JPH05312521A - Target mark - Google Patents

Abstract

PURPOSE:To make it possible to detect relative position of an arbitrary object located in a three-dimensional space by constituting a target mark of a ring mark having maximum area and five circular marks having different area. CONSTITUTION:Marks A1, B2, C3, and D4 are put, in square, on a base 7. Mark A1 has larger area than other three marks. A ring mark E5 is provided in a square defined by these four marks and a circular mark F6 is provided therein. When a camera in observing system takes in the images of the target marks and compares the areas thereof with that of a mark corresponding to the coordinates values of the center of gravity, a point corresponding to the mark E5 is determined because the mark E5 has largest area. Since the mark F6 is present in the mark E5, coordinates point of the center of gravity closest to that of the mark E5 corresponds to the mark F6. A point corresponding to the mark A1 is also determined because the mark A1 has largest area among other four marks.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark for measuring a relative position between a robot and an object, which is required when performing object gripping, assembling, docking work, etc. using a robot or the like.

[0002]

2. Description of the Related Art Conventionally, a method has been used in which a mark is attached to a target as a target in assembly, docking work, etc., and a mark image is input to a camera to perform image processing for positioning. Although some marks for positioning have been devised, two typical types of marks will be described. The first mark is a quadrilateral apex mark attached to the target and a mark on a pole standing upright from the center of the square mark, which is shown in FIG. 4 (a). Read the image of the vertices or the image of the side connecting the vertices with a camera. 4
The position and orientation of the target in three-dimensional space is estimated by the theorem of projective geometry's cross ratio using the coordinates of the vertices and the intersections of diagonal lines, and the marks on the pole improve the detection accuracy of pitch and yaw angles. It is a target mark. This mark is described in the document: Machida et al., "Prototype of Space Proximity Work Sensor", and Artificial Intelligence Robot Automation Symposium for Space, pp51-pp54 (1988).

The second mark is a three-dimensional mark called a GFT (Crabble Fixture Target) pattern, which is a pattern in which rectangles are superimposed on concentric stripes, and a cut is provided in a part of the concentric ring. In addition, the pole stands up from the center of the ring, and the tip of the pole is also marked. FIG. 4B shows a schematic view of the GFT mark. Estimate the position and orientation of the object by comparing the pattern of the central part of the GFT stored in advance, obtaining the inclination and magnification of the mark, and obtaining the coordinates of the feature points included in the mark by affine exchange or pattern matching. can do. This mark is described in, for example, Yamawaki et al., "Examination of position detection system by manipulator image", and Space Artificial Intelligence Robot Automation Symposium pp193-pp196 (1987).

[0004]

In the first mark, it is generally difficult to make correspondence between the image data of four points on the plane and the actual shape and size data of each point. In this case, the mark on the pole and the mark on the plane may overlap with each other, and the position / orientation detection range is considerably narrowed. Further, with this mark shape, it is difficult for a person to visually identify the mark and grasp the relative position relationship, and it is not suitable as a target mark for a remote-controlled robot.

The second mark has been used in the past when an operator manually operates a robot to perform work. A human can grasp the relative positional relationship to some extent, and the mark can be easily identified. However, when the relative position is automatically measured by image processing or the like, complicated processing is required, and there is a problem that the edge detection is easily affected by an error. Also, in the conventional mark, the mark is provided on the surface of the base by painting on the base material, so it is difficult to make the boundary line between the mark part and the base part clear and smooth in the manufacturing process, and the contour of the mark is uneven. Sometimes occurred.

[0006]

According to the present invention, in a system for assembling, gripping, docking, etc. an object, a ring mark having the largest area in a target mark for a proximity sensor installed on a joint surface of an object. It consists of a mark, five circular marks with different areas, and a base for installing these marks. To install these marks, a recess with the same size as each mark is provided on the base, and a ring-shaped mark is installed. On the circumference of one circle centered on the center position of the recess for use, the four circular recesses are arranged equidistantly from each other outside the ring, and one of these four circular recesses is placed. A recess for marks having different areas, a concentric circle with the recess for a ring-shaped mark, and a circular recess at the center of the bottom of the ring that is hollowed out in a cylindrical shape. Provided, fixed by fitting the respective marks in the hollow of these provided on the base, the target mark, characterized in that formed by applying different colors can be obtained from the respective mark and base.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the principle and operation of the present invention for performing relative position measurement by image measurement using a target mark will be described.

