JP2019063884A - Abnormality diagnostic device - Google Patents

Abstract

To provide an abnormality diagnostic device which can suitably diagnose abnormality.SOLUTION: A controller 30 comprises: a vibration detection part 31 which detects a vibration correlation quantity generated when rotating a joint; a frequency analysis part 32 which performs frequency analysis for the detected vibration correlation quantity, and extracts an amplitude of a specific frequency which is decided according to a mechanical element; an abnormality determination part 33 which compares an amplitude in the extracted specific frequency with a threshold, determines that there is an abnormality when the amplitude in the specific frequency is larger than the threshold, and determines that there is no abnormality when said amplitude is the threshold or less; a state determination part 34 which determines whether a state of a robot shifts to a stable state after initial setting for the robot is performed; and a threshold setting part 35 which sets a normal threshold, which is smaller than an initial threshold, as a threshold on condition that it was determined that the state of the robot has shifted to the stable state.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an abnormality diagnosis apparatus that diagnoses an abnormality of a robot.

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

  Robots deteriorate due to the passage of time and repeated operation. For this reason, it is necessary to be able to quickly detect an abnormality. With regard to abnormality determination of a robot, there is known a method of detecting a vibration pattern when the robot is in operation and performing frequency analysis of the detected vibration pattern to determine it (see, for example, Patent Document 1). In this method, if the amplitude of the waveform at the specific frequency is greater than or equal to the threshold as a result of the frequency analysis, it is determined that the abnormality is present.

JP 2008-32477 A

  However, the inventors of the present application focused on the fact that when the threshold value is constant, the robot may be erroneously determined to be abnormal even if the robot is operating normally. In particular, there is a problem that an erroneous determination is likely to occur immediately after assembling a robot, immediately after repair, or immediately after replacing a part.

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

  In order to solve the above-mentioned problems, according to a first aspect of the present invention, in an abnormality diagnosis apparatus used for a robot including a motor for driving a joint, a vibration generated when driving the joint by the motor or a vibration correlation correlated with the vibration A vibration detection unit for detecting an amount, and frequency analysis of the vibration or the vibration correlation amount detected by the vibration detection unit to extract 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 and the frequency analysis unit is compared with the threshold, and when the amplitude at the specific frequency is larger than the threshold, it is determined that there is an abnormality and it is below the threshold In the above, an abnormality determination unit that determines that there is no abnormality, and initialization are performed on the robot, and an initial threshold is set as the threshold. A state determination unit that determines whether or not the state of the robot has shifted to a stable state where abnormality determination can be made without using the initial threshold, and the state of the robot is determined to be the stable state by the state determination unit And a threshold setting unit configured to set a normal threshold smaller than the initial threshold as the threshold, on the condition that it is determined that the shift has been made.

  The amplitude at a specific frequency determined according to the mechanical factor in the frequency analysis result of the vibration correlation amount may change depending on the state of the robot even if the robot is normal. Specifically, immediately after assembly of the robot, immediately after repair, or immediately after parts replacement, the vibration may be large, and the amplitude at a specific frequency may be large. Possible causes for this are, for example, the meshing error of the reduction gear used for joints and the like, and the grease viscosity and the tension of the belt are not in an appropriate state. In any of these, it is considered that the robot is operated for a predetermined period of time, and the mechanical element becomes stable by becoming stable.

  Therefore, after the initial setting is performed on the robot and the initial threshold is set as the threshold, it is determined that the state determination unit determines whether the state of the robot has transitioned to the stable state, and the state is transitioned to the stable state And a threshold setting unit configured to set a normal threshold smaller than the initial threshold as the threshold.

  Thus, when the stable state is not established, the abnormality is determined by the initial threshold, and after transition to the stable state, the abnormality can be determined by the normal threshold smaller than the initial threshold. Therefore, the presence or absence of abnormality can be appropriately determined according to the state of the robot, and erroneous determination can be suppressed.

