Multi-channel vibrating wire strain gauge low-voltage frequency sweep detection method

Abstract

The invention discloses a multi-channel vibrating wire strain gauge low-voltage sweep frequency detection method, belongs to the technical field of vibrating wire strain gauges, and aims to solve the problems of complex low-voltage sweep frequency control and poor stability and accuracy. According to the method, the frequency value obtained by last frequency sweeping is used as the initial value of current frequency sweeping, so that the frequency sweeping process can start searching from the position closer to the resonant frequency, the unnecessary frequency scanning range is reduced, meanwhile, the relation between the excitation frequency and the resonant frequency can be rapidly judged based on the dynamic adjustment strategy of the phase difference change rate, and the accuracy of frequency sweeping is improved. Compared with a traditional low-voltage frequency sweep method, the method has the advantages that the frequency sweep time is effectively shortened, the frequency sweep efficiency is improved, an accurate frequency measurement result can be obtained more quickly, and the method is suitable for popularization and application. And the validity of the frequency value is judged by adopting a method of taking an intermediate value through sorting and calculating the data stability percentage, so that the stability and the accuracy of a measurement result are further improved.

Description

Technical Field

[0001] The invention relates to the technical field of vibrating-wire strain gauges, and in particular to a low-voltage frequency sweeping detection method for a multi-channel vibrating-wire strain gauge. Background Art

[0002] As an important measuring element, vibrating-wire strain gauge plays a key role in many fields such as engineering construction and structural health monitoring. Its core principle is that the natural frequency of the steel string is linearly related to the strain. Therefore, by accurately detecting the natural frequency of the steel string, the strain of the steel string can be calculated according to the relevant formula. In practical applications, the steel string is firmly installed on structures such as pipelines and bridges with the help of end seats, so that the strain of these objects can be obtained synchronously in real time. This is of great significance for ensuring engineering safety and timely discovering potential structural risks.

[0003] In the field of steel string frequency detection, there are traditionally two main methods: high-voltage excitation and low-voltage frequency sweeping. The high-voltage excitation method applies an instantaneous high-voltage pulse to the coil to force the steel string to vibrate, and then reads the induced frequency signal from the coil. The advantage of this method is that the required software and hardware design is relatively simple, and only a single high-voltage pulse needs to be sent to make the steel string vibrate. However, its disadvantages are also very significant. On the one hand, not all steel strings can adapt to this high-voltage excitation method to complete the excitation, which makes this method have certain limitations in its scope of application. On the other hand, the amplitude of the high-voltage excitation signal is too high, which can easily cause damage to the coil, steel string or acquisition device, thereby greatly shortening the service life of the equipment, and inevitably increasing the maintenance cost of the equipment.

[0004] The low-voltage frequency sweeping method uses a low-voltage pulse signal to excite the steel string to make it resonate. Since only a low-voltage pulse signal close to the natural frequency of the steel string can induce resonance, it is necessary to continuously change the low-voltage pulses of different frequencies for excitation and judge the validity of the sensed signal. Although the low-voltage frequency sweeping method avoids some problems of high-voltage excitation to a certain extent, its low-voltage frequency sweeping control is complex, and its stability and accuracy are poor, which makes it difficult to implement. Summary of the invention

[0005] The object of the present invention is to provide a low-voltage frequency sweeping detection method for a multi-channel vibrating-wire strain gauge, which solves the problems in the background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a multi-channel vibrating wire strain gauge low-voltage sweep frequency detection method, comprising the following steps:

[0007] S1. Program initialization: Read the number of channels configured by the user from the storage unit FLASH and the initial value of the excitation signal If the program is not running for the first time, the initial value of the excitation signal The frequency value obtained from the last frequency sweep;

[0008] S2. Channel detection cycle: through the channel switch A vibrating wire strain gauge is connected to the excitation circuit and the acquisition circuit, where As the channel index, the initial value is 1, which is incremented after each cycle to read the resistance of the excitation coil of the vibrating wire strain gauge ,judge Is it established? and is the preset reasonable range of resistance. If it is not true, the channel detection is marked as failed and the channel frequency value is set to 0. If it is true, the adaptive excitation frequency adjustment and frequency sweep steps are performed;

