Intelligent method and system for structural modal parameter determination

Abstract

The application discloses an intelligent establishment method and system of structural modal parameters, and belongs to the technical field of test and measurement. The method comprises the following steps: acquiring reference points of the outer contour of a measured object and recording the three-dimensional coordinates of each reference point; and constructing an outer contour envelope frame of the measured object based on the reference points and calculating equivalent characteristic dimensions. Through the cooperative use of the outer contour reference points, the outer contour envelope frame, the three-dimensional grid and the coordinate system transformation of the laser projector, the technical problem that the modal measurement point establishment in the prior art relies on manual planning and visual scanning reconstruction is solved, and the full-closed-loop intelligent establishment from digital measurement point generation to physical marking and then to structural modal parameter acquisition is realized. Through the quantitative correlation of the equivalent characteristic dimensions and the preset mapping principle, the technical problem that the modal measurement point quantity establishment lacks quantitative basis is solved, and the scientific establishment of the measurement point quantity and the reasonable control of the test cost are realized.

Description

Technical Field

[0001] This application belongs to the field of experimental testing technology, and specifically relates to an intelligent method and system for determining structural modal parameters. Background Technology

[0002] In structural dynamics testing, modal parameter identification is a key step in evaluating the NVH performance of the whole vehicle and body-in-white.

[0003] Current modal measurement point formulation relies primarily on manual planning and on-site point-by-point measurement, which is inefficient and prone to human error. While some visual scanning and reconstruction technologies can generate 3D digital models, they cannot directly output a regular measurement point mesh, nor do they have the ability to reverse-map digital measurement points onto the surface of a physical entity for marking. Furthermore, existing technologies have not established a quantitative mapping relationship between the geometric dimensions of the tested object and the number of modal measurement points. The determination of the number of measurement points is overly dependent on experience, making it difficult to balance experimental accuracy and testing costs. Therefore, modal testing urgently needs an intelligent formulation method that can automatically generate a regular measurement point mesh based on the outer contour reference points and achieve precise laser projection through the transformation between the coordinate system of the tested object and the coordinate system of the laser projector. This would eliminate the mapping error between digital measurement points and the physical entity, thereby improving the efficiency and accuracy of modal testing. Summary of the Invention

[0004] To address the aforementioned issues, this application provides an intelligent method and system for formulating structural modal parameters. This method solves the technical problem in the prior art where modal measurement point formulation relies on manual planning and visual scanning reconstruction, and realizes a fully closed-loop intelligent formulation process from digital measurement point generation to physical marking and then to structural modal parameter acquisition.

[0005] In a first aspect, embodiments of this application provide an intelligent method for determining structural modal parameters, comprising the following steps: Obtain the reference points of the outer contour of the object being measured and record the three-dimensional coordinates of each reference point; Construct the outer contour envelope of the object under test based on the reference points and calculate the equivalent feature dimensions; Based on the preset mapping principle, establish a quantitative relationship between the equivalent feature size and the number of measurement points, and determine the number of measurement points on each surface of the object being measured; A 3D mesh is generated within the outer contour envelope. The intersection points of the mesh are taken as candidate measurement points. Candidate measurement points outside the outer contour envelope are eliminated, and candidate measurement points inside the outer contour envelope are retained as modal measurement points. The coordinates of each modal measurement point are recorded. Establish the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector, transform the coordinates of each modal measurement point to the coordinate system of the laser projector, calculate the azimuth and elevation angles of the laser projection, control the laser generator to project the modal measurement points onto the solid surface, and obtain the modal measurement point marking results; The sensor is attached to the modal measurement point marking results and modal excitation test is performed to obtain the structural modal parameters.

[0006] In one embodiment, acquiring reference points of the outer contour of the object under test and recording the three-dimensional coordinates of each reference point includes: Benchmark points are set up on the roof, front bumper, rear bumper, and side door sills of the vehicle being tested. Establish the coordinate system of the object under test with one of the reference points as the origin; Measure and record the three-dimensional coordinates of each reference point in the coordinate system of the object being measured to obtain the set of reference point coordinates.

[0007] In one embodiment, constructing the outer contour envelope of the object under test based on reference points and calculating the equivalent feature dimensions includes: Connect the reference points of the outer contour in sequence to form a closed spatial polyline describing the outer contour of the measured object; Construct the outer contour envelope based on closed spatial polylines; Calculate the maximum span of the outer contour envelope in each coordinate axis direction to obtain the equivalent feature length; Calculate the effective projected area to obtain the equivalent feature size.

[0008] In one embodiment, a quantitative relationship between equivalent feature size and the number of measurement points is established based on a preset mapping principle, and the number of measurement points on each surface of the object being measured is determined, including: Obtain the effective projected area within the equivalent feature size; Calculate the contour complexity coefficient based on the outer contour envelope; Substitute the effective projected area and the contour complexity coefficient into the formula for calculating the number of measurement points, and combine this with the minimum measurement point constraint to obtain the number of measurement points on the surface. Summarize the number of measuring points on each surface to obtain the total number of measuring points on the object being tested.

[0009] In one embodiment, a three-dimensional mesh is generated within the outer contour envelope. Mesh intersections are taken as candidate measurement points. Candidate measurement points outside the outer contour envelope are eliminated, while candidate measurement points inside the outer contour envelope are retained as modal measurement points. The coordinates of each modal measurement point are recorded, including: Calculate the number of grid divisions and the grid step size in each direction; Within the outer contour envelope, generate regular rectangular grids along each coordinate axis direction according to the grid step size, and take the grid intersections as candidate measurement points; The in-contour criterion is used to determine whether candidate measurement points are located inside the outer contour envelope. Candidate measurement points located outside the outer contour envelope are removed, and candidate measurement points located inside the contour are retained as modal measurement points; The modal measurement points are numbered according to spatial order, and the coordinates of each modal measurement point are recorded.

