JPH09174482A - Defect diagnosing method for robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect abnormality of a robot driving system togetherwith an abnormal spot at an initial state regardless of the operation attitude of a robot and the magnitude of a load. SOLUTION: Moment M is determined from the moving position Pr of the articulated shaft of a robot, acceleration (a) is determined from a present speed Vr, and disturbance torque TG is determined from a torque command Tc by decreasing the moment M and acceleration torque J.a at S1-S7. An average value TG (ψ) of the disturbance torque at each position (a rotation angle) ψof the articulated shaft is determined at S8. When the average value TG (ψ) is increased to a value higher than a threshold, it is decided that abnormality occurs at the position (the rotation angle) ψ and an abnormality signal is outputted at S11-S13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fault diagnosis method for detecting a fault in a robot at an early stage.

[0002]

2. Description of the Related Art When an abnormality occurs in a drive system for each axis of a robot, this abnormality occurs in a part of the drive system and gradually increases with time, sometimes the abnormal area expands and the load increases, Finally, the drive system locks up. FIG. 2 is a diagram showing an example of a robot joint shaft that drives a robot arm as an example of a robot drive system. The output of the servo motor 1 that drives the joint shaft is input to the speed reducer 4 via the gear transmission mechanism 3. The arm 5 is driven by the output of the speed reducer 4. The reference numeral 2 is a servo motor 1
It is a pulse coder as a position / speed detector for detecting the position and speed of the servomotor attached to the. In such a drive system, when flaking occurs in the bearing of the speed reducer 4, the flaking is small at first, but if the robot is continuously driven as it is, the flaking expands and the load increases as the flaking expands. Increased,
Along with that, the driving torque also increases, and finally, a phenomenon occurs in which the driving system is locked and cannot be driven.

As a method for detecting such an abnormality in the drive system, a threshold value is set for the drive torque of a motor for driving a conventional joint shaft, and when the drive torque exceeds this threshold value, it is detected that an abnormality has occurred. The method is adopted.
However, according to this method, the drive torque varies depending on the operating posture of the robot and the weight of the work or the like held by the robot hand, and the threshold value needs to be changed each time. In addition, since the driving torque increases during acceleration or deceleration of each axis of the robot, the threshold value must be larger than the driving torque during acceleration / deceleration, and the abnormal state will increase. It is difficult to detect a drive system abnormality at an early stage.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention provides a robot failure diagnosis method capable of detecting an abnormality in a robot drive system regardless of the operating posture of a robot and the weight of a work or the like held by a robot hand. is there. Another object of the present invention is to provide a robot failure diagnosis method capable of detecting an initial abnormal state before the abnormality of the robot drive system expands.
Another object of the present invention is to provide a robot failure diagnosis method capable of easily identifying an abnormal part of a robot drive system.

[0005]

According to the present invention, a moving position of a robot joint axis and a disturbance torque applied to the joint axis are detected every predetermined period, and an average value of the disturbance torque detected at each detected moving position. Then, the average value is compared with the set threshold value, and if the average value is greater than or equal to the set threshold value, it is detected that an abnormality has occurred, whereby the robot failure is detected early.

Further, the detected disturbance torque is compared with a set threshold value, and if the detected disturbance torque is equal to or larger than the set threshold value, it is considered that an abnormality has occurred at the detection movement position, and the abnormality and the detection movement detecting the abnormality. The position is detected to diagnose the robot failure. Further, the average value and the set threshold value are compared, and if the average value is equal to or larger than the set threshold value, the abnormality is considered to have occurred at the detected movement position on the joint axis and the detected movement position where the abnormality is detected. And are detected to diagnose a robot failure. The disturbance torque is obtained by subtracting the acceleration torque obtained from the detected speed from the torque command value and further reducing the moment applied to the joint shaft at the detected movement position.

[0007]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram of a drive control system that drives each joint axis of the robot as shown in FIG.
A servo controller 11 is connected to the robot controller 10 for controlling the robot.
Drives the servo motor 1 via the servo amplifier 12. The servo controller 11 has a processor that performs processing for controlling the position, speed, and current of the servo motor, a ROM that stores a control program, and a non-volatile portion that stores setting values and various parameters. A RAM for temporarily storing data, and a register for counting the position feedback pulses from the pulse coder and detecting the absolute position of the servo motor are provided in connection with the present invention. The servo controller 11 then moves the movement command sent from the robot controller 10 and the position attached to the servo motor 1,
Based on the feedback signal from the pulse coder 2 of the speed detector, position loop processing, speed loop processing, and current loop processing are executed to control the position and speed of the servo motor 1.

It should be noted that only one axis drive control system is shown in FIG. 3, and the servomotors provided for each axis of the robot are controlled in the same manner. The configuration of this robot control system is as follows. This is the same as the conventional robot control system, and details thereof are omitted. The present invention detects the disturbance torque applied to each servo motor that drives each joint axis of the robot,
The above-mentioned abnormality of the drive system is detected, and FIG. 4 is a block diagram for obtaining this disturbance torque.

