JPH04174005A - Robot controller - Google Patents

Abstract

PURPOSE:To correct a cumulative pitch error and perpendicularity by correcting cumulative pitch errors of respective axes and an error in the perpendicularity between two axes when target position coordinates are given in the form of numeric data by using a local coordinate system which is defined by reference positions. CONSTITUTION:The reference positions on a printed board 20 are read by a camera 21 fitted to a robot arm 23 and its coordinate positions are sent to a robot controller 24 by a vision controller 22. Then the distance between the reference positions is inputted from a programming device 25 to define the local coordinate system. Then the robot controller 24 inputs a target position from the programming device 25 or a host computer 26 in the form of numeric data and performs coordinate conversion to place the robot arm 23 in operation. Consequently, the coordinate conversion is performed by using the local coordinate system to easily correct the absolute accuracy of the robot for necessary strokes at need.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a robot controller that has a position coordinate correction function using a local coordinate system and controls a robot equipped with a servo motor.

[Summary of the invention]

The present invention is a controller that controls a robot arm that includes two telescopic axes that are perpendicular to each other on a horizontal plane. The correction is automatically performed using a local coordinate system defined by a reference position.

[Conventional technology]

With conventional robot controllers, at the time of shipment, all robot arms are moved on their axles to measure linear accuracy, and the cumulative pitch error is calculated from the difference between the command data and the actual amount of movement. Correction values unique to the robot arm were input into the robot controller, and corrections were made uniformly over the entire stroke.

Figure 6 shows an example of the accuracy measurement results on a straight line when the robot arm is operated on the flower axis using a conventional robot controller, and Figure 7 shows the linear error tendency of the entire stroke using the data in Figure 6. This is the result of recent corrections.

Furthermore, the perpendicularity of the angle formed by the two telescopic axes that should be orthogonal on the horizontal plane depends on the machining accuracy and assembly method.

[Problem to be solved by the invention]

However, this method is effective only when the cumulative pitch error changes linearly, and in addition, it requires high-precision parts machining to ensure that the angles formed by the two expansion and contraction axes, which should be orthogonal on the horizontal plane, are exactly right angles. It requires assembly and adjustment, and has the disadvantage of being expensive.

FIG. 8 shows a case where the cumulative pitch error transition is not linear, and FIG. 9 shows the result of similar correction using a conventional correction method. That is, the large amount error after correction becomes larger than the maximum error before correction.

Figure 10 shows the robot coordinate system when the angle made by the expansion and contraction axis with 2, which should be perpendicular, is not a right angle.As expected, when operating with numerical data given, it is difficult to position accurately. It is clear that there is.

In addition, it is very difficult to correct changes in the x-area pitch error due to thermal contraction of the ball screw or the like due to differences in usage environment and time, or to correct surface angle errors when the robot arm is deformed due to some kind of trouble.

The purpose of the present invention is to locally correct the cumulative pitch error that cannot be calculated in a linear manner over the entire stroke and that may change over time, and the squareness that is not accurate due to inexpensive parts machining and assembly adjustment. An object of the present invention is to provide a robot controller having a function of correcting by defining a coordinate system.

[Means to solve the problem]

FIG. 1 is an explanatory diagram showing a procedure for correcting the perpendicularity of two telescopic axes that should be perpendicular to the cumulative pitch error of a stroke according to the present invention. As shown in FIG. 1, the present invention teaches or self-recognizes three points that serve as references: the origin, the X-direction reference point, and the Y-direction reference point, and the position coordinates of these three points, the origin, and the Define a local coordinate system using the distance between Move using the conversion result as the target position.

[Effect]

Since the correction is performed using coordinates of an external reference position that has accurate distance and perpendicularity, correction data can be input when necessary for a necessary stroke rather than for the entire stroke.

(Embodiment) Fig. 2 is a schematic explanatory diagram showing the configuration of an embodiment of a robot controller to which the present invention is applied. The camera 21 reads the reference position, and the vision controller 22 sends the coordinate position to the robot controller 24. Next, the distance between the reference positions is input using the programming device 25 to define a local coordinate system. 25 or the host computer 26 using numerical data, coordinate transformation is performed, and the robot arm 23 is operated.

FIG. 3 is an explanatory diagram showing an embodiment of a printed circuit board 2o as a work object for defining the local coordinate system of the present invention. In the same figure, a printed circuit board 20 is a workpiece for mounting work such as an IC in the embodiment of FIG.
has. These marks may be holes or protrusions;
That is, any mark that can be recognized by the camera 21 in the embodiment shown in FIG. 2 or that can be taught by manually operating the robot arm may be used.

