JP2022157982A - Abnormality detection device and abnormality detection method - Google Patents

Abstract

To quickly and surely detect an abnormality represented by cutting of a belt at each shaft of a robot with a small calculation amount.SOLUTION: An abnormality detection device for detecting an abnormality in a robot which has a vertical shaft for movement in a vertical direction and in which a motor of each shaft is controlled to drive by a servo driver comprises an abnormality detection unit 44 that detects the occurrence of an abnormality in the vertical shaft when an absolute value of a torque command value in the servo driver 45 with respect to motors 35ZA, 35ZB, and 35ZC of the vertical shaft is equal to or lower than a threshold value except an abnormality detection stop period with respect to the vertical value. The abnormality detection stop period is set in a descent acceleration period when the vertical shaft is accelerated downward by an operation command for the robot.SELECTED DRAWING: Figure 3

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detection device and an abnormality detection method for detecting an abnormality such as breakage of a driving belt in an industrial robot.

Industrial robots (hereafter referred to as robots) used for transporting workpieces are equipped with motors for driving each axis, and transmission mechanisms for transmitting the driving force of the motors to the arms of each axis. be done. The transmission mechanism is composed of, for example, a speed reducer, pulleys, and belts. When an abnormality occurs in the transmission mechanism, for example, when the belt is cut off, it is necessary to immediately stop the driving of the robot and activate the brakes so that the arms and the like of each axis do not move. Therefore, it is required to be able to quickly and reliably detect an abnormality in a transmission mechanism or the like in each axis of a robot.

In a robot, a detector such as an encoder attached to the motor detects the position and speed of the motor and feeds it back, generates a torque command for the motor based on the input position command and feedback value, and controls the motor. there is If, for example, the belt is cut in each axis of the robot, the motors are substantially in an idle state, and the torque command value is also affected. Therefore, Japanese Patent Laid-Open No. 2002-100001 discloses that the torque command signal to the motor is subjected to integral processing, and if the time until the signal becomes saturated becomes longer than a predetermined time, it is determined that the belt has been cut.

As a method for detecting a general failure of a transmission mechanism, Patent Document 2 discloses a power output on the input side based on the command angle to each drive shaft of the robot, the actual angle as the position data of the motor, and the drive current for the motor. and the power on the load side, and determine whether there is a failure in the transmission mechanism based on the ratio or difference between these powers. Patent Document 3 discloses a method for detecting an abnormality in a speed reducer provided on each axis, based on a speed command, a speed detection value, and a torque detection value, to determine whether there is an abnormality in the speed reducer. The method described in Patent Document 3 is intended to detect an abnormality in the speed reducer, and cannot be used to detect breakage of the belt.

JP-A-5-346812 JP-A-11-129186 JP 2006-102889 A

Robots used for transporting workpieces often transmit the driving force from the motor of each axis to the arm or the like of that axis via pulleys and belts, and it is required to be able to quickly and reliably detect the breakage of the belt. Focusing on the axis that moves the robot in the vertical direction, that is, the vertical axis, when the robot is stationary with respect to the vertical axis, the robot's own weight is always applied to the vertical axis. It is necessary to constantly generate holding torque to support the robot. If the belt of the vertical axis is cut here, the self-weight of the robot will not be transmitted to the motor, so the holding torque of the motor of the vertical axis will change to almost zero. On the other hand, even when the robot is accelerating in the downward direction of the vertical axis as a normal driving condition, the robot's own weight acts, so the torque command value may momentarily become close to zero. In the method described in Patent Document 1, the torque command value is near 0 because the holding torque is near 0 due to the cutting of the belt, or because the robot is descending normally. As a result, it may not be possible to properly detect vertical axis belt breakage. The method described in Patent Literature 2 uses a model to perform calculations, so it has a problem that the amount of calculation for detecting anomalies in each axis becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an abnormality detection apparatus and an abnormality detection method capable of quickly and reliably detecting an abnormality typified by belt breakage in each axis of a robot with a small amount of computation.

