A target pose measurement method based on curved surface features

Abstract

The application belongs to the field of target pose measurement, and particularly relates to a target pose measurement method based on curved surface features. The system used comprises a laser emission module, a feature recognition module and a processing module; the laser emission module and the feature recognition module are respectively arranged towards a to-be-measured curved surface target, and the to-be-measured curved surface target is provided with M feature points; the laser emission module is used for emitting N non-parallel laser beams to the to-be-measured curved surface target, forming N laser spots on the to-be-measured curved surface target, and the centroids of the N laser spots are not collinear; the field of view of the feature recognition module covers the whole different pose envelope range of the to-be-measured curved surface target; and the receiving end of the processing module is electrically connected with the sending end of the feature recognition module. The application can expand the measurement range through the expansion of the number of laser beams and the field of view of the detector, so as to realize the pose measurement of a super-large array target, and the cost is relatively low.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of target pose measurement, and particularly relates to a target pose measurement system and method based on curved surface features. BACKGROUND

[0002] The overall aperture of a large antenna is dozens of meters or even hundreds of meters, and the reflecting surface thereof is usually composed of hundreds or thousands of curved reflecting panels with a size of meters and good rigidity. Therefore, the reflecting surface is easily deformed by external environment, thereby reducing the reflecting surface precision and greatly affecting the working efficiency and performance.

[0003] Currently, the pose measurement of a large antenna mainly uses the following devices and methods: a laser tracker generally uses mature photoelectric devices, but the measurement and use conditions required are harsh, and a cooperative target needs to be set, so that the measurement system is relatively complex and often needs human intervention and operation, which is not conducive to long-term stable measurement. When a photogrammetry method is used, a large number of cooperative targets need to be set on the reflecting surface, and a large number of images are required in the shooting process to complete accurate pose solving, which greatly increases the calculation period and is difficult to realize real-time measurement, and the photogrammetry operation is extremely difficult for a spatial size of hundreds of meters.

[0004] Chinese patents CN119044991B and CN116952129A mainly complete high-precision pose measurement for a planar target, and Chinese patent CN110455181B uses a detector to directly capture laser spot information, but is limited by the size of the measurement target, and has certain limitations for the pose measurement of an ultra-large array target, and has a high cost.

[0005] Therefore, in view of the high-precision pose measurement requirement of the curved reflecting surface of an ultra-large array target, a new pose measurement system and method need to be designed to facilitate the rapid and high-precision pose measurement of the curved reflecting surface, so as to complete the real-time feedback and control of the pose adjustment system. SUMMARY

[0006] The application aims to solve the technical problem that the existing measurement method is limited by the size of the measurement target and has a high measurement cost, and provides a target pose measurement system and method based on curved surface features.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the application is as follows:

[0008] A target pose measurement system based on curved surface features, which is characterized in that:

[0009] The laser emission module, the feature recognition module and the processing module are included.

[0010] The laser emission module and the feature recognition module are respectively arranged towards the curved surface target to be measured, and M feature points are arranged on the curved surface target to be measured; M≥3.

[0011] The laser emission module is used for emitting N non-parallel laser beams to the curved surface target to be measured, forming N laser spots on the curved surface target to be measured, and the centroids of the N laser spots are not collinear; N≥3.

[0012] The field of view of the feature recognition module covers the whole different pose envelope range of the curved surface target to be measured, and is used for acquiring the two-dimensional image containing the laser spots and the feature points on the curved surface target to be measured.

[0013] The receiving end of the processing module is electrically connected with the sending end of the feature recognition module, is used for receiving the two-dimensional image sent by the feature recognition module, and according to the received two-dimensional image, the actual pose change parameter of the curved surface target to be measured is acquired, so that the target pose measurement is realized.

[0014] Further, the support platform is further included; the laser emission module and the feature recognition module are respectively installed on the support platform.

[0015] Further, the feature recognition module includes an optical lens and a detector.

[0016] The object plane of the optical lens is located at the curved surface target to be measured, and the image plane is located at the target surface of the detector; the field of view of the optical lens covers the whole different pose envelope range of the curved surface target to be measured, and is used for imaging the image information of the curved surface target to be measured to the target surface of the detector;

[0017] The detector is used for acquiring the two-dimensional image containing the laser spots and the feature points according to the image information of the curved surface target to be measured.

