JPH01247285A - Method for calibration of work locating device - Google Patents

Abstract

PURPOSE:To make precision adjustment in a service place quickly and easily by calibrating the locating robot working position on the basis of the position on the coordinates system for the robot and the position on the coordinates system in the service place of an object mounted on the robot. CONSTITUTION:As an object a light emitting diode 14 is precisely located on and fixed to a work receipt jig 6 arranged one unit per locating robot 5. Three two-dimensional cameras 15 are installed on a beam at the top of a frame 4. The light emitting diode as object mounted on this locating robot is caught by two cameras, and the one-axial working position data of the object is obtained by the principle of triangle measurement, and the locating robots are operated for all axes to sample the data. For each moving shaft, the calibration function or calibration table for operating robots actually in the command position on the coordinates system in service place is prepared on the basis of relationship between the theoretical value of the operating position and the sampling data.

Description

Detailed Description of the Invention (Industrial Application Field) This invention moves and arranges a plurality of gauge parts for positioning workpieces based on the operation of a plurality of positioning robots, and positions a plurality of workpieces relative to each other. The present invention relates to a method for calibrating the operating position of the positioning robot of a workpiece positioning device.

(Prior Art) As an example of the above-mentioned workpiece positioning device, there is one previously disclosed by the present applicant in Japanese Patent Laid-Open No. 144595/1983.

FIG. 6 shows the above-mentioned device installed in the assembly area of an automobile body.
1 is a perspective view showing a configuration using a Cartesian coordinate robot as a positioning robot, which is applied to the assembly stage of the main parts of the vehicle body that almost determines the assembly accuracy of the vehicle body;
shows a workpiece positioning device placed on the main body part assembly stage.

In this assembly line, car body panels such as the main floor, left and right side panels, rear panels, cowl top assembly, shelf panel, etc. are delivered to the main body part assembly stage, and the body panels are assembled at that stage. The workpiece positioning device 1 positions the panel at a relative position that satisfies a predetermined assembly accuracy, and then, on the same stage, the positioned panels are temporarily joined together by spot welding to improve the assembly accuracy of the car body. After that, the main body part 2 is assembled by the shuttle conveyor 3 to other stages (not shown), and additional spot welding is performed on the main part 2 of the car body at those stages. At the same time, vehicle body panels such as front and rear roof rails and roof panels are further assembled to assemble the vehicle body, and the assembly accuracy of the vehicle body is measured in the subsequent stage (not shown). In order to position each of the constituent body panels, the workpiece positioning device 1 includes a frame 4, a number of positioning robots 5 (partially omitted in the figure) attached to the frame 4, and a -stand as a hand section. Each positioning robot 5 has one or more workpiece holders equipped with a jig 6, and the positioning robot 5 is also equipped with an air cylinder-driven workpiece clamping device 7 as a hand section as required.

As shown in FIG. 7, the workpiece receiver jig 6 moves a large number of adjacent strips one by one forward and backward in the same direction using a servo motor, and shapes the leading edges of the strips into a predetermined shape. By fixing the strips together with a fixing device, it is possible to form a gauge portion 6a as a positioning means that can position and hold the workpiece. No. or patent application No. 62-12193
(Refer to No. 1), using this function, the workpiece positioning device 1 adjusts the shape of each of the numerous positions to be positioned on each body panel constituting the main part 2 of the car body, and the workpiece holder corresponding to that position is fixed. By making the shapes of the gauge portions 6a of the tools 6 match each other, and at the same time, by the operation of each positioning robot 5, the workpiece receivers are placed in the predetermined positions of the jigs 6, and by extension, the gauge portions 6a thereof, respectively. The vehicle body panels can be positioned relative to each other and fixed by operating each work clamp device 7.

Then, the control device 8 of the positioning robot 5 controls the sixth positioning robot 5.
As shown in the figure, a calculation unit 9 consisting of a normal CPU, a memory 10 used for storing operation instruction signals and calculation processing,
The workpiece holder is an interface 11 for inputting an operation instruction signal including position data of the gauge part 6a of the jig and outputting an operation confirmation signal, and the servo motor and workpiece holder provided for each coordinate axis direction of the positioning robot 5 are connected to the jig. a servo controller 12 for controlling the operation of the servo motor for driving the strips of 6;
These workpiece receivers are equipped with a controller (not shown) that controls the operation of the small piece fixing device of the jig 6 and the operation of each workpiece clamping device 7. Based on the input operation instruction signal, each positioning robot 5 and workpiece receiver control the operation of the jig 6 and workpiece clamping device 7, and when the operation is completed, output an operation confirmation signal.

