A calibration device and calibration correction method for a vibration modal testing system

Abstract

This invention discloses an overall calibration device and calibration correction method for a vibration modal testing system, belonging to the technical field of vibration metrology and testing equipment. The invention includes a fixed clamping mechanism, a standard modal component, a standard force sensor mounting structure, a push rod, an exciter, an exciter control system, a laser scanning measurement system, a signal acquisition system, and a modal characteristic analysis system. This invention accurately measures the multi-order modal characteristics of the standard modal component; by analyzing factors such as the mass introduced during the calibration process of installing the standard modal component, the additional mass of the exciter, the additional mass of the force sensor mounting structure, and the additional stiffness of the force sensor mounting structure, the relationship between the modal results and the additional mass is established, and the additional mass is further determined as M based on this relationship. x Correction parameter K for different orders of time i This solves the problem of the added mass of the force sensor mounting structure that has always existed in vibration modal measurement systems, making the modal calibration results more accurate.

Description

Technical Field

[0001] This invention relates to an overall calibration device and calibration correction method for a vibration modal testing system, belonging to the technical field of vibration metrology and testing equipment. Background Technology

[0002] Vibration modes are the inherent vibration characteristics of a structural system. Each mode has a specific natural frequency, mode shape, and damping ratio. Vibration modes are inherent and holistic characteristics of elastic structures. If the characteristics of each major mode of a structure within a certain susceptible frequency range can be understood through modal analysis, the actual vibration response of the structure under various external or internal vibration sources within this frequency band can be predicted. Therefore, modal analysis of structures is an important method for structural dynamic design and equipment fault diagnosis.

[0003] For vibration modal measurement, exciters or hammers are commonly used as excitation devices to provide sinusoidal or pulse excitation. Modal measurement methods have evolved from the earliest accelerometer measurements to the widespread use of laser vibrometers or laser displacement sensors. Vibration modal measurement and analysis have increasingly wide applications in aerospace, automotive manufacturing, civil engineering, and bridge construction. Despite the crucial role of vibration modal testing in practical engineering applications, its metrological calibration has not been completely resolved, and laboratory calibration remains the primary method. Currently, vibration modal testing systems (exciter-excited) are mainly calibrated unit by unit. Each instrument unit on the measurement channel is calibrated according to its own metrological procedures, and the accuracy of the system performance parameters on the measurement channel is obtained by combining the results. This calibration method cannot account for the systematic errors caused by the installation structure between the instrument units, mainly including the effects of added mass and added stiffness. Summary of the Invention

[0004] To address the problem of inaccurately assessing the impact of the added mass of the force sensor mounting structure on calibration results during modal calibration, one of the main objectives of this invention is to provide a comprehensive calibration device and calibration correction method for a vibration modal testing system. This method employs standard modal components for calibration, accurately measuring their multi-mode characteristics. By analyzing factors such as the mass introduced during the calibration process, the added mass of the exciter, the added mass of the force sensor mounting structure, and the added stiffness of the force sensor mounting structure, the relationship between modal results and added mass is established. Based on this relationship, a comprehensive calibration correction method for the dynamic modal testing system is constructed, further determining the added mass as M. x Correction parameter K for different orders of time i This solves the problem of the added mass of the force sensor mounting structure that has always existed in vibration modal measurement systems, making the modal calibration results more accurate.

[0005] This invention is achieved through the following technical solution.

[0006] The present invention discloses an overall calibration device for a vibration modal testing system, comprising a fixed clamping mechanism, a standard modal component, a standard force sensor mounting structure, a push rod, a vibrator, a vibrator control system, a laser scanning measurement system, a signal acquisition system, and a modal characteristic analysis system.

[0007] The fixed clamping mechanism and the standard modal component constitute the standard modal component structure.

[0008] The fixed clamping mechanism is used to fix standard modal components.

[0009] The standard force sensor mounting structure, top rod, exciter, and exciter control system constitute a sinusoidal vibration excitation structure.

