JP2001300875A - Robot system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve position detecting accuracy of a positioning marker by a visual device, in a robot for correcting an operation point of a robot arm on the basis of visual recognition of the positioning marker. SOLUTION: A CCD camera 11 is provided on the tip of a robot arm 6 of a moving robot 1, and one oval positioning marker M to be positioned in relation to a work 4 is provided on a fixed facility 3 side. In a state where the moving robot 1 is stopped before the fixed facility 3, a robot controller moves the robot arm 6, the positioning marker M is photographed by the CCD camera 11, the position and the inclination are calculated from the detection of a long axis and a short axis of the positioning marker M by an image processing device, and the position of the positioning marker M in teaching and the inclination are compared with the detected position to find the positional deviation amount. Work by the robot arm 6 is performed while correcting an operation point on the basis of the positional deviation amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot system in which a robot arm is moved to a predetermined operation point to perform a work on a work target.

[0002]

In recent years, for example, in a production line of parts for automobiles, a mobile robot having a robot arm on an unmanned carrier has a moving robot on a traveling path in front of a fixed facility to be worked. (Working station) has been provided, and a system has been provided in which work such as assembly is automatically performed. In this case, a controller (control device) mounted on the mobile robot stops the automatic guided vehicle at the stop position based on detection of a stop marker provided on the traveling path by a sensor. Further, the controller controls the robot arm based on the data of the operation points taught in advance according to the control program, and performs a predetermined operation on the fixed equipment in a state where the robot arm is stopped at the stop position.

However, when the automatic guided vehicle is stopped at the stop position based on the detection of the stop marker as described above, the normal stop position (at the time of teaching the operation point) may be determined due to, for example, slippage of the drive wheels. It may not always be possible to stop with high accuracy at the stop position), for example, stop in a state where a shift of about several mm in the X (left / right) direction and Y (front / rear) direction and further a shift in the θ (rotation) direction have occurred. May be. When the displacement of the automatic guided vehicle with respect to such a stop position (fixed equipment) occurs, the robot arm executes the work in a state including the displacement, and the work at the taught operation point is performed successfully. There is a risk of disappearing.

Therefore, as a countermeasure, for example,
A position correction method disclosed in Japanese Patent Application No. 9151 is known. In this technique, a CCD camera is provided at the tip of a robot arm, and two circular positioning markers are provided on the upper surface of a worktable on a fixed facility side. Then, when the mobile robot stops, as shown in FIG. 8, the two positioning markers M1 and M2 are photographed by the CCD camera (the visual field (photographing screen) is indicated by V), and each marker is processed by image processing. The center of gravity points O1 and O2 of M1 and M2 are obtained, and a straight line L connecting the points O1 and O2 and the center point O of the points O1 and O2 are obtained. In this way, from the position of the center point O and the angle of the straight line L with respect to the X-axis direction, the displacement amount in the X, Y, and θ directions with respect to the mobile robot equipment is calculated, and the operation taught according to the displacement amount. The point is corrected to execute a highly accurate operation.

However, correcting the operating point of the robot arm based on the visual recognition of the two positioning markers M1 and M2 has the following disadvantages. That is, for position detection, two positioning markers M1 and M2 must be placed in the field of view V of the CCD camera. For example, when the amount of displacement is large, for example, one of the markers M1 A situation may occur in which a part is missing from the visual field V. If such chipping occurs, there is a possibility that the center of gravity O <b> 1 may be found shifted from the actual position.

[0006] Further, even if the markers M1 and M2 are not cut off from the visual field V, the markers M1 and M
When 2 comes, it is affected by the distortion of the lens of the CCD camera, and accurate position detection cannot be performed. On the other hand, if the visual field V is widened, the resolution is reduced and the position detection accuracy of the markers M1 and M2 is reduced. Furthermore, the brightness may be different between the two markers M1 and M2 due to the influence of disturbance light and the like, and there is a problem that the recognition level between the two markers M1 and M2 is different. .

The present invention has been made in view of the above circumstances, and has as its object to correct the operating point of a robot arm based on visually recognizing a positioning marker provided on a work target side. Accordingly, it is an object of the present invention to provide a robot system capable of improving the position detection accuracy of a positioning marker by a visual device.

[0008]

According to a first aspect of the present invention, there is provided a robot system in which a positioning marker comprising a figure having a long axis and a short axis is fixed to an operation target. The robot arm is provided with a visual device for photographing the positioning marker, and the position and inclination of the positioning marker are detected from the image data captured by the visual device to correct the operating point of the robot arm. Things.

