CN115493616A - Method for evaluating field accuracy of laser tracking attitude angle - Google Patents
Method for evaluating field accuracy of laser tracking attitude angle Download PDFInfo
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Abstract
The invention provides a method for evaluating the field accuracy of a laser tracking attitude angle, which comprises the following steps: (1) Acquiring a space vector of a measuring field internal point and a space vector of a control field internal point of a laser tracking attitude angle on-site precision evaluation system; (2) determining a distance constraint; (3) establishing a homogeneous coordinate transformation matrix equation; (4) giving an initial value to the equation set; (5) solving and evaluating the attitude angle of the system; the laser tracking attitude angle on-site precision evaluation system comprises a laser tracking equipment unit, a cooperation target unit, an evaluation system measuring field unit, an evaluation system control field unit, a length measuring equipment unit and a calculation unit. The attitude angle field precision evaluation system and method avoid the strict requirement of coordinate system registration in the angle reference based evaluation method at present in China, and a control field and a measurement field are established on site, so that the consistency of a tracing environment and a field environment is ensured.
Description
Technical Field
The invention relates to the technical field of precision measurement, in particular to a laser tracking attitude angle on-site precision evaluation system and method.
Background
With the high-speed development of the manufacturing industry of modern large-scale equipment such as aerospace, ships and naval vessels, rail transit and the like, the six-degree-of-freedom attitude measurement system taking the laser tracking equipment as the base station provides a good solution for large-scale industrial measurement due to the advantages of high measurement precision, strong adaptability, simple and convenient operation and the like. In order to ensure the accuracy of the attitude measurement result, a reasonable attitude measurement system precision evaluation system needs to be established. The attitude angle measurement accuracy is one of key indexes of a six-degree-of-freedom laser tracking attitude measurement system, and has very important theoretical and application values in research on an attitude measurement accuracy evaluation method applied to a large-scale precision engineering field.
The conventional angle evaluation methods include a precision turntable method based on angle reference, a polyhedral prism and a photoelectric autocollimator method. Aiming at a laser tracking attitude measurement system, the currently adopted precision evaluation method is a standard component comparison method based on angle reference. And the attitude measurement precision of the six-degree-of-freedom measurement system is evaluated by taking the precise three-axis turntable as an angle reference. And comparing the angle value of the high-precision turntable with the resolution of 0.1' by using the angle value of the Zhang Shuai and Zheng Shuihui and the like as standard values with the attitude angle measured by the multi-path laser multilateral method system to verify the accuracy of the attitude angle. The azimuth angle and pitch angle accuracy of the attitude measurement system is evaluated by taking the rotation angle of the two-dimensional precision rotary table as an angle reference in the process of sailing, liu Port stretching and the like. Mengxiang et al evaluate target azimuth measurement accuracy using a multi-tooth index table that has been aligned horizontally as an angular reference. And the checked and corrected indium steel tetrahedron are utilized to provide an angle reference, so that the measurement accuracy of the dynamic pose of the multiple laser trackers is evaluated.
Although the magnitude is clearly transmitted, the requirement on coordinate system registration is high, and large environmental errors are easily introduced due to inconsistency between the source tracing environment and the field environment. The defects limit the application range of the method, so that the research on the attitude angle field accuracy evaluation method with high accuracy, high efficiency and high adaptability under industrial field conditions is of great significance.
Disclosure of Invention
Based on the problems in the prior art, the invention provides a system and a method for evaluating the field accuracy of a laser tracking attitude angle.
In one aspect, the present invention provides a laser tracking attitude angle field accuracy evaluation system, including: a laser tracking device unit, a cooperative target unit, an assessment system measurement field unit, an assessment system control field unit, a length measurement device unit, and a calculation unit.
The laser tracking equipment unit is fixed at a preset position, posture measurement is realized under the cooperation of a cooperation target, and the coordinates of the vertex of the corner cube prism in the cooperation target, the internal points of the measurement field of the evaluation system and the internal points of the control field of the evaluation system in a first coordinate system are obtained; wherein the first coordinate system is a measurement coordinate system of the laser tracking device unit. Further, the laser tracking device unit is a laser tracker or a total station, which is not limited herein.