  In the second invention, after the initial setting is performed on the robot and the initial threshold is set as the threshold, the state determination unit decreases the amplitude at the specific frequency to fall within a predetermined range. Under this condition, it is determined that the state of the robot has shifted to the stable state.

  After initialization, when operating for a predetermined period, it is empirically known that the amplitude at a specific frequency decreases, and when it shifts to a steady state, it converges within a predetermined range. Therefore, on the condition that the amplitude at the specific frequency decreases and is within the predetermined range, it is determined that the state has shifted to the stable state. This makes it possible to properly determine that the state has shifted to the stable state.

  In the third invention, the state determination unit determines that the amplitude at the specific frequency falls within the predetermined range on condition that the amplitude at the specific frequency falls below the determination threshold smaller than the normal threshold. To make it a gist.

  After initialization, when operating for a predetermined period of time, the amplitude at a specific frequency tends to generally decrease until the steady state is reached. Therefore, it has been determined that the amplitude at the specific frequency falls within the predetermined range on condition that the value falls below the determination threshold smaller than the normal threshold. This makes it possible to properly determine that the state has shifted to the stable state.

  In the fourth invention, after the initial threshold is set as the threshold, the state determination unit determines whether or not the transition to the stable state is made based on an average of 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 or a detection error in the vibration detection unit. Therefore, it has been determined whether or not the state has shifted to the stable state based on the average of the amplitude. Thereby, it can be judged more appropriately whether it has shifted to the stable state.

  In the fifth invention, the state determination unit performs the initial setting, and after the initial threshold is set as the threshold, the stable state is performed on the condition that the amplitude at the specific frequency has turned from an increase to a decrease. The gist is to determine that the

  After initialization, and operating for a predetermined period, the amplitude at a particular frequency generally does not rise until it transitions to a steady state. Therefore, on the condition that the amplitude at a specific frequency turns from a decrease to an increase, it is determined that the state has shifted to the stable state. Thus, it can be determined that the stable state has been appropriately reached.

  In the sixth invention, the robot is composed of a plurality of mechanical elements, the threshold is set for each amplitude at a specific frequency determined according to each mechanical element, and the mechanical elements When configured to be able to be initialized and initialized to any of a plurality of mechanical elements, the initial threshold is set to the threshold of the amplitude at a specific frequency determined according to the initialized mechanical element. The state determination unit is configured to determine whether or not the state has shifted to the stable state for each mechanical element of the robot, and the threshold setting unit sets the steady state to the stable state. The gist of the present invention is to set a threshold normally for the threshold of the amplitude at a specific frequency determined according to the mechanical element determined to be shifted.

  Since the threshold value is set for each mechanical element, it can be specified in which mechanical element an abnormality has occurred. In addition, the state determination unit determines, for each mechanical element, whether or not a transition to a stable state is made, and the threshold setting unit determines an amplitude at a specific frequency determined according to the mechanical element determined to transition to a stable state. Usually, the threshold is set. Therefore, when it is necessary to initialize some of the mechanical elements constituting the robot, such as parts replacement, it is not necessary to set the initial threshold for all the thresholds. Therefore, even when initialization is performed on some of the mechanical elements constituting the robot, an appropriate threshold can be set for each mechanical element, and an abnormality can be appropriately determined.

  In the seventh invention, the robot has a part consisting of a plurality of mechanical elements, and the threshold setting unit is adapted to each mechanical element contained in the part when the robot part is replaced. The gist of the present invention is to set all initial threshold values for the threshold value of the amplitude at the specific frequency to be determined.

  The part contains a plurality of mechanical elements. For this reason, when replacing a part, it is necessary to initialize all the thresholds corresponding to a plurality of mechanical elements included in the part. Therefore, when parts of the robot are replaced, the threshold setting unit sets all the threshold values of the amplitude at the specific frequency determined according to the mechanical elements included in the parts as initial threshold values. This makes it possible to avoid that only the threshold for some mechanical elements is set to the initial threshold, even though all mechanical elements included in the part have been exchanged along with the exchange of parts.