(Problems to be Solved by the Invention) By the way, when installing the workpiece positioning device 1 on the vehicle body main part assembly stage, in order to ensure sufficient positioning accuracy of each gauge part 6a, the operating position of each positioning robot 5 is adjusted. It is necessary to calibrate it to correspond to the coordinate system of the main body assembly stage mentioned above.
Conventionally, calibration data is obtained by first measuring the operating position of each positioning robot 5 in the directions of the three orthogonal coordinate axes using a measuring device such as a three-dimensional measuring device, and then the positioning robots 5 are , the frame 4 is assembled with a predetermined precision, and the positioning robot 5 is assembled in such a way that the direction of each coordinate axis matches the direction of the three orthogonal coordinate axes of the frame 4, and then the frame 4 is moved to the main body part assembly stage. Then, the frame 4 is installed so that the direction of each coordinate axis coincides with the direction of the three orthogonal coordinate axes of the stage, and the distortion of the frame 4 due to installation or transportation there is measured using a surveying device. The method used was to make corrections while doing so, and then obtain calibration data for converting the coordinate system of frame 4 to the coordinate system of the stage.

However, in the above method, in order to guarantee the operating position of each robot after assembly to the frame 4, the accuracy of the installation of the frame 4 to the main body part assembly stage,
The distortion correction accuracy of the frame 4 after installation must be extremely high, and since the frame 4 is an extremely large structure, it is extremely difficult to correct the distortion and requires a long period of time.

The present invention provides a calibration method that advantageously solves these problems.

(Means for Solving the Problems) A method for calibrating a workpiece positioning device according to the present invention involves moving and arranging a plurality of gauge parts for positioning the workpieces based on the operations of a plurality of positioning robots. When calibrating the operating position of the positioning robot of the workpiece positioning devices that position each other, the workpiece positioning device is installed at the place where it is used, and the positioning robot is provided with a target that moves based on its operation, and one of the steps is to , installing at least two cameras at predetermined positions in the use place so that their directions can be changed, and then operating the positioning robot to move the target object to a predetermined position in the coordinate system of the positioning robot. ,
The moving target is captured by two of the cameras by changing the direction of the camera,
Based on the distance between the cameras and the direction of the cameras in that state, the position of the target in the coordinate system of the place of use is determined, and the position of the target in the coordinate system of the positioning robot is determined. The operating position of the positioning robot is calibrated based on the coordinate system and the position of the use place in a coordinate system.

(Function) According to this method, the operating position of the positioning robot of the workpiece positioning device after it is installed at the place of use is captured by the two cameras installed at the place of use, and the target provided on the positioning robot is captured. The position of the target is determined based on the principle of triangulation based on the distance between the cameras and the direction of the camera, and the position of the target is calibrated based on the results, so it is easy to install the frame that supports the positioning robot of the workpiece positioning device and correct distortion. The accuracy required for the workpiece positioning device can be reduced while guaranteeing the operational accuracy of the positioning robot, and the period required for achieving accuracy of the workpiece positioning device after installation can be significantly shortened.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a perspective view showing an embodiment in which the workpiece positioning device calibration method of the present invention is applied to the workpiece positioning device shown in FIG. 6. In the figure, the same parts as the device shown in FIG. It is indicated by the same code.

That is, 1 in the figure indicates a workpiece positioning device, and this workpiece positioning device 1 is used to place workpieces such as a floor main, left and right side panels, a rear panel, a cowl top assembly, and a shelf panel on a main body assembly stage of an automobile body assembly line. The control device 8 is installed to mutually position vehicle body panels for temporary fixing, and as shown in FIG. The servo motor and workpiece receiver for each joint control the operation of the servomotor for driving the small pieces of the jig 6, and further control the operation of the workpiece clamping device 7.

To install this workpiece positioning device 1 on the stage, first, a large number of positioning robots 5 are installed on the frame 4, and a workpiece holder is equipped with a jig 6 and a workpiece clamping device 7 as a hunt part as required. The robots are temporarily assembled so that the direction of the orthogonal coordinate axes of the robots roughly coincides with the direction of the orthogonal coordinate axes set on the frame 4, and then the frame 4 is transported from the assembly location to the main body part assembly stage. so that the direction of the orthogonal coordinate axes of the frame 4 approximately coincides with the direction of the orthogonal coordinate axes of the stage.
This is done by fixing it on that stage.

