JP6926903B2 - Abnormality diagnostic device - Google Patents

Description

The present invention relates to an abnormality diagnosing device for diagnosing an abnormality of a robot.

Conventionally, an articulated robot having a plurality of joints has been put into practical use as an industrial robot. In such a robot, motors (servo motors) are provided for each joint, and each joint is rotated by driving the motors.

Robots deteriorate with the passage of time and repeated operation. Therefore, it is necessary to be able to detect an abnormality as soon as possible. Regarding the abnormality determination of the robot, a method is known in which a vibration pattern during robot operation is detected and the detected vibration pattern is frequency-analyzed to determine the abnormality (see, for example, Patent Document 1). In this method, as a result of frequency analysis, when the amplitude of the waveform at a specific frequency is equal to or greater than the threshold value, it is determined to be abnormal.

Japanese Unexamined Patent Publication No. 2008-32477

However, the inventor of the present application has noted that when the threshold value is constant, it may be erroneously determined to be abnormal even if the robot is operating normally. In particular, there is a problem that erroneous determination is likely to occur immediately after assembling the robot, immediately after repairing, or immediately after replacing parts.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an abnormality diagnosis device capable of appropriately diagnosing an abnormality.

In order to solve the above problems, as the first invention, in an abnormality diagnosis device used for a robot provided with a motor for driving a joint, a vibration generated when the joint is driven by the motor or a vibration correlation correlating with the vibration. Frequency analysis is performed on the vibration detection unit that detects the amount and the vibration or the vibration correlation amount detected by the vibration detection unit, and the amplitude at a specific frequency determined according to the mechanical elements constituting the robot is extracted. The frequency analysis unit is compared with the amplitude and the threshold value at the specific frequency extracted by the frequency analysis unit, and if the amplitude at the specific frequency is larger than the threshold value, it is determined that there is an abnormality, and if it is equal to or less than the threshold value. Is an abnormality determination unit that determines that there is no abnormality, and after the initial setting is made for the robot and the initial threshold value is set as the threshold value, the state of the robot can be determined to be abnormal without using the initial threshold value. The threshold value is higher than the initial threshold value, provided that the state determination unit determines whether or not the stable state has been reached and that the state determination unit determines that the robot state has shifted to the stable state. The gist is that a threshold value setting unit for setting a small normal threshold value is provided.

The amplitude at a specific frequency, which is determined according to the mechanical element in the frequency analysis result of the vibration correlation amount, may change depending on the state of the robot even when the robot is normal. Specifically, immediately after assembling the robot, immediately after repairing, or immediately after replacing parts, the vibration becomes large, and the amplitude at a specific frequency may become large. Possible causes for this include, for example, the meshing error of the speed reducer used for joints and the like, and the grease viscosity and belt tension are not in an appropriate state. It is considered that all of these are in an appropriate state when the robot operates for a predetermined period and the state of the mechanical element is stabilized.

Therefore, after the initial setting is performed for the robot and the initial threshold value is set as the threshold value, the state determination unit for determining whether or not the state of the robot has shifted to the stable state and the state determination unit for determining whether the state has shifted to the stable state are determined. On condition of this, it was decided to provide a threshold value setting unit for setting a normal threshold value smaller than the initial threshold value as the threshold value.

As a result, when the state is not stable, the abnormality can be determined by the initial threshold value, and after the transition to the stable state, the abnormality can be determined by the normal threshold value smaller than the initial threshold value. Therefore, it is possible to appropriately determine the presence or absence of an abnormality according to the state of the robot, and it is possible to suppress erroneous determination.

In the second invention, after the initial setting is performed on the robot and the initial threshold value is set as the threshold value, the amplitude at the specific frequency is reduced and the state determination unit is within a predetermined range. The gist is to determine that the state of the robot has shifted to the stable state on the condition that the robot has become the stable state.

It is empirically known that the amplitude at a specific frequency decreases when the product is operated for a predetermined period after the initial setting is performed, and when the frequency shifts to a stable state, the amplitude converges within a predetermined range. Therefore, it was decided that the transition to the stable state was determined on the condition that the amplitude at the specific frequency decreased and was within the predetermined range. As a result, it can be appropriately determined that the state has changed to the stable state.

In the third invention, the state determination unit determines that the amplitude at the specific frequency is within the predetermined range on condition that the amplitude at the specific frequency is lower than the determination threshold value smaller than the normal threshold value. The gist is to do.

After the initial setting, when the product is operated for a predetermined period of time, the amplitude at a specific frequency generally tends to decrease until the stable state is reached. Therefore, it is determined that the amplitude at a specific frequency is within a predetermined range on condition that the threshold value is smaller than the normal threshold value. As a result, it can be appropriately determined that the state has changed to the stable state.

In the fourth invention, after the initial threshold value is set as the threshold value, the state determination unit determines whether or not the state has shifted to the stable state based on the average of the amplitudes at the specific frequency in a predetermined period. It is a summary.