The front view which shows the outline | summary of a robot. Schematic which shows the mechanical element of a joint. The figure which shows the electric constitution of a controller. 5 is a flowchart showing an abnormality determination process. (A) And (b) is a figure which shows a frequency spectrum. Time chart showing changes in amplitude. The flowchart which shows threshold setting processing.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The present embodiment is embodied as an abnormality diagnosis apparatus applied to an industrial robot that assembles a machine and 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 six-axis robot having six 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 place such as a floor so that the first axis J1 extends in the vertical direction. In the following description, the vertical direction in FIG. 1 indicates the vertical direction.

  In the robot 10, the base 11 has a fixed portion 12 fixed to the robot installation place and a rotating portion 13 provided above the fixed portion 12. The pivoting portion 13 is pivotable relative to the fixed portion 12 about a first axis J1 extending in the vertical direction as a pivoting center. A lower arm 15 is connected to an upper end portion of the rotating portion 13. The lower arm 15 is pivotable relative to the pivoting portion 13 about a second axis J2 extending in the horizontal direction.

  An upper arm 16 is connected to a distal end (upper end) of the lower arm 15. The upper arm 16 is pivotable relative to the lower arm 15 about a third axis J3 extending in the horizontal direction. The upper arm 16 has a proximal first upper arm 16A and a distal second upper arm 16B divided in the longitudinal direction. Of the 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 a fourth axis J4 extending in the longitudinal direction of the upper arm 16 as a rotation center.

  A wrist 17 is provided at the tip of the upper arm 16 (specifically, the second upper arm 16B). The wrist portion 17 is rotatably coupled to the second upper arm 16B about a fifth axis J5 extending in the horizontal direction. 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 coupled in a twisting direction with respect to the wrist portion 17 with a sixth axis J6 as a center line thereof as a rotation center.

  As described above, the robot 10 has a plurality of (specifically, six) components (the pivoting portion 13, the lower arm 15, and the first upper arm) which can be pivoted about the axes J1 to J6. 16A, second upper arm 16B, wrist 17, and hand 18). In this case, these constituent elements respectively rotate with the rotation of the joints K1 to K6 around the axes J1 to J6.

  A motor 21 (servo motor) is provided at each of the joints K1 to K6. By driving the respective motors 21, the joints K1 to K6 rotate (drive), and thus the respective components rotate (drive).

  Next, FIG. 2 shows an outline of the motor 21 at the joint K2, and a mechanism for rotating the joint K2 by driving the motor 21 will be briefly described. FIG. 2 is a schematic block diagram showing mechanical elements of the joint K2.

  The motor 21 of the joint K2 is connected to the reduction gear 23 via the pulley 22. The motor 21 is connected to the lower arm 15 via the reduction gear 23. Therefore, when the motor 21 is driven, the lower arm 15 is driven via the pulley 22 and the reduction gear 23. The rotation shaft of the motor 21 is rotatably supported by a motor bearing 24. Further, the reduction gear 23 is also provided with a reduction gear bearing 25 and rotatably supports the reduction gear 23. In addition, a cross roller bearing 26 is provided on the sliding portion between the reduction gear 23 and the lower arm 15, and rotatably supports the lower arm 15. The motor 21, the pulley 22, the reduction gear 23, the motor bearing 24, the reduction gear bearing 25, and the 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.

  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 configured by a known microcomputer having a CPU and the like, and has a storage unit 36. The storage unit 36 stores various programs such as an operation program of the robot 10. The controller 30 realizes various functions related to the operation control 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 an electronic circuit that is hardware, or at least a part may be realized by software, that is, a process executed on a computer.

  The controller 30 is connected to a motor 21 provided at each of the joints K1 to K6. The motors 21 are driven based on control signals from the controller 30. In FIG. 3, only one motor 21 is illustrated for the sake of convenience.

