Aircraft large-size measurement system and method based on laser radar and indoor GPS system

Abstract

The present invention relates to an aircraft large-size measurement system based on a laser radar and an indoor GPS system, comprising an AGV trolley equipped with a robot, a laser radar and a standard coordinate system reference plate clamped at the end of the robot's mechanical arm, and an indoor GPS system; the indoor GPS system establishes a global coordinate system Q; the indoor GPS system monitors the position and posture of the standard coordinate system reference plate under the global coordinate system Q established by the indoor GPS system. The purpose of the present invention is to overcome the defects of the prior art such as low measurement efficiency and low measurement accuracy caused by frequent station transfers, and to provide an aircraft large-size measurement system and method based on a laser radar and an indoor GPS system.

Description

Technical Field

[0001] The present invention relates to the field of machine vision, and in particular to an aircraft large-size measurement system and method based on a laser radar and an indoor GPS system. Background Art

[0002] With the development of advanced manufacturing technology in my country, digital measurement technology has been widely used in aerospace, aviation, shipbuilding and other fields. In particular, digital large-size measurement systems have gradually been applied to the processing and assembly of large-size aircraft workpieces, which use the high-precision measurement of digital measurement systems to improve the assembly accuracy of aircraft.

[0003] At present, digital large-scale measurement technology is mainly divided into contact measurement and non-contact measurement. Contact measurement mainly includes laser trackers and indoor GPS measurement, and non-contact measurement mainly includes electronic theodolite measurement system, digital close-range industrial measurement system, and laser radar measurement system. When measuring the surface of large aircraft components, the first choice should be non-contact measurement such as laser radar, because laser radar can quickly and accurately measure a large range, but the disadvantage of laser radar is that the horizontal and vertical angle measurement range of laser radar is limited, and frequent station transfer operations are required, which will introduce cumulative errors caused by station transfer. In addition, current measurement systems generally take up a lot of space and are not mobile. For aircraft manufacturing and assembly workshops, a movable measurement system is urgently needed for the measurement of large aircraft components. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a large-size aircraft measurement system and method based on laser radar and indoor GPS system. The system and method use the global coordinate system of the indoor GPS system as the global coordinate system, and convert all the measurement data of the laser radar at multiple stations into the global coordinate system, thereby reducing the cumulative error caused by station transfer. At the same time, since the laser radar is carried for scanning in the form of an AGV cart and a robot, the measurement is flexible and meets the space requirements of the aircraft manufacturing assembly workshop.

[0005] The technical solution for achieving the purpose of the present invention is: an aircraft large-size measurement system based on a laser radar and an indoor GPS system, comprising an AGV cart equipped with a robot, a laser radar and a standard coordinate system reference plate clamped at the end of the robot's mechanical arm, and an indoor GPS system; the indoor GPS system establishes a global coordinate system Q; the indoor GPS system monitors the position and posture of the standard coordinate system reference plate in the global coordinate system Q established by the indoor GPS system.

[0006] Preferably, when the aircraft large-size measurement system is working, the relative position and posture between the laser radar and the reference plate of the standard coordinate system remains unchanged.

[0007] Preferably, the laser radar can establish a laser radar coordinate system L.

[0008] Preferably, three spherical receivers are arranged on the standard coordinate system reference plate; the centers of the three spherical receivers can establish a standard reference coordinate system S.

[0009] Preferably, a connecting line of the three spherical receivers is at a right angle, and the distances between the spherical receivers at both ends of the right angle and the spherical receiver at the right angle are different.

[0010] Preferably, the indoor GPS system comprises an IGPS transmitter, a spherical receiver respectively arranged indoors and on a reference board of a standard coordinate system, and a central processor; the IGPS transmitter is arranged at multiple locations in the indoor space.

[0011] A method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system comprises the above-mentioned large dimension measurement system for an aircraft based on a laser radar and an indoor GPS system; and further comprises the following steps:

[0012] Step 1: Indoor GPS system calibration: The indoor GPS system calibrates the relationship between various IGPS transmitters and establishes the global coordinate system Q of the aircraft large-scale measurement system;

[0013] Step 2: Determine the position relationship between the lidar coordinate system L and the standard reference coordinate system S by calibrating the lidar coordinate system L and the standard reference coordinate system S S T L :

[0014] Step 3: The AGV carries a laser radar to scan the aircraft components for data collection. The laser radar scans at multiple positions to obtain point cloud data, and then converts the point cloud data into the standard reference coordinate system S;

[0015] Step 4: Identify the position and posture of the standard reference coordinate system S in the global coordinate system Q in real time;

[0016] Step 5: Convert all collected point cloud data to the global coordinate system Q

[0017] Step 6: The point cloud data is processed by the central processing unit to complete the measurement of large aircraft components.

