JPH05180634A - Method for estimating position of virtual point by measurement with lighthouse type sensor - Google Patents

Abstract

PURPOSE:To improve the estimating accuracy of the position of a virtual point by changing the position of a lighthouse type sensor when the missing number of measuring points is more than a specified degree, performing the scanning of the surface of an object again, and obtaining the point line of the measuring points again. CONSTITUTION:A control part 9 makes a lighthouse type sensor 7 corresponding to each reference part measure the shape of the cross section of a vehicle body panel 6 by one scanning of laser light. The video signal outputted from the sensor 7 is converted into the binary-coded signal by using a threshold value with a sensor-output- signal converting part 10. The signal is further converted into the coordinate data of the point line. The point-line data are stored into a point-line data storing memory 11 as a table, wherein the coordinate values of each measuring point are described. A processing part 12 reads the point-line data for each reference part out of the memory 11 and judges whether the data are normal or abnormal. Namely, when the number of the measuring points is less than the standard number stored in a standard-value storing memory 13, it is judged that the number of the missing measuring points is many. A corresponding sensor moving mechanism 8 is operated, and the position of the sensor 7 is moved. The abnormal reference part is measured again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a lighthouse type sensor that intermittently scans the surface of an object by gradually changing the direction of the measuring light and measures the cross-sectional shape of the surface by the principle of triangulation. From the point sequence of the measured points obtained by determining the two straight lines by approximation, when estimating the position of the virtual point by obtaining the intersection of these straight lines, it relates to a method that can improve the estimation accuracy. is there.

[0002]

2. Description of the Related Art In general, a lighthouse type sensor, as shown in FIG. 9, reflects a laser beam 2 from a light source 1 on a surface of an object 4 by reflecting the laser beam 2 from a light source 1 on the surface of an object 4 and reflecting the reflected light therefrom. After being reflected by the scanning mirror 3 again, the CCD sensor 5 receives the light, and the distance between the lighthouse type sensor and the object 4 is measured from the light receiving position by the principle of triangulation, and the angle of the scanning mirror 3 is slightly changed. The irradiation position is shifted by changing each, and the surface of the object 4 is intermittently scanned,
The point sequence coordinate data of the measurement points corresponding to the two-dimensional sectional shape of the surface is obtained. In addition, the lighthouse type sensor normally performs feedback control of the operation of the light source 1 by a light receiving amount adjusting circuit (not shown) based on the light receiving amount of the CCD sensor 5,
The intensity of the laser light 2 is adjusted so that the amount of received light of is within a range suitable for distance measurement.

Such a lighthouse type sensor is used, for example, in an assembly line of an automobile body to measure the assembling accuracy of the assembled vehicle body. The portions having a roughly L-shaped two-dimensional cross-sectional shape of the vehicle body panel at those locations are set as reference portions, and the substantially linear portions corresponding to the respective sides of the L shape are approximated for each of these reference portions. The intersections of the two straight lines are set as virtual points, and within the predetermined tact time within the assembly line, as shown in FIG. 10, the above-mentioned respective criteria of the vehicle body panel 6 as the object of the actually assembled vehicle body. A lighthouse-type sensor 7 having a configuration shown in FIG. 9 is a two-dimensional cross-sectional shape of the surface between the start point and the end point of the part.
Is calculated, and _two straight lines L ₁ and L ₂ are determined by approximation from the point sequence of the measurement points obtained for each reference part from the measurement result, and the intersection points of these straight lines are calculated to obtain a virtual A method of estimating the position of the point P and comparing the mutual positional relationship between the plurality of virtual points obtained by the estimation with the mutual positional relationship between the virtual points on the designed vehicle body to obtain the position error. Has been done.