[0018] Meanwhile, the application further provides a target pose measurement method based on curved surface features, adopts the foregoing target pose measurement system based on curved surface features, and is characterized in that the method comprises the following steps.

[0019] Step 1, calibrating N laser beams emitted by the laser emission module, and acquiring the equivalent space straight line equation of the N laser beams;

[0020] Step 2, calibrating M feature points arranged on the curved surface target to be measured, acquiring the relative position relationship and distribution position data between the feature points, and simultaneously calibrating the geometric parameters of the curved surface target to be measured, the geometric parameters including the shape size and the initial pose of the curved surface target to be measured;

[0021] Step 3, the laser beam emitted by the laser emission module is incident on the curved surface target to be measured, and a two-dimensional image containing a laser spot and feature points is collected by the feature recognition module; then through image correction, a feature plane composed of feature points on the two-dimensional image is obtained according to the relative position relationship between each other and the distribution position data of the feature points, and a two-dimensional projection image composed of a projection point formed by the projection of the laser spot on the feature plane; a two-dimensional coordinate system is constructed with any feature point on the two-dimensional projection image as the origin, and the projection coordinates of the projection point and the remaining feature points on the two-dimensional coordinate system are obtained;

[0022] Step 4, based on the equivalent space straight line equation of each laser beam and the projection coordinates of each feature point and the projection point on the two-dimensional coordinate system, the three-dimensional coordinates of each projection point are calculated by using the principle that the lengths of the same space line segments are equal;

[0023] Step 5, after the pose of the curved surface target to be measured changes, the three-dimensional coordinates of each projection point after the pose changes are obtained in the same way as steps 3 and 4;

[0024] Step 6, by means of the equivalent rigid body conversion method, the pose change of the curved surface target to be measured is equivalent to the adjustment of the pointing direction of the laser beam and the position of the feature recognition module; on this basis, combined with the geometric parameters of the calibrated curved surface target to be measured and the three-dimensional coordinates of the projection points after the pose changes, an equivalent pose measurement model is established;

[0025] Step 7, based on the equivalent pose measurement model, the adjustment amount of the pointing direction of the laser beam and the position of the feature recognition module is obtained, and then the adjustment amount of the pointing direction of the laser beam and the position of the feature recognition module is restored to the actual pose change parameters of the curved surface target to be measured by means of the reverse equivalent rigid body conversion method, so as to complete the target pose measurement.

[0026] Further, in step 6, the expression of the equivalent pose measurement model is:

[0027]

[0028] In the formula:

[0029] F(x) is a nonlinear residual function;

[0030] f(X) is the standard space equation of the curved surface target to be measured, f(X) = 0, X = L + T + λ i (R(α, β, γ) x d i ), i = 1, 2, 3, …, N;

[0031] L is the initial emission point coordinate of the laser beam;

[0032] T is the translation amount;

[0033] R is the rotation amount;

[0034] λ i is a scale factor of the laser beam;

[0035] d i is a direction vector of N laser beams before calibration;

[0036] E is an initial origin of the feature recognition module;

[0037] C′ i is a three-dimensional coordinate of the projection point after the pose change;

[0038] μ i is a projection scale factor;

[0039] r ij is a function about Euler angles α, β and γ, j = 1, 2, 3, …, N;

[0040] In step 7, based on the equivalent pose measurement model, the adjustment amount of the laser beam pointing to the feature recognition module position is obtained, and the adjustment amount includes a translation amount T and a rotation amount R.

[0041] Further, the M feature points are defined as T1, T2, …, T M ;

[0042] In step 3: Taking the feature point T1 as the origin of the two-dimensional coordinate system, selecting the connecting line between the feature point T1 and the feature point T2 as the y-axis of the two-dimensional coordinate system, and making the perpendicular line of the y-axis through the feature point T1 as the x-axis of the two-dimensional coordinate system, the establishment of the two-dimensional coordinate system is realized.