An error may occur in the detected vibration due to a temperature change, a detection error in the vibration detection unit, or the like. Therefore, it was decided to determine whether or not the stable state was reached based on the average amplitude. As a result, it is possible to more appropriately determine whether or not the state has changed to the stable state.

In the fifth invention, the state determination unit is in the stable state on condition that the amplitude at the specific frequency changes from decrease to increase after the initial setting is performed and the initial threshold value is set as the threshold value. The gist is to determine that it has shifted to.

After the initial setting and operation for a predetermined period of time, the amplitude at a specific frequency generally does not increase until the stable state is reached. Therefore, it was decided that the transition to the stable state was made on the condition that the amplitude at a specific frequency changed from decreasing to increasing. As a result, it can be determined that the stable state has been appropriately established.

In the sixth invention, the robot is composed of a plurality of mechanical elements, and the threshold value is set for each amplitude at a specific frequency determined according to each mechanical element, and for each of the mechanical elements. It is configured to be initializeable, and when it is initialized for any of a plurality of mechanical elements, the initial threshold is set for the amplitude threshold at a specific frequency determined according to the initially set mechanical element. The state determination unit is configured to determine whether or not the robot has transitioned to the stable state for each mechanical element of the robot, and the threshold setting unit is set to the stable state. The gist is to set a normal threshold for the threshold of the amplitude at a specific frequency determined according to the mechanical element determined to have shifted.

Since the threshold value is set for each mechanical element, it is possible to specify which mechanical element has caused the abnormality. Further, the state determination unit determines whether or not the transition to the stable state has occurred for each mechanical element, and the threshold setting unit determines the amplitude at a specific frequency determined according to the mechanical element determined to have transitioned to the stable state. A normal threshold value is set for the threshold value of. Therefore, when it is necessary to initially set some of the mechanical elements constituting the robot such as parts replacement, it is not necessary to set the initial thresholds for all the thresholds. Therefore, even when some of the mechanical elements constituting the robot are initially set, an appropriate threshold value can be set for each mechanical element, and an abnormality can be appropriately determined.

In the seventh aspect of the invention, the robot has a component composed of a plurality of mechanical elements, and the threshold value setting unit responds to each mechanical element included in the component when the component of the robot is replaced. The gist is to set the initial thresholds for all the thresholds of the amplitude at the specified frequency.

The part contains multiple mechanical elements. Therefore, when a part is replaced, it is necessary to initialize all the threshold values corresponding to a plurality of mechanical elements included in the part. Therefore, when the parts of the robot are replaced, the threshold setting unit sets all the thresholds of the amplitude at the specific frequency determined according to each mechanical element included in the parts to the initial thresholds. As a result, it is possible to avoid setting only the threshold value for some mechanical elements as the initial threshold value even though all the mechanical elements contained in the part are exchanged with the replacement of the part.

Front view showing the outline of the robot. The schematic which shows the mechanical element of a joint. The figure which shows the electrical composition of a controller. A flowchart showing an abnormality determination process. (A) and (b) are diagrams showing frequency spectra. A time chart showing changes in amplitude. A flowchart showing a threshold setting process.

Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings. In this embodiment, it is embodied as an abnormality diagnostic device applied to an industrial robot that assembles a machine or the like in an assembly line of a machine assembly factory.

FIG. 1 is a front view showing an outline of the robot 10. As shown in FIG. 1, the robot 10 is a 6-axis robot having 6 joints K1 to K6. The robot 10 has a first axis J1, a second axis J2, a third axis J3, a fourth axis J4, a fifth axis J5, and a sixth axis J6 as rotation axes (joint axes) of the joints K1 to K6. There is. In the present embodiment, the robot 10 is installed at a robot installation location such as a floor so that the first axis J1 extends in the vertical direction. In the following description, it is assumed that the vertical direction in FIG. 1 indicates the vertical direction.

In the robot 10, the base 11 has a fixing portion 12 fixed to the robot installation location and a rotating portion 13 provided above the fixing portion 12. The rotating portion 13 is rotatable with respect to the fixed portion 12 with the first axis J1 extending in the vertical direction as the center of rotation. A lower arm 15 is connected to the upper end of the rotating portion 13. The lower arm 15 is rotatable with respect to the rotating portion 13 about the second axis J2 extending in the horizontal direction as a rotation center.

The upper arm 16 is connected to the tip end portion (upper end portion) of the lower arm 15. The upper arm 16 is rotatable with respect to the lower arm 15 with the third axis J3 extending in the horizontal direction as the center of rotation. The upper arm 16 has a first upper arm 16A on the proximal end side and a second upper arm 16B on the distal end side, which are divided in the longitudinal direction. Of these arms 16A and 16B, the first upper arm 16A is connected to the lower arm 15. The second upper arm 16B is rotatably connected to the first upper arm 16A with the fourth axis J4 extending in the longitudinal direction of the upper arm 16 as the center of rotation.

A wrist portion 17 is provided at the tip of the upper arm 16 (specifically, the second upper arm 16B). The wrist portion 17 is rotatably connected to the second upper arm 16B with the fifth axis J5 extending in the horizontal direction as the center of rotation. The wrist portion 17 is provided with a hand portion 18 for attaching a work, a tool, or the like. The hand portion 18 is rotatably connected to the wrist portion 17 in the twisting direction with the sixth axis J6, which is the center line thereof, as the center of rotation.

