A full-field vibration testing method and system based on single-point laser scanning

Abstract

The application relates to a full-field vibration test method and system based on single-point laser scanning, and belongs to the technical field of vibration test analysis. The method comprises the following steps: arranging a group of measured points on a test surface of a measured structure; determining a group of parking points of laser displacement sensors corresponding to the measured points in a two-dimensional space parallel to the test surface; arranging a motion path for traversing the parking points and a group of excitation frequencies; traversing each excitation frequency to excite the measured structure to vibrate at a set excitation period; in each excitation period, the laser displacement sensor collects the vibration signals of the measured structure at the position of each measured point on each parking point according to the arranged motion path; and performing signal analysis on the collected vibration signals at each excitation frequency to determine the mechanical dynamic characteristics of the measured structure at each excitation frequency, including the response mode and the amplitude. The application completes vibration measurement through a single laser displacement sensor, has high measurement accuracy and a wide excitation frequency range.

Description

Technical Field

[0001] This invention relates to the field of vibration testing and analysis technology, and in particular to a full-field vibration testing method and system based on single-point laser scanning. Background Technology

[0002] Vibration testing involves using sensors, amplification instruments, and data acquisition equipment to measure physical quantities such as displacement, velocity, acceleration, strain, and force of moving machinery or engineering structures under excitation or operating conditions, thereby understanding the working state and dynamic mechanical characteristics of the machinery or structure.

[0003] Among sensors, accelerometers are the most widely used due to their robustness, sensitivity, and wide bandwidth. However, because accelerometers need to be attached to the measured points on the structure, while the requirement for full-field vibration response measurement can be met by measuring point by point using a moving actuator, this greatly increases the complexity of the measurement. The development of non-contact measurement technologies such as scanning laser Doppler measurement and digital image correlation measurement has provided new methods for full-field vibration response measurement.

[0004] Scanning laser Doppler vibrometers acquire motion information of the measured point by measuring the Doppler frequency shift of the reflected laser. By controlling the beam angle, the laser endpoint reaches the measured point within the field, thus achieving in-plane vibration response measurement at multiple points. However, scanning laser Doppler vibrometers have some limitations in application, such as the scanning frequency not being able to match the vibration frequency and harmonic frequencies of the measured object, limitations in the scanning range and number of measurement points, the beam angle changing and no longer being perpendicular to the measured surface, affecting measurement accuracy, and high cost. Digital image correlation measurement technology uses algorithms to obtain full-field displacement and strain from speckle maps before and after deformation of the structural surface. However, because this method is based on dense image changes, its sensitivity is lower than that of scanning laser Doppler, and it also has high requirements for storage space and computing performance, requires multiple expensive high-speed cameras, and has high synchronization requirements. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a method and system for full-field vibration testing based on single-point laser scanning, so as to achieve accurate measurement of the full-field vibration response of a structure within a wide frequency band.

[0006] The objective of this invention is mainly achieved through the following technical solutions:

[0007] This invention discloses a full-field vibration testing method based on single-point laser scanning, comprising:

[0008] Step S1: Set a set of test points on the test surface of the structure under test; determine a set of stopping points of laser displacement sensors that correspond one-to-one with the test points in a two-dimensional space parallel to the test surface;

[0009] Step S2: Set the motion path that traverses the stopping points; the laser displacement sensor stopped at each stopping point on the motion path can illuminate the corresponding measured point in a perpendicular manner.

[0010] Step S3: Set a set of excitation frequencies; traverse each excitation frequency with the set excitation cycle to excite the structure under test; within each excitation cycle, the laser displacement sensor collects the vibration signal of the structure under test at each stop point according to the set motion path through a walking and stopping mode.

[0011] Step S4: Based on the full-field vibration response obtained by signal analysis of the vibration signals collected at each excitation frequency, determine the mechanical dynamic characteristics of the tested structure at each excitation frequency, including the response mode shape and amplitude.

[0012] Furthermore, the test points set on the test surface of the structure under test are evenly and fully covered by the test surface, and the relative coordinates and serial numbers of the test points on the test surface are recorded.

[0013] The stopping points set on the two-dimensional space parallel to the test surface correspond one-to-one with the test points and are the projections of the test points in the two-dimensional space.

[0014] When the laser displacement sensor performs measurements at each stopping point, it remains perpendicular to the surface being measured, ensuring that the laser is incident normally and that the energy of the laser spot is uniform.

[0015] The set motion path enables the laser displacement sensor to traverse each stopping point in a single pass, remaining stationary at each stopping point for a fixed duration; the initial and final points of the motion path coincide, closing the path; and the sequence number of the measured point corresponding to each stopping point traversed in the motion path is recorded.

[0016] Furthermore, a two-dimensional space parallel to the test surface is defined using a two-axis ball screw slide. A single-point laser sensor is fixed on the two-axis ball screw slide, and a stepper motor control method is used to control the two-axis ball screw slide to drive the laser displacement sensor in the two-dimensional space. According to the set motion path, the sensor travels through each stopping point by walking and stopping, and the vibration of the test point is measured by static measurement.

