A method for measuring the energy absorption capacity of a self-limiting system

Abstract

The present invention discloses a method for measuring the energy absorption capacity of a self-limiting system, which relates to the field of structural health monitoring and energy harvesting technology. The method comprises: building a test platform and arranging a signal acquisition system to collect and process data. Modal analysis is performed on the structure to be tested, and the results obtained by data processing are subjected to Fourier transform to select the excited mode. The modal velocity response is calculated according to the excited mode. Finally, the modal energy absorption rate of the system is calculated according to the proposed definition formula of the modal energy absorption rate. This method can measure the energy absorption capacity of nonlinear energy absorption systems such as self-limiting systems by simply converting the time domain data, and takes into account the dynamic response characteristics of the system. It has the characteristics of universality, low cost, and high calculation and evaluation efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of structural health monitoring and energy harvesting, and in particular to a method for measuring the energy absorption capacity of a self-limiting system. Background Art

[0002] The evaluation index and method of energy absorption capacity is one of the key parameters in engineering structure design and performance evaluation, which can intuitively reflect the basic performance and status of the structure.

[0003] Existing indicators for measuring the energy absorption capacity of self-limiting systems include energy absorption rate, maximum energy absorption capacity, energy absorption assessment based on frequency domain response, energy absorption assessment based on power flow, simulation methods based on finite element analysis, and empirical methods based on experimental testing. However, these indicators or methods have many problems and are subject to many limitations in practical engineering applications:

[0004] 1. Energy absorption rate:

[0005] The energy absorption rate is calculated by measuring the energy absorbed by the system compared to the energy input.

[0006] Disadvantages: It is difficult to measure the absorption and input energy of the system in actual engineering, and the dynamic distribution of energy and system response characteristics are not considered. It is only applicable to steady-state conditions and cannot reflect the nonlinear characteristics of the system.

[0007] 2. Maximum absorption capacity:

[0008] The maximum energy a test system can absorb under extreme conditions is a measure of its peak performance.

[0009] Disadvantages: Only applicable to test results under extreme conditions, the testing process is complicated and costly.

[0010] 3. Energy absorption evaluation based on frequency response:

[0011] The main purpose is to analyze the energy absorption characteristics of the system at different frequencies and evaluate its performance.

[0012] Disadvantages: Only applicable to linear systems, with high requirements on test equipment and data processing.

[0013] 4. Energy absorption assessment based on power flow:

[0014] Measure the system's output and input power and calculate its energy absorption capacity.

[0015] Disadvantages: It does not take into account the internal energy loss and distribution characteristics of the system, and has limited ability to evaluate transient responses.

[0016] 5. Simulation method based on finite element analysis:

[0017] Finite element simulation is used to simulate the energy absorption process of the system and evaluate its performance.

[0018] Disadvantages: The finite element simulation results may deviate from the actual situation, which depends on the accuracy of the model. The calculation cost is high and the time consumption is long.

[0019] 6. Empirical method based on experimental testing:

[0020] By measuring the input power and output power of the system, the energy absorption capacity is calculated.

[0021] Disadvantages: lack of universality, only applicable under specific conditions, high experimental cost, and difficult to promote.

[0022] Based on the above technical background, the present invention proposes an indicator and method for measuring the energy absorption capacity of a self-limiting system. Summary of the Invention

[0023] The present invention aims to provide a method for measuring the energy absorption capacity of a self-limiting system, so as to solve the problem of insufficient dynamic characteristic evaluation of traditional civil or mechanical structure indicators for measuring the energy absorption capacity of a self-limiting system, especially the problems of poor universality, neglect of dynamic characteristics, insufficient evaluation of nonlinear systems, high simulation and experimental costs, and insufficient accuracy of existing indicators for measuring the energy absorption capacity of a self-limiting system.

[0024] To achieve the above object, the present invention provides the following technical solutions:

[0025] A method for measuring the energy absorption capability of a self-limiting system, comprising:

[0026] Step 1: Build a test platform;

[0027] Build a scaled model of a bridge cable with fixed ends, later referred to as a cable structure. Install an accelerometer in the middle of the cable structure and connect the NI data acquisition instrument to the accelerometer.

[0028] Step 2: Data collection;

[0029] A blower was used to apply a fixed wind speed wind load to the cable structure, making the cable structure a test object for studying the self-limiting system. NI data acquisition was also used for data acquisition.

[0030] Step 3: Acquisition of time domain velocity signal;

[0031] Perform noise reduction on the collected signal and convert it from acceleration signal to time domain velocity signal;

[0032] Step 4: Modal analysis;

[0033] Perform modal analysis on the structure to be tested to obtain the modal vibration shape of the structure and the corresponding modal frequencies ;

[0034] Step 5: Fourier transform;

[0035] Perform Fourier transform on the velocity time history data obtained in step 3 and select the excited mode;

[0036] Step 6: Calculate modal velocity response;

[0037] Select the mode excited in step 5, project the velocity response in the physical space into the modal space, and obtain the modal velocity response time history data on the mode excited in step 5;

[0038] Step 7: Calculate the modal energy absorption ratio (EAR).