The cooperation target unit is fixedly installed on a measured object, a three-dimensional design is adopted, a pyramid prism is installed inside the cooperation target unit, and a laser beam emitted by the laser tracking equipment unit enters the pyramid prism through a light transmitting surface of the pyramid prism to obtain the coordinate of the vertex of the pyramid prism in a first coordinate system.
The measuring field unit of the evaluation system constructs a movable platform rotating along with the cooperative target for the attitude evaluation system, and the movable platform and the cooperative target unit are rigidly connected and fixedly arranged on a measured object; the evaluation system measuring field unit is provided with a plurality of coplanar evaluation system measuring field internal points which are symmetrically distributed on the same circle, the light transmission surface of the pyramid prism is parallel to the plane of the evaluation system measuring field internal points, and the internal points are sequentially distributed from top to bottom in the clockwise direction in the cooperation target front view; the method comprises the steps that a laser tracking device unit obtains coordinates of an internal point of a measuring field of an evaluation system in a first coordinate system; the detachable design is adopted so as to adjust the number, the layout and the height of the points in the measurement field of the evaluation system, and the adaptability of the precision evaluation system is enhanced.
The evaluation system control field unit is a reasonable field arranged around the cooperation target unit and the evaluation system measurement field unit, and a static platform is constructed for the posture evaluation system and fixed at a preset position; the evaluation system control field unit is provided with a plurality of coplanar internal points of the evaluation system control field which are symmetrically distributed on the same circle, and the internal points are sequentially distributed from top to bottom in the clockwise direction; obtaining the coordinates of the internal points of the control field of the evaluation system in a first coordinate system by a laser tracking equipment unit; and a detachable design is adopted so as to adjust the number, the layout and the height of the points in the control field of the evaluation system, and the adaptability of the precision evaluation system is enhanced.
The length measuring equipment unit is a length measuring instrument which is used for establishing distance constraint between an internal point of the control field of the evaluation system and an internal point of the measurement field of the evaluation system and meeting the requirement of evaluation accuracy.
The computing unit is often a device with programming and computing capabilities.
On the other hand, the invention provides a method for evaluating the field accuracy of the laser tracking attitude angle, which comprises the following steps:
(1) Acquiring space vectors of internal points of a measurement field and a control field of an evaluation system;
(2) Determining a distance constraint;
(3) Establishing a homogeneous coordinate transformation matrix equation;
(4) Giving an initial value to the equation set;
(5) And solving and evaluating the attitude angle of the system.
Specifically, the obtaining of the space vector of the internal point of the measurement field and the control field of the evaluation system in step (1) refers to obtaining a corresponding second space vector of the internal point of the measurement field of the evaluation system in a second coordinate system according to the coordinate of the internal point of the measurement field of the evaluation system in the second coordinate system, wherein the second coordinate system is a coordinate system of a cooperative target; and acquiring the coordinates of the internal points of the control field of the evaluation system in the first coordinate system by using the laser tracking equipment unit, and acquiring the corresponding first space vector of the internal points of the control field of the evaluation system in the first coordinate system according to the coordinates of the internal points of the control field of the evaluation system in the first coordinate system.
And (3) determining the distance constraint in the step (2) refers to acquiring the distance constraint between the inner point of the control field of the assessment system and the inner point of the measurement field of the assessment system by using the length measurement equipment unit.
And (3) establishing a homogeneous coordinate transformation matrix equation, namely establishing a distance constraint equation set taking the pose as an unknown quantity based on the spatial homogeneous coordinate transformation matrix, wherein the distance constraint is performed by the first space vector, the second space vector, and the distance between the inner point of the control field of the evaluation system and the inner point of the measurement field of the evaluation system.
Giving an initial value to the equation set in the step (4) means that a laser tracking equipment unit is utilized to obtain the vertex of the pyramid prism and the coordinate of the internal point of the measuring field of the evaluation system in a first coordinate system; acquiring an initial attitude value by using a common point conversion model according to coordinate values of the internal points of the measurement field of the evaluation system in a first coordinate system and a second coordinate system respectively; and acquiring an initial position value according to the coordinates of the vertex of the pyramid prism in the first coordinate system.