[0017] Furthermore, by installing piezoelectric fiber sheets on the structure under test, the structure under test is subjected to vibration excitation; by applying a set of excitation signals of a set frequency to the piezoelectric fiber sheets, the piezoelectric fiber sheets excite the structure under test to vibrate at the set frequency.

[0018] Furthermore, the set of excitation frequencies for the structure under test is a set of frequencies that are increased or decreased at equal intervals with fixed interval frequency values; the range of the maximum and minimum values ​​of this set of frequencies covers the frequency range of interest for the structural vibration response; the selection of fixed interval frequency values ​​ensures that the excitation frequency points are evenly and densely distributed in the measurement frequency band, which contains several natural frequencies.

[0019] During the test, a step-sweep excitation signal is applied to the piezoelectric fiber sheet. The sweep period is fixed and not less than the walking period of the laser displacement sensor in the motion path. Under the sweep control of each sweep period, the frequency of the excitation signal increases or decreases at fixed intervals, while the signal amplitude remains unchanged.

[0020] Further, step S4 includes:

[0021] 1) The time series of vibration signals collected by the laser displacement sensor at each excitation frequency are stored;

[0022] 2) A filter based on wavelet transform analysis is used to perform frequency domain decomposition and time domain reconstruction of the vibration signal time series to obtain the reconstructed vibration signal time series;

[0023] In the frequency domain decomposition of wavelet transform, the coefficients of each level of DWT are corrected, each excitation frequency term is retained, and other frequency terms are attenuated. After IDWT reconstruction, the reconstructed vibration signal time series with each excitation frequency term retained is obtained.

[0024] 3) Divide the reconstructed vibration signal time series into blocks according to each excitation frequency. The signal time series of each block is the reconstructed vibration signal time series at one excitation frequency.

[0025] 4) For each block of the signal time series, according to the sequence number of the test point corresponding to each stopping point recorded when setting the motion path, and according to the relative coordinates and sequence number of the test point on the test surface recorded when setting the test point, the coordinates on the test surface are assigned to each signal in the signal time series; a three-dimensional map of vibration signal distribution is formed with the test surface as the plane coordinate and the reconstructed vibration signal amplitude as the vertical coordinate, and each excitation frequency corresponds to a three-dimensional map of vibration signal distribution;

[0026] The mechanical dynamic characteristics of the tested structure, including the response mode and amplitude, are obtained from the distribution and magnitude of vibration amplitude in the three-dimensional diagram of vibration signal distribution.

[0027] The present invention also discloses a full-field vibration testing system for implementing the above-described full-field vibration testing method based on single-point laser scanning, comprising: a laser sensing module, a stepping path module, an excitation module, and a data acquisition and processing module;

[0028] The laser sensing module is fixedly connected to the stepping path module, the vibration module is fixedly connected to the structure under test, and the data acquisition and control processing module is electrically connected to the laser sensing module, the stepping path module, and the vibration module.

[0029] The excitation module is used to excite the structure under test to vibrate using a set excitation frequency under the control of the data acquisition and processing module.

[0030] The stepping path module is set on the opposite side of the test surface of the structure under test. Under the control of the data acquisition and control processing module, it drives the laser sensing module to traverse each stopping point in a set motion path by walking and stopping.

[0031] The laser sensing module is used to collect vibration signals from the corresponding test points on the test surface at each stopping point under the control of the data acquisition and processing module.

[0032] The data acquisition and control processing module is used to control the operation of the excitation module, the stepping path module and the laser sensing module, and to receive the vibration signals collected by the laser sensing module at each excitation frequency, and to perform signal analysis and mechanical dynamic characteristic analysis through signal post-processing.

[0033] Furthermore, the stepping path module includes a motor controller, a two-axis ball screw slide, and a DC power supply;

[0034] The two-axis ball screw slide is used to support the laser sensing module for two-dimensional spatial stepping motion.

[0035] The motor controller is connected to the two-axis ball screw slide table and is used for two-dimensional spatial motion control.

[0036] The DC power supply is connected to the two-axis ball screw slide and the motor controller respectively to provide DC power.

[0037] The two-axis ball screw slide includes a vertical ball screw slide and a horizontal ball screw slide that are connected to each other; the laser sensing module is fixed on the vertical ball screw slide or the horizontal ball screw slide.

[0038] Furthermore, the excitation module includes a power amplifier and a piezoelectric fiber sheet;

[0039] The piezoelectric fiber sheet is bonded to the structure under test, and the power amplifier is electrically connected to the piezoelectric fiber sheet.

[0040] The power amplifier is also electrically connected to the junction box, and receives the excitation signal from the junction box, amplifies it, and outputs it to the piezoelectric fiber sheet.

[0041] The piezoelectric fiber sheet is connected to the power amplifier and bonded to the structure under test. It converts the input excitation signal into mechanical vibration excitation of the corresponding frequency, driving the structure under test to vibrate.