[0039] According to our definition formula of energy absorption rate, the energy absorption rate of each mode is calculated using the modal velocity time history response calculated in step 6.

[0040] Furthermore, the collected acceleration signal is subjected to noise reduction processing, and the specific method is as follows:

[0041] Use the function in the Matlab signal processing toolbox to design a bandpass filter, input the acceleration time history data recorded in step 2 into the designed filter for filtering and removing environmental noise.

[0042] Furthermore, the collected acceleration signal is converted into a time domain velocity signal. The specific method is as follows:

[0043] Using the formula represents the time domain velocity signal, where is the initial velocity, t represents the time point, Indicates the value of the acceleration signal collected at time t, is the sampling time interval.

[0044] Furthermore, modal analysis is performed on the structure to be tested. The specific method is as follows:

[0045] Establish a finite element model of the cable structure, determine its boundary constraints based on the actual installation and support conditions of the cable, use the modal analysis module in the finite element software to solve the eigenvalues ​​of the structure, and obtain the modal vibration shape of the cable structure and modal frequencies .

[0046] Furthermore, the modal velocity response is calculated as follows:

[0047] Using the formula represents the modal velocity response, where t represents time, represents the speed at time t, represents the mode shape.

[0048] Furthermore, the modal energy absorption rate (EAR) is calculated as follows:

[0049] For a certain order modal velocity response, the entire velocity response data sequence is traversed to find the local velocity response maximum value (the length of the local time period is determined according to the characteristics of the data and actual needs) to form a sequence containing the maximum value and its corresponding time point. For the maximum value-time series obtained, a spline curve is used to fit the maximum envelope of each order modal velocity response. .

[0050] Using the formula Calculate the normalized energy, where represents the modal velocity response at time t;

[0051] Using the formula Calculate the energy increment, where It indicates the time required for the system to reach a stable state from the start of vibration;

[0052] Using the formula Calculate the total energy absorbed;

[0053] Using the formula Calculate the energy absorption rate of each mode.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The present invention overcomes the problem of neglecting the dynamic characteristics of the traditional indicators for measuring the energy absorption capacity of the self-limiting system, fully utilizes the dynamic characteristics of the system, and can accurately reflect the actual performance of the system;

[0056] 2. The energy absorption rate calculation method proposed in this invention is applicable to systems with geometric nonlinearity or other types of nonlinearity. It overcomes the shortcomings of traditional indicators in evaluating nonlinear systems and accurately measures the energy absorption capacity of complex systems.

[0057] 3. The calculation process of the method proposed in the present invention does not involve repeated correlation calculations, but only involves linear transformation and simple calculus and integration, etc., and has high calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0059] Figure 1 The present invention is a flow chart of a method for measuring the energy absorption capacity of a self-limiting system. DETAILED DESCRIPTION

[0060] For example, see Figure 1 As shown, a method for measuring the energy absorption capacity of a self-limiting system in this embodiment has the following process:

[0061] Step 1: Build a test platform.

[0062] Set up the test object: Build a scaled model of a bridge cable with fixed ends. For different models, the scaled model has different ratios. In this embodiment, the scale of the scaled model is 1:50. The excitation method is blowing by a blower, and the excitation signal is wind load excitation with a fixed wind speed. The combination of the cable structure and the fixed external excitation can make the cable structure a test object for studying the self-limiting system.

[0063] Data acquisition system layout: An accelerometer is installed in the middle of the cable, and the NI data acquisition instrument is connected to the accelerometer.

[0064] Step 2: Data collection.

[0065] Turn on the blower and apply a fixed wind speed wind load excitation to the structure under test. Use the NI data acquisition instrument to record the acceleration time history data, observe the change in signal amplitude, and stop recording after the system reaches a self-limiting stable state.

[0066] Step 3: Acquire time domain velocity signal.

[0067] Filtering: Use the function in the Matlab signal processing toolbox to design a bandpass filter. Input the acceleration time history data recorded in step 2 into the designed filter for filtering to remove environmental noise.

[0068] Velocity signal conversion: According to the trapezoidal rule, the collected acceleration vibration signal is expressed as ,in , n is the number of sampling points, and the calculation formula of the time domain velocity signal is:

[0069] ;

[0070] in, is the initial velocity, is the sampling time interval.

[0071] Step 4: Modal analysis.

[0072] Establish a finite element model of the cable structure, determine its boundary constraints based on the actual installation and support conditions of the cable, use the modal analysis module in the finite element software to solve the eigenvalues ​​of the structure, and obtain the modal vibration shape of the cable structure and modal frequencies .

[0073] Step 5: Fourier transform.