[0043] Further,

[0044] In step 1, the equivalent space straight line equation expression of the N laser beams is:

[0045]

[0046] In the formula: x ji , y ji and z ji are the coordinates of any point of the laser beam; X ji0 , Y ji0 , Z ji0 , X ji , Y ji and Z ji are constants of the equivalent space straight line equation; t ji is a variable parameter of the equivalent space straight line equation.

[0047] The beneficial effects of the present application are:

[0048] 1、The measuring range of the application is extremely large, and is convenient for measuring application expansion. The measuring range can be expanded through expansion of the number of laser beams and the field of view of the detector, wherein expansion of the number of laser beams only needs to simply increase the number of laser emission modules and can be completed through accurate calibration, expansion of the field of view of the detector can be completed through selection of an optical system with a larger field of view and a detector with a larger target surface, or use of multiple detectors, so that pose measurement of a super-large array target can be realized, and the cost is relatively low.

[0049] 2、The laser emission module and the feature recognition module of the application are respectively installed on the same support platform, the emission reference and the recognition reference are stable and reliable, and the measuring precision and stability are improved.

[0050] 3、The application adopts non-contact measurement, has good environmental adaptability and good operability, and can realize real-time measurement.

[0051] 4、The application uses an equivalent rigid body conversion method, simplifies the solving process, and improves the measuring speed.

[0052] 5、The application uses feature planes to convert solving of the spatial three-dimensional coordinates of the curved surface laser spot into solving of the spatial three-dimensional coordinates of the plane laser spot, which is relatively mature, and ensures the feasibility of measurement. The feature planes are fitted through feature points calibrated in advance, multiple feature planes are fitted using multiple feature points, and the measurement redundancy and solving precision can be greatly improved.

[0053] 6、The application brings the geometric parameters of the to-be-measured curved surface target into pose measurement, and the method can also be compatible with pose measurement of a plane target, and further expands the application scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is a structural schematic diagram of an embodiment of a target pose measurement system based on curved surface features of the application (the processing module is not shown in the figure);

[0055] Figure 2 is a schematic diagram of image acquisition and definition of a two-dimensional coordinate system in an embodiment of a target pose measurement method based on curved surface features of the application;

[0056] Figure 3 is a schematic diagram of a measurement system when the pose of a target curved surface changes in an embodiment of a target pose measurement system based on curved surface features of the application;

[0057] Figure 4 is a schematic diagram of an equivalent pose measurement model in an embodiment of a target pose measurement method based on curved surface features of the application;

[0058] Figure 5 is a feature plane projection diagram in an embodiment of a target pose measurement method based on curved surface features of the application.

[0059] Reference signs are as follows:

[0060] 01 - target surface to be measured;

[0061] 1 - laser emitting module, 2 - feature recognition module, 3 - support platform. DETAILED DESCRIPTION

[0062] In order to make the objects, advantages and features of the present application clearer, a kind of target pose measurement system and method based on surface feature are further described in detail below in conjunction with the drawings and specific embodiments.The advantages and features of the present application will be clearer according to the following specific embodiments.

[0063] Reference Figure 1 , the embodiment of a kind of target pose measurement system based on surface feature, it mainly includes laser emitting module 1, feature recognition module 2, support platform 3 and processing module.

[0064] Laser emitting module 1 includes at least one laser emitting component, can emit N non-parallel laser beams to the target surface to be measured, and the laser beams emitted by laser emitting module 1 are stable, which can be fitted as an equivalent spatial straight line equation based on the coordinate system of laser emitting module 1.N laser beams form N laser spots on the target surface to be measured 01, and the centroids of N laser spots are not collinear;N≥3.In the embodiment, N=3 is taken as an example.

[0065] Feature recognition module 2 includes optical lens and detector.The object plane of optical lens is located at the target surface to be measured 01, and the image plane is located at the target surface of detector;The field of view of optical lens covers the entire different pose envelope range of the target surface to be measured 01, for imaging the image information of the target surface to be measured 01 onto the target surface of detector;The detector is used to obtain a two-dimensional image containing laser spots and feature points according to the image information of the target surface to be measured 01.

[0066] Laser emitting module 1 and feature recognition module 2 are respectively arranged towards the target surface to be measured 01, and are respectively installed on the same side of support platform 3.

