JPS6224305A - Method for detecting servo abnormality of industrial robot - Google Patents

Abstract

PURPOSE:To detect the servo abnormality with high reliability by deciding the servo abnormality when the absolute value of the deviation between the command value and the present value of a drive source exceeds both the reference value and time of the deviation accordant with the relevant action mode. CONSTITUTION:When the servo control is normal, the command value (g) is fetched by a command means 12 together with the present value (d) of the position of an actuator 13 fetched by a position detector 14. While a subtractor calculates the absolute value ¦g-d¦ of the deviation E. Then it is decided whether the deviation absolute value E is larger or not than the servo abnormality detecting constant, i.e., the deviation reference value accordant with the action mode. If the value E is larger than the detecting constant, the time during which the value E last is counted. Then it is decided whether this counted time is larger or not than the servo abnormality detecting constant tR of time, i.e., the time reference value accordant with the action mode. If the constant tR is larger than the reference value, the emergency stoppage of the robot main body, the cut-off of the power supply to a servo control circuit, etc. are carried out by the servo abnormality signal. At the same time, the abnormality is displayed by the servo abnormality processing. Then the information on the servo abnormality is informed to an operator.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a servo-controlled industrial robot.
The present invention relates to a method for detecting abnormal operation of a robot body.

[Background of the invention]

In industrial robots, in order to improve reliability and safety, various methods for detecting abnormal movements of the robot body have been proposed and put into practical use.

For example, Japanese Patent Laid-Open No. 51-38982 discloses that when a movable part is positioned and stopped, an abnormality is detected when a deviation of a certain value or more occurs between the target value and the actual stopped position. Alternatively, when the movable part moves to a target value, there is a device that monitors the time taken to reach the target value and detects an abnormality when a predetermined time elapses during the movement.

In the former case, even if a deviation of a certain value or more momentarily occurs due to an external force, an abnormality is detected, so there is a risk that the working efficiency of the robot will decrease. In the latter, an abnormality cannot be detected until a predetermined period of time has elapsed, so if an abnormality occurs within a predetermined period of time, the abnormality cannot be detected immediately, resulting in poor responsiveness.

Moreover, during manual operation such as teaching, it is difficult to predict the time required to reach the target value, and if a predetermined time elapses during manual operation, there is a risk that an abnormality will be detected unnecessarily.

By the way, since general industrial robots are servo-controlled, the drive source follows the command value with a certain time delay, so a tracking error, ie, deviation, occurs between the command value and the current value of the drive source. This deviation becomes especially large when there is a sudden change in the command value, that is, when the drive source suddenly accelerates or decelerates.
Therefore, there is a wide range of deviation between the stop of the drive source, low speed, and high speed.

Therefore, in consideration of this point, in order to eliminate the above-mentioned problem, a reference value is set in advance for the deviation between the command value and the current value, and the absolute value of the deviation between the command value and the current value is It can be easily inferred that an abnormality is detected when the deviation exceeds the reference value and continues for a certain reference time.

However, in such a case, the reference value of the deviation must be set in a wide range so that it can be applied even at high speeds. Inviting danger and reducing safety.

On the other hand, if the range of the deviation reference value is reduced, safety can be improved, but since abnormalities occur frequently at high speeds, reliability is extremely reduced.

In order to solve this problem, it is necessary to manufacture a device that produces only a certain amount of deviation or less regardless of differences in operating conditions, but in that case, the capacity and rigidity of the actuator as a driving source must be The actuator must be made as large as necessary, or requires complicated control so that the actuator can be rapidly accelerated or decelerated, which poses drawbacks in terms of performance and cost.

[Purpose of the invention]

In view of the above-mentioned circumstances, an object of the present invention is to be able to detect an abnormality according to the operation mode of the robot, and to quickly detect an abnormality even within the travel time to a target value.
To provide an abnormality detection method for an industrial robot that does not needlessly detect an abnormality when an external force is momentarily applied, has excellent reliability and safety, and is suitable for actual work contents.

[Summary of the invention]

In order to achieve the above object, the present invention provides a system in which the operating mode of an industrial robot is set to a stopped state when the power is turned on.