The abnormality detection apparatus of the present invention is an abnormality detection apparatus for detecting an abnormality in a robot having vertical axes for moving in the vertical direction and motors of each axis being driven and controlled by servo drivers. An abnormality detection unit is provided for determining that an abnormality has occurred in the vertical axis when it is detected that the absolute value of the torque command value in the servo driver for the motor is equal to or less than a threshold except for the abnormality detection stop period. The abnormality detection stop period is set during the downward acceleration period during which the vertical axis is accelerated in the downward direction by an operation command to the robot.

The motor on the vertical axis of the robot always generates a holding torque due to its characteristic of supporting a load. becomes almost 0, and correspondingly, the torque command value for the motor also becomes almost 0. Therefore, it can be determined that an abnormality has occurred in the vertical axis when the absolute value of the torque command value is equal to or less than the threshold. However, even when the vertical axis is normally accelerated in the downward direction, the torque command value may approach 0, and simply comparing the absolute value of the torque command value with the threshold value may result in erroneous detection. . Therefore, in the abnormality detection apparatus of the present invention, the abnormality detection stop period is set within the downward acceleration period of the robot, and abnormality detection is not performed during the abnormality detection stop period. Thereby, the abnormality detection device of the present invention can prevent erroneous detection.

In the abnormality detection device of the present invention, when the robot is provided with motors each having a vertical axis extending over a plurality of stages, the abnormality detection section detects the torque of the motor at the lowest stage even during the abnormality detection stop period. It may be determined that an abnormality has occurred when it is detected that the absolute value of the command value is equal to or less than the threshold. In the motor at the bottom of the multi-stage vertical shaft, the load is large, so the torque command value may not approach 0 even during the regular downward acceleration period. In such a case, constant monitoring of the torque command value of the lowermost motor makes it possible to detect belt breakage more quickly.

In the abnormality detection device of the present invention, it is desirable that the abnormality detection stop period starts after a predetermined delay time has elapsed after the start of the downward acceleration period. Immediately after the start of the downward acceleration period, the torque command value is away from 0 under normal conditions. Therefore, by delaying the start of the abnormality detection stop period, it is possible to quickly detect an abnormality immediately after the start of the downward acceleration period. be possible.

In the abnormality detection device of the present invention, the robot is, for example, a horizontal articulated robot. If the robot is a horizontal multi-joint robot, the abnormality detection unit determines whether the absolute value of the torque command value in the servo driver for the motor of the axis other than the vertical axis of the horizontal multi-joint robot is equal to or less than a threshold during execution of control to move an axis other than the vertical axis of the horizontal multi-joint robot. is detected, it is preferable to determine that an abnormality has occurred in that axis. The axes other than the vertical axis in the horizontal articulated robot are the axes that move the robot in the horizontal direction or within the horizontal plane. If, for example, the belt is cut on such an axis, the torque command value for that axis approaches 0 even though an operation command to move that axis is input, so the absolute value of the torque command value is below the threshold. By detecting that, it is possible to detect the occurrence of an abnormality in that axis.

In the abnormality detection device of the present invention, it is preferable that the abnormality detection unit detects that the absolute value of the torque command value is equal to or less than the threshold when the absolute value of the torque command value is equal to or less than the threshold over a predetermined detection duration. . By configuring in this way, it is possible to eliminate the influence of noise and the influence of variations when setting the abnormality detection stop period.

The abnormality detection method of the present invention is a method for detecting an abnormality in a robot that has vertical axes that move in the vertical direction and in which the motors of the respective axes are driven and controlled by servo drivers. is accelerated in the downward direction, and the absolute value of the torque command value in the servo driver for the motor of the vertical axis is set to the threshold value excluding the abnormality detection stop period. It is determined that an abnormality has occurred in the vertical axis when the following conditions are detected.

According to the abnormality detection method of the present invention, when the abnormality of the vertical axis is detected because the torque command value for the motor of the vertical axis approaches 0, the abnormality detection stop period is set within the downward acceleration period, and the abnormality is detected. False detection can be prevented by not performing abnormality detection during the suspension period. Further, when a control device (robot controller) for driving and controlling the robot is provided, this abnormality detection method can be realized by simple arithmetic processing in the control device without providing separate hardware. is software-controlled, it can be realized by modifying the software.