The actual velocity Vr of the servomotor 1 obtained from the velocity feedback signal from the pulse coder 2 is differentiated to obtain the acceleration, and the acceleration is multiplied by all the inertia J applied to the servomotor to obtain the acceleration torque Ta (reference numeral) Processing of the block indicated by 20). The obtained acceleration torque Ta is used as the torque command Tc to the servo motor 1 obtained by the speed loop processing of the servo controller 11.
The disturbance torque is obtained by subtracting the moment M to obtain the disturbance torque and performing filter processing (processing of the block indicated by reference numeral 21) to remove the irregular component of the disturbance.
Ask for. This processing is executed by the processor of the servo controller every predetermined sampling period to obtain the disturbance torque TG, and this disturbance torque TG is compared with the set threshold value to detect an abnormality in the robot drive system.

FIG. 1 is a flow chart of a failure diagnosis process executed by the servo controller 11 every predetermined sampling period. In addition, FIG.
It is a figure explaining the outline of operation which memorizes the average value of disturbance torque for every rotation angle of the joint axis concerned. First, the outline of the failure diagnosis process will be described with reference to FIG. FIG. 5B is a diagram showing a change in the movement position (rotation angle) of the joint axis in one cycle of the robot operation.
5A, the processor detects the absolute position of the servo motor from a register that counts the position feedback pulses from the pulse coder 2 to obtain the absolute position of the servo motor 1 every predetermined sampling period, as shown in FIG. From the absolute position of 1 of the servo motor, the rotation angle (moving position) ψ of the joint shaft driven by the servo motor is obtained. Furthermore, the disturbance torque TG is obtained by performing the above-described processing of FIG. 4 (see FIG. 5C). The average value of the detected disturbance torque and the value stored at the detected rotation angle (movement position) ψ of the memory unit that stores the average value of the disturbance torque for each rotation angle (movement position) ψ provided in the RAM. And the new average value is stored in the position of the rotation angle (moving position) ψ.

Then, at the stage where the predetermined number of sampling processes are completed, the average value of the disturbance torque for each rotation angle (moving position) ψ of the memory unit for storing the average value of the disturbance torque is compared with the set threshold value. However, if the average value of the disturbance torque exceeds the set threshold value, an abnormality signal is output and an abnormality signal is output. For example, as described above, when braking occurs in the bearing of the speed reducer, the disturbance torque increases at the braking occurrence position, and the increased disturbance torque is periodically generated as shown in FIG. 5 (c). To do. Since this increase in the disturbance torque occurs at the same rotational position of the reducer, it occurs at the same movement position (rotation angle) of the joint shaft, and naturally the movement position (rotation angle) ψ stored in the memory is Since the average value of the disturbance torque also increases, the moving position (rotation angle) ψ where this average disturbance torque exceeds the threshold position.
Can also be detected.

Next, the diagnostic processing executed by the processor of the servo controller 11 at every predetermined sampling cycle is shown in FIG.
This will be described together with the flowchart shown in FIG. First, the torque command Tc obtained by the velocity loop process, the current velocity Vr of the servo motor 1 obtained from the velocity feedback signal from the pulse coder 2, and the position feedback pulse from the pulse coder 2 are counted to store the absolute position Pr of the servo motor. The absolute position Pr of the servo motor 1 is read from (step S1). Then, the moving position (rotation angle) ψ of the joint shaft driven by the servo motor is obtained from the absolute position Pr of the servo motor 1 (step S2). Next, the moment M of the joint axis at the obtained moving position (rotation angle) ψ is obtained by the equation of motion set based on the mass distribution parameter of the robot arm or the like (step S3).

The value of the register R (Vr) that stores the speed in the previous cycle is subtracted from the current speed Vr read in step S1, and the obtained value is divided by this sampling cycle T to obtain the acceleration a (step S4). , Above register R (V
The current speed Vr is stored in r) (step S5). Next, the value (acceleration torque) obtained by multiplying the acceleration a by the inertia J applied to the joint axis is subtracted from the torque command Tc read in step S1, and the moment M obtained in step S3 is subtracted to reduce the disturbance torque before filtering. Tb
Then, the disturbance torque Tb is filtered to obtain the disturbance torque TG from which the irregular component is removed (step S
6, S7).

The moving position (rotation angle) ψ obtained in step S2 of the memory unit for storing the average value of the disturbance torque in the RAM.
From the address position corresponding to, the moving position (rotation angle)
The average value TG (ψ) of the disturbance torque up to the previous cycle in ψ is read, and from the disturbance torque TG obtained in step S7,
A new average value TG (ψ) is obtained by adding 1/2 obtained by subtracting the average value TG (ψ) to the average value TG (ψ) of the disturbance torque. That is, the following equation 1 is calculated to obtain a new average value TG (ψ) of the disturbance torque. New average value of disturbance torque TG (ψ) = average value TG (ψ) + (1/2) (TG-average value TG (ψ)) up to the previous cycle ... (1) New disturbance torque average value TG (ψ)
Is stored in the memory unit at the address position corresponding to the moving position (rotation angle) ψ (step S8). It should be noted that, in the address position corresponding to each moving position (rotation angle) ψ of the memory unit that stores the average value of the disturbance torque in the RAM, the average value in the normal state that is measured and set in advance is initially set. . When the average value of the disturbance torque is not set in advance, "0" is initially set in each address position of the memory unit, and in the process of step S8, the rotation angle ψ obtained in step S2 is corresponded. When the average value stored in the address position to be set is “0”, the disturbance torque T obtained in step S7
Make sure that G is stored in the address location. When it is not "0", the average value of the disturbance torque is obtained by performing the calculation of the above formula 1 and stored in the address position.