Focusing on the fact that it can be roughly divided into three states: manual operation state such as teaching, and automatic operation state such as playback, we set the deviation reference value and time reference value in advance according to each of the three operation modes. I'll keep it.

When the drive source is controlled in any operation mode, the absolute value of the deviation between the command value for the drive source and the current value of the drive source is the deviation reference value and time reference according to that operation mode. When both values are exceeded, it is considered a servo error.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows an industrial robot for carrying out the method of the invention. This industrial robot is broadly divided into a robot body 1 and a control device 2.

The robot main body 1 is, for example, a multi-joint type welding robot, and includes a traveling table 3. Pillar 4. It includes movable parts consisting of an upper arm 5, a forearm 61, and a wrist 7, and a drive source for driving these parts. The control device 2 includes an operation section 8 for operating the robot body 1, a display 9 for displaying the operating status of the robot body 1, and a portable operation device having substantially the same functions as the operation section 8. 10. Operation unit 10
as well as .

□ 8 is configured to be able to turn on/off and start/stop the servo power source for the drive source of the robot body 1.

In addition, the control device 2 includes each of the robot main bodies 1.
.

A servo control circuit 11 is incorporated in each drive source to servo control the drive source.

The servo control circuit 11 is as shown in FIG.

The actuator 13 as a drive source is driven by a command from the command means 12, and at this time, the two position detectors 14
detects the position of the actuator 13 and outputs the detection signal to the counter circuit 15, and the counter circuit 15 counts the input signal to obtain the current value d of the actuator 13. Then, the deviation E between the command value g and the current value d is calculated, and the deviation E signal is sent to the limiter 16. By inputting it to the servo amplifier 18 via the D/A converter 17,
The servo amplifier 18 operates the actuator 13 according to the deviation E.
control the drive.

Note that 19 is a speed detector.

As shown in FIG. 3, such a servo control circuit 11 uses a microprocessor 20, and the microprocessor 20 is capable of taking in a command value g and a current value d, and calculating a deviation E thereof. There is.

Incidentally, the microprocessor 20 is constructed by connecting two CPU sections, a first program memory 22, an input port 23, and an output port 24 on a data bus 25, as shown in FIG.

Therefore, when operating the robot body 1, an industrial robot has a programming mode that teaches the operation sequence of the robot body 1, and a teaching mode that teaches the operation path, interpolation conditions, etc. by manually operating the robot body 1. There are two operating modes: a playback mode and a playback mode in which the robot body 1 is operated faithfully according to the taught contents. Each of these operation modes is configured to be selectable by the operation section 8, and the servo control circuit 11
When divided by the power supply state, there are automatic operation state in playback mode, manual operation state in teaching mode,
It is roughly divided into three types: a stopped state depending on the programming mode. The stopped state is the stopped state of the actuator when no command to start or stop is sent to the actuator while the servo control circuit 11 is energized. It is fundamentally different from state.

In the automatic operation state, manual operation state, and stop state, the command value g and the current value d are set according to the respective operation modes.
There is a difference in the deviation E from That is, in the automatic operation state, the robot body 1 may operate at high speed, so the deviation E is large, and in the manual operation state, the worker approaches the robot body 1, so the deviation is small because the robot operates at a low speed from a safety standpoint. , it can be said that there is almost no deviation in the stopped state. Therefore, the relationship between the deviations in each operating mode is as follows.

The relationship is as follows.

EA>E)J>EP・・・・・・・・・・・・・・・
・(1) However, EA: Deviation amount during automatic operation EM: Deviation amount during manual operation EP: Deviation amount during stopped state Therefore, in the method of the present invention, focusing on the above equation (1),
A reference value E is set for the deviation between the command value for the drive source 13 and the current value at which the drive source should be driven, depending on the respective operation mode.
Ai+EM i+EPi are set in advance. This deviation reference value EAit EM iy EP (is a guideline for comparison with the absolute value of the deviation, and corresponds to the automatic operation state, manual operation state, and stopped state, respectively. The value EAipEM+eEIN is selected to be an appropriate value for each drive source 13.