  The controller 30 is connected to a position detection unit 37 (encoder) that detects rotational positions of the joints K1 to K6. The position detection unit 37 is provided for each of the joints K1 to K6 (each motor 21), and only one position detection unit 37 is illustrated in FIG. 3 for convenience. The rotational position information of the joints K1 to K6 is input to the controller 30 from each position detection unit 37. The controller 30 performs feedback control of the drive of each motor 21 based on the input rotational position information.

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

  The controller 30 is connected with an operating device 40 for performing various operations. The operation device 40 is configured by a known personal computer (terminal device), and includes an operation unit 41 formed of a keyboard or the like and a display unit 42 formed of a display or the like. The operating device 40 may be configured by a teaching pendant instead of the terminal device.

  The controller 30 has a normal operation mode in which the robot 10 (specifically, each of the joints K1 to K6) is operated as an operation mode of the robot 10, and an equal speed operation mode in which predetermined joints K1 to K6 are rotated at constant speed. And is set. The switching to 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 from the operation unit 41 (the operating device 40) to the controller 30, and the controller 30 receives the mode. The operation mode is switched based on the signal.

  Next, an abnormality determination process for determining an abnormality of the robot 10 will be described based on FIG. The abnormality determination process is performed by the controller 30. In the abnormality determination processing, 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 under the switched constant velocity operation mode Triggered by being operated.

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

  In step S22, the vibration correlation amount (waveform based on the current value) generated when each joint K1 to K6 rotates at the same speed based on the detection signal from the current detection unit 38 provided for each joint K1 to K6 To detect. More specifically, when the controller 30 rotationally drives the joints K1 to K6 by the motor 21, a vibration correlation amount (current value) correlating the current value of each motor 21 input from each current detection unit 38 with vibration is used. Detected as a waveform based on Therefore, the controller 30 has a function as a vibration detection unit 31 that detects a vibration correlation amount (waveform based on a current value) that correlates to 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, if the rolling surface is damaged due to flaking or foreign matter mixing, the damaged portion is It is considered that vibration occurs every time the rolling elements pass. Therefore, when deterioration (scratching) occurs in the bearing member, it is considered that large vibrations occur periodically when the joints K1 to K6 are rotated at the same speed as described above. Further, not only the bearing members but also the mechanical elements constituting the robot 10, for example, the motor 21, the pulley 22, the reduction gear 23, etc., cause deterioration or failure of the joints K1-K6. When rotating at a constant speed, large vibrations are considered to occur periodically.

  Therefore, in step S23, the controller 30 performs frequency analysis (for example, spectrum analysis using FFT) on the vibration correlation amount during constant velocity rotation detected in step S22. By this frequency analysis, a frequency spectrum of the above-mentioned vibration correlation amount is obtained. The frequency spectrum is shown to Fig.5 (a)-FIG.5 (b).

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

  For example, the specific frequency f1 is a frequency unique to the cross roller bearing 26 determined based on various parameters related to the cross roller bearing 26, such as the diameters of the inner and outer rings in the cross roller bearing 26 which is a bearing member, the diameter and the number of rolling elements. ing. Similarly, the specific frequencies f2 and f3 are, for example, frequencies unique to the pulley 22 and the reduction gear 23. Therefore, different specific frequencies exist corresponding to the respective mechanical elements 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 the frequency analysis unit 32 which performs frequency analysis on the detected vibration correlation amount and extracts the amplitude of the specific frequency determined according to the mechanical element constituting the robot 10. It becomes.

  Then, in step S25, it is determined whether any one of the amplitudes V1 to V3 at the specific frequencies f1 to f3 is larger than predetermined threshold values Va to Vc.