[0067] The target surface to be measured 01: can be described by a certain mathematical expression-standard space equation, and has good rigidity and will not deform, and M feature points with positions calibrated in advance are arranged on the surface, M≥3, and M=4 is taken as an example in the embodiment.These feature points should form a feature plane, and can be located at the edge or inside of the target surface to be measured 01.The feature points need to have the characteristics of clearness, accuracy, easy identification and stability, and can be inherent features or additional marks of the surface of the target surface to be measured 01, so as to accurately measure and draw the relative positional relationship and distribution position data between each other.

[0068] The receiving end of the processing module is electrically connected with the sending end of the feature recognition module 2, can receive the two-dimensional image sent by the feature recognition module 2, and according to the received two-dimensional image, the actual pose change parameter of the target curved surface 01 is obtained, and the target pose measurement is realized.

[0069] The specific implementation steps are:

[0070] Step 1, calibrate the 3 laser beams emitted by the laser emitting module 1, and obtain the equivalent space straight line equation of the 3 laser beams.

[0071] Define L1, L2 and L3 as the equivalent space straight line equations of the 3 laser beams respectively;

[0072] L1:

[0073] x j1 =X j10 +t j1 ×X j1 , y j1 =Y j10 +t j1 ×Y j1 , z j1 =Z j10 +t j1 ×Z j1 ;

[0074] L2:

[0075] x j2 =X j20 +t j2 ×X j2 , y j2 =Y j20 +t j2 ×Y j2 , z j2 =Z j20 +t j2 ×Z j2 ;

[0076] L3:

[0077] x j3 =X j30 +t j3 ×X j3 , y j3 =Y j30 +t j3 ×Y j3 , z j3 =Z j30 +t j3 ×Z j13 ;

[0078] In the formula:

[0079] (x j1 , y j1 , z j1 ) is the coordinate of any point on the spatial straight line L1 in space;

[0080] (x j2 , y j2 , z j2 ) is the coordinate of any point on the spatial straight line L2 in space;

[0081] (x j3 , y j3 , z j3 ) is the coordinate of any point on the spatial straight line L3 in space;

[0082] X j10 , Y j10 , Z j10 , X j1 , Y j1 , Z j1 , X j20 , Y j20 , Z j20 , X j2 , Y j2 , Z j2 , X j30 , Y j30 , Z j30 , X j3 , Y j3 , Z j13 are constants of the equivalent spatial straight line equation; t j1 , t j2 , t j3 are variable parameters of the equivalent spatial straight line equation.

[0083] Step 2, calibrate the four feature points set on the to-be-measured curved surface target 01, obtain the relative position relationship and distribution position data between the four feature points, and at the same time calibrate the geometric parameters of the to-be-measured curved surface target 01, which are specifically the shape size and initial pose of the to-be-measured curved surface target 01.

[0084] Step 3, the laser beam emitted by the laser emission module 1 is incident on the to-be-measured curved surface target 01, and a two-dimensional image containing a laser spot and feature points is collected by the feature recognition module 2; then through image correction, a feature plane composed of feature points on the two-dimensional image is obtained according to the relative position relationship and distribution position data between the feature points, and a two-dimensional projection image composed of a projection point formed by the projection of the laser spot on the feature plane; a two-dimensional coordinate system is constructed with any feature point on the two-dimensional projection image as the origin, and the projection coordinates of the projection point and the remaining feature points on the two-dimensional coordinate system are obtained.

[0085] As shown in Figure 2 The characteristic plane is a plane composed of feature points T1, T2, T3 and T4 on the curved surface target 01 to be measured, and C1, C2 and C3 are the projection points of the laser spots P1, P2 and P3 projected onto the characteristic plane.

[0086] The feature points T1, T2, T3 and T4 in the two-dimensional projection image are calibrated in advance, and according to the rigid body characteristics of the curved surface target 01 to be measured, their relative positional relationship remains unchanged during the measurement. Accordingly, a two-dimensional coordinate system is defined in the two-dimensional projection image. The line connecting the feature points T1 and T2 is selected as the y-axis, and the perpendicular to the line connecting T1 and T2 is drawn through T1, which is taken as the x-axis. The intersection of the x-axis and the y-axis (i.e. the point T1) is taken as the origin to establish the two-dimensional coordinate system. The two-dimensional coordinates of the remaining feature points and the projection points C1, C2 and C3 are defined in this two-dimensional coordinate system, and the definition of the two-dimensional coordinate system remains unchanged in the subsequent measurement.

