 is provided at each of the rotary joints J1, J2, J3, J4, J5, and J6, but a six-axis force sensor 37 may be placed between the base 4 and the installation surface, as shown in Fig. 15. Furthermore, a force sensor 37 may be placed at the tip of the wrist unit 8, as shown in Fig. 16. Furthermore, in each of the above embodiments, a vertical six-axis articulated robot equipped with six rotary joints J1, J2, J3, J4, J5, and J6 has been exemplified, but instead, a horizontal four-axis articulated robot, a robot with a different number of rotary joints, such as seven, or a robot system equipped with any other type of robot 2 may be employed. Furthermore, as for the joints, linear joints may be provided instead of the rotary joints J1, J2, J3, J4, J5, and J6. [Explanation of symbols]

[0072] 1. Robot System 2. Robot 3. Control device (judgment unit) 9 Servo motor (motor) 10 Reduction mechanism 11 Torque sensor 13 Encoder 14 1st deceleration element (deceleration element) 15 2nd deceleration element (deceleration element) 16 Third deceleration element (deceleration element) 17 First gear (gear, mechanical part) 18 Second gear (gear, mechanical parts) 20 First bearing (bearing, mechanical part) 21 Third gear (gear, mechanical parts) 22 4th gear (gear, mechanical parts) 24 Second bearing (bearing, mechanical part) 25 5th gear (gear, mechanical parts) 26 6th gear (gear, mechanical parts) 28 Third bearing (bearing, mechanical part) 34 Judgment section (life estimation section) 35 Information Department J1 First rotational joint (joint) J2 Second rotational joint (joint) J3 3rd rotational joint (joint) J4 4th rotational joint (joint) J5 5th rotational joint (joint) J6 6th rotational joint (joint) f frequency N rotation speed Ti Ideal Torque Ts Measured torque TD1 Differential torque (first differential torque) TD2 differential value (second differential torque) Th1, Th2, Th3, Th4 thresholds R1,R2,R3 Reduction ratio

Claims

1. a robot having one or more joints; a determination unit connected to the robot, the joint unit includes a motor, a speed reduction mechanism that reduces the speed of rotation of the motor, and a torque sensor that can measure the output torque of the speed reduction mechanism; the reduction mechanism includes a plurality of reduction elements that reduce the rotation speed of the motor at a predetermined reduction ratio; the determination unit calculates time series data of input torque to the reduction gear mechanism, and determines which reduction gear element is malfunctioning based on the time series data of the rotation speed of the motor, the time series data of the calculated input torque, the time series data of the output torque measured by the torque sensor, and the reduction ratio of each reduction gear element; The robot system wherein the determination unit calculates an ideal torque, which is an ideal output torque of the reduction mechanism, based on the input torque and the reduction ratio of the entire reduction mechanism, calculates a first differential torque, which is the difference between the ideal torque and the actual torque, which is the output torque measured by the torque sensor, and the first differential torque, and determines which reduction element is malfunctioning based on the first differential torque and the reduction ratio of each of the reduction elements.

2. 2. The robot system according to claim 1, wherein the determination unit determines that a malfunction has occurred in the reduction element having a reduction ratio that is approximate to a value obtained by dividing the rotation speed of the motor by a frequency of a periodic component contained in the first differential torque.

3. 3. The robot system according to claim 1, wherein the determination unit stores reference data that is time-series data of differential torque when the reduction mechanism is normal, calculates a second differential torque that is the difference between the time-series data of the first differential torque and the reference data, and determines which reduction element is malfunctioning based on the second differential torque.

4. a temperature sensor for detecting the temperature of the reduction mechanism; The robot system according to claim 3 , wherein the determining unit includes a correcting unit that corrects the reference data based on the temperature detected by the temperature sensor.

5. The robot system according to claim 1 , further comprising a notification unit that notifies the user of the deceleration element in which a malfunction has occurred.

6. 3. The robot system according to claim 1, wherein the determination unit determines that a malfunction has occurred in a lubricant or a bearing provided in any of the reduction elements when the magnitude of a non-periodic component included in the first differential torque exceeds a predetermined threshold value.

7. an encoder for detecting the amount of movement of each of the joints; Each of the deceleration elements comprises one or more mechanical components; 3. The robot system according to claim 2, wherein the determination unit calculates time series data of a load acting on each of the mechanical parts from the time series data of the movement amount detected by the encoder and the time series data of the output torque measured by the torque sensor, and determines that a malfunction has occurred in any of the mechanical parts when a frequency of a periodic component included in the calculated load matches a frequency of a periodic component included in the first differential torque.

8. The robot system according to claim 7 , further comprising a notification unit that notifies the deceleration element and the mechanical part that have been determined by the determination unit to be malfunctioning.

9. 9. The robot system according to claim 7, further comprising a lifespan estimation unit that integrates a time during which a load equal to or greater than a predetermined threshold acts based on time-series data of the load on each of the mechanical parts, and estimates a lifespan of each of the mechanical parts based on the integrated time.

10. an encoder for detecting the amount of movement of each of the joints; Each of the deceleration elements comprises one or more mechanical components; The determination unit: a trained model trained using time-series data of a reference load, which is a load applied to each of the mechanical components calculated when the reduction gear mechanism is in a normal state; calculating time series data of the load applied to each of the mechanical components from the time series data of the movement amount detected by the encoder and the time series data of the output torque measured by the torque sensor; The robot system according to claim 2, wherein the calculated time series data of the load is input into the trained model, and the mechanical component in which a malfunction is occurring is determined based on the deviation rate from the reference load.

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