[0004]

However, if the angle change of the scanning mirror 3 is made fast so that the shape of each reference portion can be measured within a predetermined takt time, the change speed of the amount of light received by the CCD sensor 5 can be increased. Is too fast for feedback control to catch up, the amount of received light may be insufficient due to the direction of the surface of the vehicle body panel 6, dirt, etc., and some measurement points may fall out. Since the point sequence of points does not sufficiently represent the actual cross-sectional shape, in the above conventional estimation method, the position of the virtual point P estimated based on the point sequence is slightly displaced from the actual position, and the virtual point There is a problem in that the accuracy of position estimation and thus the accuracy of assembly error measurement cannot be sufficiently improved.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method that advantageously solves the problems of the conventional method of estimating the virtual point position by measuring with a lighthouse sensor. Is a lighthouse-type sensor that changes the direction of the measuring light little by little to scan the surface of the object intermittently and measure the cross-sectional shape of the surface according to the principle of triangulation. From the point sequence of, the two straight lines are determined by approximation, and when estimating the position of the virtual point by obtaining the intersection of these straight lines, the lack of the measurement points in the point sequence is investigated, and the missing point is In the case of a predetermined level or more, after changing the position of the lighthouse type sensor, the lighthouse type sensor rescans the surface of the object, and the point sequence of measurement points is obtained again. ..

[0006]

According to the virtual point position estimating method of the present invention described above, the orientation and dirt of the surface of the target object are included in the point sequence of the measurement points obtained by measuring the cross-sectional shape of the surface of the target object by the lighthouse sensor. Even if some measurement points are missing due to the lack of the amount of light received due to, the missing points at the measurement points are investigated, and if the missing points are above a certain level, the position of the lighthouse center is changed and the target Since the surface is rescanned and the point sequence of measurement points is obtained again, linear approximation is performed using a sufficient number of measurement points, and the point sequence of measurement points for the actual cross-sectional shape of the object surface It is possible to reduce the error in the cross-sectional shape represented by, and to improve the estimation accuracy of the virtual point position.

[0007]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a vehicle body assembly precision measuring device used for carrying out an embodiment in which the virtual point position estimating method of the present invention is applied to the measurement of the assembly precision of an assembled vehicle body in an automobile body assembly line described above. FIG. 1 is a configuration diagram illustrating an example, and in the method of this embodiment, similar to the conventional method, a plurality of portions of a vehicle body are preliminarily divided into portions having a substantially L-shaped two-dimensional cross-sectional shape of a vehicle body panel as reference portions. , And the intersections of two straight lines that approximate each of the substantially linear portions corresponding to the L-shaped sides for each of these reference parts are set as virtual points, and the predetermined tact time is set in the assembly line. Inside, the two-dimensional cross-sectional shape of the surface of the body panel 6 of the actually assembled vehicle body between the start point and the end point of each of the above-mentioned reference parts is measured by the lighthouse sensor 7, and the reference result is obtained for each reference part. From the sequence of points of measurement points that, two of the straight lines L _1, L ₂ respectively determined by approximation,
The virtual point P is obtained by calculating the intersection of these straight lines.
Of the vehicle body assembly by estimating the position of each of the virtual points and comparing the mutual positional relationship of the plurality of virtual points obtained by the estimation with the mutual positional relationship of the virtual points on the designed vehicle body to obtain the position error. Perform precision measurement.

In order to carry out such a procedure, the vehicle body assembly accuracy measuring device here is constituted, for example, by a lighthouse type sensor 7 having the same structure as that shown in FIG. 9 and, for example, a normal rectangular coordinate type robot. A sensor moving mechanism 8,
For example, the control unit 9 is composed of an ordinary microcomputer. Here, the sensor moving mechanism 8 supports the lighthouse type sensors 7, and a plurality of sensors are installed in a predetermined measurement process in an assembly line of an automobile body. , The lighthouse type sensor 7 is moved with respect to each of the reference parts of the vehicle body assembled in the assembly line and arranged in the measurement process, and the control unit 9 controls the swing angle of the scanning mirror of the lighthouse type sensor 7. The light emitting intensity of the light source is feedback-controlled as described above, the operation of the sensor moving mechanism 8 is controlled, and each lighthouse type sensor 7 is preset for each reference portion of the assembled vehicle body. It is placed at the specified position.