[0087] Step 4: Based on the equivalent spatial straight line equation of each laser beam and the two-dimensional coordinates of each feature point and projection point, the three-dimensional coordinates of each projection point are calculated using the principle that the lengths of the same spatial line segments are equal. For specific calculation methods, reference can be made to the specific calculation methods disclosed in Chinese Patent CN116952129A, “Attitude measurement system and method based on target plane edge characteristics”.

[0088] Step 5: After the pose of the curved surface target 01 to be measured changes, the position and spatial pointing baseline relationship of the laser emitting module 1 and the feature recognition module 2 remain fixed, while the pose of the curved surface target 01 to be measured changes, the position information of the feature points also changes, as shown in Figure 3 The laser beams form new laser spots P'1, P'2 and P'3 on the surface of the curved surface target 01 to be measured. At this time, the two-dimensional image obtained by the feature recognition module 2 changes, and the position of the characteristic plane changes. Through image correction, the two-dimensional coordinates of the new laser spot projection points C'1, C'2 and C'3 are obtained.

[0089] The curved surface target 01 to be measured has the characteristics of a rigid body, and at the same time, the position and spatial pointing baseline relationship of the laser emitting module 1 and the feature recognition module 2 remains fixed. The transmitting end (laser emitting module 1) and the receiving end (feature recognition module 2) can be regarded as a whole, so the pose transformation of the curved surface target 01 to be measured can be converted into the pose transformation of the laser emitting module 1 and the feature recognition module 2 as a whole through an equivalent rigid body conversion method, as shown in Figure 4 In the equivalent rigid body conversion method, the curved surface target 01 to be measured can be regarded as fixed and immovable, and its pose information has been determined. At the same time, the characteristic plane composed of feature points can also be regarded as fixed. Using the two-dimensional coordinates of the feature points calibrated in advance and the two-dimensional coordinates of the projection points C'1, C'2 and C'3, the three-dimensional coordinates of the projection points C'1, C'2 and C'3 can be calculated.

[0090] Step 6, the pose change of the measured curved surface target 01 is converted into the adjustment of the laser beam pointing and the detector position by the equivalent rigid body conversion method described above; on this basis, the three-dimensional coordinates of the projection points after the pose change and other geometric parameters (such as the shape and size of the measured curved surface target) calibrated in advance can establish an equivalent pose measurement model.

[0091] The equivalent pose measurement model establishment steps are as follows:

[0092] 1) Laser beam pose change representation

[0093] Before the pose change of the measured curved surface target 01 in the initial state, the spatial vector equation of each laser beam can be expressed as:

[0094]

[0095] Where, P i is the intersection of the three laser beams and the measured curved surface target 01 in the initial state, d i is the spatial direction vector of the three laser beams calibrated in advance, is the scale factor of the three laser beams in the initial state, and L is the initial emission point coordinate of the three laser beams.

[0096] Taking the ellipsoid (the form of the auxiliary reflector of the Cassegrain antenna) as an example, the standard spatial equation of the measured curved surface target 01 satisfies:

[0097] f(X)=0 (Formula 2)

[0098] After the equivalent rigid body conversion, the emission point and the spatial pointing of the laser beam are changed, which can be described as the rotation amount R (converted about the initial emission point coordinate L of the laser beam) and the translation amount T.