Next, "1" is added to the counter n and it is judged whether the value of the counter n is the set value m or more (step S9,
S10). The counter n is set to "0" by the initial setting when the robot operation is started. The set value m is determined and set so that the number of samplings is such that the rotation of each member of the drive unit such as the gear mechanism and the speed reducer becomes several cycles, preferably one cycle of robot operation or more.

When the value of the counter n is smaller than the set value m, the processing of the sampling cycle is finished. The above-described processing of steps S1 to S10 is executed for each sampling cycle, and the average value TG (ψ is calculated based on the detected disturbance torque TG at the address position of the memory corresponding to the detected movement position (rotation angle) ψ of the joint axis. ) Will be remembered. Then, in step S10, when the value of the counter n becomes equal to or larger than the set value m, the average value of the disturbance torque for each moving position (rotation angle) ψ of the joint axis stored in the memory is sequentially read out and compared with the set threshold value. (Step S11) If no threshold value is exceeded (Step S12), the counter n is set to "0" and the processing of the sampling cycle is finished (Step S14). In the process of step S14, the previously measured and set values are set for all the addresses of the memory unit that stores the average value TG (ψ) of the disturbance torque, and the average value is calculated again. Good. Further, it may be reset to "0", and in the process of step S8, the process when "0" is initially set to each address position described above may be executed.

In the processing of steps S11 and S12, if any of the disturbance torque average values TG (ψ) exceeding the set threshold is detected, an abnormal signal is output and the disturbance exceeding the threshold is detected. The moving position (rotation angle) ψ of the joint axis corresponding to the address position storing the average value TG (ψ) of the torque is displayed on the display device provided in the robot controller 10.
In the above-described embodiment, the failure diagnosis is always performed during the normal robot operation, but the failure diagnosis processing shown in FIG. 1 may be periodically executed to detect the abnormality. In this case, the angular joint shaft of the robot is driven at a low speed over the entire range of its motion, and the disturbance torque is obtained for each rotation angle.

Further, even if the average value of the disturbance torque is not necessarily obtained, when the detected disturbance torque exceeds the set threshold value, it may be detected as an abnormality at the detected rotational angle position. .

[0019]

As described above, according to the present invention, the disturbance torque is detected for each rotation angle of each joint shaft of the robot, and the abnormality of the disturbance torque is detected to detect and diagnose the failure of the rohhot drive system. The failure can be promptly detected at the initial stage of the failure occurrence without being affected by the operation posture and load of the robot. Further, since the moving position of the joint shaft in which the failure has occurred can also be detected, the failure repair work becomes easy.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a failure diagnosis process according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a drive system for one joint shaft of a robot.

FIG. 3 is a block diagram of a control system that drives and controls a joint axis of a robot.

FIG. 4 is a block diagram for obtaining a disturbance torque in the one embodiment.

FIG. 5 is an explanatory diagram of a disturbance torque detection process in the one embodiment.

[Explanation of symbols]

 1 Servo motor 2 Pulse coder 3 Gear transmission mechanism 4 Speed reducer 5 Arm

Claims (4)

[Claims] 1. A moving position of a robot joint axis and a disturbance torque applied to the joint axis are detected every predetermined period, an average value of the disturbance torque detected at each detected moving position is obtained, and the average value is set. A method of diagnosing a failure of a robot, wherein threshold values are compared, and if the average value is equal to or larger than a set threshold value, it is detected that an abnormality has occurred. 2. The movement position of the robot joint axis and the disturbance torque applied to the joint axis are detected at predetermined intervals, the detected disturbance torque is compared with a set threshold value, and the detected disturbance torque is equal to or more than the set threshold value. Then, the abnormality diagnosis method for the robot is configured to detect the abnormality and the movement position where the abnormality has occurred, assuming that the abnormality has occurred at the detected movement position. 3. A moving position of a robot joint axis and a disturbance torque applied to the joint axis are detected every predetermined period, an average value of the disturbance torque detected at each detected moving position is obtained, and the average value is set. Fault diagnosis of a robot that compares threshold values and detects an abnormality and an abnormality-occurring movement position assuming that a failure has occurred at the detected movement position on the joint axis when the average value is equal to or greater than the set threshold value. Method. 4. The disturbance torque is obtained by subtracting the acceleration torque obtained from the detected speed from the torque command value and further reducing the moment applied to the joint shaft at the detected movement position. The fault diagnosis method for a robot according to claim 3.