[0010] In one embodiment, establishing the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector includes: Place a reference point calibration target in front of the laser projector; Control the laser spot to aim at a known reference point, and record the coordinates of each reference point in the laser projector coordinate system; Based on the coordinate pairs of the reference points in the coordinate system of the object under test and the coordinate system of the laser projector, the rotation matrix and translation vector are solved to establish the transformation relationship.

[0011] In one embodiment, the coordinates of each modal measurement point are transformed to the laser projector coordinate system, the laser projection azimuth and elevation angles are calculated, and the laser generator is controlled to project the modal measurement points onto the solid surface to obtain the modal measurement point marking results, including: The coordinates of each modal measurement point are mapped to the laser projector coordinate system through a transformation relationship; Calculate the laser projection azimuth and elevation angles based on the modal measurement point coordinates in the laser projector coordinate system; The laser projection azimuth and elevation angles are sent down to the laser generator, which drives the laser generator to adjust the projection attitude and project the laser spot onto the solid surface; Switch the modal measurement points sequentially according to their numbers until all modal measurement points have been projected and marked.

[0012] In one embodiment, a sensor is attached to the modal measurement point marking results and a modal excitation test is performed to obtain structural modal parameters, including: Attach the accelerometer to the marked locations of the measurement points for each modality. Vibration tests were conducted according to modal testing standards, and vibration response data were collected at each measuring point. By processing the vibration response data at each measuring point through modal analysis, the natural frequencies, mode shapes, and damping ratios of the structure are identified, and the structural modal parameters are obtained.

[0013] In one embodiment, a method for intelligently determining structural modal parameters further includes: Continuously monitor the completion rate and coordinate deviation of modal measurement point marking results; When the coordinate deviation exceeds the preset threshold, the recalibration process is triggered to correct the transformation relationship; The modal measurement point projection is re-executed under the corrected transformation relationship to obtain the corrected modal measurement point marking results.

[0014] Secondly, embodiments of this application provide an intelligent system for determining structural modal parameters, including: The reference point acquisition unit is used to acquire the reference points of the outer contour of the object being measured and record the three-dimensional coordinates of each reference point; Envelope construction unit, used to construct the outer contour envelope of the measured object based on the reference point and calculate the equivalent feature size; The measurement point quantity determination unit is used to establish a quantitative relationship between the equivalent feature size and the number of measurement points based on a preset mapping principle, and to determine the number of measurement points on each surface of the object being measured. The mesh generation unit is used to generate a 3D mesh within the outer contour envelope, take the mesh intersections as candidate measurement points, eliminate candidate measurement points outside the outer contour envelope, retain candidate measurement points inside the outer contour envelope as modal measurement points, and record the coordinates of each modal measurement point. The laser projection unit is used to establish the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector, transform the coordinates of each modal measurement point to the coordinate system of the laser projector, calculate the laser projection azimuth and elevation angles, control the laser generator to project the modal measurement points onto the solid surface, and obtain the modal measurement point marking results. The modal testing unit is used to attach sensors to the modal measurement point markings and perform modal excitation tests to obtain structural modal parameters.

[0015] Compared with the prior art, this application has the following advantages: (1) By using the coordinated application of outer contour reference points, outer contour envelope, three-dimensional mesh and laser projector coordinate system transformation, this invention solves the technical problem that the formulation of modal measurement points in the prior art relies on manual planning and visual scanning reconstruction, and realizes the intelligent formulation of the entire closed loop from digital measurement point generation to physical marking and then to structural modal parameter acquisition. (2) This invention solves the technical problem of lack of quantitative basis for determining the number of modal measurement points by quantitatively correlating the equivalent feature size with the preset mapping principle, and realizes the scientific determination of the number of measurement points and reasonable control of testing costs; (3) This invention solves the technical problems of low efficiency and large error in mapping digital measurement points to physical entities by transforming the coordinate system of the object being measured and the coordinate system of the laser projector and calculating the azimuth and elevation angles of the laser projection, and realizes high-precision positioning of the modal measurement point marking results.

[0016] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of modal modeling provided by the present invention is shown; Figure 2 This invention illustrates the definition of benchmark points for vehicle modal testing. Figure 3 A diagram showing the establishment of the modal measurement point envelope provided by the present invention is shown; Figure 4 A diagram showing the mesh partitioning of the modal measurement point envelope provided by the present invention is illustrated. Figure 5 This invention illustrates the number and distribution of vehicle side modal measurement points provided by the present invention. Figure 6 The diagram shows a reflection of the vehicle modal measurement points provided by this invention. Figure 7 The diagram shows the automatic reflection and pointing function of the device provided by the present invention; Figure 8 A schematic diagram of the process provided by the present invention is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In related technologies, the following problems often exist when determining the measurement points for modal testing: measurement point planning relies on manual experience, leading to low efficiency; human error is easily introduced in the measurement and transcription of measurement point coordinates; the number of measurement points lacks quantitative basis, too many points increase costs, and too few points result in information loss; the mapping from digital measurement points to physical entities relies on manual point finding, which limits accuracy and efficiency. To address these issues, this application provides an intelligent method for determining structural modal parameters. It automatically constructs an envelope frame and generates a regular measurement point mesh using outer contour reference points, and utilizes laser projection to achieve accurate mapping from digital measurement points to physical entities, thereby improving the efficiency and accuracy of modal testing.

[0021] Please see Figure 8 , Figure 8This is a flowchart illustrating the intelligent method for determining structural modal parameters provided in this application embodiment. The intelligent method for determining structural modal parameters provided in this application embodiment is applied in an edge computing unit, and the method is executed by measurement point determination software installed in the edge computing unit.

[0022] It should be noted that the application scenarios described in the following embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0023] The intelligent method for determining structural modal parameters provided in this application will be described in detail below.

[0024] like Figure 8 As shown, the method includes the following steps S110 to S160.

[0025] S110. Obtain the reference points of the outer contour of the object being measured and record the three-dimensional coordinates of each reference point.