[0099] Wherein, the rotation amount R is parameterized by Euler angles (for example, zyx order), and the Euler angles are α, β and γ, which are azimuth angle, pitch angle and roll angle respectively, and the rotation amount R can be constructed as:

[0100] R=R z (γ)·R y (β)·R x (α) (Formula 3)

[0101] Wherein:

[0102]

[0103] The rotation amount R has three degrees of freedom, which describes the rotation of the system around a reference point, and the translation amount T describes the translation of the system in space, which also has three degrees of freedom. At this time, the space vector equation of the laser beam after the equivalent rigid body conversion can be expressed as:

[0104] X = L + T + λ i (R x d i ), i = 1, 2, 3 (Formula 7)

[0105] In order to obtain the intersection points P'1, P'2, P'3 of the converted laser beam and the measured curved surface target 01, it is necessary to solve the scale factor λ of the laser beam i , so that:

[0106] f(L + T + λ i (R x d i )) = 0, i = 1, 2, 3 (Formula 8)

[0107] The three laser beams constitute three nonlinear scalar constraint equations, which reflect the physical constraints of the intersection of the laser beam and the measured curved surface target 01.

[0108] 2) Three-dimensional projection representation of laser spot

[0109] In the initial state, the initial origin of the detector is located at point E, and after the translation amount T, the origin becomes E' = E + T. The intersection of the laser beam and the characteristic plane after the equivalent rigid body conversion is P i ', and the projection point of P i ' on the characteristic plane after image correction is C i '. The three-dimensional coordinates of C i ' can be obtained by the method in step 4 described above. According to the imaging model of the detector, C i ' can be represented as the intersection of the characteristic plane from the origin E' of the detector along the direction of E'P i ', then:

[0110] C i ' = E + T + μ i (P i ' - (E + T)), i = 1, 2, 3 (Formula 9)

[0111] Where μ i is the projection scale factor, which is an intermediate variable to be solved in this embodiment.

[0112] P i ' = L + T + λ i (R x d i ), i = 1, 2, 3 (Formula 10)

[0113] It can be obtained that:

[0114] C′ i = E + T + μ i ((L - E) + λ i (R · d i )), i = 1, 2, 3 (Equation 11)

[0115] Therefore, the detector observation condition corresponding to each laser spot can be written as a spatial vector equation:

[0116] E + T + μ i ((L - E) + λ i (R · d i ))- C′ i = 0, i = 1, 2, 3 (Equation 12)

[0117] This detector observation condition can provide a total of 9 scalar constraint equations.

[0118] 3) Pose solving of the surface target 01 to be measured

[0119] Combining the above nonlinear scalar constraint equations and scalar constraint equations, for each laser spot P i ′, there are two constraint conditions, i.e., (Equation 8) and (Equation 12), the former represents the physical constraint condition, and the latter represents the projection constraint condition, a total of 12 constraint equations and 12 unknowns.

[0120] Therefore, the unknown vector χ can be constructed as follows:

[0121] χ = [α β γ T x T y T z λ1 λ2 λ3 μ1 μ2 μ3] T (Equation 13)

[0122] And the nonlinear residual function is:

[0123]

[0124] Where the last three equations of (Equation 14) are expanded as:

[0125]

[0126] r ij is a function of α, β, and γ, i = 1, 2, 3, j = 1, 2, 3, i.e.:

[0127]

[0128] In step 7, the unknowns in the unknown vector χ can be obtained by solving F(χ) = 0, so as to obtain the rotation R and the translation T, and then the adjustment of the laser beam pointing and the detector position is reduced to the actual pose change parameters of the target surface 01 to be measured through the inverse equivalent rigid body conversion method, so as to complete the target pose measurement.

[0129] To verify the feasibility of the proposed target pose measurement method based on the surface feature, the embodiment carries out a pose measurement simulation example for the sub-reflector of the 110m QTT dual-reflector antenna, and evaluates the feasibility and measurement accuracy of the measurement principle.

[0130] The sub-reflector of the dual-reflector antenna is a standard ellipsoid, and the surface shape conforms to the standard spatial equation of the ellipsoid:

[0131]

[0132] Wherein, a = b = 11851.7, c = 18650. The length unit in this simulation example is mm, and the angle unit is degree.

[0133] The three-dimensional coordinates of the four feature points on the sub-reflector of the dual-reflector antenna are T1(0, 1600, 18479.27); T2(1600, 0, 18479.27); T3(0, -1600, 18479.267); T4(-1600, 0, 18479.27).

