JPS5916286B2 - Operation control method for industrial robots - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the motion of an industrial robot, and more particularly to a method for controlling the motion of an industrial robot for smoothly modifying the motion to adapt to surrounding conditions.

Conventional industrial robot motion control methods include continuous bus (CP) method and point-to-control method.
There is a point (PTP) system. The former has the advantage of being able to perform smooth movements because it continuously teaches the entire movement path and reproduces it as the robot's movement.
On the other hand, there is a drawback that the storage capacity of the control device increases in proportion to the length of the path. In addition, since the latter only stores the rough operating points, the storage capacity is small, but the
The disadvantage is that the robot's movements become discontinuous and linear, making the robot's movements awkward. In recent years, industrial robots have become more sophisticated, and attempts are being made to judge external conditions using sensory functions such as vision and touch, and to make them perform actions that are appropriate to the situation. In the case of the Cp method of operation control, it is difficult to significantly change the stored route according to external conditions due to the storage capacity and correction calculation amount, and the route within a small range is difficult to change. The drawback was that changes could only be made based on the judgment of sensory functions.

Another disadvantage of the PTP method is that after the robot has moved to the taught target position, it is only possible to judge the situation using sensory functions and correct the position in the very vicinity of the taught point. It was hot. j0 The purpose of the present invention is to automatically correct the movement path in accordance with the surrounding conditions of the robot even if a positional shift occurs in the workpiece at the work point, and to accurately and smoothly perform the movement of the robot. An object of the present invention is to provide a method for controlling the operation of an industrial robot in accordance with the present invention.

A feature of the present invention is that a plurality of teaching points are set in the movement route from the start point of the industrial robot to the taught work point, and these teaching points are used to move between the start point and the work point. This is performed by linear interpolation operation, and in response to the surrounding situation of the robot, that is, the positional deviation of the work target, the positional deviation at the work point is determined, and this deviation value is given to the work point to correct the teaching work point. At the same time, mutually different correction values distributed according to the amount of correction are given to the plurality of teaching points set in the moving route, and each correction value is set in the vicinity of the starting point. By assigning larger amounts as the distance approaches the work point, the movement path of the industrial robot can be changed to a new path from the start point to the taught work point. To provide a method for controlling the operation of an industrial robot, which automatically makes corrections and moves the robot accurately and smoothly to a work object.

Preferred embodiments of the present invention will be described below based on the drawings.

As one of the preferred embodiments of the present invention, a case will be described in which a handling work is performed using an industrial robot having an orthogonal coordinate system as shown in FIG.

In FIG. 1, the industrial robot includes a saddle 3 that reciprocates in the X-axis direction on a first column 2 by a hydraulic cylinder 1, and a second column 4 that is installed upright on the saddle 3. A cross bearing box 6 is moved up and down in the Z-axis direction by a hydraulic cylinder 5VC, a column 8 is attached to the cross-bearing box 6 and reciprocated in the Y-axis direction by a hydraulic cylinder 7, and a column 8 is fixed to the tip of the column 8. , a wrist mechanism 9 having three degrees of freedom in rotational directions: swinging, bending, and twisting. Further, a grip device 10 is attached to the tip of the wrist mechanism 9, and a non-contact sensor 11 including an ultrasonic transducer is attached to the wrist portion 9a. FIG. 2 is a block diagram showing the control system of the robot, and the digital computer 12 is constructed from one having the functionality of a small microcomputer. Position commands from the digital displacement calculator 12 are distributed to predetermined axes by the interface 13, and positioning devices 14, 15 for each of the X, Y, and Z axes are used.
16, 17, 18, 19, or 20.
Now, assume that the position command value is sent to the X-axis.
This command is sent to an arithmetic circuit 141 provided in the positioning device 14 for X-axis control, which calculates the difference between the robot's X-axis current value detected by the detector 144 and sends it to the servo circuit 142. It will be done.

The output of the servo circuit 142 connects the robot X-axis main body 143 to 1.
and its position is fed back by detector 144 as described above. Note that the obstacle detection signal from the ultrasonic sensor 11 is supplied to the computer 12 from the signal generator 23. FIG. 3 illustrates a situation in which handling work is performed by the above-mentioned industrial robot.

In this embodiment, a case will be discussed in which a workpiece 21 transported to work area A by a belt conveyor or other transport means is subjected to point TVC handling at the next stage (for example, chucking to a lathe, etc.). Here, work area A is an industrial television camera (
ITV) 22. This ITV
The visual information of the workpiece 21 obtained from the image processing apparatus 22 is processed by the image processing device 30 shown in FIG. 2, and sent to a digital computer in the form of position coordinates. Below, specific details of the operation during actual handling work will be explained.

