JPH06307812A - Method and device for measuring three-dimensional position on curved surface - Google Patents

Abstract

PURPOSE:To simply and accurately perform, with a video camera, the three-dimensional position measuring of the part on a car body coating surface where a coating flaw is generated. CONSTITUTION:A plurality of point data pieces are selected out of the CAD data for a car body expressed by the object coordinate system SIGMAb, and on the basis thereof the curved surface shape of the coated surface 4 of the car body is expressed as a curved surface approximating formula Eb, which is converted into a video camera coordinate system SIGMAc so that a curved surface approximating formula Ec is obtained. On the other hand, a line-of-view equation Ee expressing a straight line passing a coating flaw generation part Pd in the video camera coordinate system SIGMAc is calculated from the picture element position of the flaw generation part Pd on the image receiving screen of a video camera 16. Then the curved surface approximating formula and line-of-view equation Ee are solved as simultaneous equation so that the coordinates in the video camera coordinate system SIGMAc of the part Pd are calculated as the point of intersection, and the three-dimensional position measuring of the part Pd is conducted by converting the obtained coordinates into the coordinate system SIGMAw of the space to be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a three-dimensional position on a curved surface and a device for measuring the three-dimensional position of a point to be measured on an object having a curved surface such as a vehicle body using a video camera. It is about.

[0002]

2. Description of the Related Art Since the quality of finish of a vehicle body coating has a great influence on the marketability of a vehicle, a coating film defect inspection step is generally provided after the vehicle body coating step in a vehicle manufacturing line. In this coating film defect inspection step, various kinds of defect inspections are performed on the coating film applied to the vehicle body surface. For example, Japanese Patent Application Laid-Open No. 62-233710 discloses a coating film defect inspection apparatus which irradiates a coating film surface with light and inspects the coating film for defects based on information obtained from reflected light from the coating film surface. It is disclosed.

When a coating film defect is detected in the coating film defect inspection process, a coating film defect correction process such as coating film polishing is performed in a subsequent process. This correction process is automatically performed by a robot or the like. In this case, it is necessary to three-dimensionally measure the site where the coating film defect occurs and transmit it to the subsequent process.

Therefore, in the past, Japanese Patent Laid-Open No. 2-30920
A three-dimensional position measuring method by stereoscopic vision as disclosed in Japanese Patent Publication No. 2 is used.

In this measuring method, the same area on the vehicle body surface is imaged by two video cameras to inspect the coating film defect. When a coating film defect is detected, each video camera is detected. The coating film defect generation portion is three-dimensionally measured from the deviation of the pixel position of the coating film defect generation portion (measured point) on the image receiving screen.

[0006]

However, the above-mentioned conventional three-dimensional position measuring method has the following problems. That is, two video cameras are required to perform three-dimensional position measurement by stereoscopic vision.
When there are multiple coating film defect locations, it is often difficult to associate the pixel positions of each coating film defect location on the image receiving screen between both video cameras. However, there are many cases in which there is a hindrance in accurately measuring a coating film defect occurrence site.

The above problem is not limited to the case where the coating film defective portion on the vehicle body surface is measured, but is generally the same when the three-dimensional position of the measured point on the object having the curved surface shape is measured using the video camera. It is a problem that can occur.

The present invention has been made in view of the above circumstances, and it is possible to easily and accurately measure the three-dimensional position of a point to be measured on an object having a curved surface. It is an object of the present invention to provide an original position measuring method and its apparatus.

[0009]

According to the three-dimensional position measuring method and apparatus for a curved surface according to the present invention, the curved surface shape of an object such as a car body is often known in advance as CAD data. In view of this, the CAD data is used to calculate a curved surface approximation formula, and a line-of-sight equation representing a straight line passing through the measured point is calculated based on the pixel position of the measured point on the image receiving screen of the video camera. By making the equations simultaneous and obtaining the intersection, the three-dimensional position of the measured point can be measured by one video camera, and thus the above-mentioned object is achieved.