[0134] The three-dimensional coordinates of the initial emission point L of the laser beam are (0, 0, 0), and three spatial pointing laser beams are emitted from this point. In the initial state, the spatial direction vectors of the three laser beams are: d1(0, 0.0645, 0.9979); d2(0.0538, -0.0538, 0.9972); d3(-0.0538, -0.0538, 0.9970). In the initial state, the three-dimensional coordinates of the position E of the detector are (100, 100, 100).

[0135] 1) Rotational and translational working condition simulation example 1

[0136] A translation T with a direction of (2, -2, 2) and a rotation R with Euler angles of (0.5°, -0.5°, 0.5°) are applied to the sub-reflector of the dual-reflector antenna, and the rotation center is the center of the sub-reflector of the dual-reflector antenna. Through equivalent rigid body conversion, a displacement with a direction of (-2, 2, -2) and a rotation with Euler angles of (-0.5°, 0.5°, -0.5°) are applied to the laser emission module 1 and the detector, and the obtained two-dimensional projection image is as shown in Figure 5 .

[0137] The results are shown in the following table:

[0138] Table 1 Comparison of absolute error between solution value and true value of simulation example 1

[0139] pose variable true value solved value absolute error T x (mm) 2 2.0008 -0.0008 T y (mm) -2 -1.9953 -0.0047 T z (mm) 2 1.9850 0.0150 α(°) 0.5 0.497767 0.002233 β(°) -0.5 -0.49981 -0.00019 γ (°) 0.5 0.49994 0.00006

[0140] As can be seen from Table 1, in the state that the surface target 01 to be measured is in translational and rotational state, the solution value of the pose variable is small different from the true value, wherein the absolute error between the solution value and the true value of the translation T is maximum 0.0150mm, and the absolute error between the solution value and the true value of the rotation R is maximum 0.002233°, which can meet the error requirement of pose measurement.

[0141] 2) Simulation example 2 of rotational and translational working condition

[0142] A translation T with direction (20, -20, 20) and a rotation R with Euler angle (0.1°, -0.1°, 0.1°) are applied to the sub-reflector of the dual-reflector antenna, which is equivalent to applying displacement with direction (-20, 20, -20) and rotation with Euler angle (-0.1°, 0.1°, -0.1°) to the laser emitting module 1 and the detector through equivalent rigid body conversion.

[0143] The results are shown in the following table:

[0144] Table 2 Comparison of absolute error between solution value and true value of simulation example 2

[0145]

[0146]

[0147] As can be seen from Table 2, in this state, the absolute error between the solution value and the true value of the pose variable is also small, wherein the absolute error between the solution value and the true value of the translation T is in the order of e-05 to e-04 (mm), and the absolute error between the solution value and the true value of the rotation R is in the order of e-07 to e-05 (°), which can well meet the requirement of high-precision measurement of small-scale pose.