And (5) solving and evaluating the attitude angle of the system, namely performing Newton iterative solution according to the distance constraint equation set, the attitude initial value and the position initial value to obtain the attitude angle of the cooperative target unit in the first coordinate system, namely realizing the three-dimensional attitude angle measurement result traced from the length measurement reference.
Further, the step (1) specifically comprises: taking an origin of the first coordinate system as a starting point, taking an internal point of a control field of the evaluation system as an end point, and acquiring a first space vector; and taking the origin of the second coordinate system as a starting point, and taking the internal point of the measurement field of the evaluation system as an end point to obtain a second space vector. Preferably, the coordinate value of the first space vector is calculated according to the coordinate value of the origin of the first coordinate system and the coordinate value of the internal point of the control field of the evaluation system in the first coordinate system. And the coordinate value of the second space vector is obtained by calculation according to the coordinate value of the origin of the second coordinate system and the coordinate value of the internal point of the measurement field of the evaluation system in the second coordinate system.
Further, the step (2) specifically comprises: when the cooperative target moves, the second space vector A k ＝[A kx A ky A kz 1] T Can be converted into a first coordinate system through a spatial homogeneous transformation matrix and is associated with a first space vector B k ＝[B kx B ky B kz 1] T A length geometric relationship is formed.
l k ＝||T(α,β,γ,t x ,t y ,t z )×A k -B k ||
Wherein l k K =1,2,., n for the evaluation system to control the distance constraint between the interior points of the field and the evaluation system to measure the distance constraint between the interior points of the field; t (α, β, γ, T) x ,t y ,t z ) For a spatially homogeneous transformation matrix, the spatially homogeneous transformation matrix with ZXY as the rotation order can be expressed as:
establishing the pose (alpha, beta, gamma, t) according to the space distance constraint condition x ,t y ,t z ) The system of equations is constrained for the distance of the unknowns.
In the formula,
C(α,β,γ) k ＝T 11 A kx +T 12 A ky +T 13 A kz +T 14 -B kx
D(α,β,γ) k ＝T 21 A kx +T 22 A ky +T 23 A kz +T 24 -B ky
E(α,β,γ) k ＝T 31 A kx +T 32 A ky +T 33 A kz +T 34 -B kz
wherein, T ij The ith row and jth column elements of the spatially homogeneous transformation matrix T. Let X = (α, β, γ, t) x ,t y ,t z ) Sorting the distance constraint equation set to obtain
F k (X,l k )＝0
Further, the step (3) is specifically: when the field accuracy of the laser tracking attitude angle is evaluated, the coordinates of the internal point of the measuring field of the evaluation system in the first coordinate system are obtained by utilizing the laser tracking equipment unit
Measuring the coordinates of points within the field in a second coordinate system according to an evaluation system
Calculating the difference between the coordinates of each point and the centroid of the point set, and replacing the original coordinates to obtain a new point set
To eliminate the effect of the translation transformation:
calculating the integral deviation among the point sets:
wherein, R is a rotation matrix between point sets; when D is present min And then, the corresponding R is the optimal rotation matrix for realizing the transformation superposition of the point set. And D min Implementation conditions are equivalent to
Trace operations are used to collate formulas:
wherein H is defined as the base matrix of singular value decomposition:
solving singular value decomposition of the H matrix:
H＝U·S·V T
wherein U and V are left and right singular vector matrixes when Tr (R.H) exists max The rotation matrix between the point sets is
R＝VU T
Obtaining the rotation relationship between the second coordinate system and the first coordinate system
Initial attitude value alpha of cooperative target 0 、β 0 、γ 0 The specific formula is as follows:
α＝-arcsin(r 23 )
obtaining an attitude initial value azimuth angle alpha of the cooperative target under a first coordinate system 0 Angle of pitch beta 0 Transverse rolling angle gamma 0 。
Acquiring the coordinate (X) of the vertex of the corner-cube prism in a first coordinate system by using a laser tracking device unit O ,Y O ,Z O ) Obtaining the position initial value t of the cooperative target unit under the first coordinate system x ＝X O ，t y ＝Y O ，t z ＝Z O 。
Further, the step (5) is specifically: performing N-1 stage Taylor expansion on the distance constraint equation set, and taking the linear part of the Taylor expansion to obtain
F(X (N) ,l k )≈-J (N) ΔX (N)
Wherein N is the number of iterations; Δ X (N) ＝X (N+1) -X (N) (ii) a J is a Jacobian matrix; substituting the obtained initial attitude and initial position into a formula to obtain a corresponding spatial homogeneous transformation matrix T (0) Utilizing successive iteration of Newton Raphson method, taking max | delta X | less than or equal to epsilon as the operation condition for finishing the algorithm, and solving the variable X = (alpha, beta, gamma, t) x ,t y ,t z ) The optimal numerical solution of the cooperative target unit is the azimuth angle, the pitch angle and the roll angle of the cooperative target unit in the first coordinate system.