When calibrating the operating position of each positioning robot 5 of the workpiece positioning device 1, in this example, as shown in FIG. The light emitting diode 14 is positioned and fixed with high precision, and the light emitting diode 14 is connected to a power source to enable light emission.

On the other hand, here, three two-dimensional cameras 15 using, for example, a CCD are mounted via camera stands 16 on the uppermost beam of the frame 4 fixed to the vehicle main part assembly stage.

As shown in FIG. 3, the camera stand 16 here has a horizontal axis A and a vertical axis! Camera 15 around tlAB
A servo motor-driven vertical drive mechanism 16a that rotates the
and a horizontal drive mechanism 16b, and the operation of these camera stands 16 is controlled by a camera stand control device 17 which, like the control device 8, includes a CPU, memory, interface, servo controller, etc., as shown in FIG. , are controlled according to a pre-input program or operation input from the keyboard 18.

In addition, the three camera stands 16 are mounted at the same height and widely spaced apart from each other in the horizontal direction, and the optical axes of at least three cameras are aligned with the camera 15.
The three camera stands 16 are installed at a position where all of the light emitting diodes 14 can be reached without being obstructed by the frame 4, the positioning robot 5, etc. The positions of these camera stands 16 are measured with high precision using a surveying device such as a transformer or a shifter.

The three cameras 15 are each connected to an image display device 19 having a CRT, as shown in FIG.
In this way, images captured by each two-dimensional camera 15 can be displayed on the image display device 19.

After such work, the three two-dimensional cameras 15 mentioned above are
The operating position of each positioning robot 5 is calibrated using the procedure shown in FIG. 4 as appropriate.

That is, here, first, in step 101, the workpiece holder of the specific positioning robot 5 whose operating position is calibrated is set to the light emitting diode 14 provided on the jig 6, and the camera stand 16 is operated to set the camera 15 horizontally and By rotating in the vertical direction, images are captured within the screens of the three two-dimensional cameras 15. In this example, this capture is performed by inputting a program set in advance to the camera stand control device 17 based on the approximate positional relationship between the camera 15 and the light emitting diode 14, and causing the camera stand control device 17 to perform the capture according to the program. However, it is also possible to operate the keyboard 18 by hand while viewing the screen being imaged by the camera 15 using the image display device 19. Furthermore, when capturing is possible with three two-dimensional cameras 15, the three cameras with a larger distance between the cameras are selected and used in order to improve the accuracy of triangulation, which will be described later.

In the next step 102, as shown in FIG. 16 is further activated to adjust the attitude of the two-dimensional camera 15. If the image of the light emitting diode 14 is captured at the center of the screen in this way, the light passes on the optical axis of the two-dimensional camera 15, so there is less distortion in the lens system, and a clear image can be obtained at an accurate position. Can be done.

In this example, this adjustment is performed while visually checking the screen 15a.
This is done by manually operating the keyboard 18, but by recognizing the image position of the light emitting diode 14 within the screen 15a using an image processing device and inputting that position to the camera stand control device 17, the above adjustments can be made automatically. You can also do it.

Note that during this adjustment, if the lens of the two-dimensional camera 15 is provided with a filter that allows only light of the same color as that of the light emitting diode 14 to pass through, the adjustment will not be hindered by other disturbance light.

In the next step 103, as shown in FIG. The angle β between the two camera stands 16 and the horizontal line E connecting the intersections of the two axes A and B is determined from the operating positions of both camera stands 16, and from these angles α and β, The angles θ and θ2 between the horizontal line E and the optical axis C
Since the length 2 of the horizontal line 21 is constant regardless of the operating position of the camera stand 16, the value of l and the angle θ1. θ2, the distance from each two-dimensional camera 15 to the light emitting diode 14 is determined using the principle of triangulation.

Then, in step 104, light emission in the coordinate system of the stage is determined based on the distances from the three two-dimensional cameras 15 to the light-emitting diodes 14 and the previously measured positions of the two-dimensional cameras 15 on the stage. The position of the diode 14 and thus the actual operating position of the positioning robot 5 in which the light emitting diode 14 is installed is determined and recorded as operating position data, and in the subsequent step 105, the specific position of the positioning robot 5 is determined. Determining whether the collection of the operating position data for the movable axis has been completed, that is, whether a sufficient number of data has been obtained to calibrate the operating position when a specific movable axis is operated, If not obtained, the process advances to step 106.