[0042] Furthermore, the data acquisition and processing module includes a computer, digital I / O boards, and a junction box;

[0043] The digital I / O board is mounted on the computer and is used for signal transmission and acquisition;

[0044] The junction box is connected to the digital I / O board for line protection and connection, and establishes data connection between the digital I / O board and the laser sensing module, stepping path module and excitation module.

[0045] The computer is used for system control, writing functional programs, and data storage, processing, and analysis. The beneficial effects of this invention are as follows:

[0046] The whole-field vibration testing method and system based on single-point laser scanning in this invention keep the single-point laser stationary during vibration response measurement, thus not introducing noise; it adopts normal incidence measurement, resulting in uniform spot energy and high measurement accuracy; it has high step control accuracy, accurate repositioning, and small position error; at each excitation frequency, the laser sensor automatically moves along a set path to complete the whole-field vibration response measurement, requiring no manual operation during the testing process and eliminating time accumulation error; and it applies excitation through piezoelectric fiber sheets, resulting in small size, light weight, minimal intrusion, and a wide range of excitation frequencies.

[0047] In summary, this invention completes vibration measurement using a single laser displacement sensor, which is inexpensive and greatly reduces the cost of full-field vibration testing. Attached Figure Description

[0048] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0049] Figure 1 This is a flowchart of the full-field vibration testing method based on single-point laser scanning in an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the motion path for the full-field vibration test in an embodiment of the present invention;

[0051] Figure 3 This is a schematic diagram showing the relative positions of each test component in the full-field vibration test based on single-point laser scanning in an embodiment of the present invention.

[0052] Figure 4(a) shows the mechanical dynamic characteristic waveforms with excitation frequencies of 1000 Hz in the embodiment of the present invention.

[0053] Figure 4(b) shows the mechanical dynamic characteristic waveforms with excitation frequencies of 1200 Hz in the embodiment of the present invention.

[0054] Figure 4(c) shows the mechanical dynamic characteristic waveforms with excitation frequencies of 1400 Hz in the embodiment of the present invention.

[0055] Figure 4(d) shows the mechanical dynamic characteristic waveforms with excitation frequencies of 1600 Hz in the embodiment of the present invention.

[0056] Figure 5 This is a schematic diagram showing the components and connections of a full-field vibration testing system based on single-point laser scanning in an embodiment of the present invention.

[0057] Figure label:

[0058] 21-Laser displacement sensor, 22-Stepping path, 23-Dwelling point, 24-Laser beam, 25-Measured point, 26-Measured surface, 27-Return path; 31-Horizontal ball screw slide, 32-Vertical ball screw slide, 33-Sensor adapter, 34-Laser displacement sensor, 35-Piezoelectric fiber sheet, 36-Measured structure; 51-Data acquisition and control processing module, 52-Vibration module, 53-Stepping path module, 54-Laser sensing module. Detailed Implementation

[0059] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0060] Example 1

[0061] This embodiment discloses a full-field vibration testing method based on single-point laser scanning, such as... Figure 1 As shown, it includes:

[0062] Step S1: Set a set of test points on the test surface of the structure under test; determine a set of stopping points of laser displacement sensors that correspond one-to-one with the test points in a two-dimensional space parallel to the test surface;

[0063] Step S2: Set the motion path that traverses the stopping points; the laser displacement sensor stopped at each stopping point on the motion path can illuminate the corresponding measured point in a perpendicular manner.

[0064] Step S3: Set a set of excitation frequencies; traverse each excitation frequency with the set excitation cycle to excite the structure under test; within each excitation cycle, the laser displacement sensor collects the vibration signal of the structure under test at each stop point according to the set motion path through a walking and stopping mode.

[0065] Step S4: Based on the full-field vibration response obtained by signal analysis of the vibration signals collected at each excitation frequency, determine the mechanical dynamic characteristics of the tested structure at each excitation frequency, including the response mode shape and amplitude.

[0066] Specifically, in step S1, the test points set on the test surface of the structure under test are evenly and fully covered by the test surface, and the relative coordinates and serial numbers of the test points on the test surface are recorded; the number and position of the test points are given in advance by the measurement requirements.

[0067] In measurement requirements, the higher the upper limit of the vibration frequency of the structure under test, the more test points there are, and the greater the density of test points on the test surface.

[0068] The perpendicular distance between the two-dimensional space parallel to the test surface and the test surface is determined by the test environment and the laser power and frequency of the laser displacement sensor; the greater the maximum perpendicular distance, the less interference in the test environment and the higher the laser power.

[0069] The stopping points set in the two-dimensional space correspond one-to-one with the measured points, and are the projections of the measured points in the two-dimensional space parallel to the test surface; when the laser displacement sensor performs measurements at each stopping point, it always remains perpendicular to the measured surface, the laser is incident normally, the spot energy is uniform, and the measurement accuracy is high.

[0070] Specifically, in step S2, the motion path is set so that the laser displacement sensor can traverse each stopping point in a single pass, with a fixed duration of stillness at each stopping point; the initial and final points of the motion path coincide, closing the path; and the sequence number of the measured point corresponding to each stopping point traversed in the motion path is recorded. After each execution of the motion path, the laser displacement sensor returns to the starting point so that it can perform the next motion on the motion path.