In addition, the respective deviation reference values EAi+EM i, EPi
The time reference value jAiy jMiy tPi corresponds to
are also set in advance. The time reference value jAi+tMi
Each of ttPi is set to the deviation reference value EAi + EMi only at a certain moment, such as when the movable part of the robot body 1 starts operating.
Since tEP+ may be exceeded, an appropriate time is set to allow this instantaneous large deviation.

This time reference value tAi+tlJi+jP+ also has a magnitude relationship based on the above-mentioned equation (1), similar to the deviation reference value.

゛The time reference value tAiy tMi+ tPi and the deviation reference value EAiy EMip EPi are shown in Fig. 5(a),
As shown in (b), each is stored in the reference value table in the program memory 22 according to the operation mode,
It is called depending on the operating mode.

When the robot body 1 is operated, if the absolute value of the deviation between the command value and the actual current value exceeds both the deviation reference value and time reference value according to the operation mode, it is determined that the servo is abnormal. I'm starting to do that. That is, in the automatic operation state, when the absolute value of the deviation exceeds the deviation reference value EAi and the reference time value tAi, and in the manual operation state, the absolute value of the deviation exceeds the deviation reference value EMI and the reference time value tAi.
If the absolute value of the deviation exceeds the deviation reference value EPi and the reference time value tPi in the stopped state, a servo abnormality is determined.

This servo abnormality determination is made by the CPU unit 21, and the CPU unit 21 immediately performs processing such as cutting off the power to the servo control circuit 11 and displaying a message to that effect on the 2nd display 9. It has become so.

Next, the specific operation of the method of the present invention will be shown in the flowchart of FIG.

That is, it is determined whether servo control is being performed normally in Sll. As a result of this judgment, if the servo is not being operated normally, the servo abnormality processing described below is performed (520).
), on the other hand, if the execution is normal, the command value g is fetched (S12), the current value d is fetched (S13), and the absolute value of the deviation E=Ig-dl is calculated (S14).

Then, the absolute value E of the deviation is the servo abnormality detection constant ER1
That is, it is determined whether the deviation is larger than a deviation reference value according to the operation mode (S15). As a result of this determination, if the absolute value E is smaller than the servo abnormality detection constant ER, the processes from S19 onward are executed, but if it is larger than the servo abnormality detection constant ER, the time during which the absolute value E continues is counted ( 81
6) It is determined whether the counted time t is larger than a time servo abnormality detection constant tR, that is, a time reference value according to the operation mode (SL?).

If the determination result is smaller than the servo abnormality detection constant tR for the above-mentioned time, the processes from S19 onward are performed, but if it is larger, the next process (518) is performed.

That is, a servo abnormality signal is output to the hardware that should emergency stop the robot body 1, cut off the power to the servo control circuit 11, etc., and an abnormality flag is set (818).
), and after a certain period of time has elapsed (S19), the process of S11 is performed. In this case, as a result of the Sll processing, it is determined that the servo control is not being performed normally by the processing of 81g, so servo abnormality processing such as displaying an abnormality on the 1 display 9 is performed and the operator is notified to that effect. .

In this way, both the deviation reference value and the time value are set in advance according to the operating mode, and a servo abnormality is determined when both of these reference values are exceeded. can be reliably changed depending on the type of

As a result, compared to known examples in which an abnormality is determined based only on the deviation between the command value and the current value, even if an external force is momentarily applied and the deviation becomes large, the abnormality is not processed unnecessarily.
Furthermore, compared to known examples in which an abnormality is determined based on the time it takes to reach a target value, it is possible to handle the abnormality immediately when it occurs, so it is possible to provide immediate response. Furthermore, if the reference value is selected in a smaller range in the manual operation state than in the automatic operation state, the drive source 13 will not run out of control within the allowable range during automatic operation, and as a result, the movable part will hit the worker or surrounding objects. Since the fear is eliminated, safety can be improved. Moreover, since servo abnormality is precisely determined, reliability can be increased accordingly.

7 and 8 show a second embodiment of the method of the invention. In this case, we take into account that during automatic operation, there are actually both low-speed and high-speed operations.

Two types of servo abnormality detection constants are set for high speed and low speed only during automatic operation, and servo abnormalities can be detected based on these constants.