[0026] Specifically, Figure 1 This is a schematic diagram of modal modeling of a car door. Reference points are placed at key structural locations of the object under test. A coordinate system for the object under test is established with one of these reference points as the origin. The three-dimensional coordinates of each reference point in the coordinate system are measured and recorded to obtain the set of reference point coordinates.

[0027] A laser projection device, a reference point calibration target, and an edge computing unit were deployed at the test site. The laser projection device integrates a two-dimensional electronically controlled gimbal and a dual-band visible and infrared laser source. The pitch angle adjustment range is -90° to +90°, the azimuth angle adjustment range is 0° to 360°, the angular resolution is better than 0.01°, and the projection distance is 1m to 10m. These angle ranges are determined according to conventional optical design specifications for laser projectors, ensuring that the laser spot can cover the entire top and side areas of the object being measured. The angular resolution of 0.01° is determined based on the minimum step angle and reduction ratio of the gimbal's stepper motor, ensuring that the spot positioning error is better than 2mm at a 10m projection distance. The projection distance of 1m to 10m is determined based on the spatial conditions of the vehicle modal test site and the laser source power attenuation characteristics, ensuring effective operation within a typical workshop workstation. The edge computing unit is equipped with a multi-core ARM processor and a GPU acceleration module, used to run the measurement point designation software and coordinate transformation algorithms, and communicates with the laser projection device via fiber optic Ethernet.

[0028] In some embodiments, step S110 includes steps S111 to S113.

[0029] S111. Place reference points at key structural locations of the object being measured.

[0030] Specifically, Figure 2 This is a definition diagram of reference points for whole-vehicle modal testing. Taking the whole-vehicle modal testing of the body-in-white as an example, reference points are arranged at key structural locations on the outer contour of the vehicle under test. A reference point, denoted as . , Until They are distributed in key locations such as the roof, front bumper, rear bumper, and side door sills. The value is set to 11. This value is determined based on the geometric features of the vehicle's outer contour. The three-dimensional dimensions of the vehicle's length, width, and height can be completely defined by 11 reference points distributed at key structural locations. If the number is less than this, the outer contour envelope cannot be accurately constructed.

[0031] S112. Establish the coordinate system of the object under test with one of the reference points as the origin.

[0032] Specifically, based on the benchmark point Establish the coordinate system of the measured object with the origin. ,in The axis points towards the front of the vehicle along its length. The axis points towards the roof along the height of the vehicle. The axis is determined by the right-hand rule.

[0033] When establishing a coordinate system, use a total station or laser tracker to measure the reference points. to The direction of the line is used as Positive axis direction, measurement reference point To the roof reference point The direction of the line connecting them is perpendicular to... The projection on the axial plane as Positive axis direction The axis is determined by the right-hand rule. × Confirmed. After the coordinate system is established, use a total station to perform at least three repeated measurements on all reference points, and take the arithmetic mean as the final coordinate value to eliminate the error of a single measurement.

[0034] S113. Measure and record the three-dimensional coordinates of each reference point in the coordinate system of the object being measured.

[0035] Specifically, the three-dimensional coordinates of each reference point in the coordinate system of the object being measured are measured and recorded using a total station or laser tracker.

[0036] ; In the formula, For the first The three-dimensional coordinate vectors of each reference point in the coordinate system of the object being measured, in meters; For the first Each benchmark point The coordinates of the direction, in meters; For the first Each benchmark point The coordinates of the direction, in meters; For the first Each benchmark point The coordinates of the direction, in meters; The numbers are 0 to 10 in sequence.

[0037] Taking a certain B-class sedan as an example, the coordinates of each reference point obtained by total station measurement are as follows: (0,0,0) (4.7,0,0) (4.7, 1.8, 0) (0,1.8,0) (0,0,1.5) (4.7,0,1.5) (4.7, 1.8, 1.5) (0, 1.8, 1.5) (2.35, 0, 0.75) (2.35, 1.8, 0.75) (4.7, 0.9, 0.75), in meters. The above coordinate values ​​are directly output by the total station and stored as a set of reference point coordinates.

[0038] S120. Construct the outer contour envelope of the object under test based on the reference point and calculate the equivalent feature size.

[0039] Specifically, the outer contour reference points are connected in sequence to form a closed spatial polyline describing the outer contour of the measured object. The outer contour envelope is constructed based on the closed spatial polyline. The maximum span of the outer contour envelope in each coordinate axis direction is calculated to obtain the equivalent feature length. The effective projected area is calculated to obtain the equivalent feature size.

[0040] In some embodiments, step S120 includes steps S121 to S124.

[0041] S121. Connect the outer contour reference points in sequence to form a closed spatial polyline describing the outer contour of the measured object.

[0042] Specifically, will The reference points are connected sequentially in the coordinate system of the object being measured to form a closed spatial polyline describing the outer contour of the object being measured.

[0043] S122. Construct an outer contour envelope based on closed spatial polylines.

[0044] Specifically, Figure 3This is a diagram showing the establishment of the modal measurement point envelope. The minimum bounding rectangle envelope is constructed based on a closed spatial polyline.

[0045] S123. Calculate the maximum span of the outer contour envelope in each coordinate axis direction to obtain the equivalent feature length.

[0046] Specifically, the envelope is calculated in , , Maximum span in a direction.

[0047] ; ; ; In the formula, For the envelope in Maximum span in a direction, in meters; For the envelope in Maximum span in a direction, in meters; For the envelope in Maximum span in a direction, in meters; To The calculation takes the maximum value of the coordinates of each reference point. To The minimum value of each reference point coordinate is used in the calculation.

[0048] Taking the aforementioned B-class sedan as an example, substituting the coordinates of the reference point, we get: =4.7 0 = 4.7m =1.8 0 = 1.8m =1.5 0 = 1.5m.

[0049] S124. Calculate the effective projected area to obtain the equivalent feature size.