The invention provides a laser tracking attitude angle on-site precision evaluation system and method, which establish distance constraints of an internal point of an evaluation system control field and an internal point of an evaluation system measurement field by designing the structures of the evaluation system control field unit and the evaluation system measurement field unit, establish a mathematical model between a spatial distance and a cooperative target attitude by utilizing a homogeneous coordinate change matrix, and realize the evaluation of attitude measurement precision by tracing the measurement result of an attitude angle to a length measurement standard. The attitude angle on-site precision evaluation system and method avoid the strict requirement of coordinate system registration in the angle reference-based evaluation method at present in China, and can simultaneously evaluate the azimuth angle, the pitch angle and the roll angle. The control field and the measuring field are established on site, the operation process is simple, the adaptability is good, the control field can be flexibly arranged according to the site environment, the consistency of the tracing environment and the site environment is ensured, and the site use state of the measuring system can be comprehensively reflected.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a laser tracking attitude angle field accuracy evaluation system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a cooperative target and an assessment system measurement field provided by an embodiment of the present invention.
Fig. 3 is a schematic diagram of an assessment system control field according to an embodiment of the present invention.
Fig. 4 is a flowchart of a method for performing on-site accuracy evaluation on an attitude angle by using the above-mentioned laser tracking attitude angle on-site accuracy evaluation system according to an embodiment of the present invention.
Fig. 5 is a physical diagram of the laser tracking device and the length measuring device in the accuracy evaluation system shown in fig. 1.
FIG. 6 is a pictorial view of the measurement field of the cooperative target and assessment system shown in FIG. 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments, but not all embodiments, of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic structural diagram of a laser tracking attitude angle field accuracy evaluation system according to an embodiment of the present invention, as shown in fig. 1, including: a laser tracking device unit 1, a cooperation target unit 2, an evaluation system measurement field unit 3, an evaluation system control field measurement unit 4, a length measurement device unit 5, and a calculation unit 6; wherein,
the cooperation target unit 2 and the evaluation system measuring field unit 3 are fixedly arranged on the measured object; the laser tracking device unit 1 and the evaluation system control field unit 4 are fixed at preset positions, which can be set according to actual requirements, and are not limited herein.
The laser tracking device unit 1 is used to acquire the coordinates of the apex of the corner cube 21, the evaluation system measurement field internal point 31, and the evaluation system control field internal point 41 in a first coordinate system; wherein the first coordinate system is a measurement coordinate system of the laser tracking device unit. Specifically, the laser tracking device unit 1 is a laser tracker or a total station, and can be selected according to the precision requirement during actual measurement.
Specifically, during measurement, the laser tracking device unit 1 emits a laser beam to the evaluation system control field internal point 41, and the laser beam returns along the original path after aiming at the center of the cross; then, the laser tracking device unit 1 emits a laser beam to the evaluation system measurement field internal point 31, and the laser beam returns along the original path after aiming at the center of the cross; finally, the laser tracking device unit 1 emits a laser beam to the cooperative target unit 2, and after the laser beam passes through the light-transmitting surface of the corner cube 21, part of the laser beam returns along the original path at the vertex of the corner cube 21.