In the abnormality detection method of the present invention, when the robot is provided with motors each having a plurality of stages of vertical axes, the absolute value of the torque command value for the motor at the bottom stage is detected even during the abnormality detection stop period. is equal to or less than the threshold, it can be determined that an abnormality has occurred. As for the motor at the bottom of the vertical shaft of the multi-stage configuration, the torque command value may not approach 0 even during the regular downward acceleration period because the load is large. In such a case, constant monitoring of the torque command value of the lowermost motor makes it possible to detect belt breakage more quickly.

In the abnormality detection method of the present invention, it is preferable to start the abnormality detection stop period after a predetermined delay time has elapsed after the start of the downward acceleration period. Immediately after the start of the downward acceleration period, the torque command value is away from 0 under normal conditions. Therefore, by delaying the start of the abnormality detection stop period, it is possible to quickly detect an abnormality immediately after the start of the downward acceleration period. be possible.

In the abnormality detection method of the present invention, when the robot has a horizontal movement axis for moving the robot in the horizontal plane, a torque command in the servo driver for the motor of the horizontal movement axis is executed while the control for moving the horizontal movement axis is executed. It is preferable to determine that an abnormality has occurred in the in-horizontal-plane movement axis when it is detected that the absolute value of the value is equal to or less than the threshold. If, for example, a belt is cut on a horizontal movement axis, the torque command value of the horizontal movement axis approaches 0 even though an operation command to move the horizontal movement axis is input. By detecting that the absolute value of is equal to or less than the threshold value, it is possible to detect the occurrence of an abnormality in the in-horizontal-plane movement axis.

In the abnormality detection method of the present invention, the abnormality detection unit preferably detects that the absolute value of the torque command value is equal to or less than the threshold when the absolute value of the torque command value is equal to or less than the threshold over a predetermined detection duration. . By configuring in this way, it is possible to eliminate the influence of noise and the influence of variations when setting the abnormality detection stop period.

According to the present invention, an abnormality typified by belt breakage in each axis of a robot can be quickly and reliably detected with a small amount of calculation.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the robot to which the abnormality detection method of one Embodiment of this invention is applied, (a) is a schematic side view, (b) is a top view. It is a figure which shows the detail of a structure of a raising/lowering mechanism. 4 is a block diagram showing a configuration for operation control and abnormality detection; FIG. FIG. 4 is a waveform diagram showing changes in speed and changes in torque command value corresponding to the speed; It is a figure which expands and shows the change of a torque command value.

Next, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are diagrams showing a robot to which an abnormality detection method according to an embodiment of the present invention is applied, where (a) is a schematic side view and (b) is a plan view. The robot 10 is intended to transport a work such as a glass substrate, and is configured as a horizontal articulated robot. The robot 10 is electrically connected via a cable to a control device (robot controller) 40 which inputs an operation command for the robot 10 from the outside and drives and controls the robot 10 based on the operation command. . The control device 40 also functions as an abnormality detection device based on the present invention. For the sake of clarity, FIG. 1B does not depict the control device 40 and the cables connected thereto.

The robot 10 is configured as a so-called double hand robot having two hands 13A and 13B each holding a workpiece 60 (not shown in FIG. 1(a)). FIG. 1(a) shows a state in which the horizontal multi-joint mechanism of the robot 10 is raised. The control device 40 includes a control unit 41 for receiving an operation command and detecting the occurrence of an abnormality, and a servo driver 45 (Fig. 2) and the like. A detailed configuration of the control device 40 will be described later. Since the robot 10 of the present embodiment is used to transport the workpiece 60, the motion command is basically a movement motion command to which position the hands 13A and 13B should be moved. The control unit 41 generates an internal command including the speed for each axis of the robot 10 based on the motion command, and the drive circuit 42 actually drives the motor of each axis of the robot 10 according to the internal command for each axis. drive.