[0071] like Figure 2 As shown, a schematic diagram of a specific motion path for a full-field vibration test is presented.

[0072] For a set of measurement points, the motion path is not unique and does not need to be established according to the sequence of measurement point numbers. It can be set according to requirements. The preferred motion path is the shortest possible motion path while traversing all measurement points, so as to complete the measurement in the shortest time and improve measurement efficiency.

[0073] This embodiment uses a walking and stopping method to perform measurements at the stopping point, which ensures that the laser displacement sensor performs measurements under static conditions. The testing system itself does not introduce noise, thus obtaining more accurate measurement results.

[0074] In the preferred embodiment, a two-axis ball screw slide is used to define a two-dimensional space parallel to the test surface. A single-point laser sensor is fixed on the two-axis ball screw slide. The two-axis ball screw slide is controlled by a stepper motor to drive the laser displacement sensor in the two-dimensional space. The sensor travels through each stopping point by walking and stopping according to the set motion path. The vibration of the test point is measured by a static measurement method.

[0075] The two-axis ball screw slide has high control precision and accurate repositioning, which can reduce the positional error between the laser beam endpoint of the single-point laser sensor and the measured point.

[0076] Specifically, the structure under test is vibrated by installing piezoelectric fiber sheets on the structure under test; by applying a set excitation signal of a set frequency to the piezoelectric fiber sheets, the piezoelectric fiber sheets excite the structure under test to vibrate at the set frequency.

[0077] Preferably, a piezoelectric fiber sheet with a thickness of about 300 μm is used to apply the excitation, which is small in size, light in weight, has a low degree of invasiveness, and a wide range of excitation frequencies.

[0078] like Figure 3 The diagram shows the relative positions of the test components in a full-field vibration test based on single-point laser scanning.

[0079] Specifically, in step S3, the set of excitation frequencies for the structure under test is a set of frequencies that are increased or decreased at fixed intervals; the range of the maximum and minimum values ​​of this set of frequencies covers the frequency range of interest for the structural vibration response; the selection of fixed interval frequency values ​​ensures that the excitation frequency points are evenly and densely distributed in the measurement frequency band, which contains several natural frequencies.

[0080] During the test, a step-sweep excitation signal is applied to the piezoelectric fiber sheet. The sweep period is fixed and not less than the walking period of the laser displacement sensor in the motion path. Under the sweep control of each sweep period, the frequency of the excitation signal increases or decreases at fixed intervals, while the signal amplitude remains unchanged.

[0081] In the preferred embodiment, the frequency sweep control applied to the piezoelectric fiber sheet and the stepping motion of the laser displacement sensor are performed using a synchronous triggering method; that is, a trigger signal synchronized with the frequency sweep trigger signal is used to trigger the laser displacement sensor to start walking, stopping and collecting vibration signals on the motion path. Within one frequency sweep cycle, the laser displacement sensor completes the signal collection of all measured points and returns to the starting point. When the next frequency sweep trigger signal arrives, the laser displacement sensor will then perform the next walking, stopping and collecting vibration signals on the motion path.

[0082] Specifically, step S4 includes:

[0083] 1) The time series of vibration signals collected by the laser displacement sensor at each excitation frequency are stored;

[0084] 2) A filter based on wavelet transform analysis is used to perform frequency domain decomposition and time domain reconstruction of the vibration signal time series to obtain the reconstructed vibration signal time series;

[0085] In the frequency domain decomposition of wavelet transform, the coefficients of each level of DWT (Discrete Wavelet Transform) are corrected, each excitation frequency term is retained, and other frequency terms are attenuated. After reconstruction by IDWT (Inverse Discrete Wavelet Transform), the reconstructed vibration signal time series with each excitation frequency term is obtained.

[0086] 3) Divide the reconstructed vibration signal time series into blocks according to each excitation frequency. The signal time series of each block is the reconstructed vibration signal time series at one excitation frequency.

[0087] 4) For each block of the signal time series, according to the sequence number of the test point corresponding to each stopping point recorded when setting the motion path, and according to the relative coordinates and sequence number of the test point on the test surface recorded when setting the test point, the coordinates on the test surface are assigned to each signal in the signal time series; a three-dimensional map of vibration signal distribution is formed with the test surface as the plane coordinate and the reconstructed vibration signal amplitude as the vertical coordinate, and each excitation frequency corresponds to a three-dimensional map of vibration signal distribution;

[0088] The distribution and magnitude of vibration amplitude in the three-dimensional vibration signal distribution diagram provide a direct visual representation of the mechanical dynamic characteristics of the tested structure at different excitation frequencies, including the response mode and amplitude.