That is, according to the first aspect of the present invention, the three-dimensional position of the measured point on the object having a curved surface shape, which is arranged at a predetermined position in the measured space, is set on the object including the measured point. A method of measuring using a video camera for imaging a predetermined area, comprising a plurality of predetermined points from CAD data indicating points on the object stored in an object coordinate system set for the object. Data is selected, the curved surface shape of the object is represented as a curved surface approximation formula based on the selected point data, and the curved surface approximation formula is associated with a measured space coordinate system that defines the measured space and a predetermined coordinate correspondence. Is converted to the video camera coordinate system set for the video camera so that the video camera coordinates can be calculated from the pixel position of the measured point on the image receiving screen of the video camera. In the La coordinate system, a line-of-sight equation expressing a straight line passing through the measured point is calculated, and then the line-of-sight equation and the curved surface approximation formula expressed in the video camera coordinate system are simultaneously solved to solve the line-of-sight equation. A three-dimensional position measurement of the measured point is performed by calculating coordinates of the measured point in the video camera coordinate system and further converting the coordinates into the measured space coordinate system. Is.

According to a second aspect of the present invention, the three-dimensional position of a measured point on an object having a curved surface shape and arranged at a predetermined position in the measured space is set on the object including the measured point. A method of measuring using a video camera for imaging a predetermined area, comprising a plurality of predetermined points from CAD data indicating points on the object stored in an object coordinate system set for the object. The data is selected, and the curved surface shape of the object is represented as a curved surface approximation formula based on the selected point data, while having a predetermined coordinate correspondence with the measured space coordinate system that defines the measured space. In the video camera coordinate system set for the video camera,
From the pixel position of the measured point on the image receiving screen of the video camera, calculate a line-of-sight equation representing a straight line passing through the measured point, further coordinate conversion of the line-of-sight equation to the measured space coordinate system, then, The coordinate-transformed line-of-sight equation and the curved surface approximation equation are simultaneously solved to solve the three-dimensional position of the measured point.

[0012]

As shown in the above structure, the CA
The three-dimensional position of the measured point is measured as an intersection obtained by simultaneously solving the curved surface approximation formula calculated using the D data and the line-of-sight equation calculated from the pixel position of the measured point on the image receiving screen of the video camera. Thus, it is possible to measure the three-dimensional position of the measured point with one video camera.

Therefore, according to the present invention, it is possible to reduce the required number of video cameras, and it becomes unnecessary to associate the pixel positions between the two video cameras, which occurs when there are two video cameras. This makes it possible to easily and accurately measure the three-dimensional position of a measured point on an object having a curved surface even if there are a plurality of measured candidate points.

In this case, when selecting a plurality of point data from the CAD data, the selection may be performed over a wide area of the object, but in the case of an object having a complicated curved surface shape such as a vehicle body. The number of point data to be selected in order to express this curved surface shape as a curved surface approximate expression becomes enormous, and therefore the degree of the curved surface approximate expression becomes high, so that the data calculation processing time also becomes long. As described above, when a plurality of point data is selected from the CAD data, if the CAD data in the predetermined area on the object corresponding to the imaging area of the video camera is used, the curved surface shape of the object is divided. It is possible to make the shape of the curved surface relatively simple, whereby the degree of the curved surface approximation formula can be lowered and the data calculation processing time can be shortened.

By the way, in the invention described in claim 1,
In order to convert the curved surface approximate expression represented by the object coordinate system into the video camera coordinate system and represent it, it is necessary that the coordinate correspondence relationship between both coordinate systems is established. For that purpose, not only the coordinate correspondence between the measured space coordinate system and the video camera coordinate system but also the coordinate correspondence between the measured space coordinate system and the object coordinate system must be established. Similarly, in the second aspect of the invention, it is necessary that the coordinate correspondence between the measured space coordinate system and the object coordinate system is fixed. This coordinate correspondence is determined by arranging the object at the above-mentioned predetermined position in the measured space, but it is actually impossible to accurately arrange the object at the above-mentioned predetermined position. Some deviation inevitably occurs between the position and the predetermined position. Therefore, as described in claim 4, if the deviation between the actual position of the object in the measured space and the predetermined position is measured and the CAD data is corrected according to this deviation, the three-dimensional position is corrected. The measurement accuracy can be further improved.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a three-dimensional position measuring apparatus on a curved surface according to the present invention.

This three-dimensional position measuring apparatus 10 is used in a coating film defect inspection station of a vehicle body 2 of a vehicle manufacturing line.
When a coating film defect is detected, the device is a device for three-dimensionally measuring the portion where the coating film defect occurs, and includes a video camera robot 12, a host computer 14, and its peripheral devices.

The video camera robot 12 has a video camera (CCD camera) 16 attached to the arm tip of a robot body 18, and a robot control panel 20.
The robot body 18 can be operated to change the orientation of the video camera 16 three-dimensionally.