The robot 10 has a base 22 which is movable on a pair of mutually parallel rails 21 provided linearly on the floor, and a motor 35TH which is provided on the base 22 and built in the base 22. A turntable 23 that rotates in a horizontal plane around a rotating shaft 31 and an elevating mechanism 24 that is provided to stand upright with respect to the turntable 23 are provided. A cover 25 is attached to the rail 21 to cover it. The base 22 is provided with a motor 35X for horizontally moving the base 22 along the rails 21. The motor 35X horizontally moves the robot 10 together with the base 22 along the rails 21. Constructs and drives the horizontal movement mechanism. In addition, the motor 35TH and the turntable 23 constitute a rotating mechanism that rotates the lifting mechanism 24 with respect to the base 22 around the vertical rotating shaft 31, and this rotating mechanism is driven by the motor 35TH.

The elevating mechanism 24 includes a fixed portion 24A attached to the turntable 23, and a moving portion 24B vertically moved up and down with respect to the fixed portion 24A by a motor. FIG. 2 is a diagram showing the internal structure of the lifting mechanism 24. As shown in FIG. A single motor may be used to move the moving part 24B up and down with respect to the fixed part 24A. It is effective to configure This embodiment has a three-stage configuration. A lowermost Z-axis motor 35ZA is provided in the housing of the fixed part 24A. This Z-axis motor 35ZA is attached to a pulley 51A and is connected to the pulley 53C via a belt 52A and a pulley 53C which are stretched over the pulley 51A. It rotates the fixed ball screw 54A. The ball screw 54A is attached with an elevating table 55A that moves up and down as the ball screw 54A rotates. A second-stage Z-axis motor 35ZB is provided on the lifting platform 55A. The second stage Z-axis motor 35ZB similarly rotates the ball screw 54B via the pulley 51B, the belt 52B and the pulley 53B. ing. A third-stage Z-axis motor 35ZC is provided on the lift table 55B. The third-stage Z-axis motor 35ZC similarly rotates the ball screw 54C via the pulley 51C, the belt 52C, and the pulley 53C. ing. The moving part 24B of the lifting mechanism 24 is attached to the third stage lifting platform 55C.

The moving portion 24B is provided with an arm support portion 26 that holds a horizontal articulated mechanism so as to extend in the horizontal direction, and two sets of horizontal articulated mechanisms are vertically arranged at the tip of the arm support portion 26. installed. The elevating mechanism 24 is driven by motors 35ZA, 35ZB, and 35ZC to elevate the arm support section 26 with respect to the base 22 . The upper horizontal multi-joint mechanism includes a first arm 11A that is attached to the arm support portion 26 and is rotatable in the horizontal plane around the common shaft 32, and a first arm 11A that is attached to the tip of the first arm 11A and rotates in the horizontal plane around the shaft 33A. A second arm 12A rotatable inside is provided, and a hand 13A is attached to the tip of the second arm 12A. Similarly, the horizontal articulated mechanism on the lower side includes a first arm 11B that is attached to the arm support portion 26 and is rotatable in the horizontal plane around the common shaft 32, and a shaft 33B that is attached to the tip of the first arm 11B. It has a second arm 12B that can rotate in a horizontal plane around it, and a hand 13B is attached to the tip of the second arm 12B.

The hands 13A and 13B have a fork-like shape in which a plurality of rod-like members are arranged in parallel so that the plate-like workpiece 60 can be conveyed while being held in a horizontal state by being held from below. The hands 13A and 13B take out a work 60 stored in a cassette or a load lock chamber of the processing apparatus and hold it on the hands 13A and 13B, or store the held work 60 in a cassette or the like. Sometimes it advances or retreats with respect to the workpiece 60 . The advancing and retreating directions of the hands 13A and 13B coincide with the extending directions of the rod members. The width of the hands 13A and 13B in the left-right direction, ie, the direction orthogonal to the front-rear direction, is shorter than the width in the left-right direction of the workpiece 60 to be conveyed.