[0010] The scanning laser measurement system performs non-contact measurements of modal characteristic parameters such as modal frequencies and mode shapes of standard modal components under sinusoidal vibration excitation conditions.

[0011] The signal acquisition system and the modal characteristic analysis system constitute a data acquisition and analysis system. This system acquires and analyzes the excitation signal received by the standard modal component and the modal characteristic parameters measured by the scanning laser measurement system to obtain the standard modal component parameters. These parameters include the natural frequencies, mode shapes, and modal damping ratios.

[0012] After the standard modal component is fixed by a clamping mechanism, sinusoidal vibration excitation is applied to the standard modal component by an exciter. The mass of the outer mounting plate of the force sensor is changed, and the modal characteristic parameters of each order of the standard modal component are measured by a laser scanning measurement system. The modal characteristic parameters include natural frequency, mode shape, and damping ratio.

[0013] By varying the added mass of the sensor mounting structure, modal results of standard modal components with different added masses are measured. The relationship between the sensor's added mass and the modal analysis results is then fitted to accurately assess the impact of the added mass of the force sensor mounting structure on the test results. Based on this relationship, the added mass is further determined to be M. x Correction parameter K for different orders of time i Combined with the correction parameter K i The influence of the added mass of the force sensor mounting structure in the vibration modal measurement system is corrected, and the test results of the standard modal system are corrected and compensated, making the modal calibration results more accurate.

[0014] This invention discloses a method for calibrating and correcting a vibration modal testing system, implemented based on a comprehensive calibration device for the vibration modal testing system. The method for calibrating the vibration modal testing system includes the following steps:

[0015] Step 1: Adjust the controller of the vibrator to ensure that the excitation frequency f meets the requirements; adjust the power of the vibrator power amplifier to achieve the required amplitude; under the excitation of the vibrator, the standard modal component moves in a sinusoidal vibration mode, and the first n modal frequencies occur normally. Analyze the collected modal data of each order of the standard modal component in the frequency domain to identify the parameters, calculate the modal parameters, and obtain the modal parameters and mode shapes of each order of the standard modal component under fixed constraints; analyze and generate a standard component that meets the calibration requirements, record the main geometric parameters of the standard component, and then determine the geometric dimensions of the mounting end according to the installation requirements to form the standard component.

[0016] After the standard modal component is fixed, when the modal component rotates by θ, the dynamic equation is:

[0017]

[0018] Where I0 is the system's moment of inertia, K t1 The system stiffness introduced by the installation of the standard modal component is θ, where θ is the deflection angle of the standard modal component. This refers to the angular acceleration of the standard modal component.

[0019] The true intrinsic frequency:

[0020]

[0021] Where f 真实 These are the modal results calculated theoretically.

[0022] Step 2: Arrange the measurement points and excitation points for the modal standard component. The measurement points should avoid the neutral nodes of the vibration modes and be selected at points that easily excite multiple modes. These points should also be distinct to ensure a high signal-to-noise ratio in the acquired signals and avoid mode omission. Simultaneously, the excitation points should be selected at locations that facilitate the transfer of excitation energy to the standard modal component, and the stiffness of the selected excitation locations should be as high as possible. Measure the response at each measurement point using a scanning method, including displacement, velocity, and acceleration.

[0023] The actual measured moment of inertia of the entire system is:

[0024] I = I0 + ML 2 +M1L 2 (3)

[0025] Where M is the introduced mass of the exciter installation, L is the lever arm of the introduced mass of the exciter installation, and M1 is the additional mass of the sensor installation location.

[0026] The stiffness K of the entire system is:

[0027] K = K t1 +K t2+K t3 4

[0028] Where K t2 Additional stiffness introduced for force sensor mounting, K t3 Additional stiffness introduced for the exciter.

[0029] The natural frequencies of the modal testing system are:

[0030]

[0031] Where f 系统 The true value of the standard modal calibration system.