  In step S25, when the amplitudes V1 to V3 at all the specific frequencies f1 to f3 are respectively equal to or less than predetermined threshold values Va to Vc (in the case of FIG. 5A), during constant velocity rotation of the joints K1 to K6, It can be considered that large vibrations do not occur periodically. Therefore, it is determined that there is no abnormality (step S26). In this case, the abnormality determination processing is ended 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 thresholds Va to Vc (in the case of FIG. 5B), the constant speed rotation of the joints K1 to K6 It can be regarded that a large vibration is generated periodically. In this case, it is determined that there is an abnormality in any of the joints K1 to K6 (step S27). 5B shows that the amplitude V1 of the specific frequency f1 exceeds the threshold 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 controller device 40 is notified that there is an abnormality in any of the joints K1 to K6. When the process proceeds to step S26, notification that there is no abnormality in the joints K1 to K6 may be performed on the display unit 42 of the controller device 40.

  The notification does not necessarily have to be performed using the display unit 42. For example, an audio output unit such as a speaker for outputting an audio may be provided to the operation device 40, and notification may be performed by the audio output from the audio output unit. In addition, a light emitting unit that emits light may be provided in the operation device 40, and notification may be performed by the light from the light emitting unit.

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

  Incidentally, the amplitudes V1 to V3 at the specific frequencies f1 to f3 may change depending on the state of the robot 10 even if no abnormality such as deterioration or failure occurs in the robot 10. Specifically, as shown in FIG. 6, the amplitudes V1 to V3 may become large immediately after the assembly of the robot 10, immediately after the repair, and immediately after the component replacement at the time of initial operation. In FIG. 6, the amplitude V1 is illustrated.

  As a cause of the increase in the amplitudes V1 to V3, for example, a meshing error in a gear such as the reduction gear 23 used for a joint or the like can be considered. In addition, it is conceivable that the grease viscosity used for the sliding portion such as the cross roller bearing 26 is not in an appropriate state. Further, it is conceivable that the tension of the belt used to drive and connect the pulley 22 etc. is not in a proper state. All of these are considered to be stable when the robot 10 is operated for a predetermined period. That is, the meshing error is considered to be in an appropriate stable state by the initial wear. In addition, it is considered that the grease viscosity is properly stabilized by sufficiently advancing the stirring of the grease and reducing the load on the sliding portion. In addition, it is considered that the tension is properly stabilized when the belt is fitted (stretched).

  For this reason, as shown in FIG. 6, it is empirically known that the amplitudes V1 to V3 at the specific frequencies f1 to f3 gradually decrease and converge within a certain range by operating the robot 10 for a predetermined period. ing.

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

  The initial setting is performed, for example, when the robot 10 is set to the assembly line (specifically, during a test period before the start of operation of the robot 10, and the like). Also, this initial setting may be performed, for example, when parts are replaced or repaired with respect to the robot 10. The initial setting of the robot 10 and the setting of the initial thresholds Sa to Sc may be set by the user operating the operation unit 41. In addition, initial setting may be performed for each mechanical element, and initial threshold values Sa to Sc may be set for each mechanical element. Then, initial threshold values Sa to Sc may be set individually for the threshold value of each mechanical element.

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

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

  In step S101, as in step S21, constant speed rotation processing is performed on each of the joints K1 to K6.

  In step S102, as in step S22, based on the detection signals from the current detection units 38 provided in the joints K1 to K6, the vibration correlation amount generated when the joints K1 to K6 rotate at the same speed is detected. Do.

  In step S103, as in step S23, frequency analysis is performed on the amount of vibration correlation during constant velocity rotation detected in step S102. By this frequency analysis, a frequency spectrum of the above-mentioned vibration correlation amount is obtained.

  In step S104, as in 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 any one of the amplitudes V1 to V3 at the specific frequencies f1 to f3 falls below the determination value (the determination threshold) Ha to Hc. The determination values Ha to Hc are set for each of the specific frequencies 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 a determination value for determining the amplitude V2 at the specific frequency f2, and the determination value Hc is an amplitude V3 at the specific frequency f3. It is a judgment value to judge. The determination values Ha to Hc are stored in advance in the storage unit 36 for each of the thresholds Va to Vc (that is, for each mechanical element).

  As shown in FIG. 6, these determination values Ha to Hc are set to values smaller than the normal thresholds Na to Nc, respectively, and are determined empirically by experiment or the like. That is, by operating the robot 10 after transition to the stable state after initialization, each amplitude V1 to V3 tends to decrease when 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 below the determination values Ha to Hc, it is determined to shift to the stable state.