[0018] Preferably, in step 2 S T L The calculation formula is:

[0019] L T S = L T Q *Q T S

[0020] S T L = L T S -1

[0021] L T Q represents the position relationship between the global coordinate system Q and the lidar coordinate system L, Q T S Represents the pose relationship between the standard reference coordinate system S and the global coordinate system Q.

[0022] Preferably, the Q T S The solution process is as follows: Assume that the coordinates of the three spherical receivers in the global coordinate system Q are (x A ,y A ,z A ), (x B ,y B ,z B ), (x C ,y C ,z C ). With point B as the center, establish the global coordinate system Q, and AB as the X-axis of the standard reference coordinate system S, so we have:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] The position relationship of the standard reference coordinate system S established by points A, B, and C relative to the global coordinate system Q Q T S ;

[0029]

[0030] Where p = (x B ,y B ,z B ).

[0031] Preferably, the L T QThe solution process is as follows: 20 spherical receivers are placed at appropriate locations in the indoor space to ensure that the spherical receivers can be scanned by the laser radar. At the same time, their coordinates in the indoor global coordinate system Q can also be obtained. The measured point pairs are used to solve the pose relationship between the global coordinate system Q and the laser radar coordinate system L using the SVD method. The solution method is as follows:

[0032] Suppose there are two point groups p i and q i , where p i represents the point group coordinates of these 20 spherical receivers under the lidar, q i Represents the point group coordinates of these 20 spherical receivers in the global coordinate system. If the SVD decomposition method is used to solve the matrix relationship between the two point groups, then the premise must be that the centroids of the two point groups coincide. To represent the point group p i and q i The centroid of , so we have:

[0033]

[0034]

[0035] where p i ,q i , It is a vector with 3 rows and 1 column, representing the x, y, and z coordinates of a point.

[0036] According to the assumption that the centroids coincide, we have:

[0037]

[0038] Then order:

[0039]

[0040]

[0041] The last component least squares function is solved:

[0042]

[0043] The SVD decomposition algorithm process is:

[0044] (1) According to p i ,q i calculate p i 'and q i '

[0045] (2) Calculate the 3×3 matrix

[0046]

[0047] where p i 'and q i ' is a vector with 3 rows and 1 column;

[0048] (3) Perform SVD decomposition on H

[0049] H=USV T

[0050] (4) Calculate X = VU T

[0051] (5) Calculate the determinant of X det(X)

[0052] If det(X)=1, R=X; if det(X)=-1, the algorithm fails; after obtaining the rotation matrix R, the translation matrix t can be calculated by the following formula:

[0053]

[0054] So far, L T Q ,according to L T S = L T Q * Q T S , calibrate the position and posture relationship of the standard reference coordinate system S relative to the lidar coordinate system L, and then S T L = L T S -1 The position and posture relationship of the lidar coordinate system L relative to the standard reference coordinate system S is obtained.

[0055] After adopting the above technical solution, the present invention has the following positive effects:

[0056] (1) The present invention uses the global coordinate system of the indoor GPS system as the global coordinate system, and converts all the measurement data of the laser radar at multiple stations into the global coordinate system, thereby reducing the cumulative error caused by station transfer. At the same time, since the laser radar is carried out for scanning by an AGV cart plus a robot, the measurement is flexible and the requirements for indoor space are not large, thus meeting the space requirements of aircraft manufacturing assembly workshops.

[0057] (2) The calibration of the laser radar coordinate system and the standard reference system of the present invention is a key part of the system. When the system is working, the relative posture relationship between the laser radar coordinate system and the standard reference coordinate system remains unchanged, so only one calibration is required. When the system starts working subsequently, the laser radar converts the data to the standard reference coordinate system, and then converts the point cloud data from the standard reference coordinate system to the measurement coordinate system in real time according to the relative posture relationship between the current standard reference coordinate system and the indoor measurement coordinate system.