[0050] Specifically, taking the planning of measurement points on the side of a vehicle as an example, its effective projected area is approximately the product of the length and height of the envelope.

[0051] ; In the formula, Effective projected area, in meters. 2 .

[0052] Substituting the aforementioned B-segment sedan data, we get: =4.7 × 1.5 = 7.05m 2 .

[0053] The contour complexity coefficient is defined as the ratio of the perimeter of the reference point polyline to the perimeter of the envelope, and is used to characterize the degree of curvature change of the surface of the measured object.

[0054] ; In the formula, Let be the contour complexity coefficient, which is dimensionless; when equal At that time, subscript Loop up to 0.

[0055] Taking the aforementioned side profile of a B-class sedan as an example, the calculated perimeter of the reference point broken line is 10.86m, and the perimeter of the envelope is 2×(4.7+1.5)=12.4m. Therefore... =10.86 / 12.4=0.876. This value is less than 1.0, indicating that the curvature of the side profile changes relatively gently.

[0056] S130. Establish a quantitative relationship between the equivalent feature size and the number of measurement points based on the preset mapping principle, and determine the number of measurement points on each surface of the object being measured.

[0057] Specifically, the effective projected area and contour complexity coefficient are obtained, and then substituted into the formula for calculating the number of measurement points. Combined with the minimum measurement point constraint, the number of measurement points on the surface is obtained. The total number of measurement points on the object under test is obtained by summing the number of measurement points on each surface.

[0058] In some embodiments, step S130 includes steps S131 to S134.

[0059] S131. Obtain the effective projected area in the equivalent feature size.

[0060] Specifically, the effective projected area is obtained from step S120. .

[0061] S132. Calculate the contour complexity coefficient based on the outer contour envelope.

[0062] Specifically, the contour complexity coefficient is calculated according to the formula in step S124. .

[0063] S133. Substitute the effective projected area and the contour complexity coefficient into the formula for calculating the number of measurement points, and combine it with the minimum measurement point constraint to obtain the number of measurement points on the surface.

[0064] Specifically, a quantitative mapping between equivalent feature dimensions and the number of measurement points is established based on principle A. The core of principle A is that the number of measurement points increases linearly with the effective projected area, and is appropriately adjusted with the complexity coefficient, while simultaneously satisfying the minimum measurement point constraint. Taking the number of measurement points on the side as an example... For example: ; In the formula, The number of lateral measurement points is dimensionless. This is for rounding up; For reference, the coverage area of ​​a single measurement point is shown in m². 2 ; It is a dimensionless constraint based on the minimum measurement point.

[0065] The value range is 0.02m 2 up to 0.05m 2 This range is determined based on the typical spacing of accelerometer sensors in modal testing. When the sensor spacing is 0.1m to 0.2m, the coverage area of ​​a single point is approximately 0.01m². 2 up to 0.04m 2 Considering edge redundancy and signal attenuation, we take 0.02m. 2 up to 0.05m 2 .

[0066] The value is set to 20, determined based on the minimum modal order requirement for whole-vehicle modal testing. Whole-vehicle modal testing typically requires identifying the first 10 elastic body modes. Each mode requires at least two measurement points on a single surface to distinguish the mode shape nodes; therefore, the minimum measurement point constraint on a single surface is set to 20.

[0067] Taking the aforementioned B-segment sedan as an example, =0.03m2, =20, substituting into the equation, we get: The results indicate that 226 modal measurement points need to be arranged on the side to meet the requirements for capturing side modal information of B-class sedans.

[0068] Table 1 is a reference table for the number of modal measurement points corresponding to vehicle size, which is pre-stored in the edge computing unit. The edge computing unit uses this data... , , Automatically match the vehicle model level closest to the model and call up the corresponding number of measurement points.

[0069] Table 1

[0070] S134. Summarize the number of measuring points on each surface to obtain the total number of measuring points on the object being measured.

[0071] Specifically, the same logic applies to the top, front, back, and other surfaces. , , Total number of measurement points for the whole vehicle This is the sum of the number of measuring points on each surface.

[0072] ; In the formula, The total number of measurement points for the entire vehicle is dimensionless. The number of measuring points on the top surface is dimensionless. The number of measurement points is dimensionless. This represents the number of measurement points to be measured, dimensionless.

[0073] Taking the aforementioned B-class sedan as an example, the calculation shows that: =86、 =86、 =157, therefore =226+86+86+157=555. This number is consistent with the conventional number of 500 to 600 testing points in the modal test of a Class B sedan, verifying the rationality of principle A.

[0074] S140. Generate a 3D mesh within the outer contour envelope, take the mesh intersections as candidate measurement points, eliminate candidate measurement points outside the outer contour envelope, retain candidate measurement points inside the outer contour envelope as modal measurement points, and record the coordinates of each modal measurement point.

[0075] Specifically, the number of grid divisions and the grid step size in each direction are calculated. Regular rectangular grids are generated along each coordinate axis direction within the outer contour envelope according to the grid step size. The grid intersections are taken as candidate measurement points. The contour in-frame criterion is used to determine whether the candidate measurement points are located inside the outer contour envelope. Candidate measurement points located outside the outer contour envelope are eliminated, and candidate measurement points located inside the contour are retained as modal measurement points. The modal measurement points are numbered in spatial order and the coordinates of each modal measurement point are recorded.

[0076] In some embodiments, step S140 includes steps S141 to S145.

[0077] S141. Calculate the number of grid divisions and the grid step size in each direction.

[0078] Specifically, taking the side view as an example, along the inside of the envelope... and Generate regular rectangular meshes in each direction. First, calculate the number of mesh divisions in each direction.

[0079] ; ; In the formula, for The number of directional grid divisions is dimensionless. for The number of directional grid divisions is dimensionless.

[0080] The grid step size is: ; ; In the formula, for Directional grid step size, in meters; for Directional grid step size, in meters.