FIG. 1 shows the structure of the target mark. FIG. 1A is a diagram showing constituent elements of the target mark, and FIG. 1B is a diagram seen from the front after assembling the target mark. Target marks include a mark A1, a mark B2, a mark C3, and a mark D4 arranged in a square shape on the base 7. Only the mark A1 has a larger area than the other three marks. Further, there is a ring-shaped mark E5 inside the square formed by these four marks. The marks A1, B2, C3 and D4 are arranged equidistantly from each other on one circumference centered on the center position of the mark E5. The inside of the ring is hollowed out in a cylindrical shape,
A circular mark F6 is provided concentrically with the ring at the center of the bottom surface of the cylinder. These marks are made white, the base 7 is applied with black paint, and each mark is fitted into the base 7.

FIG. 2 shows an example in which a target mark image is captured by an observation system camera. As shown in the figure, the coordinate system has X and Y coordinates on the image plane 0 of the camera of the observation system,
The Z axis is taken in the direction perpendicular to the image plane 0 from the center of the image. The origin of the target mark is x, y, at the center of gravity of the mark E5.
z. The mark shape dimension, that is, the three-dimensional positions of the six marks 1 to 6 in the mark coordinate system are known.

Hereinafter, by using this target mark, the relative position from the observation system to the target mark, that is, the three degrees of freedom of the position in the X, Y, and Z directions, and X, Y, and
A measurement method for a total of 6 degrees of freedom of the attitude around the Z axis will be described.

First, the coordinate values of the center of gravity of each mark and the area of the mark in the camera image captured from the observation system are measured. In order to make the correspondence between the barycentric coordinate value and the mark, when comparing the areas of the marks corresponding to the barycentric coordinate values, the ring-shaped mark E5 has the largest area.
The corresponding points can be determined. Since the mark F6 is inside the mark E5, the barycentric coordinate point closest to the barycentric coordinate point of the mark E5 corresponds to the mark F6. Since the mark A1 has the largest area among the remaining four points, the corresponding point of the mark A1 can also be determined. For the other three points, the barycentric coordinate values in the X ', Y'coordinate system with the mark E5 shown in FIG. 2 as the image origin are obtained. For example, when the coordinates of the mark A1 are in the first quadrant, the coordinates of the mark B2 are obtained. Mark C3 in the second quadrant
It is possible to determine the correspondence between all the marks and the measured coordinate values by the condition determination such that the coordinates of are in the third quadrant. According to the relative positional relationship, the mark F6 may not be observable on the observation image plane, but even in this case, the relative position with the object can be measured by measuring the other five points.

If the correspondence between each coordinate point and the mark is determined as described above, first, regarding marks 1 to 4 on the plane 7, reference is made by Shimazaki, "A few ideas regarding the inverse matrix of the projection transformation", Electronic. The relative position of each of the four marks can be geometrically determined by using the method as described in IE79-15, IEICE Technical Committee. Furthermore, the relative position and orientation with respect to the target mark can be calculated by using the three-dimensional positions of these four points. In this case, the accuracy of detecting the pitch and yaw angle with respect to the posture is lower than that of the roll angle, but the center mark
When the coordinates of 6 are measured, it is possible to detect the pitch and yaw angle with higher accuracy by iterative convergence calculation using the Newton method or the like using this mark information.

With the above processing, it is possible to measure the relative position and orientation in the directions of 6 degrees of freedom by image processing using the target mark.

Next, specific application examples of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram of a robot remote control object gripping system showing an embodiment of the present invention. The target mark 8 and the grip grip 9 are installed on the gripping target 10, and the hand-eye camera 22 and the remote control robot arm 20,
A case where the robot hand 21 is used to perform a gripping operation on the gripping target 10 will be described. The operator inputs a robot operation command using the robot operation means 25, and operates the robot by the robot control means 23. Hand
The image data of the eye camera 22 is presented to the operator by inputting it to the robot operation means 25, and the image processing means 24 performs image measurement processing.