[0074] Perform Fourier transform on the time domain velocity signal obtained in step 3 and select the excited mode of the structure.

[0075] Step 6: Calculate the modal velocity response.

[0076] Select the mode excited in step 5, project the velocity response in the physical space into the modal space, and calculate the specific formula for the velocity response of a certain modal as follows:

[0077] ;

[0078] Step 7: Calculate the modal energy absorption rate.

[0079] The calculation method of each modal energy absorption rate is as follows: for a certain modal velocity response, traverse the entire velocity response data sequence, find the local velocity response maximum value (the length of the local time period is determined according to the characteristics of the data and actual needs), and form a sequence containing the maximum value and its corresponding time point. For the obtained maximum value-time series, use spline curve fitting to obtain the maximum envelope of each modal velocity response. , the corresponding normalized energy calculation formula is:

[0080] ;

[0081] Furthermore, the energy increment is calculated as follows:

[0082] ;

[0083] in, It indicates the time required for the system to reach a stable state from the start of vibration.

[0084] Furthermore, the total energy absorbed is calculated as:

[0085] ;

[0086] Furthermore, the energy absorption rate calculation formula for each mode is:

[0087] ;

[0088] Through the detailed introduction and comparative analysis of this embodiment, the present invention's indicator and method for measuring the energy absorption capacity of a self-limiting system requires only time-domain response data, fully utilizing the system's dynamic characteristics to accurately reflect the system's actual performance. This method is particularly suitable for scenarios where the system exhibits geometric nonlinearity or other types of nonlinearity. This method avoids repeated correlation calculations and relies solely on linear transformations and simple calculus, improving the efficiency of calculating and evaluating the system's energy absorption capacity.

[0089] The above formulas are all dimensionless and numerically calculated, and the preset parameters in the formulas are set by technicians in this field according to actual conditions.

[0090] The above embodiments can be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer program are loaded or executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center via wired or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more available media sets. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state drive.

[0091] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0092] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0093] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0094] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0095] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0096] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for measuring the energy absorption capacity of a self-limiting system, characterized in that: include: Step 1: Build a test platform; Build a scale model of the self-limiting system, hereinafter referred to as the self-limiting system, install sensors on the self-limiting system, and connect the data acquisition instrument to the sensors; Step 2: Data collection; Apply external excitation to the self-limiting system and collect data with a data acquisition instrument; Step 3: Acquisition of time domain velocity signal; Perform noise reduction on the signal collected by the data acquisition instrument and convert it into a time domain velocity signal; Step 4: Modal analysis; Perform modal analysis on the self-limiting system to obtain the modal vibration shape of the structure and the corresponding modal frequencies ; Step 5: Fourier transform; Perform Fourier transform on the time domain velocity signal obtained in step 3 and select the excited mode; Step 6: Calculate modal velocity response; For the excited mode selected in step 5, project the velocity response in the physical space into the modal space to obtain the modal velocity response time history data on the excited mode; Step 7: Calculate the modal energy absorption rate; Using the modal velocity time history response calculated in step 6, calculate the energy absorption rate of each mode; the specific calculation method includes: For a certain order modal velocity response, the entire velocity response data sequence is traversed to find the local velocity response maximum value, forming a sequence containing the maximum value and its corresponding time point; for the maximum value-time series formed, a spline curve is used to fit the maximum envelope of the modal velocity response of this order. ; Using the formula , calculate the normalized energy, where Represents the modal velocity response at time t; using the formula , calculate the energy increment, where It indicates the time required for the system to reach a stable state from the start of vibration; Using the formula , calculate the total energy absorbed; using the formula , calculate the energy absorption rate of each mode.

2. A method for measuring the energy absorption capacity of a self-limiting system according to claim 1, characterized in that: The specific method for obtaining time domain velocity signals is: Use the function in the Matlab signal processing toolbox to design a bandpass digital filter, and input the data collected in step 2 into the bandpass digital filter for filtering; use the formula , represents the time domain velocity signal, where is the initial velocity, t represents the time point, Indicates the acceleration signal value collected at time t, is the sampling time interval.

3. A method for measuring the energy absorption capacity of a self-limiting system according to claim 1, characterized in that: Perform modal analysis on the structure to be tested. The specific method is as follows: A finite element model of the self-limiting system is established. According to the actual installation and support conditions of the self-limiting system, its boundary constraints are determined. The modal analysis module in the finite element software is used to solve the eigenvalues ​​of the structure and obtain the modal vibration shape and modal frequency of the self-limiting system.

4. A method for measuring the energy absorption capacity of a self-limiting system according to claim 1, characterized in that: The calculation methods of modal velocity response include: Perform Fourier transform on the time domain velocity signal and select the excitation mode; project the velocity response in the physical space into the modal space and use the formula , calculate the velocity response of a certain modal, where t represents time, represents the speed at time t, represents the mode shape.

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