[0081] Taking the aforementioned B-segment sedan side profile as an example, =226, =4.7m, =1.5m, substituting, we get: , Therefore, we get: =4.7 / 14=0.336m, =1.5 / 17=0.088m. This grid density ensures that the sensor spacing is around 0.3m, which meets the requirements of modal testing.

[0082] S142. Generate a regular rectangular grid along each coordinate axis direction within the outer contour envelope according to the grid step size, and take the grid intersection points as candidate measurement points.

[0083] Specifically, Figure 4 This is a mesh partitioning diagram of the modal measurement point envelope. The coordinates of the candidate mesh intersection points are: ; In the formula, For the first Line 1 List the coordinates of the candidate grid intersections, in meters; From 0 to ; From 0 to ; For the side The direction is represented by coordinates, in meters (m). As a reference point Minimum coordinate value, in meters; As a reference point Minimum coordinate value, in meters (m).

[0084] ; ; Take all reference points on the side. The arithmetic mean of the coordinates, for the aforementioned B-class sedan, If there are multiple structural surfaces on the side, the representative coordinates of each surface are calculated and a mesh is generated independently.

[0085] S143. Use the contour in-contour criterion to determine whether the candidate measurement point is located inside the outer contour envelope.

[0086] Specifically, the ray casting method is used to determine candidate points. Whether it lies inside the outer contour polygon formed by sequentially connecting reference points. For contour edges to Draw a horizontal ray to the right, if the following conditions are met: ; Then the edge has a valid intersection with the ray. If the total number of valid intersections of all edges is odd, then... If the number is even, it is determined to be located inside the contour; if it is even, it is determined to be located outside the contour.

[0087] For candidate points that fall exactly on the contour edge, they are determined to be inside the contour and retained; for candidate points that fall on the reference point, if the reference point belongs to two contour edges at the same time, the valid intersection point is counted only once to avoid misjudgment caused by repeated counting.

[0088] S144. Eliminate candidate measurement points located outside the outer contour envelope and retain candidate measurement points located inside the contour as modal measurement points.

[0089] Specifically, candidate measurement points located inside the contour are retained as modal measurement points.

[0090] S145. Number the modal measurement points in spatial order and record the coordinates of each modal measurement point.

[0091] Specifically, Figure 5 This is a diagram showing the number and distribution of modal measurement points on the vehicle's side. The retained measurement points are numbered in spatial order, denoted as... , From 1 to And record its three-dimensional coordinates Access to the coordinate database of the measurement point.

[0092]

[0093] In the formula, For the first The three-dimensional coordinate vectors of each modal measurement point in the coordinate system of the object under test, in meters; For the first Modal measurement points Coordinates, in meters; For the first Modal measurement points Coordinates, in meters; For the first Modal measurement points Coordinates, in meters.

[0094] S150. Establish the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector. Transform the coordinates of each modal measurement point to the coordinate system of the laser projector. Calculate the laser projection azimuth and elevation angles. Control the laser generator to project the modal measurement points onto the solid surface and obtain the modal measurement point marking results.

[0095] Specifically, a reference point calibration target is placed in front of the laser projector. The laser spot is controlled to aim at the known reference point, and the coordinates of each reference point in the laser projector coordinate system are recorded. Based on the coordinate pairs of the reference points in the object's coordinate system and the laser projector coordinate system, the rotation matrix and translation vector are solved to establish the transformation relationship. The coordinates of each modal measurement point are mapped to the laser projector coordinate system through the transformation relationship. Based on the coordinates of the modal measurement points in the laser projector coordinate system, the laser projection azimuth and elevation angles are calculated. The laser projection azimuth and elevation angles are sent to the laser generator, which drives the laser generator to adjust the projection attitude and project the laser spot onto the solid surface. The modal measurement points are switched sequentially according to their numbers until all modal measurement points have been projected and marked.

[0096] The calibration target is a high-reflectivity aluminum plate, 100mm × 100mm in size, with a surface roughness Ra better than 0.8μm, and a crosshair engraved in the center, with a line width of 0.5mm. The calibration target is then sequentially fixed to known reference points. , , At the location, the laser projector emits a low-power visible light spot. The testers make coarse adjustments by observing the overlap between the light spot and the crosshair on the calibration target. When the deviation between the center of the light spot and the crosshair is less than 2mm, the system switches to infrared laser mode. The edge computing unit reads the azimuth and elevation angles fed back by the encoder inside the laser projector and converts them into coordinates in the laser projector coordinate system.

[0097] In some embodiments, step S150 includes steps S151 to S155.

[0098] S151. Place a reference point calibration target in front of the laser projector.

[0099] Specifically, a reference point calibration target is placed in front of the laser projector so that the laser spot is aimed at the known reference point one by one.

[0100] S152. Control the laser spot to aim at the known reference point, and record the coordinates of each reference point in the laser projector coordinate system.

[0101] Specifically, the coordinates of each reference point fed back by the encoder inside the laser projector in the laser projector coordinate system are recorded. The value is set to 3. This value is determined based on the minimum solution requirement of rigid transformation in three-dimensional space. Three non-collinear points can uniquely determine a plane, and then the rotation matrix and translation vector can be solved.

[0102] ; In the formula, For the first The three-dimensional coordinate vectors of each reference point in the laser projector coordinate system, in meters; For the first benchmark points Coordinates, in meters; For the first benchmark points Coordinates, in meters; For the first benchmark points Coordinates, in meters.

[0103] S153. Based on the coordinate pairs of the reference points in the coordinate system of the object under test and the coordinate system of the laser projector, solve for the rotation matrix and translation vector, and establish the transformation relationship.

[0104] Specifically, a rigid transformation relationship is established between the coordinate system of the object being measured and the coordinate system of the laser projector.

[0105] ; In the formula, is the coordinate vector in the laser projector coordinate system, in meters; This is the coordinate vector in the coordinate system of the object being measured, with units of meters (m). It is a 3×3 rotation matrix, dimensionless; It is a 3×1 translation vector, with units of m.