[0058] (3) The indoor GPS system of the present invention is a contact measurement system. This measurement system arranges IGPS transmitters in space and can detect the three-dimensional coordinates of the spherical receiver in the indoor GPS system without the problem of light blocking or angle limitation.

[0059] (4) The present invention avoids the problems of the prior art of arranging frog jump balls on large components, such as large workload, cumbersome calibration, and low precision. The present solution requires less calibration, has high measurement efficiency, and is highly real-time. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments and in conjunction with the accompanying drawings, wherein

[0061] Figure 1 It is the overall layout diagram of the system of the present invention;

[0062] Figure 2 A distribution diagram of the spherical receivers of the present invention on a reference plate of a standard coordinate system;

[0063] Figure 3 It is a coordinate system relationship diagram of the present invention;

[0064] Figure 4 It is a measurement flow chart of the present invention.

[0065] The reference numerals in the accompanying drawings are: AGV 10 , standard coordinate system reference plate 20 , spherical receiver 21 , connecting rod 22 , indoor GPS system 30 , IGPS transmitter 31 , laser radar 40 . DETAILED DESCRIPTION

[0066] (Example 1)

[0067] See Figures 1 to 3The present invention includes an AGV trolley 10 equipped with a robot, a laser radar 40 clamped at the end of the robot's mechanical arm, a standard coordinate system reference plate 20, and an indoor GPS system 30; specifically, the standard coordinate system reference plate 20 is fixed to the end of the robot's mechanical arm through a connecting plate 22 parallel to the ground, and the laser radar 40 is directly fixed to the lower end of the connection between the connecting plate 22 and the robot's mechanical arm; the indoor GPS system 30 establishes a global coordinate system Q; the indoor GPS system 30 monitors the position and posture of the standard coordinate system reference plate 20 in the global coordinate system Q established by the indoor GPS system 30.

[0068] More specifically, in this embodiment, when the large-scale aircraft measurement system is working, the relative position and posture between the laser radar 40 and the standard coordinate system reference plate 20 remains unchanged.

[0069] The laser radar 40 can establish a laser radar coordinate system L.

[0070] Three spherical receivers 21 are arranged on the standard coordinate system reference plate 20; a standard reference coordinate system S can be established by the centers of the three spherical receivers 21.

[0071] The connecting line of the three spherical receivers 21 is at a right angle, and the distances from the spherical receivers 21 at both ends of the right angle to the spherical receiver 21 at the right angle (i.e., the origin) are different. This allows the origin to be identified and facilitates the distinction between the X-axis and the Y-axis, thereby establishing a fixed standard reference coordinate system S.

[0072] The indoor GPS system 30 includes an IGPS transmitter 31, a spherical receiver 21 respectively arranged indoors and on a standard coordinate system reference plate 20, and a central processor; the IGPS transmitter 31 is arranged at multiple positions in the indoor space, and the specific arrangement points must meet the requirement that the spherical receiver 21 on the standard coordinate system reference plate 20 can receive signals from more than two IGPS transmitters 31, so that the coordinate position of the spherical receiver 21 on the standard coordinate system reference plate 20 can be solved.

[0073] (Example 2)

[0074] See Figure 4 , a method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system, comprising the large dimension measurement system of an aircraft based on a laser radar and an indoor GPS system described in Example 1; and further comprising the following steps:

[0075] Step 1: Calibration of the indoor GPS system 30: The indoor GPS system 30 calibrates the relationship between the various IGPS transmitters 31 and establishes the global coordinate system Q of the large-scale measurement system of the aircraft. In this system, the indoor GPS system 30 is calibrated using commercial software.

[0076] Step 2: Determine the position relationship between the lidar coordinate system L and the standard reference coordinate system S by calibrating the lidar coordinate system L and the standard reference coordinate system S S T L :

[0077] Step 3: The AGV 10 carries a laser radar 40 to scan the aircraft components for data collection. The laser radar 40 scans at multiple positions to obtain point cloud data, and then converts the point cloud data into a standard reference coordinate system S;

[0078] Step 4: Identify the position and posture of the standard reference coordinate system S in the global coordinate system Q in real time;

[0079] Step 5: Convert all collected point cloud data to the global coordinate system Q

[0080] Step 6: The point cloud data is processed by the central processor to complete the measurement of the large components of the aircraft;