That is, during automatic operation, in addition to setting the deviation reference value EAt and time reference value iAi as servo abnormality detection constants for high speed, the deviation reference value EALi and time reference value jALi are set as servo abnormality detection constants for low speed. are set in advance. In this case, the respective reference values are set to be several times to several tens of times larger than each other as EAi>EALi LA+<tAt+.

Then, when the operation mode is switched to automatic operation, the absolute value E of the deviation between the command value g and the current value d is.

When the deviation reference value EAL as a low-speed servo abnormality detection constant exceeds the time reference value tAL, or the deviation reference value E^ and the reference time value t as a high-speed servo abnormality detection constant
Servo abnormality can be detected when the value exceeds A. Note that in FIG. 8, processing contents similar to those in FIG. 6 are designated by the same reference numerals, and therefore will not be described here.

Therefore, according to this embodiment, since servo abnormality is detected based on the two criteria of low speed and high speed, it is possible to detect it more precisely in accordance with the actual situation of automatic driving.

Furthermore, the processing contents for low speed (S105 to S107) and the processing contents for high speed (3108 to S110) are different from those for low speed to
Since the process is always performed between high speeds, the processing of the control section can be simplified compared to the case where speed determination is performed separately at low speeds and high speeds. Moreover, the processing content for low speed (S L
05 to S107) do not function during manual operation or in a stopped state, so that the processing can be further simplified.

〔Effect of the invention〕

As described above, in the method of the present invention, when the deviation reference value and the time reference value are set in advance according to each operation mode, and the drive source is controlled in either operation mode, the absolute value of the deviation is Since a servo abnormality is determined when both the deviation reference value and the time reference value according to the operating mode are exceeded, the abnormality can be quickly detected even within the time required to reach the target value. Even if an external force is momentarily applied, no abnormality will be detected unnecessarily. Moreover, since abnormalities can be detected precisely, safety and reliability can be improved, and servo abnormalities can be detected in accordance with the actual work contents.

[Brief explanation of the drawing]

Fig. 1 is an overall diagram of a welding robot showing one embodiment of the method of the present invention, Fig. 2 is a servo control circuit diagram, Fig. 3 is a servo control circuit diagram using a microprocessor, and Fig. 4 is a microprocessor Schematic diagram of FIG. 5(a) and (b)
are explanatory diagrams and flowcharts showing the main parts of the method of the present invention,
No. 6 @ is a flowchart showing the processing contents, FIG. 7 is an explanatory diagram showing the second embodiment of the method of the present invention, and FIG. 8 is a flowchart showing the processing contents. 1...Robot body, 3-7...Movable part, 13...
- Drive source, 2...Control unit, 11...Servo control circuit, EA...Difference reference value in automatic operation state, EM...Deviation reference value in manual operation state, EP...Difference reference value in stopped state Deviation reference value, tA...Time reference value in automatic operation state, tM...
・Time reference value in manual operation state, tp...Time reference value in stop state, g...command value, d...current value, E...deviation, EAL...low speed value in automatic operation state. Deviation reference value, tAL: Time reference value for low speed in automatic driving state.

Claims (1)

[Scope of Claims] 1. In an industrial robot in which a drive source for driving each movable part is servo-controlled in one of the operation modes of a stopped state under energization, a manual operation state, and an automatic operation state, the above-mentioned A reference value is set in advance for the deviation between the command value for the drive source and the current value at which the drive source should be driven, depending on the operation mode, and a time reference value is set in correspondence with each deviation reference value. However, when the drive source is controlled in one of the operation modes, the absolute value of the deviation between the command value and the actual current value is equal to both the deviation reference value and the time reference value according to the operation mode. A method for detecting a servo abnormality in an industrial robot, characterized in that a servo abnormality is determined when the abnormality is exceeded. 2. In claim 1, the reference value and time reference value of the deviation are set to two types, one for high speed and one for low speed, in the automatic driving state, and either one of the deviation reference value and time reference value is set. A method for detecting a servo abnormality in an industrial robot, characterized in that a servo abnormality is detected in an automatic operation state when the abnormality is exceeded.