[0106] Using the coordinate pairs of the calibration reference points, the problem is solved through orthogonal Procrustes problems: ; The constraints are: ; ; In the formula, Minimize operation; It is an identity matrix, dimensionless; This refers to matrix determinant operations.

[0107] The specific solution steps are as follows: First, calculate the centroids of the reference points in the coordinate system of the object under test and the coordinate system of the laser projector, and denote them as follows: and Then, the two sets of coordinates are decentroided to obtain the matrix. For the matrix Perform singular value decomposition. ,in and It is an orthogonal matrix. If the matrix is ​​diagonal, then the rotation matrix is... Translation vector The SVD decomposition process described above is automatically executed by the linear algebra library in the edge computing unit, achieving a decomposition accuracy better than 10. -6 .

[0108] S154. Map the coordinates of each modal measurement point to the laser projector coordinate system through transformation relationship, and calculate the laser projection azimuth and elevation angles based on the modal measurement point coordinates in the laser projector coordinate system.

[0109] Specifically, after the solution is completed, the coordinates of any modal measurement points are... Transform to the laser projector coordinate system.

[0110] ; ; In the formula, For the first The coordinate vectors of each modal measurement point in the laser projector coordinate system, in meters; For the first Modal measurement points Coordinates, in meters; For the first Modal measurement points Coordinates, in meters; For the first Modal measurement points Coordinates, in meters.

[0111] For modal measurement points Calculate the azimuth angle of the laser pan-tilt unit using the coordinates in the laser projector coordinate system. With pitch angle .

[0112] ; ; In the formula, This is the azimuth angle of the laser projection, in rad. The elevation angle of the laser projection is expressed in rad.

[0113] The laser projection distance is: ; In the formula, This represents the laser projection distance, measured in meters (m).

[0114] S155. Send the laser projection azimuth and elevation angles to the laser generator, drive the laser generator to adjust the projection attitude, project the laser spot onto the solid surface, and switch the modal measurement points in sequence according to the number until all modal measurement points are projected and marked.

[0115] Specifically, Figure 6 It is a reflection of the vehicle modal measurement points. Figure 7 This is a diagram illustrating the device's automatic reflection and pointing functions. The edge computing unit will... , , The message is sent to the laser projection device, which then receives it. , Then, the servo motor first drives the gimbal to rotate horizontally to the azimuth angle. Then, the pitch motor drives the laser head to rotate in the vertical direction to the pitch angle. Both had positioning errors of less than 0.01°. Subsequently, according to... Adjust the laser source focal length to keep the spot diameter within 3mm to 5mm on the solid surface. The experimenter marks the center of the spot using a reflective marker or scratch pen. After marking, a confirmation signal is sent to the edge computing unit via a foot switch or voice command. Upon receiving the confirmation signal, the unit automatically loads the necessary data. The coordinates are determined and the next projection is executed. If no confirmation signal is received three times consecutively, the measurement point is determined to be obstructed, triggering the point replacement process.

[0116] S160. Paste the sensor on the modal measurement point marking results and perform modal excitation test to obtain the structural modal parameters.

[0117] Specifically, accelerometers are attached to the marked locations at each modal measurement point, and vibration tests are conducted according to modal testing standards. Vibration response data at each measurement point are collected, and the vibration response data at each measurement point are processed through modal analysis to identify the natural frequency, mode shape, and damping ratio of the structure, thereby obtaining the structural modal parameters.

[0118] In some embodiments, step S160 includes steps S161 to S163.

[0119] S161. Paste the accelerometer at the marked result of each modal measurement point.

[0120] Specifically, after all modal measurement points were marked, the test personnel attached accelerometers to each marked point.

[0121] The accelerometer sensor is an ICP-type piezoelectric accelerometer with a sensitivity of 100mV / g, a range of ±50g, a frequency range of 0.3Hz to 10kHz, and a mass of less than 5g to minimize its impact on the structural mass. Before attaching the sensor, clean the marked surface with alcohol, allow it to dry, apply a special coupling agent, and then attach the sensor base to the surface, applying approximately 5N of pressure for 10 seconds to ensure a firm bond.

[0122] S162. Perform vibration testing according to the modal testing standard and collect vibration response data at each measuring point.

[0123] Specifically, either a hammer or an electromagnetic vibrator is used for excitation. When using a hammer, the hammer head is made of nylon, the force sensor sensitivity is 11.2 mV / N, and the excitation force is controlled within the range of 100 N to 200 N to ensure the structure is in the linear response region. When using an electromagnetic vibrator, the excitation force amplitude is set to 50 N, the frequency scanning range is 5 Hz to 200 Hz, and the scanning rate is 2 Hz / s. The sampling frequency is set to 1024 Hz, the sampling duration is 32 seconds, and the frequency resolution is better than 0.03 Hz. All measuring points are acquired synchronously, and the vibration response time-domain signal of each measuring point is recorded through a multi-channel data acquisition system.

[0124] S163. By processing the vibration response data of each measuring point through modal analysis, the natural frequency, mode shape and damping ratio of the structure are identified, and the structural modal parameters are obtained.

[0125] Specifically, the natural frequencies, mode shapes, and damping ratios of the structure are identified using experimental modal analysis software.

[0126] The acquired time-domain signal was windowed, and a Hanning window was used to suppress spectral leakage. A fast Fourier transform was then performed to obtain the frequency response function. Modal parameters were identified using the least squares complex frequency domain method, with stability plot criteria set as follows: frequency deviation less than 1%, damping ratio deviation less than 5%, and modal confidence criterion (MAC) value greater than 0.95. The first 10 modal parameters of the elastic body, including natural frequencies, mode shape vectors, and modal damping ratios, were extracted to obtain the structural modal parameters.

[0127] In some embodiments, the method further includes steps S170 to S190.

[0128] S170. Continuously monitor the completion rate and coordinate deviation of modal measurement point marking results.