[0089] Figure 4 shows a schematic diagram of the full-field vibration response results. Stable values ​​of the vibration response amplitude at each measured point under each excitation frequency were extracted from the wavelet transform analysis results to form the full-field vibration response within the measurement frequency range. In the figure, the horizontal and vertical axes represent the relative coordinates of the measured points on the test surface, and the vertical axis represents the response amplitude. The excitation frequencies of Figures 4(a), (b), (c), and (d) are 1000 Hz, 1200 Hz, 1400 Hz, and 1600 Hz, respectively. The figure shows the mechanical dynamic characteristics of the structure, such as the mode shape and amplitude, at each excitation frequency. It can be observed that the response amplitudes at excitation frequencies of 1400 Hz and 1600 Hz are significantly larger than those at 1000 Hz and 1200 Hz, with the maximum response occurring around the perimeter of the structure.

[0090] When the measurement frequency range is too large, the number and density of test points set on the test surface based on the highest measurement frequency value will result in data redundancy when measuring at the lowest measurement value. This will increase the amount of data to be processed and stored, and degrade the test efficiency.

[0091] Therefore, this embodiment further discloses a full-field vibration testing method with a wide measurement frequency range;

[0092] Specifically, during the full-field vibration test with a wide measurement frequency range:

[0093] In step S1, when setting the measured points, the position and density of the measured points are set according to the highest frequency point in the measurement frequency range;

[0094] In step S2, during motion path planning, the wide measurement frequency range is divided into frequency band segments, and a corresponding motion path is set for each frequency band. The initial and final points of each motion path coincide, and the path is closed. Among them, the motion path of the highest frequency band traverses all measured points with the goal of making the path as short as possible. As the frequency of the frequency band decreases, the measured points on the motion path of the highest frequency band are sampled at equal intervals, and the density of measured points on the path is gradually reduced. The lower the frequency of the frequency band, the lower the density of measured points on the corresponding path. During the density reduction process, the initial and final points of each motion path are kept coincident and unchanged. The sequence number of each measured point in each motion path is recorded. A fixed stationary time is set at each stopping point. Since the movement time of the laser displacement sensor between test points on the path is much shorter than the stationary time at the stopping point, as the frequency of the frequency band decreases, the proportion of equal-interval sampling of the traversal time of the laser displacement sensor on each path decreases. The traversal time of each motion path is recorded.

[0095] In step S3, the excitation period of each frequency band segment is set according to the traversal time of each motion path; the excitation frequency is generated starting from the highest or lowest frequency point, and the structure under test is vibrated with the corresponding excitation period, and the laser displacement sensor is triggered synchronously. In each excitation period, the laser displacement sensor collects the vibration signal of the structure under test at the corresponding test point position at each stop point by walking and stopping according to the corresponding motion path.

[0096] In step S4, the above-mentioned wavelet transform-based analysis method is used to analyze the vibration signals collected at each excitation frequency in each frequency band segment to obtain the full-field vibration response, thereby determining the mechanical dynamic characteristics of the tested structure in each frequency band segment, including the response mode shape and amplitude.

[0097] This enables full-field vibration testing over a wide measurement frequency range, improving testing efficiency while ensuring testing accuracy.

[0098] In summary, the full-field vibration testing method based on single-point laser scanning in this invention maintains a stationary single-point laser during vibration response measurement, thus introducing no noise; it employs normal incidence measurement, resulting in uniform spot energy and high measurement accuracy; it features high step control precision, accurate repositioning, and minimal positional error; at each excitation frequency, the laser sensor automatically moves along a set path to complete the full-field vibration response measurement, requiring no manual operation during the testing process and eliminating time accumulation errors; it applies excitation through a piezoelectric fiber sheet, resulting in a small size, light weight, minimal intrusion, and a wide excitation frequency range; and it completes vibration measurement using a single laser displacement sensor, making it inexpensive and significantly reducing the cost of full-field vibration testing.

[0099] Example 2

[0100] This embodiment discloses a full-field vibration testing system that implements the full-field vibration testing method based on single-point laser scanning described in Embodiment 1, such as... Figure 5 As shown, it includes: a laser sensing module, a stepping path module, a vibration module, and a data acquisition and processing module;

[0101] The laser sensing module is fixedly connected to the stepping path module, the vibration module is fixedly connected to the structure under test, and the data acquisition and control processing module is electrically connected to the laser sensing module, the stepping path module, and the vibration module.

[0102] The excitation module is used to excite the structure under test to vibrate at a set excitation frequency under the control of the data acquisition and processing module.

[0103] The stepping path module is set on the opposite side of the test surface of the structure under test. Under the control of the data acquisition and control processing module, it drives the laser sensing module to traverse each stopping point in a set motion path by walking and stopping.

[0104] The laser sensing module is used to collect vibration signals from the corresponding test points on the test surface at each stopping point, under the control of the data acquisition and processing module.

[0105] The data acquisition and control processing module is used to control the operation of the excitation module, the stepping path module and the laser sensing module, and to receive the vibration signals collected by the laser sensing module at various excitation frequencies. The module performs signal analysis and mechanical dynamic characteristic analysis through signal post-processing.

[0106] Specifically, the data acquisition and processing module includes a computer, digital I / O boards, and junction boxes;

[0107] Digital I / O boards are mounted on computers and used for signal transmission and acquisition;

[0108] The junction box connects to the digital I / O board for line protection and connection, and establishes data connection between the digital I / O board and the laser sensing module, stepper path module and excitation module.