[0009] S3. Adaptive excitation frequency adjustment and frequency sweep:

[0010] S31. Frequency adjustment based on phase difference, applying excitation signal to the excitation coil At the same time, another set of induction coils is used to measure the induced electromotive force generated by the vibration of the vibrating string. , using phase-locked loop technology to accurately measure The phase-locked loop technology compares the phase of the input signal and the feedback signal, continuously adjusts the frequency and phase of the voltage-controlled oscillator to lock the phase with the input signal, and thus accurately obtains the phase difference. ,in is the excitation signal amplitude, is the angular frequency, is the excitation frequency, is the amplitude of the induced electromotive force; calculate the rate of change of the phase difference , assuming that the excitation frequencies of two consecutive measurements are and , the corresponding phase difference is and , then the phase difference change rate is approximately , set the phase difference change rate threshold ,like , adjust the excitation frequency step , to quickly approach the resonant frequency, if , indicating that it is close to the resonance frequency, then , is the step size of the last adjustment, the initial step size At the same time, in order to reduce the influence of noise interference on the calculation of phase difference change rate, sliding average filtering is used to process the phase difference change rate. The sliding window size is set to Phase difference change rate after filtering , establish a historical database of phase difference-frequency relationship curves, and calculate the similarity between the current phase difference-frequency curve and the historical curve ,like , re-evaluate the frequency adjustment direction, where is the similarity threshold, The correlation coefficient method is used for calculation, and the formula is:

[0011] ;

[0012] in and are the average values ​​of historical frequency and phase difference, is the number of historical data groups;

[0013] S32. Excitation frequency setting: according to the adjusted frequency step , assuming the initial excitation frequency is , with the initial excitation frequency Based on this, a series of excitation frequency sequences are generated. ,in , used to excite the vibrating wire strain gauge during the frequency sweep process; Excitation and signal acquisition: For each excitation frequency , output amplitude is 8V low voltage excitation signal And keep it for 30ms to ensure that the vibrating string can produce stable vibration under this excitation, turn off the output switch, turn on the input switch, read the frequency of the induced signal through the capture circuit, and get a set of frequency sequence data , is the number of data points collected;

[0014] S4. Frequency data processing and judgment:

[0015] S41. Data preprocessing: removing frequency series data The first 10 and last 10 data of the sequence are used to reduce the impact of unstable factors that may exist in the starting and ending stages on the final result, and the remaining sequence is obtained. ;

[0016] S42. Intermediate value calculation: for the remaining sequence To sort, if If it is an even number, take the middle value ,like is an odd number, then ;

[0017] S43. Stationarity calculation: Calculate the difference between each value in the remaining sequence and the middle value , statistical difference exist arrive The number of data in the range , calculate the stationarity percentage ;

[0018] S44. Frequency value judgment and storage: If the stability percentage , then save the frequency value of this channel ,like , mark the channel frequency sweep failure, set ,Will stored in the storage location of the corresponding channel;

[0019] S5. Channel switching and end condition judgment: After completing the detection of a channel, the channel index Increment by 1, that is , prepare to test the next channel, if , then return to the channel detection loop step and continue to detect the next channel; if , indicating that all channels have been detected. At this time, the frequency values ​​of each channel collected this time are stored, except for those that failed to sweep, and these values ​​are used as the initial values ​​of the excitation frequency for the next sweep, ending the entire sweep process.

[0020] Furthermore, the excitation circuit and the acquisition circuit are shared by multiple channels, and the connection with different vibrating-wire strain gauges is achieved through a channel switch.

[0021] Furthermore, the frequency series data During the data collection process, the number of data points collected is determined according to the actual measurement needs and accuracy requirements.

[0022] Furthermore, the sliding window size of the sliding average filter is Adjust according to the measurement environment and vibrating wire strain gauge characteristics.