[0129] Specifically, the system continuously monitors the completion rate and coordinate deviation of the laser-projected markers.

[0130] Edge computing units record each projection , , The actual positioning feedback value is used to calculate the positioning deviation. Simultaneously, after marking, the test personnel use a total station to randomly check no less than 10% of the measuring points, measuring their actual three-dimensional coordinates and comparing them with the theoretical coordinates. Compare and calculate coordinate deviation

[0131] ; In the above formula, This refers to the coordinate deviation, in mm. For the sampled test points measured by total station Direction coordinates; For the sampled test points measured by total station Direction coordinates; For the sampled test points measured by total station Direction coordinates; The theory for the m-th modal measurement point coordinate; The theory for the m-th modal measurement point coordinate; The theory for the m-th modal measurement point coordinate.

[0132] S180. When the coordinate deviation exceeds the preset threshold, the recalibration process is triggered to correct the transformation relationship.

[0133] Specifically, if the marking deviation of a certain batch exceeds a preset threshold... This triggers the recalibration process, correcting the rotation matrix. With translation vector .

[0134] A threshold of 5mm is chosen, determined based on the allowable deviation of the sensor's mounting position during modal testing. When the deviation exceeds 5mm, the correlation error between the measured vibration mode data and the theoretical coordinates will exceed the default tolerance of the modal analysis software, leading to distorted vibration mode identification. Therefore, 5mm is chosen as the recalibration trigger condition.

[0135] During correction, the deviation data from the current sampling is used as the new calibration point pair, and the SVD decomposition step in S153 is re-executed to update the rotation matrix. Translation vector After the update, the first 20 projected measurement points are re-measured. If the deviation of the re-measurement is less than 3mm, the correction is confirmed to be effective and subsequent projections continue; otherwise, the correction is repeated until the accuracy requirements are met.

[0136] S190. Under the corrected transformation relationship, re-execute the modal measurement point projection to obtain the corrected modal measurement point marking results.

[0137] Specifically, modal measurement point projection is re-executed under the corrected transformation relationship to obtain the corrected modal measurement point marking results.

[0138] If individual measuring points cannot be positioned due to structural obstruction or marking errors, the coordinates of adjacent modal measuring points are called through the edge computing unit to locally fill the points, and the laser projection marking is re-executed, forming a closed-loop iteration of measuring point selection, marking, testing, and point filling.

[0139] The rules for supplementing points are as follows: If the measuring point If the point is obstructed, extract the numbered measurement points adjacent to it on the same surface. and Calculate the coordinates of the midpoint. The midpoint is then used as a candidate for a replacement point. The ray casting method is used to determine if the candidate point lies inside the contour; if it does, a new number is assigned. And perform laser projection; if located externally, then along... The direction is shifted 0.5 times inwards towards the contour. The process is repeated until a valid replacement point is found. After replacement, the list of measurement point coordinates is updated in the modal analysis software to ensure that the dimension of the frequency response function matrix matches the number of measurement points.

[0140] The intelligent method for determining structural modal parameters provided in this application involves acquiring reference points of the outer contour of the object under test and recording their three-dimensional coordinates. Based on these reference points, an outer contour envelope is constructed, and equivalent feature dimensions are calculated. A quantitative relationship between the equivalent feature dimensions and the number of measurement points is established according to a preset mapping principle to determine the number of measurement points on each surface. A three-dimensional mesh is generated within the envelope, and modal measurement points are selected. A coordinate system transformation relationship is established, and precise mapping from digital measurement points to the physical entity is achieved through laser projection. Finally, sensors are attached to perform modal excitation testing to obtain the structural modal parameters. This application achieves a complete closed loop from digital generation to physical marking of modal measurement points, avoiding errors from manual planning and measurement, and improving the efficiency and accuracy of modal testing.

[0141] This application also provides an intelligent system for determining structural modal parameters, which is used to execute any of the aforementioned intelligent methods for determining structural modal parameters.

[0142] Specifically, the system includes a reference point acquisition unit, an envelope construction unit, a measurement point quantity determination unit, a mesh generation unit, a laser projection unit, and a modal testing unit.

[0143] The reference point acquisition unit is used to acquire the reference points of the outer contour of the object being measured and record the three-dimensional coordinates of each reference point; Envelope construction unit, used to construct the outer contour envelope of the measured object based on the reference point and calculate the equivalent feature size; The measurement point quantity determination unit is used to establish a quantitative relationship between the equivalent feature size and the number of measurement points based on a preset mapping principle, and to determine the number of measurement points on each surface of the object being measured. The mesh generation unit is used to generate a 3D mesh within the outer contour envelope, take the mesh intersections as candidate measurement points, eliminate candidate measurement points outside the outer contour envelope, retain candidate measurement points inside the outer contour envelope as modal measurement points, and record the coordinates of each modal measurement point. The laser projection unit is used to establish the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector, transform the coordinates of each modal measurement point to the coordinate system of the laser projector, calculate the laser projection azimuth and elevation angles, control the laser generator to project the modal measurement points onto the solid surface, and obtain the modal measurement point marking results. The modal testing unit is used to attach sensors to the modal measurement point markings and perform modal excitation tests to obtain structural modal parameters.

[0144] It should be noted that those skilled in the art can clearly understand that the intelligent system for formulating structural modal parameters and the specific implementation process of each unit can be found in the corresponding descriptions in the foregoing method embodiments. For the sake of convenience and brevity, these details will not be repeated here.