[0032] Step 3: Modify the sensor mounting structure, using the mass of the mounting base as a variable, and set M mass points to complete the measurement processes of Step 1 and Step 2. Measure the modal characteristic parameters of the standard modal component under different added mass conditions of the force sensor mounting structure; the modal characteristic parameters include the modal natural frequency, mode shape, and damping ratio. The different added mass conditions of the force sensor mounting structure include the mass introduced by the installation of the standard modal component, the added mass of the exciter, the added mass of the force sensor mounting structure, and the added stiffness of the force sensor mounting structure.

[0033] Step 4: By analyzing the mass introduced during the standard modal component installation, the added mass of the exciter, the added mass of the force sensor mounting structure, and the added stiffness of the force sensor mounting structure, the relationship between the modal results and the added mass is established. Based on this relationship, the added mass is further determined to be M. x Correction parameter K for different orders of time i Combined with the correction parameter K i The influence of the added mass of the force sensor mounting structure in the vibration modal measurement system is corrected to make the modal calibration results more accurate.

[0034] Within the strength requirements for normal load application, by changing the magnitude of the added mass of the force sensor mounting structure, the relationship between the added mass and the modal results of the standard modal component is obtained. The modal results and the added mass should satisfy the following:

[0035]

[0036] Where p i K represents the curve fitting coefficients. t1 The system stiffness introduced for the installation of standard modal components, K t2 Additional stiffness introduced for force sensor mounting, K t3 The additional stiffness introduced for the exciter, M x M is the added mass of the force sensor mounting structure, and f is the introduced mass of the exciter mounting. iThe result is the modal test result of the i-th order standard modal test system.

[0037] The influence of different added masses on the modal test results of the force sensor mounting structure was determined using the MAC modal verification method, and the added mass was further determined to be M. x Time correction parameter K i The corrected accurate calibration result f of the i-th order 标准 for:

[0038] f 标准 =K i f i (7)

[0039] Where K i To correct the parameter coefficients, f i f represents the modal measurement results of the i-th order standard modal calibration system. 标准 This is the corrected result for the i-th mode.

[0040] During the calibration process, the vibration modal testing system under calibration measures the standard modal component and compares the results with the overall calibration device of the vibration modal testing system. 标准 Complete the evaluation of the calibration results.

[0041] Beneficial effects:

[0042] 1. The present invention provides an overall calibration device and calibration correction method for a vibration modal testing system. It applies the same fixing and constraint methods to the same standard modal component and measures modal characteristic parameters such as modal natural frequency, mode shape, and damping ratio under different additional mass conditions of the force sensor mounting structure. The standard modal component can be designed with various shapes and sizes to adapt to the testing requirements of different vibration modal measurement systems. The method of transferring modal values ​​using the standard modal component enables the overall calibration of a modal measurement system based on exciter excitation.

[0043] 2. This invention provides an overall calibration device and calibration correction method for a vibration modal testing system. Using a standard modal component structure, a vibrator is used as the excitation method in a laboratory to excite multiple natural vibration modal characteristics in the standard modal component. Non-contact laser scanning measurement is used to accurately measure the modal characteristic parameters of each order of the standard modal component, such as natural frequencies, mode shapes, and modal damping ratios, to obtain the modal characteristics of each order of the standard modal component. By testing a standard modal component under fixed constraints, the influence of the force sensor fixing method on the modal test results is determined. By analyzing factors such as the mass introduced during the installation of the standard modal component, the added mass of the vibrator, the added mass of the force sensor mounting structure, and the added stiffness of the force sensor mounting structure during the calibration process, the relationship between the modal results and the added mass is established. Based on this relationship, an overall calibration correction method for the dynamic modal testing system is constructed, further determining the added mass as M. x Correction parameter K for different orders of time i This solves the problem of the added mass of the force sensor mounting structure that has always existed in vibration modal measurement systems, making the modal calibration results more accurate.

[0044] 3. The present invention provides an overall calibration device and calibration correction method for a vibration modal testing system. It uses the MAC modal verification method to determine the influence of different added masses on the modal test results of the force sensor mounting structure, and further determines the added mass as M. x Correction parameter K for vibration test results of different orders i This method addresses the issue of the impact of the added mass of the force sensor mounting structure on the test results during modal testing, which was not accurately considered.