In FIG. 4, the moving path of the robot's hand section for performing the above-mentioned handling is as follows: start point S -> work gripper -> transfer point T -> start point (stop point S).

Here, let us consider the moving operation between the start point S and the grasping point WO.In order to make the movement smoother, points Pl, P2, and P3 are defined between the start point S and the grasping point WO as shown in the figure. In other words, the movement path of the robot becomes the starting point S→Pl, P2→P3→WO.
First, the taught coordinates of each point are input to the computer 12, and interpolation calculations between the points are performed. This interpolation calculation is performed on the X axis and Y axis.
Movement in the axial direction is performed in proportion to the difference in coordinate positions between two adjacent points, and movement between two points can be obtained as linear movement regardless of the saturation characteristics of the control device and the delay of the drive device. . Based on the interpolation coefficients and teaching point data thus calculated, the robot hand is first positioned at the start point S, and then starts interpolation and moves to point P1. Point PlVC. When the robot arrives, the interpolation coefficient is changed and interpolation operation to point P2 is performed.
This operation is repeated until the point WO is reached. Now, in an actual operating state, the position where the workpiece 21 is placed by the transport device generally varies and is the initially taught position W.

It doesn't necessarily have to be. Taking this into consideration, it may be possible to attach a tactile sense or the like to the inside of the grasping device at the robot's hand, but in that case, the robot's movement will be as shown by the solid arrow in Figure 5, after it has moved to the WO. There was a drawback that the movement to W1 was a wasteful operation. Further, if the workpiece is shifted to the position W2 as shown by the dashed line in FIG. 5, it cannot be handled. Furthermore, in the case of position W3 indicated by the broken line in Fig. 5, the robot collides with the workpiece,
There were drawbacks such as damage to the workpiece. According to the method of the present invention, the position of the workpiece is corrected and taught in advance.
That is, the preset area A of the workpiece 21 is constantly monitored by the TV 22, and the difference between the initial teaching point of the workpiece position and the current position is monitored. FIG. 6 shows an image on the television monitor, where point WO is the initial teaching position of the workpiece, and point W1 is the position of the workpiece currently being handled by the robot. In this embodiment, it is assumed that the workpiece is placed on a horizontal plane, and among the three axis coordinates, only the X and Y coordinates are related to the positional shift of the workpiece.

Therefore, it is sufficient to know the components in the X and Y directions (converted to values on the robot coordinates) of the difference in position between points WO and Wl in the monitor image of FIG. The image processing device 30 that receives the output from the TV 22 recognizes the position of the workpiece 21, calculates the difference from the initial position, and calculates its X and Y direction components ΔX and ΔY. Based on this, the digital computer 12 shifts the coordinates of the aforementioned teaching points Pl, P2, P3 by proportional allocation, as shown in FIG.
Change the coordinate value to 3O and replace point WO with W1. Here, the interpolation calculation is performed again, and if the interpolation coefficient is determined, the robot will move to the starting point S→PlO−+P2O→P3O→
The grip point W1 can be moved extremely smoothly while performing interpolation operations. Regarding the above method of the present invention,
A more detailed explanation will be given based on FIG. First, the coordinates (X, Y) of each point are determined as follows. Crystal bυ′1′1
1) Todoroki Uυ)06Uυ'1υυ1 At this time, the positional deviation information △X, △Y obtained from the ITV image processing device will be expressed as follows.

If there is a deviation, then the points Pl, P2,
P3 is corrected to points PlO, P2O, and P3O, respectively.

In other words, if the vector WOwl=a, the points Pl, P
2. Find and correct the points PlO, P2O, and P3O so that P3 becomes L1 −7PlplO=-・a.

Then, the interpolation operation is performed using the thus corrected values in place of the original teaching points. In the above description, the position W1 of the positional deviation of the work point WO is replaced with one teaching point P3, and each teaching point Pl, P2 set on the operation path between the start point S and the teaching point P3 is The interpolation calculation may be performed by correcting the position of .

Also, if the starting point S is misaligned,
It is clear that the interpolation calculation may be performed by correcting the position of the teaching point set on the motion path between the starting point and the work point in accordance with the amount of positional deviation of the starting point, as in the above explanation. Therefore, according to the method described above, since the teaching method is the same as that in the conventional PTP method, it is extremely easy to correct the robot's operation in response to the positional deviation of the workpiece 21, and even in the corrected operation, the CP method can be used. It is possible to perform exactly the same smooth and highly accurate movement movement as in the previous example.