In step 106, the positioning robot 5 is further operated for the specific movable axis, and then in step 10
Return to step 1 and collect the operating position data again.

In step 105, actuation for a specific movable axis is performed.
``If it is determined that a sufficient number of position data have been obtained, the process proceeds to step 107. In step 107, it is determined whether or not operating position data have been obtained for all movable axes of the specific positioning robot 5, and all If it is determined that the data has not been obtained for the movable axis, the movable axis to be operated is switched in step 108, and then the process returns to step 101 to collect the actuation position data again.Also, in step 107
If it is determined that the operating position data has been obtained for all movable axes, the process proceeds to step 109, and in step 109, the operating position data for each movable axis is determined based on the relationship between the theoretical value of the operating position and the collected data. , a calibration function or a calibration table is created to actually operate the positioning robot at the indicated position in the coordinate system of the stage.

Furthermore, as a result of comparing the above theoretical values and the collected data, if there is a deviation in the coordinate axis direction of the positioning robot 5 with respect to the coordinate axis direction of the stage, the positioning robot 5 should be mounted on the frame 4 to eliminate the deviation. Correct your posture.

By performing this procedure for all the positioning robots 5, it is possible to obtain highly accurate calibration data for making the operating positions of all the positioning robots 5 of the workpiece positioning device 1 correspond to the coordinate system of the main body assembly stage. Moreover, according to this method, the positioning robot 5 can be mounted on the frame 4 without significantly increasing the accuracy and the accuracy of the installation position of the frame 4 on the stage, and with little or no distortion correction of the frame 4. Since the operating position of the positioning robot 5 can be guaranteed at any time, the accuracy of the workpiece positioning device 1 at the place of use can be easily achieved in a short period of time.

Although the above description has been made based on the illustrated examples, the present invention is not limited to the above-mentioned examples. For example, objects other than light emitting diodes may be used as targets, and the number of cameras may be changed as required. Can be changed.

(Effects of the Invention) Thus, according to the method of the present invention, the operating position of the positioning robot of the workpiece positioning device after it is installed at the place of use can be captured by three cameras as the target moves based on the operation. Since the measurement is performed by triangulation and calibration is performed based on the results, the accuracy required for installing the frame that supports the positioning robot and correcting distortion of the workpiece positioning device can be reduced while guaranteeing the operating accuracy of the positioning robot. As a result, the period required for achieving accuracy of the workpiece positioning device after installation can be significantly shortened.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the workpiece positioning device calibration method of the present invention, Fig. 2 is a configuration diagram showing the structure of the workpiece positioning device used in the above example, and Fig. 3 is a triangulation diagram in the above example. FIG. 4 is a flowchart showing the implementation procedure of the above example. FIG. 5 is an explanatory drawing showing the method of capturing the light emitting diode in the above example. FIG. 6 is a perspective view showing a conventional workpiece positioning device. FIG. 7 is a configuration diagram showing the configuration of the above-mentioned conventional device. l...Work positioning device 2...Main part of the vehicle body 5...Positioning robot 6...Workpiece holder is jig 6a...Gauge part 8...
・Control device 13... Main control device 14...
Light emitting diode 15... Two-dimensional camera 16...
Camera stand I7...Camera stand control device patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Scope of Claims] 1. A workpiece positioning device in which a plurality of workpiece positioning gauge parts are moved and arranged based on the operation of a plurality of positioning robots, and a plurality of workpieces are mutually positioned. When calibrating the operating position, the workpiece positioning device is installed at the place where it is used, and a target object that moves based on the operation of the positioning robot is provided, and at least two cameras are installed at predetermined positions in the place where it is used. is installed so that its direction can be changed, and then the positioning robot is operated to move the target object to a predetermined position in the coordinate system of the positioning robot, and the moved target object is set so that the direction of the camera can be changed. By changing the image, it is captured by two of those cameras,
Determine the position of the target object in the coordinate system of the location of use based on the distance between the cameras and the orientation of the cameras in that state, and determine the position of the target object in the coordinate system of the positioning robot. A method for calibrating a workpiece positioning device, the method comprising: calibrating the operating position of the positioning robot based on the coordinate system and the position of the use place in a coordinate system.