[0109] Computers are used for system control, writing functional programs, and data storage, processing, and analysis.

[0110] The excitation module includes a power amplifier and a piezoelectric fiber sheet;

[0111] The piezoelectric fiber sheet is bonded to the structure under test, and the power amplifier is electrically connected to the piezoelectric fiber sheet; the power amplifier is also electrically connected to the junction box, and receives the excitation signal from the junction box, amplifies it, and outputs it to the piezoelectric fiber sheet.

[0112] The piezoelectric fiber sheet is connected to the power amplifier and bonded to the structure under test. It converts the input excitation signal into mechanical vibration excitation of the corresponding frequency, driving the structure under test to vibrate.

[0113] The stepper path module includes a motor controller, a two-axis ball screw slide, and a DC power supply;

[0114] The two-axis ball screw slide is used to support the laser sensing module for two-dimensional spatial stepping motion.

[0115] The motor controller is connected to the two-axis ball screw slide for two-dimensional spatial motion control;

[0116] The DC power supply is connected to the two-axis ball screw slide and the motor controller respectively to provide DC power.

[0117] More specifically, the two-axis ball screw slide includes a vertical ball screw slide and a horizontal ball screw slide that are connected to each other;

[0118] In one embodiment, the laser sensing module is fixed on a vertical ball screw slide, and the horizontal ball screw slide enables the horizontal movement of the vertical ball screw slide, thereby enabling the horizontal movement of the laser sensing module; the vertical ball screw slide enables the vertical movement of the laser sensing module.

[0119] In another scheme, the laser sensing module is fixed on a horizontal ball screw slide, and a vertical ball screw slide realizes the vertical movement of the horizontal ball screw slide, thereby realizing the vertical movement of the laser sensing module; the horizontal ball screw slide realizes the horizontal movement of the laser sensing module.

[0120] Both schemes have motion planes parallel to the structure under test, ensuring that when the laser displacement sensor in the laser sensing module measures at any stationary point, the laser beam can be perpendicularly directed to the corresponding measured point, and the energy of the light spot is uniform.

[0121] The laser sensing module includes a laser displacement sensor and a sensor adapter; the laser displacement sensor is fixed on the sensor adapter; the sensor adapter is fixed on the vertical ball screw slide or the horizontal ball screw slide of the stepping path module.

[0122] When implementing the method of Embodiment 1 using the system of this embodiment, a test task program is written in the computer.

[0123] The test task program records the relative coordinates and serial numbers of the test points set on the test surface of the structure under test;

[0124] The test points uniformly and fully cover the test surface of the structure under test, and the number and location are given in advance by the measurement requirements.

[0125] In the test task program, the two-dimensional spatial motion path of the stepping path module is set; the number and position of the test points set on the test surface of the structure under test are given in advance by the measurement requirements, and are generally set to uniformly and fully cover the test surface of the structure under test; a series of stopping points are determined in the two-dimensional space; the stopping points are the projections of the test points in the two-dimensional space.

[0126] The defined motion path allows the laser displacement sensor to traverse each stopping point in a single pass, remaining stationary at each point for a fixed duration. Furthermore, the motion path is closed, meaning the initial and final points coincide. After each pass of the motion path, the laser displacement sensor returns to the starting point to prepare for the next pass along the path. The motion path is compiled into an instruction stream and uploaded to the motor controller.

[0127] In the test procedure, the excitation signal required to drive the piezoelectric fiber sheet during vibration by the excitation module is set. The excitation signal is a stepped frequency sweep signal, with the signal frequency increasing or decreasing by a fixed value at fixed time intervals, while the signal amplitude remains constant. The selection of the fixed value should ensure that the generated signal frequency points are evenly and densely distributed within the measurement frequency band. The measurement frequency band should cover the frequency range of interest for the structural vibration response, which may contain several natural frequencies.

[0128] The frequency sweep period of the excitation signal is greater than the time required for the laser displacement sensor to complete one full-field vibration response measurement along the motion path. Whenever the excitation signal frequency changes, the digital I / O board synchronously outputs a trigger signal, which is sent to the motor controller via the junction box. Upon receiving the trigger signal, the motor controller executes the motion path command stream once, causing the horizontal and vertical ball screw slides to move along the set two-dimensional spatial path. No time error accumulates between the excitation module and the stepping path module.

[0129] In this embodiment, the pre-set excitation signal is output to the excitation module via a digital I / O board. The signal is then sent to a power amplifier via a junction box. The power amplifier amplifies the signal power and sends it to the piezoelectric fiber sheet. The piezoelectric fiber sheet is approximately 300 μm thick, small in size, lightweight, and has low intrusion, without altering the dynamic performance of the structure under test. The piezoelectric fiber sheet converts the electrical signal into mechanical vibration, exciting the structure under test. The piezoelectric fiber sheet can still operate stably at high frequencies, and has a wide excitation frequency range.