As described above, the robot 10 has a plurality of (specifically six) components (rotating portion 13, lower arm 15, first upper arm) that can be rotated around each axis J1 to J6. 16A, second upper arm 16B, wrist portion 17, hand portion 18). In this case, each of these components rotates with the rotation of the joints K1 to K6 centered on the axes J1 to J6.

Motors 21 (servo motors) are provided for each of the joints K1 to K6. By driving each of these motors 21, the joints K1 to K6 rotate (drive), and by extension, each component rotates (drives).

Next, FIG. 2 shows an outline of the motor 21 in the joint K2, and briefly describes the mechanism by which the joint K2 is rotated by driving the motor 21. FIG. 2 is a schematic configuration diagram showing the mechanical elements of the joint K2.

The motor 21 of the joint K2 is connected to the speed reducer 23 via the pulley 22. The motor 21 is connected to the lower arm 15 via the speed reducer 23. Therefore, when the motor 21 is driven, the lower arm 15 is driven via the pulley 22 and the speed reducer 23. The rotating shaft of the motor 21 is rotatably supported by the motor bearing 24. Further, the speed reducer 23 is also provided with a speed reducer bearing 25 to rotatably support the speed reducer 23. A cross roller bearing 26 is provided on the sliding portion between the speed reducer 23 and the lower arm 15 to rotatably support the lower arm 15. The motor 21, pulley 22, speed reducer 23, motor bearing 24, speed reducer bearing 25, and cross roller bearing 26 all correspond to mechanical elements constituting the robot 10.

Next, the controller 30 as an abnormality diagnosis device will be described. FIG. 3 is a diagram showing an electrical configuration of the controller 30.

As shown in FIG. 3, the robot 10 includes a controller 30 that controls various operations of the robot 10. The controller 30 is mainly composed of a well-known microcomputer having a CPU or the like, and has a storage unit 36. Various programs such as an operation program of the robot 10 are stored in the storage unit 36. The controller 30 realizes various functions related to operation control and the like of the robot 10 based on various programs stored in the storage unit 36. The various functions of the controller 30 may be realized by electronic circuits that are hardware, or at least a part of them may be realized by software, that is, processing executed on a computer.

Motors 21 provided at the joints K1 to K6 are connected to the controller 30. These motors 21 are driven based on a control signal from the controller 30. Note that, for convenience, only one motor 21 is shown in FIG.

A position detection unit 37 (encoder) that detects the rotational position of the joints K1 to K6 is connected to the controller 30. The position detection unit 37 is provided for each of the joints K1 to K6 (each motor 21), and in FIG. 3, only the position detection unit 37 of 1 is shown for convenience. Rotational position information of joints K1 to K6 is input to the controller 30 from each position detection unit 37. The controller 30 feedback-controls the drive of each motor 21 based on the input rotation position information.

A current detection unit 38 that detects the value of the current flowing through the motor 21 is connected to the controller 30. The current detection unit 38 is provided for each motor 21, and only one current detection unit 38 is shown in FIG. 3 for convenience. The current value of each motor 21 is input to the controller 30 from each current detection unit 38.

An operating device 40 for performing various operations is connected to the controller 30. The operation device 40 is composed of a well-known personal computer (terminal device), and has an operation unit 41 including a keyboard and the like, and a display unit 42 including a display and the like. The operating device 40 may be configured by a teaching pendant instead of the terminal device.

The controller 30 has, as operation modes of the robot 10, a normal operation mode in which the robot 10 (specifically, each joint K1 to K6) is normally operated, and a constant speed operation mode in which predetermined joints K1 to K6 are rotated at a constant speed. And are set. Switching to each of these modes is performed based on the operation of the operation unit 41. Specifically, when the mode switching operation is performed by the operation unit 41, a mode signal corresponding to the switching operation is input to the controller 30 from the operation unit 41 (operation device 40), and the controller 30 is in the input mode. The operation mode is switched based on the signal.

Next, the abnormality determination process for determining the abnormality of the robot 10 will be described with reference to FIG. This abnormality determination process is executed by the controller 30. In the abnormality determination process, the operation mode is switched from the normal operation mode to the constant velocity operation mode by the operation of the operation unit 41, and the start button provided on the operation unit 41 is provided under the switched constant velocity operation mode. It is started with the operation as a trigger.

As shown in FIG. 4, first, in step S21, constant velocity rotation processing is performed on each of the joints K1 to K6. In this constant-velocity rotation process, by outputting a constant-velocity drive signal to the motors 21 provided on the joints K1 to K6, the motors 21 drive the joints K1 to K6 to rotate at a constant velocity.