In this robot, the horizontal multi-joint mechanism moves the hand 13A linearly in a direction orthogonal to the extending direction of the arm support portion 26 by a link mechanism incorporated in the first arms 11A, 11B and the second arms 12A, 12B. , 13B are arranged for forward and backward movement. That is, both hands 13A and 13B move forward and backward in the same direction. Forward movement is movement in which the tips of the hands 13A and 13B move away from the central axis 32, and backward movement is movement in the direction opposite to the forward movement. The first arms 11A, 11B and the second arms 12A, 12B as a whole perform a bending motion, and in spite of that, the hands 13A, 13B are kept in a constant orientation in the horizontal plane. They are attached at the positions of the tips of the second arms 12A and 12B so as to be rotatable in the horizontal plane around the wrist shafts 34A and 34B. In the upper horizontal multi-joint mechanism, the first arm 11A and the second arm 12A are moved by driving the link mechanism by the motor 35RU provided in the arm support 26, and the hand 13A maintains its orientation. It moves in a direction perpendicular to the extending direction of the arm support portion 26 . Similarly, in the lower horizontal multi-joint mechanism, the link mechanism is driven by the motor 35RD provided on the arm support 26 to move the first arm 11B and the second arm 12B, and the hand 13B maintains its orientation. It moves in a direction perpendicular to the direction in which the arm support portion 26 extends. In this robot, the hands 13A and 13B can be moved forward and backward independently. The movement of the hands 13A, 13B forward or backward due to the bending motions of the first arms 11A, 11B and the second arms 12A, 12B is called extension and contraction of the arms.

Ultimately, the movement of the robot 10 of the industrial robot shown in FIG. Rotation with respect to the base about the axis 31 (this is the movement of the .theta.-axis or the rotation axis) and forward and backward movement of the hands 13A and 13B in the horizontal direction, i.e. telescopic movement of the arms (this is the movement of the R-axis). ), and the vertical movement of the arm support portion 26 by the lifting mechanism 24 (this is defined as the movement of the vertical axis or the Z axis). By providing two horizontal articulated mechanisms corresponding to the two hands 13A and 13B, in this robot, the R axis corresponds to the RU axis corresponding to the upper hand 13A and the lower hand 13B. RD axis. The RU axis and the RD axis are independent of each other. The X-axis, θ-axis, RU-axis and RD-axis are driven via pulleys and belts by motors 35X, 35TH, 35RU and 35RD corresponding to the respective axes. The X-axis, the θ-axis, the RU-axis, and the RD-axis are axes for moving the robot 10 in the horizontal plane, so they are movement axes in the horizontal plane. The Z-axis, which is the vertical axis, is driven by three-stage motors 35ZA, 35ZB, 35ZC via pulleys 51A, 51B, 51C, 53A, 53B, 53C and belts 52A, 52B, 52C. The robot 10 performs an operation to move only one of these axes or an operation to simultaneously move two or more axes by drive control based on an internal command from the control device 40 in response to the motion command. . When driving the Z-axis, basically the three-stage motors 35ZA, 35ZB, and 35ZC are driven simultaneously.

FIG. 3 is a block diagram showing a control system of the robot 10 for explaining motion control and abnormality detection of the robot 10 in this embodiment. As described above, the robot 10 includes three-stage motors 35ZA, 35ZB, and 35ZC for driving the lifting mechanism 24, which is a vertical axis, as motors for each axis, and the arms corresponding to the upper and lower hands 13A and 13B. Motors 35RU and 35RD that drive the horizontal movement mechanism, a motor 35X that drives the horizontal movement mechanism, and a motor 35TH that drives the rotation mechanism are provided. All of these motors are motors with encoders, and are servo-controlled by servo drivers 45 provided for each motor in a drive circuit 42 in the control device 40 . The servo driver 45 of each axis is supplied with an internal command for each axis from the control unit 41 in the control device 40, and drives the corresponding motor according to the internal command. A signal indicating a torque command value for the corresponding motor is also output from the servo driver 45 of each axis.

An operation command for causing the robot 10 to perform a desired operation is input to the control unit 41 of the control device 40 . The motion command is generated, for example, as a result of teaching the robot, and includes, for example, the start point and end point of movement of the hand 13A. The controller 41 is provided with a trajectory calculator 43 that analyzes the input motion command to generate the trajectory of the robot, calculates the movement required for each axis based on the trajectory, and generates an internal command for each axis. ing. The internal command output by the trajectory calculator 43 includes at least one of a position command and a speed command for the motor of each axis.