[0130] In the test task program, the information acquisition and storage of the laser sensing module are set. The vibration signals collected by the laser sensing module at each stopping point are acquired by the digital I / O board through the junction box and stored in the computer's memory.

[0131] Post-processing of vibration signals acquired in a computer includes:

[0132] 1) The time series of vibration signals collected by the laser displacement sensor at each excitation frequency are stored;

[0133] 2) A filter based on wavelet transform analysis is used to perform frequency domain decomposition and time domain reconstruction of the vibration signal time series to obtain the reconstructed vibration signal time series;

[0134] In the frequency domain decomposition of wavelet transform, the coefficients of each level of DWT (Discrete Wavelet Transform) are corrected, each excitation frequency term is retained, and other frequency terms are attenuated. After reconstruction by IDWT (Inverse Discrete Wavelet Transform), the reconstructed vibration signal time series with each excitation frequency term is obtained.

[0135] 3) Divide the reconstructed vibration signal time series into blocks according to each excitation frequency. The signal time series of each block is the reconstructed vibration signal time series at one excitation frequency.

[0136] 4) For each block of the signal time series, according to the sequence number of the test point corresponding to each stopping point recorded when setting the motion path, and according to the relative coordinates and sequence number of the test point on the test surface recorded when setting the test point, the coordinates on the test surface are assigned to each signal in the signal time series; a three-dimensional map of vibration signal distribution is formed with the test surface as the plane coordinate and the reconstructed vibration signal amplitude as the vertical coordinate, and each excitation frequency corresponds to a three-dimensional map of vibration signal distribution;

[0137] The distribution and magnitude of vibration amplitude in the three-dimensional vibration signal distribution diagram provide a direct visual representation of the mechanical dynamic characteristics of the tested structure at different excitation frequencies, including the response mode and amplitude.

[0138] Other technical details and beneficial effects of this embodiment are the same as those disclosed in Embodiment 1. Please refer to them for details, and they will not be repeated here.

[0139] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A full-field vibration testing method based on single-point laser scanning, characterized in that, The method comprises the following steps: S1, a set of measured points are arranged on a test surface of a measured structure; a set of stationary points of laser displacement sensors corresponding to the measured points are determined in a two-dimensional space parallel to the test surface; the positions and densities of the measured points are arranged according to a highest frequency point in a wide measurement frequency range; S2, a motion path traversing the stationary points is arranged; the laser displacement sensors at each stationary point on the motion path can irradiate the corresponding measured point in a perpendicular manner; when the motion path is planned, the wide measurement frequency range is segmented into frequency bands, and a corresponding motion path is arranged for each frequency band; the initial point and the terminal point of each motion path coincide, and the path is closed; the motion path of the frequency band with the highest frequency traverses all the measured points with the shortest path as the target; as the frequency of the frequency band decreases, the measured points on the motion path of the frequency band with the highest frequency are sampled at equal intervals, and the measured points on the path are gradually thinned out; the lower the frequency of the frequency band, the lower the density of the measured points on the corresponding path; the initial point and the terminal point of each motion path remain unchanged during the thinning process; the serial numbers of each measured point in each motion path are recorded; a stationary fixed time length is arranged at each stationary point; the moving time of the laser displacement sensors between the test points on the path is much smaller than the stationary time at the stationary points; as the frequency of the frequency band decreases, the traversal time length of the laser displacement sensors on each path decreases at an equal interval; the traversal time length of each motion path is recorded; S3, the vibration excitation cycle of each frequency band is arranged according to the traversal time length of each motion path; the vibration excitation frequency is generated from the highest or lowest frequency point, the measured structure is vibrated and excited at the corresponding vibration excitation cycle, and the laser displacement sensors are triggered synchronously; in each vibration excitation cycle, the laser displacement sensors collect the vibration signals of the measured structure at the positions of the corresponding measured points on each stationary point according to the corresponding motion path through walking and stopping; S4, the mechanical dynamic characteristics of the measured structure at each vibration excitation frequency, including the response mode and the amplitude, are determined according to the full-field vibration response obtained by analyzing the vibration signals collected at each vibration excitation frequency.

2. The full-field vibration test method based on single-point laser scanning according to claim 1, wherein the measured points arranged on the test surface of the measured structure uniformly and sufficiently cover the test surface, and the relative coordinates and serial numbers of the measured points on the test surface are recorded; the stationary points arranged on the two-dimensional space parallel to the test surface correspond to the measured points one by one, and are the projections of the measured points in the two-dimensional space; the laser displacement sensors always keep perpendicular to the test surface when measuring at each stationary point, the laser is normally incident, and the spot energy is uniform; the motion path is arranged so that the laser displacement sensors can traverse each stationary point at a time, and the stationary fixed time length is arranged at each stationary point; the initial point and the terminal point of the motion path coincide, and the path is closed; the serial numbers of the corresponding measured points of each stationary point traversed in the motion path are recorded.