Further, the vehicle body assembly accuracy measuring device herein includes a sensor output signal conversion unit 10 composed of, for example, an ordinary microcomputer, a point sequence data storage memory 11 composed of, for example, a readable / writable memory, and Processing unit 12 composed of a normal microcomputer
And a standard value storage memory 13 composed of, for example, a normal read-only memory, in which the sensor output signal conversion unit is provided.
Reference numeral 10 converts the output signal of the lighthouse sensor 7 into coordinate data of a point sequence of measurement points, and the point sequence data storage memory 11 stores the point sequence coordinate data output by the sensor output signal conversion unit 10 and a processing unit. 12 reads the point sequence coordinate data in the point sequence data storage memory 10 and performs the determination of the point sequence data, the virtual point position estimation processing, and the vehicle body assembly accuracy determination based on it, and the standard value storage memory 13 For example, as shown in FIGS. 2A to 2C, each measurement point P _S (s is a measurement point number; s = 1,2,3 ,. .
n) Positions and coordinates of virtual point positions based on those measurement points, and the standard number of normal measurement points that is set in advance for each reference part and is the minimum number of normal measurement points required to perform linear approximation with sufficient accuracy. Number M _k (k is the reference site number; k = 1,2,3 ,.
..) and stores them as required by the processing unit 12
To provide.

This vehicle body assembly accuracy measuring device constructed as described above follows the procedure shown in the flow chart of FIG.
As described below, the virtual point position is estimated based on this embodiment and the vehicle body assembly accuracy is measured based on the estimation. That is, here, first, in step 101, the control unit 9 causes the lighthouse type sensor 7 corresponding to each reference portion to once measure the cross-sectional shape of the vehicle body panel 6 by one scanning with the laser light,
As a result, if the lighthouse type sensor 7 is normal at each measurement point, as shown in FIG. 4A, a video signal having a sufficiently high chevron waveform that exceeds an appropriately set threshold value is sequentially output. Sensor output signal converter 10
However, first, it is converted into a binarized signal as shown in FIG. 4 (b) by using the above-mentioned threshold value first, and the pixel position where the binarized signal is 1 is indicated by a broken line in the figure as shown in FIG. 4 (c). The orthogonal coordinate value of each measurement point P _S representing the panel shape as shown in FIG.
At 102, the point sequence data storage memory 11 temporarily stores it as a table describing the coordinate values of each measurement point as shown in FIG.

By the way, the position of the lighthouse type sensor 7 with respect to each reference part of the vehicle body arranged in the above-mentioned measuring step is such that a video signal can be surely obtained over the entire reference part.
As shown in FIGS. 5 (a) and 5 (d), a straight line c connecting the L-shaped apex of the designed vehicle body panel and the lighthouse sensor 7 in the direction shown by the imaginary line in the figure corresponds to each side of the L-shape. The positions are set such that they are at the same angle with respect to the parts (the parts corresponding to the respective sides of the L-shape are symmetrical with respect to the straight line c), but the actual orientation of the vehicle body panel 6 is, for example, as shown in FIG. And Figure 5 (d)
As shown by the solid line, it may be inclined with respect to the direction of the designed vehicle body panel, and in such a case, with respect to the straight line c as shown by reference characters a and b in FIG. 5B and FIG. The amount of received laser light reflected at the measurement point on the side of the side where the angle is wide open is likely to be insufficient. Even if the actual surface orientation of the vehicle body panel 6 is substantially the same as the designed vehicle body panel orientation, the amount of received light may be insufficient due to stains on the panel surface.

In the case of such an insufficient amount of received light, the lighthouse type sensor 7 is shown in FIG.
As shown in (e), the sensor output signal conversion unit sequentially outputs a video signal having a low mountain-shaped waveform that does not exceed the threshold value.
10 indicates the video signal sequentially using the above threshold value.
Although it is converted into a binarized signal as shown in (f), since the position of the pixel whose binarized signal is 1 is not determined,
An orthogonal coordinate value of the measurement point P _S of the received light amount shortage, as shown in (g) (0, 0) is converted into coordinate data of point sequence as followed point sequence data storage memory 11 in step 102 is the orthogonal coordinates
The point sequence data including (0, 0) is temporarily stored as a table as shown in FIG.

Next, here, in step 103, the processing unit 12
The point sequence data is read out from the point sequence data storage memory 11 for each reference part, and it is determined whether the point sequence data is normal or abnormal. This judgment processing is performed according to the flow chart shown in FIG. 6. Here, first, in step 201, the number of normal measurement points whose Cartesian coordinate values are not (0, 0) in the point sequence data is counted, and the numerical value is m. _k , then step
In 202, from the standard number of normal measurement points for each reference part stored in the standard value storage memory 13 in advance as described above,
The standard number M _k of the reference site corresponding to the point sequence data is read, the standard number M _k compared to the number m _k of the normal measurement point, a normal number of measurement points m _k exceeds the standard number M _k If so, it can be determined that the number of missing measurement points is small, and therefore the point sequence data is determined to be normal in step 203, while if the number of normal measurement points m _k is equal to or less than the standard number M _k , Since it can be determined that the number is large, the point sequence data is determined to be abnormal in step 204.

As a result of the judgment processing, when it is judged that the point sequence data is abnormal for any of the reference parts, in order to change the measurement state, steps 103 to 103 in FIG.
Proceeding to 104, the processing unit 12 instructs the control unit 9 to operate the sensor moving mechanism 8 corresponding to the abnormal reference portion to move the position of the lighthouse type sensor 7 there, and then step 101 Return to and re-measure the reference part where the abnormality occurred. The position of the lighthouse type sensor 7 is deviated to which side of FIGS. 5 (a) and 5 (d), or to which side the light receiving amount can be further increased. First, as shown by an arrow in FIG. 5C, the lighthouse sensor 7 is moved in a predetermined direction from the initial measurement position so that the direction with respect to the vehicle body panel 6 changes in a plane including the cross section of the vehicle body panel 6. If the point sequence data is still abnormal as a result of making the above determination again after performing the above remeasurement,
As shown by the arrow in (f), the lighthouse sensor 7 is temporarily returned to the initial measurement position and then slightly displaced in the opposite direction (upward in the figure) to the direction in which the lighthouse sensor 7 has been previously displaced in the plane. Done in.

As a result of the above judgment processing after the first measurement or remeasurement, when it is judged that the point sequence data is normal for all the reference parts, the routine proceeds from step 103 to step 105 in FIG. Part 12 is for each reference part,
By approximating _two straight lines L ₁ and L ₂ from the portions corresponding to both sides of the L-shape of the two-dimensional cross-sectional shape of the vehicle body panel 6 represented by the point sequence data, and calculating the intersection points of these straight lines. The position of the virtual point P is estimated, and then the virtual point position on the designed vehicle body for each reference part that is stored in advance from the standard value storage memory 13 is read out, and the plurality of virtual points P obtained by the above estimation are calculated. If the positional error is calculated by comparing the mutual positional relationship with the mutual positional relationship of virtual points on the designed vehicle body, and the error is within a predetermined range, the assembly accuracy is normal, and if the error is outside the predetermined range. The assembly accuracy is determined to be abnormal, and the determination result is output.

As described above, according to the method of this embodiment, when the angle change of the scanning mirror of the lighthouse type sensor 7 is made fast so that the shape of each of the reference parts can be measured within a predetermined tact time. In addition, the rate of change in the amount of light received by the CCD sensor was too fast for feedback control to catch up, the amount of light received was insufficient due to the direction of the surface of the vehicle body panel 6 and dirt, and some measurement points were missed. Even if
After checking the number of missing measurement points and changing the position of the lighthouse type center 7 when the number of missing points is more than a predetermined number, the amount of light received at the part where the measurement points are missing is increased, and then the vehicle body panel Since the surface of 6 is rescanned and the point sequence of the measurement points is obtained again, linear approximation is performed using a sufficient number of measurement points. Therefore, measurement of the actual cross-sectional shape of the surface of the vehicle body panel 6 is performed. The error of the cross-sectional shape represented by the point sequence of points can be reduced, and the estimation accuracy of the position of the virtual point P can be improved, and the reliability of the determination of the vehicle body assembly accuracy can be improved. Moreover, the above method is performed in steps 101-
Since the scanning of the surface of the vehicle body panel 6 which takes less time in 104 is performed again and the time-consuming virtual point calculation calculation in step 105 is performed only once, it can be sufficiently executed within the predetermined tact time.

By the way, since the position of the measuring point P _S normally makes the accuracy of the linear approximation good, as shown in FIG. 7A, the intervals d ₁ , d ₂ ,. Is set to be constant. Therefore, when the amount of received light is insufficient due to the direction of the surface of the vehicle body panel 6 or dirt, and some measurement points fall out, FIG. As shown in, the distances d ₁ , d ₂ , ... Of the measurement points are also different from each other. Another embodiment of the estimation method of the present invention, which has been made with attention to such points, will be described below.

In the method of this embodiment, instead of the standard number M _k in the standard value storage memory 13 of the apparatus in the previous embodiment, it is found from the originally set measurement point position preset for each reference part. A standard number D _k (k is a reference site number; k = 1,2,3 ,.
.) Is stored, and instead of the point sequence data determination process shown in FIG. 6 in step 103 of FIG. 3 in the previous embodiment,
The point sequence data determination process shown in FIG. 8 is performed, and the other parts are the same as those in the previous embodiment.

That is, here, in step 101 and step 102 of FIG. 3, the cross-sectional shape of the vehicle body panel 6 is measured and the measurement point P _S (s is the measurement point number; s =
1,2,3, .. .n) point sequence data (where the coordinates are
Do not include the measurement point with (0, 0) in the point sequence data. ) Is stored, the processing unit 12 reads the above-mentioned point sequence data for each reference part from the point sequence data storage memory 11 in step 103 of FIG. 3 to determine whether the point sequence data is normal or abnormal. The determination is made according to the flowchart shown in FIG. In this determination, first, in step 301 of FIG. 8, the average distance between measurement points is calculated by the following equation and the value is set as d _k .

[Equation 1]

Next, in step 302, the standard number D _k of the reference part corresponding to the point sequence data is read from the standard number for each reference part stored in the standard value storage memory 13 in advance as described above. Then, the standard number D _k is compared with the average inter-measurement-point distance d _k, and if the average inter-measurement-point distance d _k is less than the standard number D _k , it can be determined that the number of missing measurement points is small. While the point sequence data is determined to be normal, the point sequence data is determined to be abnormal in step 304 because it can be determined that the number of missing measurement points is large if the average inter-measurement point distance d _k is greater than or equal to the standard number D _k. .. Then, after that, from step 103 of FIG. 3 to step 10 according to the judgment result.
4 or proceeds to step 105 to perform the same processing as in the previous embodiment.

According to this embodiment, when the amount of received light is insufficient due to the direction of the surface of the vehicle body panel 6 or dirt, and some measurement points are missing, the missing measurement points are averaged. After investigating based on the distance between the measurement points, if the lack is more than a predetermined level, the position of the lighthouse type center 7 is changed so that the amount of light received at the part where the measurement points are missing is increased. Since the rescanning of the surface is performed and the point sequence of the measurement points is obtained again, the linear approximation is performed using a sufficient number of measurement points as in the previous embodiment. Error in the cross-sectional shape represented by the point sequence of the measurement points with respect to the cross-sectional shape can be reduced, and by extension, the virtual point P
The position estimation accuracy can be improved, and the reliability of the vehicle body assembly accuracy determination can be improved. Also in this embodiment, as in the previous embodiment, steps 101 to 104 of FIG.
Since the scanning of the surface of the vehicle body panel 6 which does not take much time is performed again and the virtual point calculation and the like in step 105 are performed only once, they can be sufficiently executed within the predetermined tact time.