The control unit 41 is also provided with an abnormality detection unit 44 in order to detect an abnormality in each axis of the robot 10, particularly an abnormality such as breakage of the belt in the transmission mechanism of each axis. Command output information indicating what kind of internal command is currently being output to the servo driver 45 of each axis from the trajectory calculation unit 43 is input to the abnormality detection unit 44, and the torque command from each servo driver 45 is input to the abnormality detection unit 44. A signal indicating the value is also output. Instead of the command output information, an internal command for each servo driver 45 may be given to the abnormality detection section 44 as it is. The abnormality detection unit 44 detects the absolute values of the torque command values of the servo drivers 45 for the motors 35ZA, 35ZB, and 35ZC of the vertical axes ZA, ZB, and ZC except for the abnormality detection stop period. When it is detected that the axis is equal to or less than the threshold value, it is determined that an abnormality has occurred in that axis. Here, the abnormality detection stop period is a period set in the downward acceleration period in which the vertical axis is accelerated in the downward direction by an operation command to the robot 10. For example, a predetermined delay from the start of the downward acceleration period is set. It is a period that starts after the time has passed. As will be described later, the delay time and the length of the abnormality detection suspension period are determined in advance based on the configuration and operating conditions of the robot 10 . When the abnormality detection unit 44 learns that the descending acceleration period has started from the command output information from the trajectory calculation unit 43, the abnormality detection unit 44 recognizes the point at which the delay time has elapsed from that time as the start point of the abnormality detection stop period, and detects the abnormality. Abnormality detection based on the absolute value of the torque command value is not performed during the stop period. After the abnormality detection stop period has elapsed, the abnormality detection unit 44 resumes abnormality detection based on the absolute value of the torque command value.

The abnormality detection unit 44 also detects an abnormality with respect to the X-axis, θ-axis, RU-axis, and RD-axis, which are movement axes in the horizontal plane. In the case of a moving axis in the horizontal plane, if the torque command value for the motor of that axis is almost 0 even though the internal command to move that axis is output from the trajectory calculation unit 43, an abnormality such as belt breakage will occur. can be determined to occur. Therefore, when the command output information from the trajectory calculation unit 43 outputs an internal command to move a horizontal movement axis, the abnormality detection unit 44 detects the torque command value in the servo driver 45 for the motor of the horizontal movement axis. is detected to be equal to or less than the threshold value, it is determined that an abnormality has occurred in that in-horizontal-plane movement axis.

When it is determined that there is an abnormality in the vertical axis and when it is determined that there is an abnormality in the movement axis in the horizontal plane, the abnormality detection section 44 outputs a signal indicating that an abnormality has been detected to the outside. In order to avoid the influence of noise and the influence of variation when setting the abnormality detection stop period, the abnormality detection unit 44 determines that the absolute value of the torque command value of the corresponding shaft is equal to or less than the threshold over the predetermined detection duration. Sometimes it is preferable to detect that the absolute value of the torque command value is less than or equal to a threshold.

The detection of an abnormality in the vertical axis of the robot 10 according to this embodiment will be described in more detail below. FIG. 4 shows speed changes in the ZA, ZB, and ZC axes when the lifting mechanism 24 is lifted from a certain position, temporarily stopped, then lowered and returned to its original position, and corresponding to speed changes. FIG. 10 is a waveform diagram showing changes in the torque command value. (a) shows changes in speed, and (b) shows changes in torque command value. A solid line indicates a change along the ZA axis, a dashed line indicates a change along the ZB axis, and a dashed line indicates a change along the ZC axis. In the torque command value graph, the ascending direction and descending direction on the vertical axis indicate whether the torque command value is for rotating the motor in the ascending direction or the torque command value for rotating the motor in the descending direction. In the velocity graph, the ZB-axis velocity waveform and the ZC-axis velocity waveform overlap. In the ascending phase, the robot first accelerates and then reaches a constant speed (constant speed section), then decelerates and stops. In the descending phase, there is first an acceleration period (descending acceleration period), followed by a constant speed section, and finally a decelerating period (descending deceleration period).