According to this, the operation point of the robot arm can be corrected by detecting the position of the positioning marker fixedly positioned with respect to the work object. Is composed of a figure having a long axis and a short axis, and the position (center point or edge position) and the angle of the long axis (or short axis) are detected by photographing one positioning marker. It becomes possible. Therefore, unlike one in which two positioning markers are photographed in one field of view, one positioning marker can be easily photographed in the central part of the visual field of the visual device, and as a result, the position detection accuracy of the positioning marker by the visual device and, consequently, the operation can be improved. The point correction accuracy can be improved.

In this case, the shape of the positioning marker composed of a figure having a long axis and a short axis can be more specifically an elliptical shape or a rectangular shape (the invention of claim 2). By using one positioning marker having a relatively simple shape, it is possible to enhance the position detection accuracy of the positioning marker by the visual device.

According to a third aspect of the present invention, there is provided a robot system, wherein a positioning marker comprising a non-circular figure is provided at a fixed position with respect to a work object, and a visual device for photographing the positioning marker is provided by a robot arm. The position and inclination of the positioning marker are detected by pattern matching from the captured image data of the visual device, and the operating point of the robot arm is corrected.

According to this, the operating point of the robot arm can be corrected by detecting the position of the positioning marker fixedly positioned with respect to the work object. Is composed of a non-circular figure, it is possible to detect the deviation position from the reference position and the deviation angle from the reference position by pattern matching by photographing one positioning marker. Therefore, unlike one in which two positioning markers are photographed in one field of view, one positioning marker can be easily photographed in the central part of the visual field of the visual device, and as a result, the position detection accuracy of the positioning marker by the visual device and, consequently, the operation can be improved. The point correction accuracy can be improved.

In this case, the shape of the positioning marker composed of a non-circular figure can be more specifically a rectangular shape (the invention of claim 4). With the positioning markers, it is possible to enhance the position detection accuracy of the positioning marker by the visual device.

Further, the present invention can be applied to a system in which a robot arm is fixedly provided and a work object is sent while being supported on, for example, a pallet. Mounted on
The present invention can also be applied to a system including a mobile robot that is moved with respect to the work target (the invention of claim 5), and thereby, even if the stop position accuracy of the mobile robot with respect to the work target is relatively low, displacement correction is performed. This makes it possible to perform a highly accurate operation, which is effective.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment (corresponding to claims 1, 2, and 5) in which the present invention is applied to a mobile robot system for assembling automobile parts using a mobile robot will be described.
This will be described with reference to FIGS. First, a configuration of a mobile robot system, which is a robot system according to the present embodiment, will be briefly described. As shown in FIGS. 1 and 2, a mobile robot 1 travels on a floor on a traveling path. 2 and a plurality of fixed facilities 3 (1
(Only one is shown).

In this case, for example, a work 4 handled by the mobile robot 1 is supplied to a fixed position on the fixed equipment 3. The mobile robot 1 stops at a predetermined stop position in front of each fixed facility 3 while moving between the fixed facilities 3 along the traveling path 2 in the front-rear direction (arrow A and the direction opposite thereto). Work such as acquisition and assembly of the work 4 is automatically executed. It is to be noted that a plurality of mobile robots 1 are loaded, for example, and work is simultaneously performed on a plurality of fixed facilities 3. Further, on the fixed facility 3, a marker placement unit 10 described later is fixedly provided at a position close to the traveling path 2.

Here, the mobile robot 1 will be described. As shown in FIG. 1 and FIG.
Is configured such that a robot arm 6 is mounted on a rear side portion of the automatic guided vehicle 5. Although not shown in detail, the automatic guided vehicle 5 includes a traveling mechanism 7 (shown only in FIG. 3) including a plurality of wheels and a traveling and steering motor for driving the plurality of wheels at the bottom. Although not shown,
At the bottom of the automatic guided vehicle 5, a pair of front and rear guide sensors for detecting a guide line 8 laid along the traveling path 2 and a stop for detecting a stop marker provided in front of each of the fixed facilities 3. A marker sensor and the like are also provided.

On the other hand, the robot arm 6 is composed of, for example, a vertical articulated type (6-axis type) robot, and a hand 9 for gripping the work 4 and the like is attached to the tip of the robot arm 6. At the end of the robot arm 6, a CCD camera 11 with a light source, for example, is attached as a visual device. An image signal from the CCD camera 11 is input to an image processing device 12 (see FIG. 3) incorporated in the automatic guided vehicle 5 and processed.