[0081] L T S = L T Q * Q T S

[0082] S T L = L T S -1

[0083] L T Q represents the position relationship between the global coordinate system Q and the lidar coordinate system L, Q T S Represents the pose relationship between the standard reference coordinate system S and the global coordinate system Q;

[0084] Where the solution Q T S , that is, to find the relationship between the standard reference coordinate system S and the global coordinate system Q. When solving this relationship, let the AGV car 10 carry the laser radar 40 and the standard coordinate system reference plate 20 to a suitable position in the indoor space. Since the coordinate values ​​of the three spherical receivers 21 on the standard coordinate system reference plate 20 in the global coordinate system Q of the indoor GPS system 30 can be obtained, then the position and posture relationship of the coordinate system established with these three points relative to the global coordinate system Q can be calculated.

[0085] Assume that the coordinates of the three spherical receivers 21 in the global coordinate system Q are (x A ,y A ,z A ), (xB ,y B ,z B ), (x C ,y C ,z C ). With point B as the center, establish the global coordinate system Q, and AB as the X-axis of the standard reference coordinate system S, so we have:

[0086]

[0087]

[0088]

[0089]

[0090]

[0091] The position relationship of the standard reference coordinate system S established by points A, B, and C relative to the global coordinate system Q T S ;

[0092]

[0093] Where p = (x B ,y B ,z B );

[0094] Solution L T Q , that is, to solve the pose relationship of the global coordinate system Q relative to the laser radar coordinate system L. At this time, keep the position of the laser radar 40 unchanged, place 20 spherical receivers 21 at appropriate positions in the indoor space, ensure that these 20 spherical receivers 21 can be scanned by the laser radar 40, and also obtain their coordinates in the indoor global coordinate system Q. The SVD method is used to solve the pose relationship between the global coordinate system Q and the laser radar coordinate system L for the 20 groups of measured points. The solution method is as follows:

[0095] Suppose there are two point groups p i and q i , where p i represents the point group coordinates of these 20 spherical receivers under the lidar, q i represents the point group coordinates of these 20 spherical receivers in the global coordinate system, where p i ,q i If we use SVD decomposition to solve the matrix relationship between the two point groups, then the premise is that the centroids of the two point groups must coincide. To represent the point group p i and qi The centroid of , so we have:

[0096]

[0097]

[0098] where p i ,q i , It is a vector with 3 rows and 1 column, representing the x, y, and z coordinates of a point.

[0099] According to the assumption that the centroids coincide, we have:

[0100]

[0101] Then order:

[0102]

[0103]

[0104] The last component least squares function is solved:

[0105]

[0106] The SVD algorithm is already very mature, so the detailed derivation will not be repeated here.

[0107] The SVD algorithm process is:

[0108] (1) According to p i ,q i calculate p i 'and q i '

[0109] (2) Calculate the 3×3 matrix

[0110]

[0111] where p i 'and q i ' is a vector with 3 rows and 1 column;

[0112] (3) Perform SVD decomposition on H

[0113] H=USV T

[0114] (4) Calculate X = VU T

[0115] (5) Calculate the determinant of X det(X)

[0116] If det(X)=1, R=X; if det(X)=-1, the algorithm fails; after obtaining the rotation matrix R, the translation matrix T can be calculated by the following formula:

[0117]

[0118] So far, L T Q ,according to L T S = L T Q * Q T S , calibrate the position and posture relationship of the standard reference coordinate system S relative to the lidar coordinate system L, and then S T L = L T S -1 The position and posture relationship of the lidar coordinate system L relative to the standard reference coordinate system S is obtained.