In the torque command value graph, all of the ZA-axis, ZB-axis, and ZC-axis have torque command values in the upward direction over almost the entire range because the vertical axis is the axis that supports the weight of the robot 10 and the weight of the workpiece 60. This is because the motor needs to generate a holding torque even when it is not moving vertically (for example, during the "stop" period in the figure). The difference between the vertical axis and the horizontal plane movement axis is that the torque command value is not 0 even when the robot is stopped. However, as indicated by area P in the figure, the torque command values for the ZB and ZC axes approach zero during the downward acceleration period. If an abnormality such as belt breakage occurs on the vertical axis, the torque command value will approach 0. If this is detected, the presence or absence of an abnormality can be determined. If the value approaches 0, it cannot be determined that there is an abnormality based on whether or not the torque command value approaches 0. Therefore, in the present embodiment, as described above, the abnormality detection stop period is set within the downward acceleration period, and in the abnormality detection stop period, even if the torque command value approaches 0, it is not judged to be abnormal, and erroneous detection is prevented. Prevent. Abnormalities in the vertical axis can be quickly and reliably detected with a small amount of calculation. Regarding the ZA axis, which is the lowest stage, the torque command value does not approach 0 even during the downward acceleration period. This is probably because the ZA-axis has a larger load weight than the ZB-axis and ZC-axis. Therefore, as for the ZA axis, it can be determined that there is an abnormality when the torque command value approaches 0 even within the abnormality detection stop period.

Next, the detection of abnormality and the setting of the abnormality detection suspension period will be described with reference to FIG. FIG. 5 is an enlarged view of region P in FIG. In this embodiment, when the torque command value becomes a value between +a (which is the upper threshold) and -a (which is the lower threshold), with the positive constant a as the threshold, that is, When the absolute value of the torque command value becomes equal to or less than a, it is determined that the torque command value approaches 0 and an abnormality has occurred. In practice, the detection continuation time is set in consideration of the influence of noise and variations in the abnormality detection stop period, and when the absolute value of the torque command value is equal to or less than the threshold over the detection continuation time, it is determined that an abnormality has occurred. The length of the detection continuation time is, for example, sufficiently shorter than the length of the abnormality detection stop period.

As for the abnormality detection stop period, the absolute value of the torque command value is determined to be equal to or less than the threshold value during the downward acceleration period when the robot 10 is in a normal state, and that period is set as the abnormality detection stop period. In the example shown in FIG. 5, the period from elapsed time t0 to t3 is the downward acceleration period. Focusing on the torque command value of the ZC axis, this torque command value is equal to or less than the upper threshold value +a during the period from elapsed time t1 to t2. Therefore, the period from the elapsed time t1 to t2 may be set as the abnormality detection stop period. A period from the elapsed time t0 to t1 is a delay time from the start of the downward acceleration period to the start of the abnormality detection stop period. For the robot 10, once the abnormality detection stop period and the delay time are determined according to the mechanism and operating conditions, the vertical axis can be detected without erroneous detection by using the abnormality detection stop period and the delay time. Anomalies can be found quickly.

In the abnormality detection method described above, the abnormality detection stop period is determined based on the start time of the downward acceleration period. Therefore, unless it is known when the falling acceleration period starts, it is impossible to accurately detect an abnormality. The start time of the downward acceleration period may be determined, for example, by monitoring the speed command in the vertical axis and based on when the speed command value changes, or by actually measuring the rotation speed of the motor and determining the start time on the basis of the change in rotation speed. may be specified.

According to the present embodiment described above, it is possible to quickly detect the occurrence of an abnormality with a small amount of calculation without erroneously detecting the vertical axis. It is also possible to quickly find the occurrence of anomalies with a small amount of calculation for the moving axes in the horizontal plane.

The present inventors simulated the vertical axis of the robot 10 for transportation, the motor, the inertia ring attached to the rotating shaft of the motor, the belt wound around the inertia ring, and the belt provided at the tip of the belt. An experimental apparatus consisting of a weight and a weight was assembled. Then, an experiment was conducted in which a holding torque was applied to the motor using a servo driver, and the belt was instantaneously cut in that state. As a result, within about 100 milliseconds, the absolute value of the torque command value became equal to or less than the threshold, and the occurrence of abnormality could be detected. It was proved that the occurrence of an abnormality can be determined quickly by detecting that the torque command value approaches 0 with respect to the vertical axis.