As shown in fig. 2, the cooperative target unit 2 is designed in a three-dimensional manner, a pyramid prism 21 is installed inside, and a laser beam emitted by the laser tracking device unit 1 passes through a light-transmitting surface of the pyramid prism 21 and then is incident into the pyramid prism to obtain coordinates of a vertex of the pyramid prism in a first coordinate system; the evaluation system measuring field unit 3 is used for constructing a movable platform rotating along with a cooperation target for the attitude evaluation system, and the cooperation target unit 2 is in rigid connection with the evaluation system measuring field unit 3; a plurality of coplanar evaluation system measurement field internal points 31 which are symmetrically distributed on the same circle are arranged on the movable platform, the light transmission surface of the corner cube 21 is parallel to the plane of the evaluation system measurement field internal points 31, the evaluation system measurement field internal points are divided into a first evaluation system measurement field internal point, a second evaluation system measurement field internal point and a third evaluation system measurement field internal point from top to bottom in a clockwise direction from a cooperation target transverse view, and coordinates of the evaluation system measurement field internal points 31 in a second coordinate system are obtained from the first evaluation system measurement field internal point, the second evaluation system measurement field internal point and the third evaluation system measurement field internal point. Wherein the second coordinate system is a measurement coordinate system of the cooperative target unit 2; a cross hair is carved on the surface of the internal point 31 of the measurement field of the evaluation system, and the laser beam emitted by the laser tracking equipment unit 1 aims at the center of the cross to obtain the coordinate of the internal point 31 of the measurement field of the evaluation system in a first coordinate system; the detachable design is adopted so as to adjust the number, the layout and the height of the points in the measurement field of the evaluation system, and the adaptability of the precision evaluation system is enhanced.
The cooperative target unit 2 and the evaluation system measuring field unit 3 are fixed on the measured object and move along with the measured object, and the attitude angle of the cooperative target unit 2 is the attitude angle of the measured object.
As shown in fig. 2, the first, second, and third evaluation system measurement site interior points are arranged on the right side of the cooperative target unit 2, and F4, F5, and F6 are symmetrically arranged on the left side of the cooperative target unit 2, and the specific height and spacing are determined according to the external dimensions of the actual cooperative target, which is not limited herein.
As shown in fig. 3, the evaluation system control field unit 4 is a reasonable field arranged around the cooperation target unit 2 and the evaluation system measurement field unit 3, and constructs a static platform for the posture evaluation system; the static platform is provided with a plurality of coplanar and symmetrically distributed evaluation system control field inner points 41 on the same circle, cross hairs are carved on the surface, laser beams emitted by the laser tracking equipment unit 1 aim at the cross center to obtain the coordinates of the evaluation system control field inner points, and a detachable design is adopted so as to adjust the number, the layout and the height of the evaluation system control field inner points.
The length measuring device unit 5 is used to establish a distance constraint between the evaluation system control field internal point 41 and the evaluation system measurement field internal point 31. In this embodiment, the rangefinder in the length measuring device unit 5 is an articulated arm coordinate measuring machine.
The computing unit 6 is often a device with programming and computing functions, such as a laptop, desktop, etc.
The second coordinate system can be understood as a coordinate system corresponding to the cooperative target unit 2, and when the cooperative target unit 2 moves (i.e., the object to be measured moves), the second coordinate system also moves correspondingly along with the cooperative target unit 2, so that the attitude angle of the second coordinate system relative to the first coordinate system is the attitude angle of the cooperative target unit 2 in the first coordinate system. The coordinates of the evaluation system measurement field internal points 31 in the second coordinate system can be converted into the first coordinate system through spatial homogeneous coordinate transformation, and according to the relation, a spatial distance relation between the first spatial vector and the second spatial vector can be obtained, namely, distance constraint between the evaluation system control field internal points 41 and the evaluation system measurement field internal points 31 can be constructed, further the attitude angle of the cooperation target unit 2 in the first coordinate system can be obtained, and the measurement result of the attitude angle is traced to the length measurement reference to realize the evaluation of the attitude measurement precision.
The embodiment of the invention provides a laser tracking attitude angle on-site precision evaluation system and method, which are characterized in that the distance constraints of an internal point 41 of an evaluation system control field and an internal point 31 of an evaluation system measurement field are established by designing the structures of an evaluation system control field unit 4 and an evaluation system measurement field unit 3, a homogeneous coordinate change matrix is utilized to establish a mathematical model between a space distance and a cooperative target attitude, and the evaluation of the attitude measurement precision is realized by tracing the measurement result of the attitude angle to a length measurement reference.