  It is desirable that the determination values Ha to Hc be smaller than the normal thresholds Na to Nc in consideration of environmental factors such as temperature. Further, as shown in FIG. 6, the stable state is a state in which the state of the robot 10 (mechanical element) can be determined as abnormal without using the initial threshold. After the controller 30 performs initial setting on the robot 10 and sets the initial thresholds Sa to Sc as the thresholds Va to Vc in this step S105, the state of the robot 10 does not use the initial thresholds Sa to Sc. It has a function as the state determination unit 34 that determines whether or not a transition has been made to a stable state in which an abnormality determination can be made.

  In step S105, when any one of the amplitudes V1 to V3 at the specific frequencies f1 to f3 falls below the determination value Ha to Hc, it is determined that the mechanical element corresponding to the amplitude below the transitioned to the stable state Since it can be done, the normal threshold values Na to Nc are set (step S106).

  More specifically, when the amplitude V1 falls below 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 threshold value Na for the threshold Va of the amplitude V1 at the specific frequency f1 is usually set Do. When the amplitude V2 falls below 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 Nb is set for the threshold Vb of the amplitude V2 at the specific frequency f2. When the amplitude V3 falls below 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 threshold value Nc is usually set for the threshold Vc of the amplitude V3 at the specific frequency f3. The controller 30 has a function as the threshold setting unit 35 that sets the normal thresholds Na to Nc as the thresholds Va to Vc under the condition that it is determined that the state of the robot 10 has shifted to the stable state in step S106. It will be.

  When the amplitudes V1 to V3 do not fall below the determination values Ha to Hc, the initial thresholds Sa to Sc are maintained as they are for the thresholds 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 controller device 40 performs notification of transition to the stable state or notification that the normal thresholds Na to Nc have been set. It may be informed which mechanical element has shifted to the stable state.

  On the other hand, if the amplitudes V1 to V3 at all the specific frequencies f1 to f3 are equal to or greater than the determination values Ha to Hc, respectively, it can be determined that the state has not shifted to the stable state. . In addition, it may be notified that it has not shifted to the stable state.

  According to the configuration of the embodiment described 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 elements change according to the state of the robot 10 even if the robot 10 is normal. There is a case. Specifically, immediately after assembly of the robot 10, immediately after repair, or immediately after parts replacement, the vibration may be large, and the amplitudes V1 to V3 of the specific frequencies f1 to f3 may be large. As this cause, for example, the meshing error of the reduction gear 23 used for the joints K1 to K6 or the like, the grease viscosity and the tension of the belt may not be appropriate. In any of these, it is considered that the robot 10 is operated for a predetermined period, and the mechanical element becomes stable by becoming stable.

  Therefore, after the controller 30 performs initial setting on the robot 10 and sets the initial thresholds Sa to Sc as the thresholds Va to Vc, the controller 30 determines whether the robot 10 has shifted to the stable state. . Then, on the condition that it is determined that the state has shifted to the stable state, normal thresholds Na to Nc smaller than the initial thresholds Sa to Sc are set as the thresholds Va to Vc.

  Thus, from the initial setting to before the transition to the stable state, an abnormality is determined by the initial thresholds Sa to Sc, and after the transition to the stable state, the normal threshold Na to smaller than the initial thresholds Sa to Sc An abnormality can be determined by Nc. Therefore, the presence or absence of 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 the specific frequencies f1 to f3 decrease when the operation is performed for a predetermined period after the initial setting is performed, and converges within a predetermined range when the stable state is entered. Therefore, on the condition that the amplitudes V1 to V3 at the specific frequencies f1 to f3 decrease and fall within the predetermined range, it is determined that the state is shifted to the stable state. More specifically, it was determined that the amplitudes V1 to V3 at the specific frequencies f1 to f3 fall within the predetermined range on condition that the determination values Ha to Hc smaller than the normal threshold values Na to Nc are below. This makes it possible to properly determine that the state has shifted to the stable state.