[0045] 4. The vibration modal testing system overall calibration device and calibration correction method of the present invention arranges the measurement points to avoid the neutral node of the vibration mode, selects response points that are easy to excite multiple modes, and the different points are mutually exclusive, so as to ensure that the collected measurement point signals have a high signal-to-noise ratio and avoid mode omission. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of an overall calibration device for a vibration modal measurement system disclosed in this invention.

[0047] Among them: 1-fixed clamping mechanism, 2-standard modal component, 3-standard force sensor, 4-top rod, 5-exciter, 6-exciter control system, 7-laser scanning measurement system, 8-signal acquisition system, 9-modal characteristic analysis system.

[0048] Figure 2 This is the force sensor mounting structure used in this invention.

[0049] Wherein: 10-Mounting plate of force sensor, 11-Outer mounting plate of force sensor, 12-Connecting bolt, 13-Connecting rod, 14-Force sensor.

[0050] Figure 3 This is a schematic diagram illustrating the vibration characteristics of the standard modal component used in this invention.

[0051] Where: K t1 The standard modal component is installed with stiffness.

[0052] Figure 4 This is a schematic diagram illustrating the principle of the modal testing system used in this invention for measuring the vibration characteristics of a standard modal component.

[0053] Where: K t1 For the standard modal component mounting stiffness, K t2 K is the additional stiffness of the connection between the connecting rod and the standard modal component. t3 M is the spring stiffness inside the exciter, and M is the total additional mass of the moving coil of the exciter and the connecting rod of the exciter. x Add mass to the force sensor installation and structure. Detailed Implementation

[0054] To better illustrate the purpose and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0055] Example 1:

[0056] like Figure 1 As shown in the figure, this example discloses an overall calibration device for a vibration modal testing system, including a fixed clamping mechanism 1, a standard modal component 2, a standard force sensor mounting structure 3, a push rod 4, an exciter 5, an exciter control system 6, a laser scanning measurement system 7, a signal acquisition system 8, and a modal characteristic analysis system 9. The fixed clamping mechanism 1 is used to fix the standard modal component 2; the standard force sensor structure 3 is mounted on the top of the push rod 4 near the top of the standard modal component 2; the push rod 4 and the exciter 5 constitute the sinusoidal vibration excitation mechanism of the standard modal component 2; the exciter control system 6 is used to drive the exciter 5 to generate sinusoidal vibration excitation; the laser scanning measurement system 7 performs non-contact measurement of the modal shapes of the standard modal component 2 after being subjected to sinusoidal vibration excitation or pulse excitation; the signal acquisition system 8 is used to acquire the output signals of the standard force sensor 3 and the laser scanning measurement system 7; and the modal characteristic analysis system 9 is used for data processing, analyzing the various signals acquired by the signal acquisition system 8 to obtain various modal parameters of the standard modal component 2 under sinusoidal vibration excitation, such as modal shapes, frequencies, and excitation forces.

[0057] The sinusoidal vibration excitation system is used to generate a sinusoidal excitation force with a certain energy and adjustable frequency. The amplitude and frequency of the sinusoidal excitation force can be continuously adjusted arbitrarily, and after adjustment, the amplitude and frequency can remain stable. The signal is transmitted to the modal characteristic analysis system for calculation and analysis through the signal acquisition system.

[0058] The clamping mechanism is used to fix the standard modal component. The signal acquisition system performs analog-to-digital conversion on the excitation and response signals after preamplification and amplification, and then stores them in digital form for signal analysis. The modal characteristic analysis system consists of a computer and modal analysis software, and its function is to calculate the transfer function of the test signal, and complete data analysis and modal fitting.