If you try to perform such a correction operation using the pure CP method, the position coordinates of all points will be shifted and the calculation will be performed.
The data must be corrected, the storage capacity is more than twice that of the conventional one (including the memory area for calculations), and the calculation time becomes enormous, making it difficult to use a computer from an economical point of view. This is virtually impossible in terms of the performance of the machine or the duct for transporting the workpieces. On the other hand, if it is a PTP method,
Although the above correction calculation is possible, as mentioned above, the PTP method alone has the disadvantage that circular operation cannot be obtained. As described above, the present invention provides a dual motion control method in which the macroscopic motion of an industrial robot is specified, and the microscopic changes in motion are made using visual feedback or tactile tagtail feedback. This makes it possible to apply it to a wide variety of fields.

FIG. 8 shows the application of the present invention to a painting robot. In this case, the positions of the painting gun 40 are the starting point S, the workpiece 2,
1 (for example, a car body) nearby painting point Dl,
D2, D3, . . . are taught.

During actual painting, if the ITV22 detects the positional shift of the workpiece, corrects the painting points DlO, D2O, etc., performs interpolation calculations, and moves the robot, the dimensions of the workpiece can be adjusted. It is possible to perform coating that is highly adaptable to errors and positional errors. FIG. 9 shows another embodiment of the invention.

This is an example of application of the diamond-shaped coil 50 to taping work, in which the taping start position FO of the coil 50, the taping corner point F1, etc. are taught, and a tactile type consisting of a potentiometer etc. Sensor 51,5
Steps 2 and 53 involve performing taping work while correcting the teaching points. In this case, of course, IT
Although it is effective to use V, the taping head 54
Due to the structural characteristics of the head, arranging the tactile senses in a circumferential manner around the head can produce a sufficient effect. As explained above, according to the present invention, at the work point 3. When a positional deviation occurs in the work target at the robot, the teaching work point is set to correct the positional deviation of the work point among multiple teaching points set during the robot's movement path from the start point to the work point. The mutually different correction values distributed according to the amount of correction given to the teaching point are set and applied in such a way that they become larger as the position of the teaching point approaches the work point from the vicinity of the start point. Since the movement path of the robot is automatically corrected to a new one, it becomes possible to smoothly and accurately move the robot from the starting point to the work object whose position has been misaligned. In addition, the robot's movement path is automatically adjusted so that the difference in position between the initially set path and the new movement path near the start point is small, and the difference between the two gradually increases as they get closer to the work point. Since this has been corrected, it is possible to eliminate the large movement of the robot's position around the starting point, where there are often obstacles around, and thus prevent damage to the robot due to collisions between the robot and obstacles. This has the effect of being able to prevent this.

[Brief Description of the Drawings] Figure 1 is a configuration diagram of an industrial robot to which the present invention is applied;
Figure 2 is a configuration diagram of the control system of the robot shown in Figure 1;
The figure is a schematic diagram of the configuration and working situation of a handling system as an embodiment of the present invention, FIG. 4 is a plan view for explaining the operation of the system in FIG. 3, and FIG. FIG. 6 is an ITV monitor image diagram in this embodiment, FIG. 7 is a schematic diagram of the operation correction method of the present invention, FIG. 8 is an explanatory diagram of a painting robot as another embodiment of the present invention, and FIG. It is an explanatory view of a taping work robot as still another example of the present invention. Explanation of symbols, S...start point, WO...work point,
W1...Correction work point, Pl, P2, P3...Teaching point, PlO}P2O, P3O゜゜゜Correction teaching point.

Claims (1)

[Claims] 1 Multiple teaching points are set to ensure the robot's movement during the movement route from the start point of the industrial robot to the taught work point, and movement between the start point and the work point is performed using these teaching points. This is performed by linear interpolation, and the positional deviation of the work object at the taught work point is determined in advance, and this deviation value is given to the taught work point to correct the taught work point, and the teaching work point is corrected. Each of the correction values, which are different from each other and distributed according to the amount of correction, is applied to each of the plurality of teaching points set in the moving route, and each of the correction values is larger than the one at which the teaching point is located near the starting point. The movement path of the industrial robot can be automatically corrected to a new path from the start point to the taught teaching point by assigning it so that it becomes larger as it approaches the work point. A method for controlling the motion of an industrial robot, characterized in that: