JP2005186193A - Calibration method and three-dimensional position measuring method for robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calibration method for a robot having two cameras. <P>SOLUTION: First a measurement object is photographed at three or more measuring points set on an XY plane of robot coordinates, monitor coordinates of the measurement object concerning the virtual image formation plane are measured by processing the photographed image, and on the basis of the monitor coordinates of the measurement object and the measuring points, a conversion factor in a conversion formula for converting monitor coordinates to the robot coordinates is calculated. Subsequently, the measurement object is photographed at two or more measuring points set on the Z-axis of the robot coordinate, the monitor coordinate of the measurement object concerning the virtual image formation surface is measured by processing the photographed image, the robot coordinate of the measurement object is calculated by substituting the monitor coordinates of the measurement object for the conversion formula from which the conversion factor is calculated, and on the basis of the robot coordinates of the measurement object and the measuring point set on the Z-axis, the robot coordinates of two cameras are calculated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a calibration method using a stereo method and a method for measuring a three-dimensional position of an object, and more particularly to a technique applied to a so-called bin picking operation in which a workpiece is taken out by an industrial machine such as a robot.

  The bin picking system is a system in which the position and orientation of an object is detected by an image measuring device, and the object is handled by a robot arm based on the information. In the image measuring device used in this system, for example, the feature data having the three-dimensional position data and the data obtained by approximating the features such as the contour, unevenness, and pattern of the object obtained from the input image with straight lines, arcs, etc. The three-dimensional position and orientation of the target object is obtained by matching with the feature data having the three-dimensional position data of the model of the target object.

As a three-dimensional position measurement method for obtaining three-dimensional position data, a stereo method has been conventionally employed. The stereo method uses two cameras to determine the three-dimensional shape of an object using the principle of triangulation. A three-dimensional position measurement method using this stereo method is disclosed in, for example, Patent Document 1 and Patent Document 2. Among them, the method according to Patent Document 1 is to obtain the height from the reference plane based on the angle formed by the lens optical axes between the imaging devices and the position data on each imaging plane. The method according to Patent Document 2 is to obtain the world coordinates of measurement points by interpolation based on the curved surface polynomial of each curved surface formed by a plurality of points in the monitor coordinate system.
Japanese Patent Laid-Open No. 62-162912 JP-A-10-221066

  However, in the method according to Patent Document 1 described above, it is necessary to obtain the positional relationship between the imaging devices in advance. Also, with this method, it is difficult to accurately determine the angle formed by the lens optical axis. On the other hand, in the method according to Patent Document 2 described above, it is necessary to prepare a calibration plate on which a plurality of patterns are drawn. However, the positions, distances, and directions of the plurality of patterns must be known. Since the field of view (imaging range) changes according to the above, in order to approximate the curved surface with high accuracy, various calibration plates corresponding to the field of view are required.

  The present invention has been made to solve the problems of the related art, and a first object of the invention is to calibrate a robot without obtaining an angle formed by a lens optical axis or using a calibration plate. Is to provide an alternative method. A second object of the present invention is to provide a robot three-dimensional position measurement method to which the robot calibration method is applied.

  In order to achieve the first object described above, in the invention according to claim 1, in the robot configured to measure the three-dimensional position of the measurement object by the two cameras attached to the robot arm tip, A calibration method by the following method is provided.

That is, first, as a first step, the object to be measured is placed at three or more different measurement points (P ₀ , P ₁ ,..., P _i ) set on the XY plane of the robot coordinates by operating the robot. By photographing and processing the captured image, the monitor coordinates (I _L0 , I _L1 ,..., I _Li , I _R0 , I _{R1 ,.} ), And the monitor coordinates (I _L0 , I _L1 ,..., I _Li , I _R0 , I _R1 ,..., I _Ri ) of the measurement object and the measurement points (P ₀ , P ₁ , ..., P _i ), a conversion coefficient in a conversion equation for converting from monitor coordinates to robot coordinates is calculated.

Next, as a second stage, the object to be measured is photographed at two or more different measurement points (Q ₀ , Q ₁ ,..., Q _i ) set on the Z axis of the robot coordinates by operating the robot. Then, the monitor coordinates (I _ZL0 , I _ZL1 ,..., I _ZLi , I _ZR0 , I _{ZR1 ,.} Measure, and _substitute the monitor coordinates (I _ZL0 , I _ZL1 ,..., I _ZLi , I _ZR0 , I _ZR1 ,..., I _ZRi ) of the measurement _object into the conversion formula in which the conversion coefficient is calculated. robot coordinate of the measurement object by _{(W ZL0, W ZL1, ···} , W ZLi, W ZR0, W ZR1, ···, W ZRi) calculates the robot coordinates of the measurement object _{(W ZL0, ZL1, ···, W ZLi, W} ZR0, W ZR1, ···, W ZRi) and the two or more different measuring points set on the Z axis of the robot coordinate _{(Q 0,} Q _1, ··· , Q _i ), the robot coordinates (W _LC , W _RC ) of the two cameras are calculated.

  In order to achieve the second object described above, in the invention according to claim 2, a robot configured to measure a three-dimensional position of an object to be measured by two cameras attached to the robot arm tip. In the above, a three-dimensional position measurement method by the following method is provided.

That is, in this three-dimensional position measurement method, there are the first stage to the third stage, but the first stage to the second stage are the same as the first stage to the second stage in the means according to claim 1 described above. It is. In the third stage, two cameras are arranged at the robot coordinates (W _LC , W _RC ) calculated in the second stage by operating the robot, and then the measurement object is photographed, and the photographed image is processed by image processing. By measuring the monitor coordinates of the measurement object on the virtual imaging plane, and substituting the monitor coordinates of the measurement object into the conversion formula in which the conversion coefficient is calculated, the robot coordinates (W _LM , W _RM) is calculated, the robot coordinate _(W LM of the measurement _{object, W RM)} and the two cameras of the robot coordinate _{(W LC,} based on the _{W RC),} measures the three-dimensional position of the measurement object I tried to do it.

  In the present invention, since the calibration is performed by moving the robot to three or more different measurement points, it is not necessary to calculate an unknown amount such as an angle formed by the lens optical axis as in the prior art. Further, since the measurement object itself is used for calibration, it is not necessary to prepare a special calibration board as in the prior art. Therefore, by using the function that a robot equipped with a camera normally has, it becomes possible to easily measure the camera mounted on the robot and measure the three-dimensional position of the measurement object.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram illustrating an example of a bin picking system to which a robot calibration method and a three-dimensional position measurement method according to the present embodiment are applied. In FIG. 1, reference numeral 1 denotes a robot having a vertical articulated structure. Reference numeral 2 denotes a connecting member attached to the flange surface at the tip of the arm of the robot 1. Reference numeral 3 denotes a hand for taking out the measurement object 6 and is attached to the connecting member 2. Reference numerals 4 and 5 denote first and second cameras that capture images necessary for performing three-dimensional position measurement and the like, and are attached to the connecting member 2. The first camera 4 and the second camera 5 are installed such that their optical axis directions are different in order to obtain images from two angles by the stereo method.

  FIG. 2 is a block diagram illustrating an example of a robot control apparatus for carrying out the robot calibration method and the three-dimensional position measurement method according to the present embodiment. The robot controller stores various data such as a servo amplifier that drives a servo motor that operates each joint axis of the robot 1, an interface 1 of the servo amplifier, a CPU that performs various arithmetic processes, an operation program, parameters, and imaging data. A memory (RAM-ROM or auxiliary storage device), an image processing board for processing image data acquired from the cameras 4 and 5, and the like are configured. Further, the robot control apparatus is connected to a keyboard, a display, and a mouse via an interface, thereby enabling data exchange with the outside. The image processing board described above digitizes a video signal input from an imaging device such as a camera and forms image data on a memory.

  FIG. 3 shows an example of an image of the measurement object 6 photographed by the first camera 4 and the second camera 5. The example of the captured image illustrated in FIG. 3 illustrates an image obtained by capturing the donut-shaped measurement target 6 on a dark background.

  Next, a processing procedure of the calibration method according to the present embodiment will be described. FIG. 4 is an explanatory diagram showing a measurement state in the processing procedure of the robot calibration method according to the present embodiment. FIG. 5 is a flowchart showing the processing procedure of the robot calibration method according to this embodiment. The notation of “S *” (* is an integer) shown in this flowchart indicates a step number and corresponds to the notation of “S *” (* is an integer) in the following description. In this embodiment, since the first camera 4 and the second camera 5 are fixed to the robot arm tips, the first camera 4 and the second camera 5 are similar to the robot on the robot coordinates along with the robot arm operation. Will move.

  In this embodiment, the robot coordinates of the cameras 4 and 5 are obtained with an arbitrary position on the robot coordinates as the origin.

  First, the conversion coefficient in the conversion formula (1) from the position on the virtual imaging plane, that is, the monitor coordinates to the robot coordinates, is obtained by the processing on the left side of the flowchart shown in FIG.

  In the flowchart shown in FIG. 5, “n” is a camera number. In the flowchart shown in FIG. 5, since the process related to the first camera 4 is first performed and then the process related to the second camera 5 is performed, first, the camera number n is set to 1 (S1). Further, the coordinate point number i is initialized to 0 (S2).

An arbitrary position where the measurement object 6 can be photographed by the first camera 4 and the second camera 5 is set as a reference position (origin) P _0, and the robot 1 is moved to the reference position P ₀ . Then, the measurement object 6 is photographed by the first camera 4 at the point P ₀ on the robot coordinates, and the reference position I _L0 on the monitor coordinates for the virtual imaging plane at this time is measured by image processing (S3). .

  Next, 1 is added to the coordinate point number i (S4). Therefore, i becomes 1 at this time.

Next, the robot 1 is moved on the XY plane (S5). For example, to move to a point P ₁ on the X-axis showing the robot 1 in FIG. And this by the first camera 4 at a point P ₁ on the robot coordinate photographed measurement object 6, for measuring the position I _L1 on the monitor coordinates of the virtual image plane of this time by image processing (S6).

Next, it is determined whether or not the coordinate point number i is equal to N (S7). By the way, when obtaining the conversion coefficient in the conversion formula (1), since at least three measurement points are necessary on the XY plane, in this embodiment, three measurement points including the reference point P ₀ are set. Therefore, N in S7 is set to 2. In this embodiment, since the coordinate point number i is 1 at this time, the process returns to S4.

  That is, returning to S4, the coordinate point number i is incremented by 1, and i becomes 2 at this point.

In S5, the robot 1 is moved on the XY plane as described above. For example, to move to a point P ₂ on the Y axis showing the robot 1 in FIG. And this in that P ₂ on the robot coordinate photographed measurement object 6 by the first camera 4, to measure the position I _L2 on the monitor coordinates of the virtual image plane of this time by image processing (S6).

  Next, it is determined whether i is equal to N (S7). At this time, i is 2 and equals N, so the process proceeds to S8.

  By the way, the conversion formula from the position on the virtual imaging plane, that is, the monitor coordinate to the robot coordinate can be expressed by the following equation (1).

  In this equation (1), P is the robot coordinate, I is the monitor coordinate, θ is the rotation angle of the coordinate space, K is the shear of the coordinate space, A is the aspect ratio, S is the scaling of the coordinate space, and T is the monitor coordinate space. It is a movement vector to the robot coordinate space.

Therefore, in S8, the three positions I _L0 , I _L1 , I _L2 on the virtual imaging plane obtained in the processing up to S7, and the positions I _L0 , I _L1 , I _L2 on the virtual imaging plane, Based on the robot coordinates P ₀ , P ₁ , P ₂ of the first camera 4 when each of the above is measured, the transformation coefficient in equation (1), that is, the rotation angle θ of the coordinate space, the shear K of the coordinate space, the aspect ratio A, a coordinate space scaling S, and a movement vector T from the monitor coordinate space to the robot coordinate space are calculated.

Here, the conversion coefficient calculation method described above will be described with reference to FIG. FIG. 7 illustrates the processing results of S1 to S7 described above. In FIG. 7, the monitor coordinate space is defined by 0-X _i -Y _i . The robot coordinate space is defined by P ₀ -XY. The coordinate space P ₀ -X′-Y ′ is a coordinate space obtained by translating the monitor coordinates from the origin 0 to the robot coordinate origin P ₀ . The coordinate space P ₀ -X—Y ″ is a coordinate space obtained by rotating the coordinate space P ₀ -X′-Y ′ by an angle θ around the point P ₀ .

Here, the robot coordinates P ₀ , P ₁ , P ₂ are p ₀ (xw ₀ , yw ₀ ), p ₁ (xw ₁ , yw ₁ ), p ₂ (xw ₂ , yw ₂ ), respectively. The monitor coordinates at which the measurement object 6 is measured at the coordinates P ₀ , P ₁ , P ₂ are p ₀ (xi ₀ , yi ₀ ), p ₁ (xi ₁ , yi ₁ ), p ₂ (xi ₂ , yi ₂ ), respectively. ), The relational expression relating to the scaling of the coordinate space can be expressed by Expression (2) and Expression (3).

  In these equations (2) and (3), Sx is the X-axis scaling of the coordinate space, and Sy is the Y-axis scaling of the coordinate space. By solving these equations (2) and (3), the scaling S (= Sx) and the aspect ratio A (= Sy / Sx) of the coordinate space can be obtained.

The moving vector T from the monitor coordinate space to the robot coordinate space, scaling S coordinate space calculated by the aforementioned equation (2) and (3), and the measurement object 6 in the robot coordinate P ₀ is measured Further, based on the monitor coordinates p ₀ (xi ₀ , yi ₀ ), it can be obtained by Expression (4).

In addition, the rotation angle θ of the coordinate space is determined by the coordinate space scaling S calculated by the above equations (2) and (3), and the monitor coordinates at which the measurement object 6 is measured at the robot coordinates P ₀ and P ₁ . Based on p ₀ (xi ₀ , yi ₀ ) and p ₁ (xi ₁ , yi ₁ ), it can be obtained by equation (5).

Furthermore, the shear K of the coordinate space is the measurement object 6 at the rotation angle θ of the coordinate space, the scaling S of the coordinate space calculated by the above equations (2) and (3), and the robot coordinates P ₀ and P ₁ . Can be obtained by the equation (6) based on the monitor coordinates p ₀ (xi ₀ , yi ₀ ) and p ₁ (xi ₁ , yi ₁ ) where the values are measured.

  As described above, all the conversion coefficients in the conversion equation (1) from the position on the virtual imaging plane, that is, the monitor coordinates to the robot coordinates are obtained.

  Although a simple linear transformation has been described here as an example, since the virtual imaging plane is generally nonlinear, the sample points may be increased and the polynomial transformation may be obtained by least square approximation. Expression (7) is a general expression of a polynomial.

In this equation (7), P _x and P _y are robot coordinates, I _x and I _y are monitor coordinates, n is a polynomial degree, and a _ij and b _ij are polynomial coefficients.

  Next, the robot coordinates of the cameras 4 and 5 are obtained by the processing on the right side of the flowchart shown in FIG. 5, that is, S9 to S18.

  First, the coordinate point number j is initialized to 0 (S9).

Next, move the robot 1 to the reference coordinate _{P 0} on the XY plane described above (S10).

Next, the robot 1 is moved on the Z axis (S11). Specifically, as shown in FIG. 4, the robot 1 is moved from the reference coordinate P ₀ to a point Q ₁ on the Z axis.

In this respect _{Q 1,} the first camera 4, to measure the position _{I LZ1} on the monitor coordinates of the virtual image plane by image processing (S12).

Then, the position I _LZ1 on the monitor coordinates obtained in S12 is converted into the robot coordinates W _LZ1 by using the above-described conversion equation (1) in which the conversion coefficient is obtained in S8 (S13).

  Next, 1 is added to the coordinate point number j (S14). Therefore, j becomes 1 at this time.

  Next, it is determined whether or not the coordinate point number j is equal to M (S15). By the way, when obtaining the robot coordinates of each of the cameras 4 and 5, since at least two measurement points are necessary, in this embodiment, two measurement points are set, and therefore M is 2. In this embodiment, since the coordinate point number j is 1 at this time, the process returns to S11.

The processing in S11 to S13 is the same as described above. That is, the robot 1 from the point to Q ₁ on the Z axis above the point Q ₂ on the Z-axis to move the Z-axis (S11), at this point Q _2, the first camera 4, the virtual image plane _Is measured by image processing (S12), and the above-described conversion equation (1) is used to determine the position I _LZ2 on the monitor coordinates for the virtual imaging plane obtained in S12. The coordinates W _LZ2 are converted (S13).

  Next, 1 is added to the coordinate point number j (S14). Therefore, j becomes 2 at this time.

  Next, it is determined whether j is equal to M (S15). Since j is 2 and equal to M at this time, the process proceeds to S16.

In S16, obtained in S13 in the foregoing, based on two robot coordinate _{W LZ1, W LZ2} of the virtual image plane, and calculates the robot coordinate _{W LC} of the first camera 4. The calculation of the robot coordinate _WLC can be performed by the following procedure.

That is, in the above-described embodiment, the measurement object 6 is measured by moving the robot 1 on the Z coordinate, but this is because the measurement object 6 is in a state where the robot 1 is stationary as shown in FIG. Can be considered to be the same as moving on the Z coordinate of the robot 1. Given this way, the robot coordinate _{W LC} of the first camera 4 to be calculated would obtained as an intersecting point between the straight line _W LZ1 _{Q 1} and _W LZ2 _{Q 2.} In practice, the straight lines W _LZ1 Q ₁ and W _LZ2 Q ₂ are often not on the same plane, and in this case, the positional relationship between them is twisted. The robot coordinates _WLC of the first camera 4 to be calculated are used. Therefore, when considering the condition that the distance between these two straight lines is minimized, these conditions are pq⊥da and pq⊥db ("⊥" indicates that they are orthogonal to each other). Here, da is the direction vector of the straight line W _LZ1 Q ₁ , db is the direction vector of the straight line W _LZ2 Q ₂ , p is an arbitrary point on the straight line W _LZ1 Q ₁ , and q is an arbitrary point on the straight line W _LZ2 Q ₂ It is. Therefore, if the inner product of the direction vectors of the straight line is set to 0, the position where the two straight lines are closest, that is, the robot coordinates _WLC of the first camera 4 to be calculated can be obtained as a solution of simultaneous equations.

  Next, 1 is added to the camera number n (S17). Therefore, n becomes 2 at this time.

  Next, it is determined whether n is equal to 3 (S18). In the present embodiment, since one camera is installed on each of the left and right cameras, when the processing in these two cameras is completed, that is, when n is 3, a series of processing is terminated (END). However, at this point in time, only the processing of the first camera 4 is completed and the processing of the second camera 5 is not completed, and n is 2. Therefore, the processing returns to S2, and thereafter the first described above. The processing of the second camera 5 is performed similarly to the processing of the camera 4. Regarding the processing of the second camera 5, “L” may be replaced with “R” in the description of the above-described embodiment.

As described above, any robot coordinate of each camera 4,5 when the origin position, that is, the first camera 4 of the robot coordinate W _LC and the second camera 5 of the robot coordinate W _RC on the robot coordinate Therefore, the calibration of the cameras 4 and 5 is completed.

Next, a processing procedure for measuring the three-dimensional position of the measurement object 6 will be described. In order to accurately obtain the three-dimensional position of the measurement object 6, it is necessary to calibrate the two cameras 4 and 5 prior to measurement. That is, the first camera 4 and second camera 5, or respectively installed in the robot coordinate W _LC and W _RC of the aforementioned cameras, or by the procedure described above, the first camera 4 and a second that was installed each robot coordinate _{W LC} and _{W RC} of the camera 5 is determined in advance. Next, the measurement object 6 at an arbitrary position in the space is photographed by the first camera 4 and the second camera 5, and the monitor coordinates of the measurement object 6 are obtained by performing image processing on the photographed image. By converting the coordinates according to the conversion formula (1) described above, the robot coordinates of the measurement object 6, that is, the measurement point robot coordinates are obtained. That is, the first camera 4 obtains the measurement point robot coordinates _WLM , and the second camera 5 obtains the measurement point robot coordinates _WRM . Finally, the first camera 4 at the obtained measurement point the robot coordinate W _LM and the line connecting the robot coordinate W _LC of the first camera 4, and a second of the resulting measurement points robot coordinate by the camera 5 For a straight line connecting _WRM and the robot coordinates _WRC of the second camera 5, the intersection of these two straight lines is obtained by the method described above. Let the intersection of these two straight lines be the three-dimensional position of the measurement object 6.

  The embodiment of the present invention has been described above. In the above-described embodiment, the number N of measurement points when obtaining the conversion coefficient is set to 2, but the present invention is not limited to this. That is, since at least three measurement points are necessary on the XY plane as described above, the number N of measurement points may be set to 3 or more, and if this number is set large, the processing time is reduced. Although it becomes longer, the calculation accuracy of the conversion coefficient becomes higher.

  Similarly, in the above-described embodiment, the number M of measurement points when obtaining the robot coordinate transformation for the virtual imaging plane is set to 2, but the present invention is not limited to this. That is, as described above, in order to obtain the robot coordinates of the camera, at least two straight lines are required, so at least two measurement points are required. However, the number M of measurement points is set to 3 or more. However, if this number is set to a large value, the processing time becomes longer, but the calculation accuracy of the robot coordinates of the camera becomes higher. When the number M of measurement points is set to 3 or more, the position where the distance between the straight lines is minimum, that is, the robot coordinates of the camera may be obtained by least square approximation.

  In the above-described embodiment, two cameras are arranged such that their optical axes are different from each other. However, the present invention is not limited to such a form. That is, in this embodiment, it is only necessary to photograph the measurement object 6 from two angles at the same position of the robot. For example, only one camera is attached to the connecting member 2 and the wrist axis of the robot to which the connecting member 2 is attached. Only one operation may be performed to obtain images from two angles with one camera.

  In this embodiment, calibration is performed by moving the robot to three or more different measurement points, so that it is not necessary to calculate an unknown amount such as an angle formed by the lens optical axis as in the prior art. Further, since the measurement object itself is used for calibration, it is not necessary to prepare a special calibration board as in the prior art. Therefore, by using the function that a robot equipped with a camera normally has, the camera mounted on the robot can be easily calibrated and the three-dimensional position of the measurement object can be measured.

1 is a configuration diagram showing an example of a bin picking system to which a robot calibration method and a three-dimensional position measurement method are applied according to the best mode for carrying out the present invention. It is a block diagram which shows an example of the robot control apparatus for implementing the calibration method and the three-dimensional position measuring method of the robot based on the best form for implementing this invention. An example of the image of the measuring object 6 photographed by the first camera 4 and the second camera 5 is shown. It is explanatory drawing shown about the state of the measurement in the process sequence of the calibration method of the robot which concerns on this embodiment. It is the flowchart shown about the process sequence of the calibration method of the robot which concerns on this embodiment. It is a figure shown about the calculation theory of a robot coordinate. It is a coordinate diagram for demonstrating the calculation method of a conversion coefficient.

Explanation of symbols

1 Articulated Robot 2 Connecting Member 3 Hand 4 Camera 1
5 Camera 2
6 Measurement object

Claims (2)