[0059] After the standard modal component is mounted using a fixture, additional mass and stiffness are introduced. The stiffness parameters in the dynamic equations of the standard modal component change due to the addition of additional mass and stiffness from the force sensor mounting section and the exciter itself. The modal parameter f of the standard modal component... 真实 and f 系统 The relationships between them satisfy the equations (2) and (5):

[0060] like Figure 2 As shown, by changing the mass of the inner mounting plate of the force sensor mounting structure, modal results of the standard modal component are collected when the added mass of the force sensor mounting structure is different. The modal results under different working conditions are fitted to obtain the relationship between the modal results and the added mass. The i-th order modal vector of the test mode is taken as {Φ 试验}, the theoretical mode vector is {Φ 理论 The theoretical modes are then verified according to the MAC criterion. The expression for MAC is:

[0061]

[0062] Where {Φ 试验} represents the modal vector matrix obtained from experimental analysis, {Φ 理论} is the theoretical mode vector matrix. For {Φ 试验 The transpose of} For {Φ 理论 The transpose of}.

[0063] Based on equations (1) and (2), it can be seen that there is an error between the theoretical and experimental values ​​of the standard modal component, and the MAC value is not equal to 1. Therefore, a correction parameter K is proposed. i After correction, MAC should be close to 1, provided that the uncertainty requirement is met.

[0064]

[0065] Where {K i} is the correction coefficient matrix, {K i Φ 试验} is the corrected mode vector matrix, (K i Φ 试验 ) T For {K i Φ 试验 The transpose of}.

[0066] Provided that the error requirements are met, the test results of the standard system can be used as standard data to carry out calibration work and guide the installation of standard modal components and modal systems to be calibrated.

[0067] Therefore, by comparing the modal parameters measured by the vibration modal testing system with the standard modal parameters measured in the laboratory, the overall calibration of the vibration modal testing system is completed.