[0145] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for intelligently determining structural modal parameters, characterized in that, Includes the following steps: Obtain the reference points of the outer contour of the object being measured and record the three-dimensional coordinates of each reference point; Construct the outer contour envelope of the object under test based on the reference points and calculate the equivalent feature dimensions; A quantitative relationship between equivalent feature size and the number of measurement points is established based on the preset mapping principle, and the number of measurement points on each surface of the object being measured is determined. A 3D mesh is generated within the outer contour envelope. The intersection points of the mesh are taken as candidate measurement points. Candidate measurement points outside the outer contour envelope are eliminated, and candidate measurement points inside the outer contour envelope are retained as modal measurement points. The coordinates of each modal measurement point are recorded. Establish the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector, transform the coordinates of each modal measurement point to the coordinate system of the laser projector, calculate the azimuth and elevation angles of the laser projection, control the laser generator to project the modal measurement points onto the solid surface, and obtain the modal measurement point marking results; The sensor is attached to the modal measurement point marking results and modal excitation test is performed to obtain the structural modal parameters.

2. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, Obtain the reference points for the outer contour of the object being measured and record the three-dimensional coordinates of each reference point, including: Benchmark points are set up on the roof, front bumper, rear bumper, and side door sills of the vehicle being tested. Establish the coordinate system of the object under test with one of the reference points as the origin; Measure and record the three-dimensional coordinates of each reference point in the coordinate system of the object being measured to obtain the set of reference point coordinates.

3. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, Constructing the outer contour envelope of the object under test based on reference points and calculating the equivalent feature dimensions, including: Connect the reference points of the outer contour in sequence to form a closed spatial polyline describing the outer contour of the measured object; Construct the outer contour envelope based on closed spatial polylines; Calculate the maximum span of the outer contour envelope in each coordinate axis direction to obtain the equivalent feature length; Calculate the effective projected area to obtain the equivalent feature size.

4. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, Based on a pre-defined mapping principle, a quantitative relationship between equivalent feature dimensions and the number of measurement points is established, and the number of measurement points on each surface of the object being measured is determined, including: Obtain the effective projected area within the equivalent feature size; Calculate the contour complexity coefficient based on the outer contour envelope; Substitute the effective projected area and the contour complexity coefficient into the formula for calculating the number of measurement points, and combine this with the minimum measurement point constraint to obtain the number of measurement points on the surface. Summarize the number of measuring points on each surface to obtain the total number of measuring points on the object being tested.

5. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, A 3D mesh is generated within the outer contour envelope. Mesh intersections are selected as candidate measurement points. Candidate measurement points outside the outer contour envelope are eliminated, while those inside are retained as modal measurement points. The coordinates of each modal measurement point are recorded, including: Calculate the number of grid divisions and the grid step size in each direction; Within the outer contour envelope, generate regular rectangular grids along each coordinate axis direction according to the grid step size, and take the grid intersections as candidate measurement points; The in-contour criterion is used to determine whether candidate measurement points are located inside the outer contour envelope. Candidate measurement points located outside the outer contour envelope are removed, and candidate measurement points located inside the contour are retained as modal measurement points; The modal measurement points are numbered according to spatial order, and the coordinates of each modal measurement point are recorded.

6. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, Establish the transformation relationship between the coordinate system of the object being measured and the coordinate system of the laser projector, including: Place a reference point calibration target in front of the laser projector; Control the laser spot to aim at a known reference point, and record the coordinates of each reference point in the laser projector coordinate system; Based on the coordinate pairs of the reference points in the coordinate system of the object under test and the coordinate system of the laser projector, the rotation matrix and translation vector are solved to establish the transformation relationship.

7. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, The coordinates of each modal measurement point are transformed to the laser projector coordinate system. The laser projection azimuth and elevation angles are calculated. The laser generator is then controlled to project the modal measurement points onto the solid surface, resulting in the modal measurement point markings, including: The coordinates of each modal measurement point are mapped to the laser projector coordinate system through a transformation relationship; Calculate the laser projection azimuth and elevation angles based on the modal measurement point coordinates in the laser projector coordinate system; The laser projection azimuth and elevation angles are sent down to the laser generator, which drives the laser generator to adjust the projection attitude and project the laser spot onto the solid surface; Switch the modal measurement points sequentially according to their numbers until all modal measurement points have been projected and marked.

8. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, After marking the modal measurement points with sensors and performing modal excitation tests, the structural modal parameters are obtained, including: Attach the accelerometer to the marked locations at each modal measurement point; Vibration tests were conducted according to modal testing standards, and vibration response data were collected at each measuring point. By processing the vibration response data at each measuring point through modal analysis, the natural frequencies, mode shapes, and damping ratios of the structure are identified, and the structural modal parameters are obtained.

9. The intelligent method for determining structural modal parameters according to claim 1, characterized in that, Also includes: Continuously monitor the completion rate and coordinate deviation of modal measurement point marking results; When the coordinate deviation exceeds the preset threshold, the recalibration process is triggered to correct the transformation relationship; The modal measurement point projection is re-executed under the corrected transformation relationship to obtain the corrected modal measurement point marking results.

10. An intelligent system for determining structural modal parameters, characterized in that, include: The reference point acquisition unit is used to acquire the reference points of the outer contour of the object being measured and record the three-dimensional coordinates of each reference point; Envelope construction unit, used to construct the outer contour envelope of the measured object based on the reference point and calculate the equivalent feature size; The measurement point quantity determination unit is used to establish a quantitative relationship between the equivalent feature size and the number of measurement points based on a preset mapping principle, and to determine the number of measurement points on each surface of the object being measured. The mesh generation unit is used to generate a 3D mesh within the outer contour envelope, take the mesh intersections as candidate measurement points, eliminate candidate measurement points outside the outer contour envelope, retain candidate measurement points inside the outer contour envelope as modal measurement points, and record the coordinates of each modal measurement point. The laser projection unit is used to establish the transformation relationship between the coordinate system of the object under test and the coordinate system of the laser projector, transform the coordinates of each modal measurement point to the coordinate system of the laser projector, calculate the laser projection azimuth and elevation angles, control the laser generator to project the modal measurement points onto the solid surface, and obtain the modal measurement point marking results. The modal testing unit is used to attach sensors to the modal measurement point markings and perform modal excitation tests to obtain structural modal parameters.

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