In step S22, based on the detection signal from the current detection unit 38 provided in each joint K1 to K6, the vibration correlation amount (waveform based on the current value) generated when each joint K1 to K6 rotates at a constant speed is calculated. To detect. More specifically, when the motor 21 rotationally drives the joints K1 to K6, the controller 30 uses the current value of each motor 21 input from each current detection unit 38 as a vibration correlation amount (to the current value) that correlates with the vibration. Detect as (based waveform). Therefore, the controller 30 has a function as a vibration detection unit 31 that detects a vibration correlation amount (waveform based on the current value) that correlates with the vibration generated when the joints K1 to K6 are rotated by the motor 21.

By the way, in the bearing members of the joints K1 to K6 such as the motor bearing 24, the reduction gear bearing 25, and the cross roller bearing 26, when the rolling surface is damaged due to flaking, foreign matter, etc., the damaged portion is removed. It is considered that vibration is generated every time the rolling element passes. Therefore, when the bearing member is deteriorated (damaged), it is considered that a large vibration is periodically generated when the joints K1 to K6 are rotated at a constant speed as described above. Further, not only the bearing member but also the mechanical elements constituting the robot 10, for example, the motor 21, the pulley 22, the speed reducer 23, and the like, when deterioration or failure occurs, the joints K1 to K6 are described above. It is considered that a large vibration is periodically generated when the robot is rotated at a constant speed.

Therefore, in step S23, the controller 30 performs frequency analysis (for example, spectrum analysis using FFT) on the vibration correlation amount at the time of constant velocity rotation detected in step S22. By this frequency analysis, the frequency spectrum of the vibration correlation amount can be obtained. 5 (a) to 5 (b) show the frequency spectrum thereof.

In FIGS. 5A to 5B, a plurality of specific frequencies (in FIG. 5, three specific frequencies f1 to f3 are exemplified for convenience) are shown on the horizontal axis. The specific frequencies f1 to f3 are determined according to the mechanical elements constituting the robot 10.

For example, the specific frequency f1 is a frequency peculiar to the cross roller bearing 26 determined based on various parameters related to the cross roller bearing 26 such as the diameter of the inner ring and the outer ring of the cross roller bearing 26 which is a bearing member and the diameter and number of rolling elements. ing. Similarly, the specific frequencies f2 and f3 are frequencies unique to the pulley 22 and the speed reducer 23, for example. Therefore, different specific frequencies exist corresponding to each mechanical element constituting the robot 10. The correspondence between the specific frequency and each mechanical element is stored in advance in the storage unit 36.

In step S24, the amplitudes V1 to V3 of the waveform at the specific frequencies f1 to f3 are specified (extracted) with reference to the frequency spectrum of the vibration. Therefore, the controller 30 has a function as a frequency analysis unit 32 that performs frequency analysis on the detected vibration correlation amount and extracts the amplitude of a specific frequency determined according to the mechanical elements constituting the robot 10. It becomes.

Then, in step S25, it is determined whether or not any of the amplitudes V1 to V3 at the specific frequencies f1 to f3 is larger than the predetermined threshold values Va to Vc.

In step S25, when the amplitudes V1 to V3 at all the specific frequencies f1 to f3 are equal to or less than the predetermined threshold values Va to Vc (in the case of FIG. 5A), the joints K1 to K6 are rotated at a constant velocity. It can be considered that a large vibration is not generated periodically. Therefore, it is determined that there is no abnormality (step S26). In this case, the abnormality determination process is terminated as it is.

On the other hand, when any of the amplitudes V1 to V3 at the specific frequencies f1 to f3 is larger than the predetermined threshold values Va to Vc (in the case of FIG. 5B), the joints K1 to K6 are rotated at a constant velocity. It can be considered that a large vibration is periodically generated in the frequency. In this case, it is determined that there is an abnormality in any of the joints K1 to K6 (step S27). Note that FIG. 5B illustrates that the amplitude V1 of the specific frequency f1 exceeds the threshold value Va of the amplitude V1 at the specific frequency f1. After step S27, the process proceeds to step S28.

In step S28, the display unit 42 of the operating device 40 is made to notify that there is an abnormality in any of the joints K1 to K6. In addition, when proceeding to step S26, the display unit 42 of the operation device 40 may be made to notify that there is no abnormality in the joints K1 to K6.

Note that the notification does not necessarily have to be performed using the display unit 42. For example, the operation device 40 may be provided with a voice output unit such as a speaker that outputs voice, and notification may be performed by the voice output from the voice output unit. Further, the operating device 40 may be provided with a light emitting unit that emits light, and the light from the light emitting unit may be used for notification.

As shown in steps S25 to S27 above, the controller 30 compares the extracted amplitude at the specific frequency with the threshold value. If the amplitude at a specific frequency is larger than the threshold value, it is determined that there is an abnormality. If it is equal to or less than the threshold value, it is determined that there is no abnormality. Therefore, the controller 30 has a function as an abnormality determination unit 33.

By the way, the amplitudes V1 to V3 at the specific frequencies f1 to f3 may change depending on the state of the robot 10 even if the robot 10 does not have an abnormality such as deterioration or failure. Specifically, as shown in FIG. 6, the amplitudes V1 to V3 may increase immediately after the robot 10 is assembled, immediately after repair, or during initial operation immediately after parts replacement. Note that FIG. 6 illustrates the amplitude V1.