Further, a robot controller 13 for controlling the entire mobile robot 1 is provided in the automatic guided vehicle 5 as shown only in FIG. The robot controller 13 is mainly configured by a microcomputer including a CPU, a ROM, a RAM, an input / output circuit, and the like, and according to a control program stored in advance, the traveling mechanism 7,
The robot arm 6, the hand 9, and the like are controlled to execute a series of operations. The image processing device 12 is connected to the robot controller 13.

At this time, the robot controller 13
Each guide sensor controls the traveling mechanism 7 based on the detection of the guide line 8, and moves the automatic guided vehicle 5 to the traveling path 2.
, And the automatic guided vehicle 5 is stopped at a stop position in front of the fixed facility 3 based on the detection of the stop marker by the stop marker sensor. Then, the robot controller 13 controls the operation of the robot arm 6 based on operation points based on a unique robot coordinate system (orthogonal coordinate system) in accordance with the control program in a state where the automatic guided vehicle 5 is stopped at the stop position. , Etc., for handling the work 4.

A teaching pendant 14 (see FIG. 3) is connected to the robot controller 13. The teaching (teaching) of the operating point stops the automatic guided vehicle 5 at a stop position. In the state where the teaching pendant 1 is
4 by manually operating the robot arm 6. As described below,
In the present embodiment, at the time of this teaching, the positioning marker is photographed by the CCD camera 11, and its position and inclination are detected and stored, and the operation point is stored as a relative position with respect to the positioning marker. ing.

In this embodiment, as shown in FIGS. 1 and 4, the marker placement section 10 provided in the fixed equipment 3 is used.
Is provided with one positioning marker M. The positioning marker M is a figure having a major axis L1 and a minor axis L2, in this case an elliptical shape, and a position fixed with respect to the position of the work 4 such that the major axis extends in the X-axis direction. Is provided.

On the other hand, as will be described later, the robot controller 13 of the mobile robot 1 will be described.
In the software configuration, when the robot arm 6 is stopped at the work position and the work is started, the robot arm 6 is moved so that the CCD camera 11 is directly above the marker placement section 10, and the robot arm 6 is positioned by the CCD camera 11. The image of the marker M is photographed from directly above. At this time, as shown in FIG. 4, the photographing is performed such that the positioning marker M is located substantially at the center of the visual field (photographing screen) V of the CCD camera 11. Note that this photographing is also performed during teaching.

The data of the photographed image is stored in the image processing device 1
2, the position of the positioning marker M (in this case, the X and Y coordinates of the center of gravity O where the long axis L1 and the short axis L2 intersect) is detected, and the reference axis of the long axis L1 (in this case, the X axis) Is detected. Thus, the image processing device 12 functions as a position detecting unit. In this case, the method of recognizing the positioning marker M may be binarization processing, gray processing, or another method.

The robot controller 13
Is based on the detected position and inclination of the positioning marker M and the position and inclination of the positioning marker M whose position has been detected and stored during teaching, in the front-rear and left-right directions (X, Y directions) of the stop position of the automatic guided vehicle 5. ) And rotation direction (θ
Direction), and the robot arm 6 performs the work while correcting the operation point based on the position shift amount (δX, δY, δθ). Therefore, the robot controller 13 functions as a displacement correcting means.

Next, the operation of the above configuration will be described with reference to FIGS. First, as described above, teaching is performed by the operator before the mobile robot 1 performs an actual operation. The flowchart of FIG. 6 schematically shows a processing procedure of a portion related to positioning executed by the robot controller 13 during the teaching.

That is, the mobile robot 1 is mounted on a predetermined fixed facility 3.
When the robot is stopped at the previous stop position (step S11), the CCD camera 11 is positioned directly above the marker placement section 10 (positioning with the center of the visual field V) based on manual operation of the robot arm 6 by the teaching pendant 14. The marker M is moved so as to come to a position where the center coincides with the center of the marker M (step S12). Then, step S1
3, the CCD camera 11 controls the positioning marker M
The part is photographed and the photographed image data is captured. still,
The position (photographing position) of the robot arm 6 taught at this time is stored in the memory of the robot controller 13.

In the next step S14, the CCD camera 1
1, the image processing device 12 detects the position of the positioning marker M (the center of gravity O).
Are calculated by calculation, and the position and the inclination are stored in the memory. In this case, since the positioning marker M has an elliptical shape having a long axis L1 and a short axis L2, the long axis L1 and the short axis L2
By obtaining the intersection with the center, the position of the center of gravity O can be easily detected, and by obtaining the inclination of the long axis L1 with respect to the X axis, the inclination θ can be easily detected.