Claims

1. A target pose measurement method based on curved surface features, comprising a target pose measurement system based on curved surface features, the system comprising a laser emission module (1), a feature recognition module (2), and a processing module; The laser emission module (1) and the feature recognition module (2) are respectively positioned facing the surface target (01) to be tested, and M feature points are set on the surface target (01); M≥3； The laser emitting module (1) is used to emit N non-parallel laser beams to the surface target (01) to be tested, forming N laser spots on the surface target (01), and the centroids of the N laser spots are not collinear; N≥3; The field of view of the feature recognition module (2) covers all different pose envelopes of the surface target (01) under test, and is used to obtain a two-dimensional image of the surface target (01) under test containing laser spot and feature points; The receiving end of the processing module is electrically connected to the sending end of the feature recognition module (2) to receive the two-dimensional image sent by the feature recognition module (2), and obtain the actual pose change parameters of the surface target (01) to be measured based on the received two-dimensional image, so as to realize the target pose measurement. Its characteristic is that it includes the following steps: Step 1: Calibrate the N laser beams emitted by the laser emitting module (1) and obtain the equivalent spatial linear equations of the N laser beams; Step 2: Calibrate the M feature points set on the surface target (01) to be tested, and obtain the relative positional relationship and distribution data between each pair of feature points; at the same time, calibrate the geometric parameters of the surface target (01) to be tested, including the shape, size and initial pose of the surface target (01) to be tested; Step 3: The laser beam emitted from the laser emitting module (1) is incident onto the surface target (01) to be tested. A two-dimensional image containing the laser spot and feature points is acquired through the feature recognition module (2). Then, through image correction, the feature plane formed by the feature points on the two-dimensional image is obtained based on the relative positional relationship and distribution data between the feature points, and the two-dimensional projection image formed by the projection points formed by the laser spot projected onto the feature plane. A two-dimensional coordinate system is constructed with any feature point on the two-dimensional projection image as the origin, and the projection coordinates of the projection point and the other feature points on the two-dimensional coordinate system are obtained. Step 4: Based on the equivalent spatial straight line equation of each laser beam and the projected coordinates of each feature point and projection point in the two-dimensional coordinate system, the three-dimensional coordinates of each projection point are calculated using the principle that the length of the same spatial line segment is equal. Step 5: After the pose of the target surface (01) is changed, the three-dimensional coordinates of each projection point after the pose change are obtained in the same way as in Step 3 and Step 4. Step 6: By using the equivalent rigid body transformation method, the pose change of the target surface (01) to be measured is equivalently converted into the adjustment of the laser beam pointing and the position of the feature recognition module (2); on this basis, combined with the calibrated geometric parameters of the target surface (01) to be measured and the three-dimensional coordinates of the projection point after the pose change, an equivalent pose measurement model is established. The expression for the equivalent pose measurement model is: In the formula: F(χ) is a nonlinear residual function; f(X) is the standard space equation of the surface target (01) to be measured, f(X) = 0, X = L + T + λ i (R(α, β, γ) × d i ), i=1, 2, 3,...,N; L represents the initial emission point coordinates of the laser beam; T is the translation amount; R is the amount of rotation; λ i The scaling factor for the laser beam; d i The direction vectors of the N laser beams are pre-calibrated; E is the initial origin of the feature recognition module (2); C i ′ The three-dimensional coordinates of the projection point after the pose change; μ i The projection scale factor; r ij Let be a function of Euler angles α, β, and γ, where j = 1, 2, 3, ..., N; Step 7: Based on the equivalent pose measurement model, obtain the adjustment amount of the laser beam pointing and the position of the feature recognition module (2), and then restore the adjustment amount of the laser beam pointing and the position of the feature recognition module (2) to the actual pose change parameters of the surface target (01) under test by the reverse equivalent rigid body transformation method, and complete the target pose measurement.

2. The target pose measurement method based on curved surface features according to claim 1, characterized in that: It also includes the support platform (3); The laser emission module (1) and the feature recognition module (2) are respectively installed on the support platform (3).

3. A target pose measurement method based on curved surface features according to claim 1 or 2, characterized in that: The feature recognition module (2) includes an optical lens and a detector; The object plane of the optical lens is located at the surface target (01) to be tested, and the image plane is located at the target surface of the detector; the field of view of the optical lens covers all different pose envelopes of the surface target (01) to be tested, and is used to image the image information of the surface target (01) to be tested onto the target surface of the detector. The detector is used to acquire a two-dimensional image containing laser spot and feature points based on the image information of the surface target (01) to be tested.

4. The target pose measurement method based on curved surface features according to claim 3, characterized in that, In step 6, In step 7, based on the equivalent pose measurement model, the adjustment amount between the laser beam direction and the position of the feature recognition module is obtained. The adjustment amount includes translation T and rotation R.

5. The target pose measurement method based on curved surface features according to claim 4, characterized in that: Define M feature points as T1, T2, ..., T M ; In step 3: with feature point T1 as the origin of the two-dimensional coordinate system, the line connecting feature point T1 and feature point T2 is selected as the y-axis of the two-dimensional coordinate system, and a perpendicular line from feature point T1 to the y-axis is drawn as the x-axis of the two-dimensional coordinate system, thus realizing the establishment of the two-dimensional coordinate system.

6. The target pose measurement method based on curved surface features according to claim 5, characterized in that, In step 1, the equivalent spatial linear equation for the N laser beams is expressed as: In the formula: x ji y ji and z ji Let X be the coordinates of any point on the laser beam; ji0 Y ji0 Z ji0 X ji Y ji and Z ji t is a constant in the equation of the equivalent space line; ji The variable parameters are the equations of the equivalent spatial lines.

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