As a cause of the large amplitudes V1 to V3, for example, a meshing error in a gear such as a speed reducer 23 used for a joint or the like can be considered. Further, it is considered that the grease viscosity used for the sliding portion of the cross roller bearing 26 or the like is not in an appropriate state. Further, it is conceivable that the tension of the belt used for driving and connecting the pulley 22 and the like is not in an appropriate state. It is considered that all of these become stable when the robot 10 operates for a predetermined period. That is, it is considered that the meshing error becomes an appropriate stable state due to the initial wear. Further, it is considered that the grease viscosity becomes an appropriate stable state when the grease is sufficiently agitated and the load on the sliding portion is reduced. In addition, when the belt fits (stretches), it is considered that the tension becomes an appropriate stable state.

Therefore, as shown in FIG. 6, it is empirically known that by operating the robot 10 for a predetermined period, each amplitude V1 to V3 at specific frequencies f1 to f3 gradually decreases and converges within a certain range. ing.

Therefore, in the present embodiment, the threshold values Va to Vc are configured to be changeable according to the state of the robot 10. First, a case where the state of the robot 10 is reset (initial setting) to the initial state will be described. When the initial setting is performed on the robot 10 to indicate that the state of the robot 10 is the initial state, the controller 30 inputs a signal indicating that the initial setting has been performed from the robot 10 and inputs a threshold value. Initial thresholds Sa to Sc are set as Va to Vc. The initial threshold values Sa to Sc are stored in advance in the storage unit 36 for each threshold value Va to Vc (that is, for each mechanical element).

The initial setting is performed, for example, when the robot 10 is set on the assembly line (specifically, during the test period before the start of operation of the robot 10). Further, this initial setting may be performed even when, for example, parts replacement or repair is performed on the robot 10. The initial setting of the robot 10 and the setting of the initial threshold values Sa to Sc may be set by the user operating the operation unit 41. Further, the initial setting may be performed for each mechanical element, and the initial threshold values Sa to Sc may be set for each mechanical element. Then, the initial threshold values Sa to Sc may be individually set for the threshold values for each mechanical element.

Then, the threshold setting process is executed after the initial setting is performed for the robot 10 until the normal thresholds Na to Nc are set for all the thresholds Va to Vc. The normal thresholds Na to Nc are smaller than the initial thresholds Sa to Sc, respectively. Normally, the threshold values Na to Nc are stored in advance in the storage unit 36 for each threshold value Va to Vc (that is, for each mechanical element).

Hereinafter, the threshold value setting process will be described with reference to FIG. 7. The threshold value setting process is executed by the controller 30. The threshold value setting process is executed, for example, at predetermined intervals. The execution timing of the abnormality determination process can be changed arbitrarily. For example, it may be executed in a predetermined period after the power is turned on to the robot 10.

In step S101, the constant velocity rotation process is performed on each of the joints K1 to K6 in the same manner as in step S21.

In step S102, similarly to step S22, the amount of vibration correlation generated when each joint K1 to K6 rotates at a constant speed is detected based on the detection signal from the current detection unit 38 provided in each joint K1 to K6. do.

In step S103, similarly to step S23, frequency analysis is performed on the vibration correlation amount at the time of constant velocity rotation detected in step S102. By this frequency analysis, the frequency spectrum of the vibration correlation amount can be obtained.

In step S104, similarly to step S24, the amplitudes V1 to V3 at the specific frequencies f1 to f3 are specified with reference to the frequency spectrum of the vibration.

In step S105, it is determined whether or not any of the amplitudes V1 to V3 at the specific frequencies f1 to f3 is lower than the determination value (determination threshold value) Ha to Hc. The determination values Ha to Hc are set for each specific frequency f1 to f3, that is, for each mechanical element. The determination value Ha is a determination value for determining the amplitude V1 at the specific frequency f1, the determination value Hb is the determination value for determining the amplitude V2 at the specific frequency f2, and the determination value Hc is the amplitude V3 at the specific frequency f3. It is a judgment value to be judged. The determination values Ha to Hc are stored in advance in the storage unit 36 for each threshold value Va to Vc (that is, for each mechanical element).

As shown in FIG. 6, these determination values Ha to Hc are usually set to values smaller than the threshold values Na to Nc, and are empirically determined by experiments and the like. That is, by operating the robot 10 after the initial setting and before the transition to the stable state, each amplitude V1 to V3 tends to gradually decrease if environmental factors such as temperature are not taken into consideration. .. Therefore, values smaller than the normal threshold values Na to Nc are set as the determination values Ha to Hc, and when the determination values are lower than the determination values Ha to Hc, it is determined that the stable state has been reached.

It is desirable that the determination values Ha to Hc are smaller than the normal threshold values Na to Nc in consideration of environmental factors such as temperature. Further, the stable state is a state in which the state of the robot 10 (mechanical element) can be abnormally determined without using the initial threshold value, as shown in FIG. In step S105, the controller 30 is initially set for the robot 10, and after the initial thresholds Sa to Sc are set as the thresholds Va to Vc, the state of the robot 10 does not use the initial thresholds Sa to Sc. It has a function as a state determination unit 34 for determining whether or not the state has shifted to a stable state in which an abnormality can be determined.