3. The full-field vibration test method based on single-point laser scanning according to claim 2, wherein ​ The two-axis ball screw slide table is used to determine the two-dimensional space parallel to the test surface, the single-point laser sensor is fixed on the two-axis ball screw slide table, the two-axis ball screw slide table is controlled by the stepping motor in a step-by-step manner to drive the laser displacement sensor in the two-dimensional space, the laser displacement sensor moves according to the set motion path, stops at each stop point, and the vibration measurement of the measured point is performed by using the static measurement method.

4. The full-field vibration test method based on single-point laser scanning according to any one of claims 1-3, characterized in that, The piezoelectric fiber sheet is installed on the measured structure to perform vibration excitation on the measured structure; a group of excitation signals with set frequencies are applied to the piezoelectric fiber sheet to make the piezoelectric fiber sheet excite the measured structure to vibrate at the set frequencies.

5. The full-field vibration test method based on single-point laser scanning according to claim 4, characterized in that, The step S4 comprises: 1) storing the vibration signal time series collected by the laser displacement sensor at each excitation frequency; 2) performing frequency domain decomposition and time domain reconstruction of the vibration signal time series by using a filter based on wavelet transform analysis to obtain the reconstructed vibration signal time series; In the frequency domain decomposition of the wavelet transform, the DWT coefficients at each level are modified to retain the excitation frequency terms and attenuate other frequency terms, and the reconstructed vibration signal time series retaining the excitation frequency terms are obtained after IDWT reconstruction; 3) dividing the reconstructed vibration signal time series according to the excitation frequencies, and the signal time series of each block is the reconstructed vibration signal time series at one excitation frequency; 4) for the signal time series of each block, the serial numbers of the measured points corresponding to each stop point are recorded according to the motion path setting, the relative coordinates of the measured points on the test surface and the serial numbers are recorded according to the setting of the measured points, the coordinates of the signal time series on the test surface are allocated, and the vibration signal distribution three-dimensional graph with the test surface as the plane coordinates and the reconstructed vibration signal amplitude as the vertical coordinates is formed, and each excitation frequency corresponds to one vibration signal distribution three-dimensional graph; The mechanical dynamic characteristics of the measured structure corresponding to different excitation frequencies, including the response mode and the amplitude, are obtained from the distribution and amplitude of the vibration signal in the vibration signal distribution three-dimensional graph.

6. A full-field vibration testing system implementing the full-field vibration testing method based on single-point laser scanning according to any one of claims 1-5, characterized in that, It comprises: a laser sensing module, a stepping path module, an excitation module, and a data acquisition and control processing module; the laser sensing module is fixedly connected with the stepping path module, the excitation module is fixedly connected with the measured structure, and the data acquisition and control processing module is electrically connected with the laser sensing module, the stepping path module, and the excitation module; the excitation module is used to excite the measured structure to vibrate at the set excitation frequencies under the control of the data acquisition and control processing module; the stepping path module is arranged on the opposite side of the test surface of the measured structure, and is used to drive the laser sensing module to move according to the set motion path and stop at each stop point under the control of the data acquisition and control processing module; the laser sensing module is used to collect the vibration signals of the measured points on the test surface at each stop point under the control of the data acquisition and control processing module. The data acquisition and control processing module is configured to control the operation of the vibration excitation module, the stepping path module and the laser sensing module, receive the vibration signals collected by the laser sensing module at different vibration frequencies, and perform signal analysis and dynamic mechanical property analysis through signal post-processing.

7. The full-field vibration testing system according to claim 6, wherein, The stepping path module comprises a motor controller, a two-axis ball screw sliding table and a direct current power supply. The two-axis ball screw sliding table is configured to carry the laser sensing module to perform two-dimensional space stepping motion. The motor controller is connected with the two-axis ball screw sliding table and is configured to control two-dimensional space motion. The direct current power supply is connected with the two-axis ball screw sliding table and the motor controller respectively and is configured to supply direct current power. The two-axis ball screw sliding table comprises a vertical ball screw sliding table and a horizontal ball screw sliding table which are connected with each other. The laser sensing module is fixed on the vertical ball screw sliding table or the horizontal ball screw sliding table.

8. The full-field vibration testing system according to claim 7, wherein, The vibration excitation module comprises a power amplifier and a piezoelectric fiber sheet. The piezoelectric fiber sheet is bonded to the measured structure, and the power amplifier is electrically connected with the piezoelectric fiber sheet. The power amplifier is further electrically connected with a junction box, receives the vibration excitation signals from the junction box, amplifies the vibration excitation signals and outputs the amplified vibration excitation signals to the piezoelectric fiber sheet. The piezoelectric fiber sheet is connected with the power amplifier, is bonded to the measured structure, converts the input vibration excitation signals into mechanical vibration excitation signals of corresponding frequencies, and drives the measured structure to vibrate.

9. The full-field vibration testing system according to claim 7, wherein, The data acquisition and control processing module comprises a computer, a digital I / O board and a junction box. The digital I / O board is mounted on the computer and is configured to send and collect signals. The junction box is connected with the digital I / O board, is configured to protect and connect lines, and establishes data connection between the digital I / O board and the laser sensing module, the stepping path module and the vibration excitation module. The computer is configured to perform total control of the system, write function programs, and store and process data.

Images