The vehicle body 2 is conveyed in the direction of the arrow in the figure by the conveyor 24 while being placed at a predetermined position on the pallet 22. The host computer 14 has a conveyor 2
The position information of the vehicle body 2 is input from the sequencer 28 based on the encoder pulse from the encoder 26 arranged in No. 4. When information that the vehicle body 2 has been conveyed to the coating film defect inspection station is input from the sequencer 28, the host computer 14 outputs this to the robot control panel 20. As a result, the robot control panel 20 activates the robot body 18 so that the direction of the video camera 16 is changed to the body 2
Then, three-dimensionally changing along the surface of the vehicle body 2 at a predetermined interval, a defect inspection of the coating film surface 4 applied to the vehicle body 2 is performed. This defect inspection method for the coating film surface 4 is disclosed in Japanese Patent Laid-Open No. 4-204314, so a detailed description thereof will be omitted, but only in one direction in a plane parallel to the coating film surface 4. While irradiating the coating film surface 4 with irradiation light whose characteristics change, the coating film surface 4 is imaged by the video camera 16 and the image receiving screen is analyzed by the image processing device 38 to detect the coating film defect. It has become.

As shown in FIG. 2, the robot control panel 20 has a coordinate axis Xc with respect to the video camera 16 in the horizontal and vertical directions of the CCD (pixel) array on the image receiving screen and in the optical axis direction of the video camera 16. , Yc, Zc respectively are set, and coordinate conversion of the video camera coordinate system Σc to the measured space coordinate system Σw that defines the space (measured space) in which the video camera robot 12 is installed is set. Parameters are input to the host computer 14 as needed. Alternatively, the teaching data may be stored in the memory in advance and taken out at any time.

The host computer 14 applies the coating film in the video camera coordinate system Σc from the pixel position Pp (see FIG. 3) on the image receiving screen 30 of the video camera 16 corresponding to the coating film defect occurrence site Pd (measured point). A line-of-sight equation Ee representing a straight line passing through the defect occurrence site Pd is calculated. Note that the calibration data stored in the calibration data memory 32 is used to calculate the line-of-sight equation Ee. This calibration data is data used when calculating the line-of-sight equation Ee corresponding to each pixel position on the image receiving screen 30 based on the calibration result of the video camera 16 at the time of shooting.

Three-dimensional position measuring apparatus 10 according to this embodiment
Includes a CAD data memory 34 that stores CAD data indicating points on the surface of the vehicle body 2. This CAD data is represented by the object coordinate system Σb set for the vehicle body 2. This object coordinate system Σb is used when the vehicle body 2 is accurately placed at a predetermined position on the pallet 22. The coordinates uniquely correspond to the measurement space coordinate system.

From the CAD data stored in the CAD data memory 34, the host computer 14 selects a plurality of predetermined point data from the CAD data in the area corresponding to the imaging area of the video camera 16 on the coating surface 4. And a minimum of 2 based on these selected point data
The curved surface shape of the coating film surface 4 of the vehicle body 2 is expressed as a curved surface approximate expression Eb by calculation using the multiplication method.

That is, as shown in FIG. 4, the coating film surface 4 to be inspected for coating film defects is divided into five parts in the front-rear direction from the first surface part 4A to the fifth surface part 4E, and each of these surface parts is divided. Then, the curved surface approximation formula Eb is calculated. Since the curved surface shape of each of the divided surface portions is simplified with respect to the original curved surface shape of the entire coating film surface 4, the point data to be selected in order to represent this as a curved surface approximate expression Eb having a predetermined accuracy. A small number is enough. Therefore, the degree of the curved surface approximation equation Eb can be lowered to shorten the data calculation processing time.

The host computer 14 converts the curved surface approximation formula Eb into a video camera coordinate system Σc to obtain a curved surface approximation formula Ec. The host computer 14 further inputs the curved surface approximation equation Ec and the line-of-sight equation Ee to the processor 36. The processor 36 calculates the coordinates Pd (xc, yc, zc) in the video camera coordinate system Σc of the coating film defect occurrence portion Pd by solving the curved surface approximation formula Ec and the line-of-sight equation Ee in parallel. That is, the coordinates Pd (xc, yc, zc) are calculated as the intersection of the curved surface represented by the curved surface approximation equation Ec and the straight line represented by the line-of-sight equation Ee. The host computer 14 further performs coordinate conversion of the coordinates Pd (xc, yc, zc) into the coordinates Pd (xw, yw, zw) of the measured space coordinate system Σw to measure the coating film defect occurrence portion Pd. Performs three-dimensional position measurement in space.