Thereafter, in step S15, the operator uses the teaching pendant 14 to
The teaching of the operation point (the position and the posture at which the work 4 is handled by the hand 9) is performed based on the manual operation of. In step S16, the operation point is calculated as a relative position (vector data) from the position of the positioning marker M fixedly provided to the workpiece 4, and is stored in the memory. .

After the teaching is performed in this manner, the mobile robot 1 performs an actual operation (specifically, an operation of moving between the fixed facilities 3 and handling the work 4). At this time, the stop accuracy of the mobile robot 1 at the stop position is not always sufficiently high. For example, a positional deviation of about ± several mm in the X and Y directions and ± several degrees in the rotational direction is inevitable. Therefore, a slight displacement occurs between the stop position during teaching and the stop position during actual work.

If such a position shift occurs in the stop position of the mobile robot 1, the robot arm 6 executes the work in a state including the position shift, and the work (handling) to the operation point cannot be performed properly. There is a fear. Therefore, in this embodiment, the robot arm 6
When the mobile robot 1 (the automatic guided vehicle 5) stops at the stop position in front of the fixed facility 3 in order to perform the operation according to (1), the robot controller 13 executes the processing shown in the flowchart of FIG.

That is, the mobile robot 1 is mounted on the predetermined fixed equipment 3
When the robot arm 6 stops at the previous stop position (step S1), the robot arm 6 is moved to the photographing position at step S2 and
The CD camera 11 is moved to a position directly above the marker placement unit 10, and in step S3, the positioning marker M is photographed by the CCD camera 11, and the photographed image data is captured. In this case, since one positioning marker M is photographed, even if there is a slight shift in the stop position of the mobile robot 1, the field of view (photographing screen) V of the CCD camera 11, as shown in FIG. The positioning marker M can be photographed at the center of the image.

In the next step S4, in the same manner as in the above-described teaching, based on the image data captured by the CCD camera 11, the image processing device 12
The position and the inclination of the positioning marker M are detected.
In step S5, the difference between the detection result of the position and the inclination of the positioning marker M by the image processing device 12 and the position and the inclination of the positioning marker M at the time of teaching stored in advance, that is, the X-axis direction and the Y-axis direction , The amount of displacement (δX, δY, δθ) in the rotation direction is calculated.

Next, in step S6, the stored operating points are corrected based on the obtained positional deviation amounts (δX, δY, δθ). In this case, since the positioning marker M is provided at an absolute position with respect to the workpiece 4, the positional deviation amount of the positioning marker M detected based on the visual recognition is the deviation of the stop position of the automatic guided vehicle 5 as it is. The operation point is corrected so that the deviation is eliminated. Then, an operation (handling) by the robot arm 6 is performed based on the corrected operation point (step S7). When the operation is completed, the mobile robot 1 starts moving to the next operation (fixed equipment 3) ( Step S8).

As described above, according to the present embodiment, the fixed equipment 3
Based on visually recognizing the positioning marker M fixedly provided on the side by the CCD camera 11 provided on the robot arm 6, the amount of displacement from the normal stop position of the automatic guided vehicle 5 is calculated, Since the operation point of the robot arm 6 is corrected, highly accurate work can be performed.

The positioning marker M is a figure having a long axis L1 and a short axis L2, and is formed in an elliptical shape in this case. Therefore, by photographing one positioning marker M, its position and inclination are detected. It became possible. For this reason, unlike the conventional one in which the two positioning markers M1 and M2 are photographed in one field of view, there is a possibility that chipping or distortion may occur, so that one positioning marker M is located at the central portion of the field of view V of the CCD camera 11. This makes it easy to take a picture, and it is possible to prevent a problem that the recognition degree between the two markers M1 and M2 is different due to the influence of disturbance light or the like. As a result, the position detection accuracy of the positioning marker M and the operation can be prevented. The point correction accuracy can be improved.

In the above embodiment, the positioning marker M
Is an ellipse as a figure having a long axis and a short axis. Similarly, a figure having a long axis and a short axis may be rectangular, and the same effect can be obtained. When a rectangular positioning marker is adopted, the coordinates of a predetermined edge (corner) instead of the center of gravity may be used as the position of the marker. Obviously, the inclination θ may be obtained based on the short axis L2.

FIG. 7 shows another embodiment of the present invention.
4). This embodiment is different from the above-described embodiment in that a non-circular, in this case, a square marker is adopted as the positioning marker N, and the position detecting means (image processing device 12) is used for the positioning marker N by pattern matching. Is configured to detect the position and the inclination of.