In step S105, when any one of the amplitudes V1 to V3 at the specific frequencies f1 to f3 is lower than the determination values Ha to Hc, it is determined that the mechanical element corresponding to the lower amplitude has shifted to the stable state. Therefore, the threshold values Na to Nc are usually set (step S106).

More specifically, when the amplitude V1 is lower than the determination value Ha, it is determined that the mechanical element corresponding to the specific frequency f1 has shifted to the stable state, and the normal threshold value Na is set for the threshold value Va of the amplitude V1 at the specific frequency f1. do. When the amplitude V2 is lower than the determination value Hb, it is determined that the mechanical element corresponding to the specific frequency f2 has shifted to the stable state, and the normal threshold value Nb is set for the threshold value Vb of the amplitude V2 at the specific frequency f2. When the amplitude V3 is lower than the determination value Hc, it is determined that the mechanical element corresponding to the specific frequency f3 has shifted to the stable state, and the normal threshold value Nc is set for the threshold value Vc of the amplitude V3 at the specific frequency f3. In step S106, the controller 30 has a function as a threshold setting unit 35 that sets normal thresholds Na to Nc as thresholds Va to Vc on condition that the state of the robot 10 has been determined to have shifted to the stable state. It will be.

When the amplitudes V1 to V3 are not lower than the determination values Ha to Hc, the initial threshold values Sa to Sc are maintained as they are for the threshold values Va to Vc of the amplitudes V1 to V3. Then, after step S106, the process proceeds to step S107.

In step S107, the display unit 42 or the like of the operation device 40 is made to notify that the stable state has been reached or that the normal threshold values Na to Nc have been set. It may inform which mechanical element has transitioned to the stable state.

On the other hand, when the amplitudes V1 to V3 at all the specific frequencies f1 to f3 are equal to or higher than the determination values Ha to Hc, it can be determined that the stable state has not been reached, so that the threshold setting process is terminated as it is. .. It should be noted that the notification that the stable state has not been reached may be notified.

According to the configuration of the present embodiment described in detail above, the following excellent effects can be obtained.

-In the frequency analysis result of the vibration correlation amount, the amplitudes V1 to V3 at the specific frequencies f1 to f3 determined according to the mechanical element change according to the state of the robot 10 even when the robot 10 is normal. In some cases. Specifically, immediately after assembling, repairing, or replacing parts of the robot 10, the vibration becomes large, and the amplitudes V1 to V3 of the specific frequencies f1 to f3 may become large. Possible causes for this include, for example, the meshing error of the speed reducers 23 used for the joints K1 to K6, the grease viscosity, and the belt tension not being in an appropriate state. It is considered that all of these are in an appropriate state when the robot 10 operates for a predetermined period and the state of the mechanical element is stabilized.

Therefore, the controller 30 determines whether or not the robot 10 has transitioned to the stable state after the initial settings have been made for the robot 10 and the initial thresholds Sa to Sc have been set as the thresholds Va to Vc. .. Then, on condition that it is determined that the state has shifted to the stable state, the normal thresholds Na to Nc smaller than the initial thresholds Sa to Sc are set as the thresholds Va to Vc.

As a result, from after the initial setting to before the transition to the stable state, the abnormality is determined by the initial thresholds Sa to Sc, and after the transition to the stable state, the normal threshold Na ~ which is smaller than the initial thresholds Sa to Sc. The abnormality can be determined by Nc. Therefore, the presence or absence of an abnormality can be appropriately determined according to the state of the robot 10, and erroneous determination can be suppressed.

-It is empirically known that the amplitudes V1 to V3 at specific frequencies f1 to f3 decrease when the operation is performed for a predetermined period after the initial setting is performed, and converge within a predetermined range when the state shifts to the stable state. Therefore, it is determined that the state has shifted to the stable state on the condition that the amplitudes V1 to V3 at the specific frequencies f1 to f3 decrease and fall within a predetermined range. More specifically, it is determined that the amplitudes V1 to V3 at the specific frequencies f1 to f3 are within a predetermined range on condition that the determination values Ha to Hc, which are smaller than the normal threshold values Na to Nc, are lower. As a result, it can be appropriately determined that the state has changed to the stable state.

-Since the threshold values Va to Vc are set for each mechanical element, it is possible to specify which mechanical element has an abnormality. Further, the controller 30 determines whether or not the transition to the stable state has occurred for each mechanical element, and the threshold values Va to Vc corresponding to the mechanical elements determined to have transitioned to the stable state are usually threshold values Na to Nc. To set. Therefore, when it is necessary to initially set some of the mechanical elements constituting the robot 10 such as parts replacement, it is not necessary to set the initial thresholds Sa to Sc for all the thresholds Va to Vc. Further, even when the initial setting is performed or needs to be performed for a part of the mechanical elements constituting the robot 10, an appropriate threshold value can be set for each mechanical element, which is appropriate. It is possible to judge an abnormality.