As a condition, the position where the grip grip 9 is gripped by the robot hand 21 is set as a target position, and at the target position, the relative position between the target mark 8 and the hand-eye camera 22 has a certain value only in the Z-axis direction, and other free positions. Regarding the degree direction, the target mark 8, the grip grip 9, and the hand-eye camera 22 are arranged so that there is no difference in relative position and orientation. The coordinate system of the hand-eye camera 22 at this time is the same as that in FIG. In addition, the relative position from the target mark 8 to the grip grip 9 and the shape and size, the camera 22
The relative position from the robot hand 21 to the robot hand 21 and the geometrical dimensions are known.

First, the operator searches the object to be grasped 10 by using the hand-eye camera 22 while operating the robot arm 20. If the grasped object 10 can be found, the target mark 8 installed on the grasped object 10 is further identified, and the robot arm 20 is remotely operated so that the lowest mark A1 to the mark E5 can be discriminated within the camera visual field. Make adjustments. Once the above-described mark image is obtained, the relative position from the camera 21 to the target mark 8 can be measured later by image processing. In order to further improve the measurement accuracy, first, based on the measurement data, the Z-axis direction is kept constant and the arm is moved in a direction in which the relative position error in the other degrees of freedom is eliminated. Therefore, the relative position is measured again by measuring the image. If higher precision is required, the Z-axis direction may be gradually approached, and the relative position may be measured each time.

Finally, when the hand is moved to the target relative position in the Z-axis direction, the positioning of the hand is completed, so that the target object can be gripped by the gripping operation of the hand. Furthermore, at this time, if the current image of the mark and the reference image such as the outline at the time of joining are superposed,
A human can visually confirm the positioning situation.

[0019]

According to the present invention, the relative position of an arbitrary object placed in a three-dimensional space can be detected by the configuration of the proximity sensor including the camera system and the target mark. In the above-described process, a human can easily recognize the target mark by remote control while viewing the image with the ring-shaped mark as a target, and the relative positional relationship can be grasped to some extent by visual observation. If the target mark image to be further processed is obtained, the relative position can be measured by image processing. Further, since it is a concave three-dimensional mark, it is possible to measure the posture direction with high accuracy, and for example, it is possible to measure the relative position even if another mark which is not on the plane having five marks cannot be observed. In this case, it is possible to improve the measurement accuracy by changing the observation position and repeating the measurement after the measurement. Further, since each mark and the base are separately manufactured and painted, and the mark is fitted into the recess provided in the base, the boundary line between the mark and the base becomes clear and smooth, and the detection accuracy of the position of the center of gravity of the mark can be improved.

From the above description, this mark has the characteristics of a plane mark and a three-dimensional mark, and by providing a ring-shaped mark, even a human can grasp the relative positional relationship from the mark shape to some extent, and the mark can be easily recognized. This is especially effective in a robot system that performs remote control in addition to simple image measurement.

Therefore, according to the present invention, it is possible to obtain a target mark having the above-mentioned effects and solving the problems of the conventional target mark.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a target mark of the present invention,
(A) is a figure which shows the component of a mark, (b) is a figure which shows the front view of the mark after an assembly.

FIG. 2 is a diagram showing a camera image of a target mark.

FIG. 3 is a configuration diagram of a system for gripping an object using this mark as an example.

FIG. 4 is a diagram showing an example of a conventional target mark.

[Explanation of symbols]

 0 camera image plane 1 mark A 2 mark B 3 mark C 4 mark D 5 mark E 6 mark F 7 base 8 target mark 9 gripping grip 10 gripping target 20 robot arm 21 robot hand 22 hand-eye camera 23 robot control means 24 Image processing means 25 Robot operating means

Claims (1)

[Claims] 1. In a system for assembling, gripping, docking an object, etc., in a target mark for a proximity sensor installed on a joint surface of an object, a ring-shaped mark having the largest area and only one area having a different area are used. It consists of two circular marks and a base for installing these marks.The base has a recess with the same size as each mark to install these marks, centered on the center position of the recess for installing the ring mark. On the circumference of one circle, the four circular depressions are arranged at equal distances from each other on the outside of the ring, and one of the four circular depressions is used as a depression for the mark having the different area, These are provided on the base, which is concentric with the recess for the ring-shaped mark and has a circular recess at the center of the bottom of the ring that is hollowed out cylindrically. The target mark is characterized in that each mark is fitted and fixed in the hollow, and a color different from that of each mark and the base is applied.