Fig. 4 is a flowchart of a method for performing on-site evaluation of attitude angle accuracy by using the above-mentioned laser tracking attitude angle on-site accuracy evaluation system according to an embodiment of the present invention, and as shown in fig. 4, the method includes:
s401, acquiring coordinates of the internal points of the evaluation system control field in a first coordinate system by using the laser tracking equipment unit, and acquiring corresponding first space vectors of the internal points of the evaluation system control field in the first coordinate system according to the coordinates of the internal points of the evaluation system control field in the first coordinate system; acquiring a corresponding second space vector of the internal point of the measurement field of the evaluation system in a second coordinate system according to the coordinate of the internal point of the measurement field of the evaluation system in the second coordinate system;
s402, acquiring distance constraint between an inner point of the evaluation system control field and an inner point of the evaluation system measurement field by using the length measurement equipment unit;
s403, based on a spatial homogeneous coordinate transformation matrix, performing distance constraint on the first space vector, the second space vector, the inner point of the evaluation system control field and the inner point of the evaluation system measurement field, and establishing a distance constraint equation set with the pose as an unknown quantity;
s404, acquiring the vertex of the corner cube prism and the coordinate of the internal point of the measuring field of the evaluation system in a first coordinate system by using the laser tracking equipment unit; acquiring an initial attitude value by using a common point conversion model according to coordinate values of the internal points of the measurement field of the evaluation system in a first coordinate system and a second coordinate system respectively; acquiring an initial position value according to the coordinate of the vertex of the pyramid prism in a first coordinate system;
s405, performing Newton iterative solution according to the distance constraint equation set, the attitude initial value and the position initial value, and obtaining an attitude angle of the cooperative target unit in the first coordinate system, namely, a three-dimensional attitude angle measurement result traced by the length measurement reference is realized.
In step S401, the second coordinate system can be understood as a coordinate system corresponding to the cooperative target unit 2, and when the cooperative target unit 2 moves (i.e. the measured object moves), the second coordinate system also follows the cooperative target unit 2 to make corresponding movement, so that the attitude angle of the second coordinate system relative to the first coordinate system is the attitude angle of the cooperative target unit 2 in the first coordinate system.
In steps S402-S405, the coordinate of the evaluation system measurement field internal point 31 in the second coordinate system may be converted into the first coordinate system through spatial homogeneous coordinate transformation, and according to this relationship, a spatial distance relational expression between the first spatial vector and the second spatial vector may be obtained, that is, a distance constraint between the evaluation system control field internal point 41 and the evaluation system measurement field internal point 31 may be constructed, so as to obtain the attitude angle of the cooperation target unit 2 in the first coordinate system, and trace the measurement result of the attitude angle to the length measurement reference to realize the evaluation of the attitude measurement accuracy.
FIG. 5 is a pictorial view of a laser tracking device and a length measuring device of the accuracy assessment system shown in FIG. 1;
the laser tracking device unit 1 is used for acquiring the coordinates of the apex of the corner cube 21, the evaluation system measurement field internal point 31 and the evaluation system control field internal point 41 in a first coordinate system; wherein the first coordinate system is a measurement coordinate system of the laser tracking device unit 1; in this example, the laser tracking device unit is a total station Leica TM50, as shown in fig. 5 (a).
Said length measurement device unit 5 is adapted to establish a distance constraint between said assessment system control field interior point 41 and said assessment system measurement field interior point 31; the choice in this example was made using FARO Quantum M The space length measuring precision of the movable flexible measuring arm can reach 0.027mm, as shown in figure 5 (b).