DESCRIPTION OF SYMBOLS 10... Robot; 11A, 11B... 1st arm; 12A, 12B... 2nd arm; 13A, 13B... Hand; 21... Rail; 24B... Moving part; 25... Cover; 26... Arm supporting part; 31... Rotating shaft; 32... Common shaft; 35ZC motor; 40 control device; 41 control unit; 42 drive circuit; 43 trajectory calculation unit; 44 abnormality detection unit; 52A, 52B, 52C... Belt; 54A, 54B, 54C... Ball screw; 55A, 55B, 55C... Elevator; 60... Work.

Claims (10)

An anomaly detection device for detecting an anomaly in a robot having a vertical axis for vertical movement and a motor of each axis being driven and controlled by a servo driver,
With respect to the vertical axis, it is determined that an abnormality has occurred in the vertical axis when it is detected that the absolute value of the torque command value in the servo driver for the motor of the vertical axis is equal to or less than a threshold except for the abnormality detection stop period. Equipped with an abnormality detection unit that determines
The abnormality detection device, wherein the abnormality detection stop period is set within a downward acceleration period during which the vertical axis is accelerated in the downward direction by an operation command to the robot. In the robot, the vertical axis is provided with the motors provided over a plurality of stages,
With respect to the motor at the bottom, the abnormality detection unit determines that the abnormality has occurred when detecting that the absolute value of the torque command value is equal to or less than the threshold value even during the abnormality detection stop period. The abnormality detection device according to claim 1, wherein 3. The abnormality detection device according to claim 1, wherein the abnormality detection stop period starts after a predetermined delay time has elapsed after the start of the downward acceleration period. The robot is a horizontal articulated robot,
The abnormality detection unit detects that an absolute value of a torque command value of the servo driver for the motor of the axis other than the vertical axis of the horizontal articulated robot is equal to or less than the threshold value during execution of control to move the axis other than the vertical axis of the horizontal articulated robot. 4. The abnormality detection device according to any one of claims 1 to 3, wherein when an abnormality is detected, it is determined that an abnormality has occurred in the shaft. 5. The abnormality detection unit detects that the absolute value of the torque command value is equal to or less than the threshold value when the absolute value of the torque command value is equal to or less than the threshold value for a predetermined detection duration. The abnormality detection device according to any one of 1. An anomaly detection method for detecting an anomaly in a robot having a vertical axis for vertical movement and a motor of each axis being driven and controlled by a servo driver,
setting an abnormality detection stop period during a downward acceleration period in which the vertical axis is accelerated in a downward direction by an operation command to the robot;
Regarding the vertical axis, when it is detected that the absolute value of the torque command value in the servo driver for the motor of the vertical axis is equal to or less than a threshold except for the abnormality detection stop period, an abnormality has occurred in the vertical axis. An anomaly detection method that determines that When the robot is provided with the motors in which the vertical axis is provided over a plurality of stages, the absolute value of the torque command value for the motor at the bottom stage is the same as the torque command value even during the abnormality detection stop period. 7. The abnormality detection method according to claim 6, wherein it is determined that said abnormality has occurred when it is detected that it is equal to or less than a threshold. 8. The abnormality detection method according to claim 6, wherein the abnormality detection stop period is started after a predetermined delay time has elapsed after the start of the downward acceleration period. When the robot has a horizontal plane movement axis for moving the robot in the horizontal plane, absolute torque command value in the servo driver for the motor of the horizontal plane movement axis during execution of control to move the horizontal plane movement axis 9. The abnormality detection method according to any one of claims 6 to 8, wherein it is determined that an abnormality has occurred in said in-horizontal-plane movement axis when it is detected that the value is equal to or less than said threshold. 10. The method according to any one of claims 6 to 9, wherein when the absolute value of said torque command value is equal to or less than said threshold value over a predetermined detection duration, it is detected that said absolute value of said torque command value is equal to or less than said threshold value. The anomaly detection method described.

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