  -Since threshold value Va-Vc are set up for every mechanical element, it can be specified with which mechanical element abnormality occurred. Further, the controller 30 determines whether or not the mechanical state has shifted to the stable state for each mechanical element, and the threshold values Va to Vc corresponding to the mechanical elements determined to have shifted to the stable state are generally threshold Na to Nc. Set Therefore, when it is necessary to initialize 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. In addition, even when initialization is performed for some of the mechanical elements that make up the robot 10, or even when it needs to be performed, an appropriate threshold can be set for each mechanical element, which is appropriate. Can determine the abnormality.

  In the abnormality determination processing and the threshold setting processing, the joints K1 to K6 are rotated at the same speed by the motor 21. And the vibration which generate | occur | produces in the case of the constant velocity rotation was detected, and frequency analysis was performed about the vibration in the case of the constant velocity rotation. Here, when there is an abnormality in the mechanical element or when it does not shift to the stable state, it is considered that when the joints K1 to K6 are rotated at a constant speed, large vibrations occur at a constant cycle. Therefore, in frequency analysis, it is considered that the amplitudes of the specific frequencies f1 to f3 tend to be large. Therefore, it is easy to determine the transition of the abnormal state and the stable state suitably.

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

  In the above embodiment, the operation mode of the robot 10 is set to the constant velocity operation mode, and the frequency analysis is performed by detecting the vibration or vibration correlation amount generated when rotating the joints K1 to K6 at the same velocity. You may change it. For example, frequency analysis may be performed by detecting a vibration or a vibration correlation amount generated when rotating the joints K1 to K6 during normal operation of the robot 10 (normal operation mode). Also in this case, if the rotation is at or near constant speed, it is possible to determine the abnormality determination and the transition to the stable state 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 rotationally driving the joints K1 to K6 by the motor 21 is detected. However, the method of detecting such 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 above-mentioned vibration correlation amount. In this case, frequency analysis is performed on the waveform based on the torque value as the detected vibration correlation amount.

  Further, in the motor 21, feedback control (speed feedback control) is performed 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 the speed feedback, and the above-mentioned vibration correlation amount may be detected based on the calculated target torque.

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

  Although the present invention is applied to a six-axis robot having six joints K1 to K6 in the above embodiment, the present invention may be applied to other articulated robots such as a five-axis robot and a four-axis robot. Also, the present invention may be applied to a single-axis 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 performed every predetermined cycle. Also, it may be always executed.

  In the embodiment described above, it is determined that there is an abnormality in any of the joints K1 to K6, but a portion where an abnormality exists may be specified. For example, if mechanical elements corresponding to specific frequencies f1 to f3 having amplitudes V1 to V3 exceeding thresholds Va to Vc are identified, mechanical elements having an abnormality can be identified.

  Although all the joints K1 to K6 are rotated in the abnormality determination process and the threshold value setting process of the embodiment, the joints K1 to K6 to be rotated may be set by the operation of the operation unit 41. Thereby, it is possible to narrow down the target, and to determine whether or not the transition to the abnormality determination and the stable state is made. By narrowing the target, the frequency spectrum of the vibration or vibration correlation amount decreases and can be suitably determined.

  In the threshold setting process of the above embodiment, the controller 30 may determine whether or not the state has shifted to the stable state based on the average of the amplitudes V1 to V3 at the specific frequencies f1 to f3 in a 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, it is possible to more appropriately determine whether or not the transition to the stable state is made by determining whether or not the transition to the stable state is made based on the average of the amplitudes V1 to V3.

  In the threshold setting process of the above embodiment, after initial setting, 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 a decrease to an increase. . The amplitudes V1 to V3 at the specific frequencies f1 to f3 generally do not rise until the transition to the stable state after the initialization. Therefore, on the condition that the amplitudes V1 to V3 at the specific frequencies f1 to f3 have changed from a decrease to an increase, it is determined that the stable state is entered. Thus, it can be determined that the stable state has been appropriately reached.