[0119] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring large dimensions of an aircraft based on laser radar and indoor GPS system, characterized in that: The invention relates to an aircraft large-size measurement system based on a laser radar and an indoor GPS system; the system comprises an AGV trolley (10) equipped with a robot, a laser radar (40) clamped at the end of a mechanical arm of the robot, a standard coordinate system reference plate (20), and an indoor GPS system (30); the indoor GPS system (30) establishes a global coordinate system Q; the indoor GPS system (30) monitors the position and posture of the standard coordinate system reference plate (20) in the global coordinate system Q established by the indoor GPS system (30); and three spherical receivers (21) are arranged on the standard coordinate system reference plate (20); The following steps are also included: Step 1: Calibration of the indoor GPS system (30), the indoor GPS system (30) calibrates the relationship between the various IGPS transmitters (31), and establishes a global coordinate system Q of the aircraft large-scale measurement system; Step 2: Determine the position relationship between the lidar coordinate system L and the standard reference coordinate system S by calibrating the lidar coordinate system L and the standard reference coordinate system S S T L : Step 3: The AGV (10) carries a laser radar (40) to scan the aircraft components for data collection. The laser radar scans at multiple positions to obtain point cloud data, and then converts the point cloud data into a standard reference coordinate system S; Step 4: Identify the position and posture of the standard reference coordinate system S in the global coordinate system Q in real time; Step 5: Convert all collected point cloud data to the global coordinate system Q; Step 6: The point cloud data is processed by the central processing unit to complete the measurement of large aircraft components.

2. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 1, characterized in that: When the large-scale aircraft measurement system is working, the relative position and posture between the laser radar (40) and the standard coordinate system reference plate (20) remains unchanged.

3. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 2, characterized in that: The laser radar (40) establishes a laser radar coordinate system L.

4. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 1, 2 or 3, characterized in that: The centers of the three spherical receivers (21) establish a standard reference coordinate system S.

5. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 4, characterized in that: The connecting line of the three spherical receivers (21) is at a right angle, and the distances between the spherical receivers (21) at both ends of the right angle and the spherical receivers (21) at the right angle are different.

6. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 5, characterized in that: The indoor GPS system (30) comprises an IGPS transmitter (31), a spherical receiver (21) respectively arranged indoors and on a standard coordinate system reference plate (20), and a central processor; the IGPS transmitter (31) is arranged at multiple locations in the indoor space.

7. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 1, characterized in that: In step 2 S T L The calculation formula is: L T S = L T Q * Q T S S T L = L T S -1 L T Q represents the position relationship between the global coordinate system Q and the lidar coordinate system L, Q T S Represents the pose relationship between the standard reference coordinate system S and the global coordinate system Q.

8. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 7, characterized in that: Said Q T S The solution process is as follows: Assume that the coordinates of the three spherical receivers (21) in the global coordinate system Q are (x A ,y A ,z A ), (x B ,y B ,z B ), (x C ,y C ,z C ) ; Establish the global coordinate system Q with point B as the center, and AB as the X-axis of the standard reference coordinate system S, so we have: The position relationship of the standard reference coordinate system S established by points A, B, and C relative to the global coordinate system Q Q T S ; Where p = (x B ,y B ,z B ).

9. The method for measuring large dimensions of an aircraft based on a laser radar and an indoor GPS system according to claim 7, characterized in that: Said L T Q The solution process is as follows: 20 spherical receivers (21) are placed at appropriate positions in the indoor space to ensure that the 20 spherical receivers (21) are scanned by the laser radar (40), and their coordinates in the indoor global coordinate system Q are obtained. The measured (20) groups of point pairs are used to solve the pose relationship between the global coordinate system Q and the laser radar coordinate system L using the SVD method. The solution method is as follows: Suppose there are two point groups p i and q i , where p i represents the point group coordinates of these 20 spherical receivers under the lidar, q i Represents the point group coordinates of these 20 spherical receivers in the global coordinate system. If the SVD decomposition method is used to solve the matrix relationship between the two point groups, then the premise must be that the centroids of the two point groups coincide. To represent the point group p i and q i The centroid of , so we have: where p i ,q i , It is a vector of 3 rows and 1 column, representing the x, y, and z coordinates of a point; According to the assumption that the centroids coincide, we have: Then order: The last component least squares function is solved: The SVD decomposition algorithm process is: (1) According to p i ,q i calculate p i 'and ' q i (2) Calculate the 3×3 matrix where p i 'and q i ' is a vector with 3 rows and 1 column; (3) Perform SVD decomposition on H H=USV T (4) Calculate X = VU T (5) Calculate the determinant of X det(X) If det(X)=1, R=X; if det(X)=-1, the algorithm fails; after obtaining the rotation matrix R, the translation matrix t is calculated by the following formula: So far, L T Q ,according to L T S = L T Q * Q T S , calibrate the position and posture relationship of the standard reference coordinate system S relative to the lidar coordinate system L, and then S T L = L T S -1 Find the relationship between the lidar coordinate system L and the standard reference coordinate system S.

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