In a robot calibration method in which the three-dimensional position of a measurement object is measured by two cameras attached to the tip of a robot arm,
By photographing the measurement object at three or more different measurement points (P ₀ , P ₁ ,..., P _i ) set on the XY plane of the robot coordinates by operating the robot,
The monitor coordinates (I _L0 , I _L1 ,..., I _Li , I _R0 , I _R1 ,..., I _Ri ) of the measurement object with respect to the virtual imaging plane are measured by processing the captured image. And
Monitor coordinates (I _L0 , I _L1 ,..., I _Li , I _R0 , I _R1 ,..., I _Ri ) of the measurement object and the measurement points (P ₀ , P ₁ ,..., P Based on _i ), a conversion coefficient in a conversion formula for converting from monitor coordinates to robot coordinates is calculated,
By photographing the measurement object at two or more different measurement points (Q ₀ , Q ₁ ,..., Q _i ) set on the Z axis of the robot coordinates by operating the robot,
The captured image is processed to measure monitor coordinates (I _ZL0 , I _ZL1 ,..., I _ZLi , I _ZR0 , I _ZR1 ,..., I _ZRi ) about the virtual imaging plane. And
Measurement is performed by _substituting the monitor coordinates (I _ZL0 , I _ZL1 ,..., I _ZLi , I _ZR0 , I _{ZR1 ,. Calculate} the robot coordinates (W _ZL0 , W _ZL1 ,..., W _ZLi , W _ZR0 , W _ZR1 ,..., W _ZRi ) of the _object ,
The robot coordinates (W _ZL0 , W _ZL1 ,..., W _ZLi , W _ZR0 , W _ZR1 ,..., W _ZRi ) of the measurement _object and two or more different values set on the Z axis of the robot coordinates Calibration of the robot characterized in that the robot coordinates (W _LC , W _RC ) of the two cameras are calculated based on the measurement points (Q ₀ , Q ₁ ,..., Q _i ). Method. In the three-dimensional position measurement method for a robot that is configured to measure the three-dimensional position of an object to be measured by two cameras attached to the robot arm tip,
By photographing the measurement object at three or more different measurement points (P ₀ , P ₁ ,..., P _i ) set on the XY plane of the robot coordinates by operating the robot,
The monitor coordinates (I _L0 , I _L1 ,..., I _Li , I _R0 , I _R1 ,..., I _Ri ) of the measurement object with respect to the virtual imaging plane are measured by processing the captured image. And
Monitor coordinates (I _L0 , I _L1 ,..., I _Li , I _R0 , I _R1 ,..., I _Ri ) of the measurement object and the measurement points (P ₀ , P ₁ ,..., P Based on _i ), a conversion coefficient in a conversion formula for converting from monitor coordinates to robot coordinates is calculated,
By photographing the measurement object at two or more different measurement points (Q ₀ , Q ₁ ,..., Q _i ) set on the Z axis of the robot coordinates by operating the robot,
The monitor coordinates (I _ZL0 , I _ZL1 ,..., I _ZLi , I _ZR0 , I _ZR1 ,..., I _ZRi ) of the measurement object with respect to the virtual imaging plane are measured by image processing the captured image. And
Measurement is performed by _substituting the monitor coordinates (I _ZL0 , I _ZL1 ,..., I _ZLi , I _ZR0 , I _{ZR1 ,. Calculate} the robot coordinates (W _ZL0 , W _ZL1 ,..., W _ZLi , W _ZR0 , W _ZR1 ,..., W _ZRi ) of the _object ,
The robot coordinates (W _ZL0 , W _ZL1 ,..., W _ZLi , W _ZR0 , W _ZR1 ,..., W _ZRi ) of the measurement _object and two or more different values set on the Z axis of the robot coordinates Based on the measurement points (Q ₀ , Q ₁ ,..., Q _i ), the robot coordinates (W _LC , W _RC ) of the two cameras are calculated,
After the two cameras are arranged at the robot coordinates (W _LC , W _RC ) by operating the robot, the measurement object is photographed,
By measuring the captured image, the monitor coordinates of the measurement object about the virtual imaging plane are measured,
The robot coordinates (W _LM , W _RM ) of the measurement object are calculated by substituting the monitor coordinates of the measurement object into the conversion formula in which the conversion coefficient is calculated,
The three-dimensional position of the measurement object is measured based on the robot coordinates (W _LM , W _RM ) of the measurement object and the robot coordinates (W _LC , W _RC ) of the two cameras. A three-dimensional position measurement method for robots.

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