JPH02139167A - Control method for grinding work by robot - Google Patents

Abstract

PURPOSE:To perform an efficient grinding work with good stability by suspending the work only in case of the generation time intervals of an abnormal state being less than a 1st set value and yet the number of times thereof being more than a 2nd set value. CONSTITUTION:In case of grinding burrs, etc., of a rotor 4 by the grinder 2 fitted to the arm 1a tip of a robot 1, the load current of this grinder 2 is detected by a detector 8. In case of this detected value being more than specified value, the feeding of the grinder is stopped and whether the time intervals from the detection of the abnormal state of the previous time to the detection of the abnormal state of this time are less than a 1st set value or not is decided. As the result of this decision, the number of abnormal detection times is checked only in the case of less than the 1st set value and in case of this times being more than a 2nd set value, a magnet switch is opened, the grinder 2 is stopped and the grinding work is suspended. However, in case of less than the 2nd set value, this switch 7 is closed and the grind feeding of the grinder 2 is executed.

Description

[Detailed Description of the Invention] A. Industrial Application The present invention relates to a method for limiting grinding work by a robot, and is devised to improve work efficiency.

B. Summary of the Invention The present invention monitors the load current of a grinder attached to a robot arm, and when an abnormal load current is detected, stops or slows down the feed of the grinder, and also detects the abnormal load current. The size of objects to be detected, such as burrs, is detected based on the interval and number of times that burrs are detected, and deburring work is carried out efficiently by keeping the grinder's grinding feed speed high and without stopping the robot as much as possible. It was designed to be obtained.

C0 Conventional technology In the past, for example, burrs on castings were ground and removed by workers with a grinder, but in recent years, as part of labor-saving efforts,
A robot that automatically performs this deburring work has been developed and put into practical use. In this method, a grinder is attached to the tip of a robot arm, and the grinder is moved along a pre-stored trajectory by teaching.

D Problems to be Solved by the Invention When performing deburring work using the four bots described above, in order to improve work efficiency as much as possible, the grinding feed rate must be set according to the size of burrs that normally occur. ing.

Therefore, if a burr larger than normal or an abnormal burr occurs (baked sand, mold drop), an overload will be applied to the grinder, causing the robot to stop and be unable to continue work, or damaging the grinder's whetstone. Such problems were occurring. Also,
Considering these problems, it is necessary to reduce the grinding speed, resulting in a decrease in work efficiency.

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, it is an object of the present invention to provide a safe and efficient control method for grinding work by robots without stopping the four robots as much as possible.

E. Means for Solving the Problems The configuration of the present invention that achieves the above object detects the load current of the grinder and detects the If the load current value exceeds a predetermined value, the grinder feed is stopped or slowed down, and the time interval between the detection of the previous abnormality and the current abnormality is less than or equal to the first set value. If the first set value is exceeded, the number of abnormality detections is reset, and the acceleration time, which is the time it takes to reach the set grinding feed speed of the grinder, is determined, and the grinding feed of this grinder is adjusted. At the same time, if the number is less than the first set value, the number of times an abnormality is detected is checked, and if this number is more than the second set value, the grinder is stopped and the grinding operation is interrupted. In this case, the present invention is characterized in that the grinding feed of the grinder is carried out in the same manner as described above.

F. Effect According to the present invention having the above configuration, the work is interrupted only when the time interval at which the abnormal state occurs is less than or equal to the first set value and the number of times is greater than or equal to the second set value, and in other cases, the work is interrupted. The grinding operation is repeated at a set grinding speed while controlling the load current to return to its normal value.

G. Example Embodiments of the present invention will now be described in detail based on the drawings.

FIG. 2 is an explanatory diagram showing a robot device that implements an embodiment of the present invention.

As shown in the figure, the four-bot 1 moves a grinder 2 attached to the tip of its arm 1a along a trajectory memorized by teaching in advance, and burrs a workpiece 4 placed on a positioning device 3. It is now time to collect the items. The robot 1 at this time is controlled by the robot controller 5. Further, power is supplied to the grinder 2 from a power source 6 via a magnet switch 7. The current detection sensor 8 detects the load current supplied to the grinder 2, and its output signal is supplied to the grinder overload detector 9. The grinder overload detector 9 is
The details of its functions will be described later based on Figure 1, but
The magnetic switch 7 is opened and closed based on the load current detected by the current detection sensor 8, and the feed speed (stop, start, acceleration, etc.) of the arm 1a is controlled.