When a plurality of coating film defects are detected in the image pickup area of the video camera 16, the host computer 14 measures the three-dimensional position of each coating film defect occurrence site Pd in the above procedure.

The coating film defect site Pd measured in this way is temporarily stored in the defect site memory 40 and then transmitted to the repair system 42 in the subsequent step, and the repair system 4 is then transmitted.
In 2, the coating film is corrected by polishing the coating film.

As described above in detail, in the present embodiment, it is calculated from the curved surface approximation formula Ew calculated using the CAD data and the pixel position Pp of the coating film defect occurrence site Pd on the image receiving screen 30 of the video camera 16. Line-of-sight equation Ee
As a point of intersection obtained by arranging and, the three-dimensional position of the coating film defect occurrence site Pd can be measured by one video camera 16.

Therefore, according to this embodiment, it is possible to reduce the required number of video cameras required for the above-mentioned position measurement, and the case where there are two video cameras occurs.
Correspondence of pixel positions between both video cameras becomes unnecessary, and thereby the three-dimensional position of the coating film defect occurrence site Pd can be easily and accurately measured.

In the above embodiment, the conveyor 24 is installed while the vehicle body 2 is accurately placed at a predetermined position on the pallet 22.
The three-dimensional position measurement is performed on the premise that the vehicle body 2 is transferred to the coating film defect inspection station. It does not completely match the actual position of, and some deviation inevitably occurs between the two. As a result, the unique coordinate correspondence between the object coordinate system Σb and the measured space coordinate system Σw is broken, and the three-dimensional position measurement accuracy cannot be sufficiently ensured. Therefore,
It is preferable to measure the positional deviation and correct the CAD data according to the positional deviation in order to further improve the measurement accuracy. This correction is performed, for example, by providing a posture sensor near the conveyor 24 to detect the posture of the vehicle body 2 and correcting the coordinates of the CAD data so as to eliminate the difference between the detection result and the posture of the vehicle body 2 which should be supposed. Will be realized.

In the above embodiment, the line-of-sight equation Ee and the curved surface approximation formula Ec are solved simultaneously in the video camera coordinate system Σc, but these two formulas are solved simultaneously in the measured space coordinate system Σw. You may By doing so, coordinate conversion is not required for the curved surface approximation formula Eb, and it is sufficient to perform coordinate conversion of the line-of-sight equation Ec represented by the video camera coordinate system Σc into the measured space coordinate system Σw, and thus the three-dimensional position The calculation for measurement can be simplified.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a three-dimensional position measuring apparatus on a curved surface according to the present invention.

FIG. 2 is an explanatory diagram showing an outline of three-dimensional position measurement in the above embodiment.

FIG. 3 is a diagram showing an image receiving screen for explaining the three-dimensional position measurement.

FIG. 4 is a perspective view showing a vehicle body for explaining the three-dimensional position measurement.

[Explanation of symbols]

2 vehicle body 4 coating film surface 10 three-dimensional position measuring device 12 video camera robot 14 host computer (curved surface approximate expression creation conversion means, line-of-sight equation calculation means, measured point coordinate conversion means) (C
AD data correcting means) 16 video camera 30 image receiving screen 32 calibration data memory 34 CAD data memory 36 processor (measurement point coordinate calculation means) Σb object coordinate system Σc video camera coordinate system Σw measurement space coordinate system Pd coating film defect occurrence Part (measured point) Pp Pixel position corresponding to coating film defect occurrence part Eb Curved surface approximation formula in object coordinate system Σb Ec Curved surface approximation formula in video camera coordinate system Σc Ee Line-of-sight equation

Claims (8)