Fig. 6 shows a real object of the cooperation target unit 2 and the evaluation system measuring field unit 3, the cooperation target unit 2 is designed in a three-dimensional manner, a pyramid prism 21 is installed inside the cooperation target unit, and a laser beam emitted by the laser tracking device unit 1 passes through a light transmission surface of the pyramid prism 21 and then is incident into the pyramid prism to obtain coordinates of a vertex of the pyramid prism in a first coordinate system. The cooperative target unit 2 is made of 6160 aluminum alloy, and the surface of the cooperative target unit is subjected to anodic oxidation and blackening treatment. The evaluation system measuring field unit 3 is used for constructing a movable platform rotating along with a cooperation target for a posture evaluation system, and the cooperation target unit 2 is in rigid connection with the evaluation system measuring field unit 3; the movable platform is provided with a plurality of coplanar evaluation system measurement field internal points 31 which are symmetrically distributed on the same circle, the light transmission surface of the pyramid prism 21 is parallel to the plane of the evaluation system measurement field internal points 31, the evaluation system measurement field internal points are divided into a first evaluation system measurement field internal point, a second evaluation system measurement field internal point and a third evaluation system measurement field internal point from top to bottom in a clockwise direction from a cooperation target transverse view, and coordinates of the evaluation system measurement field internal points in a second coordinate system are obtained from the first evaluation system measurement field internal point, the second evaluation system measurement field internal point and the third evaluation system measurement field internal point. Wherein the second coordinate system is a measurement coordinate system of the cooperative target unit; the surface of the internal point of the measurement field of the evaluation system is carved with a cross wire, and the laser beam emitted by the laser tracking equipment unit 1 aims at the center of the cross to obtain the coordinate of the internal point of the measurement field of the evaluation system in a first coordinate system; the detachable design is adopted so as to adjust the number, the layout and the height of the points in the measurement field of the evaluation system, and the adaptability of the precision evaluation system is enhanced.
The second coordinate system is a three-dimensional coordinate system with the origin coinciding with the vertex of the pyramid prism 21, and the Z-axis of the second coordinate system is perpendicular to the light transmission surface of the pyramid prism. In this example, the six evaluation systems measure the coordinates of the points within the field in the second coordinate system as
In this embodiment, the computing unit is a device with programming and computing functions, such as a notebook computer, a desktop computer, and the like, and the computing is performed by software.
The measuring step is that the cooperation target unit and the measuring field unit of the evaluation system are fixed on the measured object, and the total station and the measuring field unit of the evaluation system are fixed at the preset position. The length measuring equipment adopts FARO Quantum M A movable flexible measuring arm, which is provided with a flexible measuring arm,in the embodiment, the measurement distance is 3m, and the coordinates of the internal point of the control field of the evaluation system obtained by the total station under the first coordinate system are
The joint arm measures the distance between the inner point of the control field of the evaluation system and the inner point of the measurement field of the evaluation system to obtain the length reference of
Carrying out spatial homogeneous transformation on coordinates of the internal points of the measurement field of the evaluation system in a second coordinate system to obtain a spatial distance relational expression between the internal points of the control field of the evaluation system and the internal points of the measurement field of the evaluation system, and utilizing the length measurement equipment unit to obtain a distance constraint value and establish a distance constraint equation set;
l k ＝||T(α,β,γ,t x ,t y ,t z )×A k -B k ||
let X = (α, β, γ, t) x ,t y ,t z ) Sorting the distance constraint equation set to obtain
F k (X,l k )＝0
The vertex of the pyramid prism has coordinates of (500, -500, 3000) (unit: mm) under the first coordinate system; the coordinates of the points in the measuring field of the evaluation system in the first coordinate system are
According to the coordinates of the internal points of the measurement field of the evaluation system in the first coordinate system and the second coordinate system respectively, the initial attitude value is obtained by using a common point conversion model, and the specific calculation steps are as follows:
the evaluation system measures the coordinates of points within the field in a second coordinate system
The coordinates in the first coordinate system are
Carrying out barycenter processing on the point set to obtain a new point set
To eliminate the effect of translation transformation; obtaining a left and right singular vector matrix by singular value decomposition to obtain a rotation matrix R between a second coordinate system and a first coordinate system LT Thereby obtaining an initial attitude value alpha 0 ＝30.0905°、β 0 ＝34.8033°、γ 0 =39.9449 °. The specific calculation formula is as follows:
α＝-arcsin(r 23 )
obtaining the initial position value t by using the coordinate of the vertex of the pyramid prism in the first coordinate system x 0 ＝499.9138mm、t y 0 ＝-499.9131mm、t z 0 ＝2999.4905mm。
According to said distanceCarrying out Newton iteration processing on the beam equation set, the initial attitude value and the initial position value, and solving a variable X = (alpha, beta, gamma, t) x ,t y ,t z ) I.e. the azimuth, pitch and roll of the cooperative target unit in the first coordinate system.