A grinding speed control signal, an abnormal burr signal, a grinder abnormal signal, a grindstone abnormal signal, and a power abnormality signal are respectively supplied to the robot controller 5.

An embodiment method using such a robot device is as shown in the flowchart of FIG. 1 as follows.

1) Workpiece 3 has a larger burr than usual.
When the grinder 2 grinds this burr, the load current of the grinder 2 increases, but the load current to the grinder 2 is adjusted to a predetermined level by the grinder load detector 9 which detects this load current via the current detection sensor 8. If it is detected that the grinding speed has exceeded the value (see block 10), the grinder overload detector 9 sends a grinding speed control signal to the robot controller 5 to suddenly stop the robot 1 (see block 11). This reduces the load current of the grinder 2.

2) Detect the time interval between the previous sudden stop and the current sudden stop (see block 12), and if this time interval exceeds the first set value, reset the number of sudden stops (block 13).
(see block 14), and if it is less than the first set value, the number of sudden stops is checked (see block 14).

3) If the number of sudden stops is less than the second set value, a no-load check of the grinder 2 is performed (see block 15). This no-load check is performed by monitoring the no-load current of the grinder 2 and detecting fluctuations in the no-load current. This allows abnormalities due to wear of the bearings and gears of the grinder 2, and by detecting pulsations in the no-load current, cracks, chips, III wear, etc. of the grindstone attached to the grinder 2 are detected. That is, in these cases, the no-load current value becomes an overload state exceeding the set value, so the time period during which this overload state lasts is counted (block 16).
), and if this duration exceeds the set time, the magnetic switch 7 is opened to stop the grinder 2 (see block 17), and a grinder abnormality signal or grindstone abnormality signal is sent to the robot controller 5. Then, the robot 1 is stopped and the work is temporarily interrupted.

On the other hand, if the duration of the overload state is less than the set value, the grinder no-load check subroutine is executed again.

4) As a result of the grinder no-load check, if there is no abnormality, set the acceleration time, which is the time it takes for the grinder 2 to reach the set grinding speed (see block 18), and send a grinding speed control signal to the four-bot controller 5. This restarts robot 1 (see block 10) and returns it to the main loop.

5) If it is detected in the process of block 14 that the number of sudden stops is equal to or greater than the second set value, the magnetic switch 7 is opened to stop the grinder 2 in the same way as when an abnormality in the grinder 2 is detected. At the same time, an abnormal burr signal is sent to the robot controller I/roller 5, the robot 1 is stopped, and the work is temporarily interrupted.

If a very large burr occurs due to mold drop, etc., sudden stops will occur frequently, so if the number of sudden stops is counted and the number exceeds the second set value, it is an abnormal burr. It is determined that this is the case and the work is temporarily suspended.

Furthermore, if one of the three-phase ffS wires that supplies power to the grinder 2 is disconnected, the current flowing through the other two normal wires will increase, so this will be detected and a power abnormality signal will be sent to the robot. It may be sent to the controller 5 to stop the four bots 1. Further, in the embodiment described above, the robot 1 is stopped when the load current of the grinder 1 exceeds a set value, but it is not necessary to do this and the robot 1 may be driven at a slow feed speed. Even in this case, the load current can be lowered below the set value.

■ Effects of the Invention As specifically explained above in conjunction with the embodiments, according to the present invention, when the time interval at which an abnormal state occurs is equal to or less than the first set value,
Moreover, only when this number of times is equal to or greater than the second set value, the work is interrupted, and in other cases, the grinding work is repeated at the set grinding speed while controlling the load current to return to the normal value. Therefore, efficient work can be performed stably.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a four-bot device that implements the embodiment. In the drawings, 1 is a robot, 1a is an arm, 3 is a workpiece, and 9 is a grinder overload detector.

Claims (1)

[Claims] When grinding burrs etc. on a workpiece with a grinder attached to the tip of a robot arm, the load current of the grinder is detected, and if this load current value exceeds a predetermined value, the grinder feed is stopped or or slow down
It is determined whether the time interval from the detection of the previous abnormal state to the detection of the current abnormal state is less than or equal to a first set value, and the first
If the set value of If the number of times an abnormality is detected is greater than or equal to the second set value, the grinder is stopped and the grinding operation is interrupted, while if the number is less than the second set value, the grinder is stopped in the same manner as described above. A control method for grinding work by a robot, characterized by performing grinding feed.