[0068] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. The above description is only a specific embodiment of the present invention. The present invention should not be limited to the content disclosed in the embodiment and the accompanying drawings. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A calibration device for a vibration modal testing system, characterized in that: It includes a fixed clamping mechanism, standard modal components, standard force sensor mounting structure, push rod, exciter, exciter control system, laser scanning measurement system, signal acquisition system, and modal characteristic analysis system; The fixed clamping mechanism and the standard modal component constitute the standard modal component structure. The fixing and clamping mechanism is used to fix standard modal components; The standard force sensor mounting structure, top rod, exciter, and exciter control system constitute a sinusoidal vibration excitation structure. The laser scanning measurement system performs non-contact measurements of the modal frequencies and mode shapes of a standard modal component under sinusoidal vibration excitation conditions. The signal acquisition system and the modal characteristic analysis system constitute a data acquisition and analysis system. The system acquires and analyzes the excitation signal received by the standard modal component and the modal characteristic parameters measured by the laser scanning measurement system to obtain the standard modal component parameters. The standard modal component parameters include the natural frequencies, mode shapes, and modal damping ratios of each order. After the standard modal component is fixed by a clamping mechanism, sinusoidal vibration excitation is applied to the standard modal component by an exciter. The mass of the outer mounting plate of the force sensor is changed, and the modal characteristic parameters of each order of the standard modal component are measured by a laser scanning measurement system. The modal characteristic parameters of each order include natural frequency, mode shape and modal damping ratio. By varying the added mass of the sensor mounting structure, modal results of standard modal components with different added masses are measured. The relationship between the sensor's added mass and the modal analysis results is then fitted to accurately assess the impact of the added mass of the force sensor mounting structure on the test results. Based on this relationship, the added mass is further determined to be M. x Correction parameter K for different orders of time i Combined with the correction parameter K i The influence of the added mass of the force sensor mounting structure in the vibration modal measurement system is corrected, thereby correcting and compensating for the test results of the standard modal system and making the modal calibration results more accurate. The method for calibrating and correcting a vibration modal testing system based on the overall calibration device of the vibration modal testing system includes the following steps: Step 1: Adjust the controller of the vibrator to ensure that the excitation frequency f meets the requirements; adjust the power of the vibrator power amplifier to achieve the required amplitude; under the excitation of the vibrator, the standard modal component moves in a sinusoidal vibration mode, and the first n modal frequencies occur normally. Parameter identification is performed on the collected modal data of the standard modal component in the frequency domain, and modal parameter calculation is performed to obtain the modal parameters and mode shapes of the standard modal component under fixed constraints; analyze and generate a standard component that meets the calibration requirements, record the main geometric parameters of the standard component, and then determine the geometric dimensions of the mounting end according to the installation requirements to form the standard component; After the standard modal component is fixed, when the modal component rotates by θ, the dynamic equation is: Where I0 is the moment of inertia of the system, K t1 The system stiffness introduced by the installation of the standard modal component is θ, where θ is the deflection angle of the standard modal component. The angular acceleration of the standard modal component; The true intrinsic frequency: Where f 真实 These are the modal results calculated theoretically. Step 2: Arrange the measurement points and excitation points for the modal standard component. The measurement points should avoid the neutral nodes of the mode shapes and be selected to easily excite multiple modes. Furthermore, the different points should be distinct to ensure a high signal-to-noise ratio in the acquired measurement signals and avoid mode omission. Simultaneously, the excitation points should be selected at locations that facilitate the transfer of excitation energy from the standard modal component, and the stiffness of the selected excitation locations should be as large as possible. Measure the response of each measurement point using a scanning method, including displacement, velocity, and acceleration. The actual measured moment of inertia of the entire system is: I=I0+ML 2 +M1L 2 ⑶ Where M is the introduced mass of the exciter installation, L is the force arm of the introduced mass of the exciter installation, and M1 is the additional mass of the sensor installation location. The stiffness K of the entire system is: K=K t1 +K t2 +K t3 ⑷ Where K t2 Additional stiffness introduced for force sensor mounting, K t3 Additional stiffness introduced for the exciter; The natural frequencies of the modal testing system are: Where f 系统 The true value of the standard modal calibration system; Step 3: Modify the sensor mounting structure, using the mass of the mounting base as a variable, and set M mass points to complete the measurement process of Step 1 and Step 2. Measure the modal characteristic parameters of the standard modal component under different additional mass conditions of the force sensor mounting structure. The modal characteristic parameters include the modal natural frequency, mode shape, and modal damping ratio. The different additional mass conditions of the force sensor mounting structure include the mass introduced by the installation of the standard modal component, the additional mass of the exciter, the additional mass of the force sensor mounting structure, and the additional stiffness of the force sensor mounting structure. Step 4: By analyzing the mass introduced during the standard modal component installation, the added mass of the exciter, the added mass of the force sensor mounting structure, and the added stiffness of the force sensor mounting structure, the relationship between the modal results and the added mass is established. Based on this relationship, the added mass is further determined to be M. x Correction parameter K for different orders of time i Combined with the correction parameter K i The influence of the added mass of the force sensor mounting structure in the vibration modal measurement system is corrected to make the modal calibration results more accurate; Within the strength requirements for normal load application, by changing the magnitude of the added mass of the force sensor mounting structure, the relationship between the added mass and the modal results of the standard modal component is obtained. The modal results and the added mass should satisfy the following: Where p i K represents the curve fitting coefficients. t1 The system stiffness introduced for the installation of standard modal components, K t2 Additional stiffness introduced for force sensor mounting, K t3 The additional stiffness introduced for the exciter, M x M is the added mass of the force sensor mounting structure, and f is the introduced mass of the exciter mounting. i The modal test results are for the i-th order standard modal test system. The influence of different added masses on the modal test results of the force sensor mounting structure was determined using the MAC modal verification method, and the added mass was further determined to be M. x Time correction parameter K i The corrected accurate calibration result f of the i-th order 标准 for: f 标准 =K i f i ⑺ Where K i To correct the parameter coefficients, f i f represents the modal measurement results of the i-th order standard modal calibration system. 标准 This is the corrected i-th modal result; During the calibration process, the vibration modal testing system under calibration measures the standard modal component and compares the results with the overall calibration device of the vibration modal testing system. 标准 Complete the evaluation of the calibration results.

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