At this time, the image processing device 12
A reference pattern P having the same shape as the positioning marker as shown in FIG.
And the degree of coincidence with the positioning marker N on the captured image is compared at each pixel level, and the position and inclination (angle) with the highest degree of coincidence are calculated, thereby increasing the position detection accuracy of the positioning marker N. be able to. As a matter of course, the shape of the positioning marker N may be a non-circular shape such as a rectangular shape or a triangular shape.

In each of the above embodiments, the present invention is applied to a system using a mobile robot. However, the present invention is applied to a fixed robot (robot arm) in a state where a work is placed on a pallet, for example. The present invention can also be applied to a robot system that is transported by a conveyor device or the like. In this case, on the pallet,
Similarly, one positioning marker may be provided at a position fixed to the workpiece, and the operation point of the robot arm may be corrected based on visual recognition of the positioning marker on the robot arm side.

In addition, the present invention is not limited to the above-described embodiments. For example, the shape of the positioning marker may be a diamond, an arrow, a part of a circle, a ring, Various shapes are conceivable, such as a shape in which a part of is notched. The work performed by the robot arm is not limited to handling, and the visual device is not limited to a CCD camera. Further, the present invention is not limited to an assembly line for automobile parts, and can be widely applied to systems using various robots.
The present invention can be appropriately changed and implemented without departing from the gist.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing an embodiment of the present invention, in which a mobile robot stops before a fixed facility.

FIG. 2 is a side view schematically showing a state where the mobile robot has stopped before a fixed facility.

FIG. 3 is a block diagram schematically showing an electric configuration of the mobile robot.

FIG. 4 is a diagram showing a field of view of a CCD camera and a state of a positioning marker photographed.

FIG. 5 is a flowchart showing a processing procedure of a portion related to position correction during actual work of the mobile robot.

FIG. 6 is a flowchart illustrating a processing procedure of a portion related to position correction during teaching of the mobile robot.

FIG. 7 shows another embodiment of the present invention, and shows a side view of a reference pattern (a) and a state (b) of a photographed positioning marker.

FIG. 8 is a diagram corresponding to FIG. 4 showing a conventional example.

[Explanation of symbols]

In the drawings, 1 is a mobile robot, 3 is a fixed facility (work target), 4 is a work, 5 is an unmanned carrier, 6 is a robot arm, 9 is a hand, 10 is a marker placement unit, and 11 is a CCD camera (visual device). , 12 are image processing devices (position detecting means), 13 is a robot controller (positional deviation correcting means), M and N are positioning markers, V is a visual field, L1 is a long axis, L2 is a short axis, O is a center of gravity, and P is The reference pattern, θ indicates the inclination.

Continued on the front page F-term (reference) 3F059 AA03 AA13 BA02 BA08 BB07 CA06 DA02 DA05 DA09 DB04 DB09 DC08 DD01 FA03 FA05 FA08 FB01 FB16 FB26 FC02 FC13 FC14 5H269 AB33 BB03 CC11 EE05 FF05 FF06 JJ09 JJ20 SA03 5A01 BB10 BB10 EE01 EE03 EE07 EE09 FF13 HH05 HH09 LL03 9A001 BB06 HH21 HH34 JJ49 KK54

Claims (5)

[Claims] 1. A robot system in which a robot arm is moved to a predetermined operation point to perform a work on a work target, the robot system being provided at a fixed position with respect to the work target, A positioning marker formed of a figure having a short axis; a visual device provided on the robot arm for photographing the positioning marker; and a position detecting means for detecting the position and inclination of the positioning marker from image data captured by the visual device. And a displacement correcting means for correcting an operation point of the robot arm based on the detection of the position detecting means. 2. The robot system according to claim 1, wherein the positioning marker has an elliptical shape or a rectangular shape. 3. A robot system in which a robot arm is moved to a predetermined operation point to perform a work on a work target, wherein the robot system is provided at a fixed position with respect to the work target and has a non-circular shape. A positioning marker formed of a graphic of the following, a visual device provided on the robot arm for photographing the positioning marker, and a position detecting means for detecting the position and inclination of the positioning marker by pattern matching from photographed image data of the visual device, A robot system comprising: a position shift correcting unit that corrects an operating point of the robot arm based on the detection of the position detecting unit. 4. The robot system according to claim 3, wherein the positioning marker has a rectangular shape. 5. The robot according to claim 1, wherein the robot arm is mounted on an automatic guided vehicle and configured as a mobile robot that is moved with respect to the work target.
The robot system according to any one of the above.