Although the present invention has been described above based on the illustrated example, the present invention is not limited to the above example. For example, one microcomputer may be shared by the control section 9 and the processing section 12 in the above embodiment. Good to Further, the method of the present invention can be applied to the vehicle body assembly accuracy measurement outside the vehicle body assembly line and the shape accuracy measurement of the vehicle body panel alone, and can also be applied to the measurement of objects other than the vehicle body panel. ..

[0023]

As described above, according to the virtual point position estimating method of the present invention, the orientation and dirt of the surface of the object are included in the point sequence of the measurement points obtained by measuring the cross-sectional shape of the surface of the object by the lighthouse type sensor. Even if some measurement points are missed due to lack of received light due to, etc., the missing points at the measurement points are investigated. Since the object surface is rescanned and the point sequence of measurement points is obtained again, linear approximation is performed using a sufficient number of measurement points, and the points of measurement points for the actual cross-sectional shape of the object surface It is possible to reduce the error of the cross-sectional shape represented by the row, and consequently to improve the estimation accuracy of the virtual point position.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating a vehicle body assembly accuracy measuring device used in an embodiment in which a virtual point position estimating method according to the present invention is applied to measurement of an assembly accuracy of an assembled vehicle body in an assembly line of an automobile body. ..

2A to 2C are explanatory views illustrating the measurement point positions of respective reference parts stored in advance in a standard value storage memory of the vehicle body assembly accuracy measuring device.

FIG. 3 is a flowchart showing a processing procedure when the vehicle body assembly accuracy measuring device executes virtual point position estimation and vehicle body assembly accuracy measurement based on the method of the embodiment.

4 (a) to (h) are explanatory views showing operating states when the vehicle body assembly accuracy measuring device measures a measurement point position based on the method of the embodiment.

5 (a) to (f) are explanatory views showing operating states when the vehicle body assembly accuracy measuring device moves the position of the lighthouse type sensor based on the method of the embodiment.

FIG. 6 is a flowchart showing a processing procedure when the vehicle body assembly accuracy measuring device determines normality / abnormality of point sequence data based on the method of the embodiment.

7 (a) and 7 (b) are explanatory views showing states of measurement points of point sequence data in a normal state and an abnormal state, respectively.

FIG. 8 shows a processing procedure for judging normality / abnormality of point sequence data based on the method of another embodiment of the present invention, which is made by paying attention to the difference between the states shown in FIGS. 7 (a) and 7 (b). It is a flowchart shown.

FIG. 9 is an explanatory view showing a configuration of a lighthouse type sensor used in the methods of the conventional example and the above-described both examples.

FIG. 10 is an explanatory diagram showing a method of estimating a virtual point position by measurement with a conventional lighthouse sensor.

[Explanation of symbols]

 6 Body panel 7 Lighthouse type sensor 8 Sensor moving mechanism 9 Control unit 10 Sensor output signal conversion unit 11 Point sequence data storage memory 12 Processing unit 13 Standard value storage memory

Claims (1)

[Claims] 1. A lighthouse sensor for intermittently scanning the surface of an object by gradually changing the direction of measurement light,
When estimating the position of the virtual point by determining the two straight lines by approximation from the point sequence of the measurement points obtained by measuring the cross-sectional shape of the surface by the principle of triangulation and determining the intersection of these straight lines , Investigating the lack of measurement points in the point sequence, and if the lack is more than a predetermined level, re-scan the object surface with the lighthouse type sensor after changing the position of the lighthouse type sensor. A method of estimating a virtual point position by measuring with a lighthouse sensor, characterized in that the point sequence of the measurement points is obtained again.