  In the embodiment described above, the robot 10 may have a part composed of a plurality of mechanical elements. In this case, when parts of the robot 10 are replaced, the controller 30 may set initial threshold values for all the threshold values of the amplitude of the specific frequency determined according to the mechanical elements included in the parts. . When replacing a part, it is necessary to initialize all thresholds corresponding to a plurality of mechanical elements included 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 the mechanical elements included in the parts to the initial threshold values. This makes it possible to avoid that only the threshold for some mechanical elements is set to the initial threshold, even though all mechanical elements included in the part have been exchanged along with the exchange of parts. In addition, when 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 input of the component may be performed by the operation unit 41.

  Although the controller 30 is provided to the robot 10 in the above embodiment, the controller 30 may be provided independently of the robot 10. In this case, the robot 10 and the controller 30 may be connected communicably.

  The robot 10 according to the above embodiment adopts the joints K1 to K6 that rotate based on the drive of the motor 21. However, based on the drive of the motor 21, a joint that moves linearly (reciprocates) is adopted It is also good. In this case, it is desirable to reciprocate periodically.

  DESCRIPTION OF SYMBOLS 10 ... Robot, 30 ... Controller, 31 ... Vibration detection part, 32 ... Frequency analysis part, 33 ... Abnormality determination part, 34 ... State determination part, 35 ... Threshold value setting part.

Claims (7)

In an abnormality diagnosis apparatus used for a robot including a motor for driving a joint,
A vibration detection unit that detects a vibration generated when the joint is driven by the motor or a vibration correlation amount correlated with the vibration;
A frequency analysis unit which 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 a threshold, and if the amplitude at the specific frequency is larger than the threshold, it is determined that there is an abnormality, and if it is less than the threshold, no abnormality An abnormality determination unit that determines that
A state where it is determined whether or not the state of the robot has shifted to a stable state where abnormality determination can be made without using the initial threshold after the initial setting is performed on the robot and the initial threshold is set as the threshold. A judgment unit,
And a threshold setting unit configured to set a normal threshold smaller than the initial threshold as the threshold on condition that the state determination unit determines that the state of the robot has shifted to the stable state. .   The state determination unit performs the initial setting on the robot, sets an initial threshold as the threshold, and then reduces the amplitude at the specific frequency 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 state determination unit according to claim 2, wherein the amplitude at the specific frequency falls within the predetermined range on the condition that the amplitude at the specific frequency falls below a determination threshold smaller than the normal threshold. Abnormality diagnosis device.   4. The state determination unit according to claim 2, wherein after the initial threshold value is set as the threshold value, the state determination unit determines whether or not transition to the stable state is made based on an average of amplitudes at the specific frequency in a predetermined period. The abnormality diagnosis device according to any one of the above.   The state determination unit determines that transition to the stable state is performed on the condition that the amplitude at the specific frequency turns from increase to decrease after the initial setting is performed and the initial threshold is set as the threshold. The abnormality diagnosis device according to claim 1. The robot is composed of a plurality of mechanical elements,
The threshold is set for each amplitude at a specific frequency determined according to each mechanical element,
The mechanical elements are configured to be able to be initialized, and when initialized for any of a plurality of mechanical elements, the amplitude at a specific frequency determined according to the initialized mechanical elements An initial threshold is set for the threshold, and
The state determination unit is configured to determine whether or not transition to the stable state is performed for each mechanical element of the robot.
The threshold setting unit generally sets a threshold for an amplitude threshold at a specific frequency determined according to a mechanical element determined to be shifted to the stable state. Abnormality diagnosis device. The robot has parts consisting of a plurality of mechanical elements,
The said threshold value setting part sets an initial threshold value all about the threshold value of the amplitude in the specific frequency defined according to each mechanical element contained in the said components, when the components of the said robot are replaced | exchanged. Abnormality diagnosis device.

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