[Claims] 1. A video camera for imaging a three-dimensional position of a measured point on an object having a curved surface arranged at a predetermined position in a measured space, and a predetermined region on the object including the measured point. A method of measurement using a plurality of predetermined point data selected from CAD data indicating points on the object stored in an object coordinate system set for the object, The curved surface shape of the object is represented as a curved surface approximation formula based on the point data, and the curved surface approximation formula has a predetermined coordinate correspondence with a measured space coordinate system that defines the measured space. Coordinate conversion to the video camera coordinate system set with respect to, and, on the other hand, the measured point in the video camera coordinate system from the pixel position of the measured point on the image receiving screen of the video camera. A line-of-sight equation representing a straight line passing therethrough is calculated, and thereafter, the line-of-sight equation and the curved surface approximation formula represented by the video camera coordinate system are simultaneously solved to solve the line-of-sight equation in the video camera coordinate system of the measured point. The coordinates are calculated, and further, the coordinates are converted into the measured space coordinate system to perform the three-dimensional position measurement of the measured point.
A method for measuring a three-dimensional position on a curved surface, which is characterized in that 2. A video camera for imaging a three-dimensional position of a measured point on an object having a curved surface arranged at a predetermined position in a measured space, and a predetermined area on the object including the measured point. A method of measurement using a plurality of predetermined point data selected from CAD data indicating points on the object stored in an object coordinate system set for the object, The curved surface shape of the object is represented as a curved surface approximation formula on the basis of the point data, and is set for the video camera so as to have a predetermined coordinate correspondence with the coordinate system of the measured space that defines the measured space. In the video camera coordinate system, a line-of-sight equation representing a straight line passing through the point-to-be-measured is calculated from the pixel position of the point-to-be-measured on the image receiving screen of the video camera, and the line-of-sight equation is further calculated as the line-of-sight equation. A three-dimensional position measurement of the measured point is performed by converting the coordinate transformation into a space coordinate system and then solving the coordinate-transformed line-of-sight equation and the curved surface approximation equation at the same time. Above three-dimensional position measurement method. 3. The selection of the plurality of point data is performed from CAD data in a predetermined area on the object according to an imaging area of the video camera.
Alternatively, the three-dimensional position measuring method on the curved surface described in 2. 4. The curved surface according to claim 1, wherein a deviation between an actual position of the object and the predetermined position is measured, and the CAD data is corrected according to the deviation. 3D position measurement method. 5. A video camera for imaging a three-dimensional position of a measured point on an object having a curved surface arranged at a predetermined position in a measured space, and a predetermined area on the object including the measured point. A device for measuring using a plurality of predetermined point data selected from CAD data indicating points on the object stored in an object coordinate system set for the object, and selecting the selected points. The curved surface shape of the object is represented as a curved surface approximation formula based on the data, and the curved surface approximation formula is provided to the video camera so as to have a predetermined coordinate correspondence with the measured space coordinate system that defines the measured space. A curved surface approximate expression creating / converting unit that performs coordinate conversion to the set video camera coordinate system, and a pixel position of the measured point on the image receiving screen of the video camera, The line-of-sight equation calculation means for calculating a line-of-sight equation expressing a straight line passing through the point to be measured, and the line-of-sight equation and the line-of-sight equation represented by the video camera coordinate system are solved simultaneously to solve the line-of-sight equation. And a measured point coordinate conversion means for calculating coordinates of the point in the video camera coordinate system, and a measured point coordinate conversion means for converting the coordinates into the measured space coordinate system. Three-dimensional position measuring device on a curved surface. 6. A video camera for imaging a three-dimensional position of a measured point on an object having a curved surface arranged at a predetermined position in a measured space, and a predetermined area on the object including the measured point. A device for measuring by using a plurality of predetermined point data selected from CAD data indicating points on the object stored in an object coordinate system set for the object, Curved surface approximation formula creating means for expressing the curved surface shape of the object as a curved surface approximation formula based on the point data, and the video camera so as to have a predetermined coordinate correspondence with the measured space coordinate system that defines the measured space. In the video camera coordinate system set for the video camera, a line-of-sight equation representing a straight line passing through the measured point is calculated from the pixel position of the measured point on the image receiving screen of the video camera, and the line-of-sight equation is calculated. The line-of-sight equation calculation conversion means for performing coordinate conversion of the equation to the measured space coordinate system, and the line-of-sight equation represented in the measured space coordinate system and the curved surface approximation formula are solved simultaneously to solve the measured line equation. A three-dimensional position measuring device on a curved surface, comprising: a measured point coordinate calculating means for calculating coordinates of a point in the measured space coordinate system. 7. The curved surface approximate expression creating and converting means is configured to select the plurality of point data from CAD data in a predetermined area on the object according to an imaging area of the video camera. The three-dimensional position measuring device on a curved surface according to claim 5 or 6, characterized in that. 8. A CAD data correcting means for measuring a deviation between an actual position of the object and the predetermined position and correcting the CAD data according to the deviation. , 6 or 7 three-dimensional position measuring device on a curved surface.