In this embodiment, the position coordinates of these three points are read by the camera 21 and the vigilance controller 22 in FIG. 2, and sent to the robot controller 24 as numerical data. Furthermore, the robot controller 22 has an origin mark 31
The local coordinate system 34 can be defined using the distance between and the X-direction reference mark 32 and the distance between the origin mark 31 and the Y-direction mark 33.

FIG. 4 is a diagram showing the relationship between the robot coordinate system 41 and the local coordinate system 34 when the angles formed by the two telescopic axes that should be orthogonal on the horizontal plane of the robot arm 23 are not right angles.

FIG. 5 is an explanatory diagram of a state in which the robot coordinate system 41, which is different from the actual robot coordinate system, is assumed to be orthogonal, and the local coordinate system 34 is relatively distorted, in order to explain the means of coordinate transformation in the present invention.

That is, in reality, the robot coordinate system 41 as shown in FIG.
Even if they are not orthogonal, the robot controller 24 does not check that they are not orthogonal, so the robot coordinate system 41 is orthogonal as shown in FIG. 5, and the local coordinate system 3
4 are not perpendicular to each other, and the position coordinate correction calculation is performed.

In Figure 5, for simplicity, the position of the origin mark is A,
Let B be the position of the X-direction reference mark, C be the position of the Y-direction reference mark, and D be the target position.

Also, the X coordinate of each point A-B-C in the robot coordinate system is
Assuming that Ax-Bx-Cx, the Y coordinate of each point in the robot coordinate system is Ay-By-Cy, the AB distance is Ll, and the AC distance is L2, these numerical data are known.

Here, the XY coordinates of vector AB and vector AC starting from point A and heading toward point B and point 0 are as follows,
The actual lengths of each are Ll and L2.

AB= (Bx-Ax, By-Ay) AC= (Cx-Ax, Cy-Ay) Also, since the given target position is data on the local coordinate system, from the origin ○ of the robot coordinate system to the target position The vector OD is expressed as the sum of the vector OA and the vector AD by the following determinant.

AD=OA+AD In this way, the position coordinate data on the robot coordinate system is calculated, so the robot controller makes the robot arm perform normal movements based on this data to reach the target position. be able to.

〔Effect of the invention〕

As described above, according to the present invention, by performing coordinate transformation using a local coordinate system, it is possible to easily correct the absolute accuracy of a robot when necessary for a necessary stroke. In other words, during work such as board mounting, it is possible to self-recognize the three reference positions on each board and correct cumulative pitch errors and squareness, making it possible to correct board dimensional errors caused by thermal deformation. .

In addition, high-precision parts processing and assembly adjustment of the robot arm are no longer required, and the manufacturing cost of the robot arm can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the procedure for correcting the cumulative pitch error of the stroke of the present invention and the perpendicularity of two telescopic axes that should be perpendicular to each other, and FIG. 2 shows the configuration of an embodiment of a robot controller to which the present invention is applied. A schematic explanatory diagram; FIG. 3 is an explanatory diagram showing an embodiment of a work object for defining a local coordinate system of the present invention;
Fig. 4 is an explanatory diagram of the coordinate system when the angles formed by the two telescopic axes that should be orthogonal on the horizontal plane of the robot arm are not perpendicular, Fig. 5 is an explanatory diagram of the coordinate transformation means in the present invention, and Fig. 6 Figure 7 is an example of the results of straight-line accuracy measurement when the axle of the robot arm is operated using a conventional robot controller, Figure 7 is the result of correcting the data in Figure 6 using the conventional method, and Figure 8 is the cumulative pitch error. As a result of accuracy measurement when the transition of is not linear, Figure 9 shows the result of correcting Figure 8 using the conventional method, and Figure 10 shows the result when the angle formed by the expansion and contraction axis with 2, which should be perpendicular, is not a right angle. shows the robot coordinate system. 20...Printed circuit board 21...Camera 22...Visigin controller 23...Robot arm 24...Robot controller 25...Programming device! 26...Host computer 31...Origin mark 32...X direction reference mark 33...Y direction reference mark 34...Local coordinate system 35...IC 41...Robot coordinate system 51... ...Above the target position Applicant Seiko Electronic Industries Co., Ltd. Agent Patent Attorney Keinosuke Hayashi Figure 1 Figure 2 Figure 5 []

Claims (1)

[Claims] (a) 3 on an object having an origin and a reference point in the X and Y directions
Means for teaching or self-recognizing the positional coordinates of a point (b) Means for inputting the distances between the origin and the X-direction reference point and the origin and the Y-coordinate reference point (c) Using the positional coordinates of the three points and the two distances Means for defining a local coordinate system (d) Means for inputting target coordinates on the local coordinate system to which the tip of the robot arm is to be moved; (e) Means for converting the input position coordinates on the local coordinate system into the robot coordinate system ( f) A robot controller comprising means for moving the tip of the robot arm to position coordinates converted onto the robot coordinate system.