In the abnormality determination process and the threshold value setting process, the joints K1 to K6 were rotated at a constant speed by the motor 21. Then, the vibration generated during the constant velocity rotation was detected, and the frequency analysis was performed on the vibration during the constant velocity rotation. Here, when there is an abnormality in the mechanical element or when the joints K1 to K6 are not shifted to the stable state, it is considered that a large vibration is generated at a constant cycle when the joints K1 to K6 are rotated at a constant speed. Therefore, it is considered that the amplitude of the specific frequencies f1 to f3 tends to be large in the frequency analysis. Therefore, it is easy to preferably determine the transition between the abnormal state and the stable state.

The present invention is not limited to the above embodiment, and may be implemented as follows, for example.

In the above embodiment, the operation mode of the robot 10 is set to the constant velocity operation mode, and the vibration or the vibration correlation amount generated when the joints K1 to K6 are rotated at the constant velocity is detected and the frequency analysis is performed. You may change it. For example, frequency analysis may be performed by detecting the vibration generated when the joints K1 to K6 are rotated during the normal operation of the robot 10 (in the normal operation mode), or the amount of vibration correlation. Even in this case, if the rotation is at or near a constant velocity, the abnormality determination and the transition to the stable state can be determined based on the frequency spectrum of the vibration generated during the rotation.

In the above embodiment, based on the current value of the motor 21 detected by the current detection unit 38, the vibration correlation amount (waveform based on the current value) generated when the joints K1 to K6 are rotationally driven by the motor 21 is detected. However, the method for detecting such a vibration correlation amount is not necessarily limited to this. For example, the torque value of the motor 21 may be calculated (estimated) based on the current value of the motor 21 detected by the current detection unit 38, and the calculated torque value may be detected as the vibration correlation amount described above. In this case, frequency analysis is performed on the waveform based on the torque value as the detected vibration correlation amount.

Further, the motor 21 is subjected to feedback control (speed feedback control) based on the rotational positions of the joints K1 to K6 detected by the position detection unit 37 (encoder). Therefore, the target torque of the motor 21 may be calculated based on the target speed at the time of performing the speed feedback, and the vibration correlation amount may be detected based on the calculated target torque.

Further, a vibration sensor for detecting vibration may be provided in the joints K1 to K6, and the vibration (vibration waveform) generated when the joints K1 to K6 are rotationally driven by the vibration sensor may be detected.

In the above embodiment, the present invention is applied to a 6-axis robot having 6 joints K1 to K6, but the present invention may be applied to other articulated robots such as a 5-axis robot and a 4-axis robot. Further, the present invention may be applied to a uniaxial robot having only one joint.

In the above embodiment, the execution timing of the abnormality determination process may be arbitrarily changed. For example, it may be executed at predetermined intervals. Moreover, you may execute it all the time.

In the above embodiment, it is determined that there is an abnormality in any of the joints K1 to K6, but the location where the abnormality exists may be specified. For example, if the mechanical element corresponding to the specific frequencies f1 to f3 having the amplitudes V1 to V3 exceeding the threshold value Va to Vc is specified, the abnormal mechanical element can be specified.

In the abnormality determination process and the threshold value setting process of the above embodiment, all the joints K1 to K6 are rotated, but the joints K1 to K6 to be rotated may be set by the operation of the operation unit 41. As a result, it is possible to narrow down the target and determine whether or not the abnormality has been determined and whether or not the state has shifted to the stable state. By narrowing down the target, the frequency spectrum of vibration or vibration correlation amount is reduced, and it is possible to make a suitable judgment.

In the threshold value setting process of the above embodiment, the controller 30 may determine whether or not the transition to the stable state has occurred based on the average of the amplitudes V1 to V3 at the specific frequencies f1 to f3 in the predetermined period after the initial setting. An error may occur in the detected vibration correlation amount due to a temperature change, a detection error in the current detection unit 38, or the like. Therefore, by determining whether or not the state has shifted to the stable state based on the average of the amplitudes V1 to V3, it is possible to more appropriately determine whether or not the state has shifted to the stable state.

In the threshold value setting process of the above embodiment, the controller 30 may determine that the state has shifted to the stable state on the condition that the amplitudes V1 to V3 at the specific frequencies f1 to f3 have changed from decreasing to increasing after the initial setting. .. After the initial setting and before the transition to the stable state, the amplitudes V1 to V3 at the specific frequencies f1 to f3 generally do not increase. Therefore, it is determined that the state has shifted to the stable state on the condition that the amplitudes V1 to V3 at the specific frequencies f1 to f3 have changed from decreasing to increasing. As a result, it can be determined that the stable state has been appropriately established.

In the above embodiment, the robot 10 may have a component composed of a plurality of mechanical elements. In this case, when the parts of the robot 10 are replaced, the controller 30 may set the initial thresholds for all the thresholds of the amplitude of the specific frequency determined according to each mechanical element included in the parts. .. When a part is replaced, it is necessary to initialize all the threshold values corresponding to a plurality of mechanical elements contained in the part. Therefore, when the parts of the robot 10 are replaced, the controller 30 sets all the threshold values of the amplitude of the specific frequency determined according to each mechanical element included in the parts to the initial threshold values. As a result, it is possible to avoid setting only the threshold value for some mechanical elements as the initial threshold value even though all the mechanical elements contained in the part are exchanged with the replacement of the part. Further, when the parts are replaced, it is possible to save the trouble of initializing all the threshold values corresponding to the mechanical elements included in the parts. The parts may be input by the operation unit 41.

In the above embodiment, the controller 30 is provided in the robot 10, but may be provided independently of the robot 10. In this case, the robot 10 and the controller 30 need only be connected so as to be able to communicate with each other.

The robot 10 of the above embodiment employs joints K1 to K6 that rotate based on the drive of the motor 21, but employs joints that move linearly (reciprocating motion) based on the drive of the motor 21. May be good. In this case, it is desirable to reciprocate periodically.

10 ... Robot, 30 ... Controller, 31 ... Vibration detection unit, 32 ... Frequency analysis unit, 33 ... Abnormality determination unit, 34 ... State determination unit, 35 ... Threshold setting unit.

Claims (6)

In an abnormality diagnostic device used in a robot equipped with a motor that drives a joint,
A vibration detection unit that detects vibration generated when the joint is driven by the motor or a vibration correlation amount that correlates with the vibration.
A frequency analysis unit that performs frequency analysis on the vibration or the vibration correlation amount detected by the vibration detection unit and extracts an amplitude at a specific frequency determined according to a mechanical element constituting the robot.
The amplitude at the specific frequency extracted by the frequency analysis unit is compared with the threshold value, and if the amplitude at the specific frequency is larger than the threshold value, it is determined that there is an abnormality, and if it is less than the threshold value, there is no abnormality. Abnormality judgment unit that determines
A state in which the robot is initially set, and after the initial threshold is set as the threshold, it is determined whether or not the state of the robot has shifted to a stable state in which an abnormality can be determined without using the initial threshold. Judgment part and
A threshold setting unit for setting a normal threshold value smaller than the initial threshold value as the threshold value is provided on condition that the state determination unit determines that the state of the robot has shifted to the stable state .
The robot is composed of a plurality of mechanical elements.
The threshold value is set for each amplitude at a specific frequency determined according to each mechanical element.
It is configured so that it can be initialized for each mechanical element, and when it is initialized for any one of a plurality of mechanical elements, the amplitude at a specific frequency determined according to the initially set mechanical element. Regarding the threshold value, the initial threshold value is set,
The state determination unit is configured to determine whether or not the robot has transitioned to the stable state for each mechanical element of the robot.
The threshold value setting unit is an abnormality diagnostic device that normally sets a threshold value for an amplitude threshold value at a specific frequency determined according to a mechanical element determined to have shifted to the stable state. The state determination unit is subject to the condition that the initial setting is performed on the robot, the initial threshold value is set as the threshold value, and then the amplitude at the specific frequency is reduced to be within a predetermined range. The abnormality diagnosis device according to claim 1, wherein it is determined that the state of the robot has shifted to the stable state. The second aspect of claim 2, wherein the state determination unit determines that the amplitude at the specific frequency is within the predetermined range on condition that the amplitude at the specific frequency is lower than the determination threshold value smaller than the normal threshold value. Abnormality diagnostic device. The state determination unit determines whether or not the state has transitioned to the stable state based on the average of the amplitudes at the specific frequency in a predetermined period after the initial threshold value is set as the threshold value. The abnormality diagnostic device according to item 1. The robot has parts composed of a plurality of mechanical elements.
The threshold setting unit sets initial thresholds for all thresholds of amplitude at a specific frequency determined according to each mechanical element included in the parts when the parts of the robot are replaced . The abnormality diagnostic device according to any one of the items. In an abnormality diagnostic device used in a robot equipped with a motor that drives a joint,
A vibration detection unit that detects vibration generated when the joint is driven by the motor or a vibration correlation amount that correlates with the vibration.
A frequency analysis unit that performs frequency analysis on the vibration or the vibration correlation amount detected by the vibration detection unit and extracts an amplitude at a specific frequency determined according to a mechanical element constituting the robot.
The amplitude at the specific frequency extracted by the frequency analysis unit is compared with the threshold value, and if the amplitude at the specific frequency is larger than the threshold value, it is determined that there is an abnormality, and if it is less than the threshold value, there is no abnormality. Abnormality judgment unit that determines
A state in which the robot is initially set, and after the initial threshold is set as the threshold, it is determined whether or not the state of the robot has shifted to a stable state in which an abnormality can be determined without using the initial threshold. Judgment part and
A threshold setting unit for setting a normal threshold value smaller than the initial threshold value as the threshold value is provided on condition that the state determination unit determines that the state of the robot has shifted to the stable state.
The state determination unit determines that the stable state has been entered on the condition that the initial setting is performed, the initial threshold is set as the threshold value, and then the amplitude at the specific frequency changes from decrease to increase. Abnormality diagnostic device.

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