Specifically, the distance constraint equation set is expanded by N-1 stage Taylor, and the linear part of the N-1 stage Taylor is taken to obtain
F(X (N) ,l k )≈-J (N) ΔX (N)
Wherein N is the number of iterations; Δ X (N) ＝X (N+1) -X (N) (ii) a J is a Jacobian matrix; substituting the obtained initial attitude and initial position into a formula to obtain a corresponding spatial homogeneous transformation matrix T (0) Utilizing successive iteration of Newton Raphson method, taking max | delta X | less than or equal to epsilon as the operation condition for finishing the algorithm, and solving the variable X = (alpha, beta, gamma, t) x ,t y ,t z ) The optimal numerical solution of (3), namely the attitude angle of the cooperative target unit in the first coordinate system, realizes the measurement result of the attitude angle tracked by the length measurement reference field tracing laser.
The pose of the cooperative target unit in the first coordinate system is finally obtained as α =30.0011 °, β =34.9865 °, γ =39.9912 °, x =499.9815mm, y = -499.9745mm, and z =2999.9815mm.
Compared with the prior art, the method has the advantages of strong adaptability, high measurement precision, no need of coordinate system registration, difficulty in being limited by the constraint of space size, flexible layout of a control field according to the field environment, guarantee of consistency of the tracing environment and the field environment, avoidance of introduction of large environmental errors and realization of field evaluation of the precision of the attitude angles in the three directions.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (6)
1. A method for evaluating the field accuracy of a laser tracking attitude angle comprises the following steps:
(1) Acquiring a space vector of a measuring field internal point and a space vector of a control field internal point of a laser tracking attitude angle on-site precision evaluation system;
(2) Determining a distance constraint;
(3) Establishing a homogeneous coordinate transformation matrix equation;
(4) Giving an initial value to the equation set;
(5) Solving and evaluating the attitude angle of the system;
the laser tracking attitude angle on-site precision evaluation system comprises a laser tracking equipment unit, a cooperation target unit, an evaluation system measuring field unit, an evaluation system control field unit, a length measuring equipment unit and a calculation unit.
2. The assessment method according to claim 1, wherein said obtaining spatial vectors of the interior points of the assessment system measurement field and the control field in step (1) is to obtain corresponding second spatial vectors of the interior points of the assessment system measurement field in a second coordinate system according to the coordinates of the interior points of the assessment system measurement field in the second coordinate system, wherein the second coordinate system is a cooperation target coordinate system; and acquiring the coordinates of the internal points of the control field of the evaluation system in the first coordinate system by using the laser tracking equipment unit, and acquiring the corresponding first space vector of the internal points of the control field of the evaluation system in the first coordinate system according to the coordinates of the internal points of the control field of the evaluation system in the first coordinate system.
3. The assessment method according to any one of claims 1 or 2, wherein said determining a distance constraint of step (2) is to use a length measuring device unit to obtain a distance constraint between an interior point of the control field of the assessment system and an interior point of the measurement field of the assessment system.
4. The assessment method according to claim 3, wherein the establishing of the homogeneous coordinate transformation matrix equation in the step (3) means that distance constraints are established by the first space vector, the second space vector, the assessment system control field interior points and the assessment system measurement field interior points, and a distance constraint equation set with the pose as an unknown quantity is established based on the space homogeneous coordinate transformation matrix.
5. The evaluation method according to claim 4, wherein the assigning of the initial value of the equation set in step (4) is to use a laser tracking device unit to obtain the vertex of the corner cube prism and the evaluation system to measure the coordinates of the point inside the field in the first coordinate system; acquiring an initial attitude value by using a common point conversion model according to coordinate values of the internal points of the measurement field of the evaluation system in a first coordinate system and a second coordinate system respectively; and acquiring an initial position value according to the coordinates of the vertex of the pyramid prism in the first coordinate system.
6. The assessment method according to claim 5, wherein the solving of the attitude angle of the assessment system in the step (5) is to perform Newton iterative solution according to the distance constraint equation set, the initial attitude value and the initial position value to obtain the attitude angle of the cooperative target unit in the first coordinate system, that is, to obtain the three-dimensional attitude angle measurement result traced back by the length measurement reference.
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