[0023] Furthermore, the phase difference change rate threshold and similarity threshold Set according to the specific model and application scenario of the vibrating wire strain gauge.

[0024] Furthermore, the initial excitation frequency During the first run, the frequency can be set according to the nominal frequency range and empirical value of the vibrating wire strain gauge; the excitation signal amplitude is 8V and is maintained for 30ms. The parameter setting is determined according to the excitation requirements and measurement stability of the vibrating wire strain gauge.

[0025] Furthermore, in the frequency value determination and storage step, the stability percentage Threshold It can be adjusted according to the measurement accuracy requirements and the stability of the vibrating wire strain gauge.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The invention provides a multi-channel vibrating wire strain gauge low-voltage sweep frequency detection method, which effectively avoids the damage to the coil, steel wire and acquisition device caused by high-voltage excitation by adopting a low-voltage sweep frequency mode and combining an adaptive excitation frequency adjustment strategy. In particular, in the frequency adjustment process based on phase difference, the excitation frequency can be accurately controlled according to the actual state of the vibrating wire, reducing the risk of equipment damage due to over-excitation, thereby significantly improving the reliability and service life of the equipment and reducing maintenance costs.

[0028] The present invention uses the frequency value obtained in the last frequency sweep as the initial value of this frequency sweep, so that the frequency sweep process can start searching from a position closer to the resonant frequency, reducing unnecessary frequency scanning ranges. At the same time, based on the dynamic adjustment strategy of the phase difference change rate, it is possible to quickly determine the relationship between the excitation frequency and the resonant frequency, and flexibly adjust the step size according to the situation, greatly accelerating the speed of approaching the resonant frequency. Compared with the traditional low-voltage frequency sweeping method, the present invention effectively reduces the frequency sweeping time, improves the frequency sweeping efficiency, and can more quickly obtain accurate frequency measurement results;

[0029] In addition, by removing 10 data before and after the frequency sequence data, the impact of unstable factors at the beginning and end stages on the results is reduced. The validity of the frequency value is judged by using the method of sorting and taking the middle value and calculating the data stability percentage, which further improves the stability and accuracy of the measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of the method of the present invention;

[0031] Figure 2 It is the hardware circuit diagram of the present invention. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In order to solve the technical problems of complex low-voltage sweep frequency control, poor stability and accuracy, such as Figure 1-Figure 2 As shown, the following preferred technical solutions are provided:

[0034] A multi-channel vibrating wire strain gauge low-voltage sweep frequency detection method comprises the following steps:

[0035] S1. Program initialization: Read the number of channels configured by the user from the storage unit FLASH and the initial value of the excitation signal If the program is not running for the first time, the initial value of the excitation signal The frequency value obtained from the last frequency sweep;

[0036] S2. Channel detection cycle: through the channel switch A vibrating wire strain gauge is connected to the excitation circuit and the acquisition circuit, where As the channel index, the initial value is 1, which is incremented after each cycle to read the resistance of the excitation coil of the vibrating wire strain gauge ,judge Is it established? and is the preset reasonable range of resistance. If it is not true, the channel detection is marked as failed and the channel frequency value is set to 0. If it is true, the adaptive excitation frequency adjustment and frequency sweep steps are performed;

[0037] S3. Adaptive excitation frequency adjustment and frequency sweep:

[0038] S31. Frequency adjustment based on phase difference, applying excitation signal to the excitation coil At the same time, another set of induction coils is used to measure the induced electromotive force generated by the vibration of the vibrating string. , using phase-locked loop technology to accurately measure The phase-locked loop technology compares the phase of the input signal and the feedback signal, continuously adjusts the frequency and phase of the voltage-controlled oscillator to lock the phase with the input signal, and thus accurately obtains the phase difference. ,in is the excitation signal amplitude, is the angular frequency, is the excitation frequency, is the amplitude of the induced electromotive force; calculate the rate of change of the phase difference , assuming that the excitation frequencies of two consecutive measurements are and , the corresponding phase difference is and , then the phase difference change rate is approximately , set the phase difference change rate threshold ,like , adjust the excitation frequency step , to quickly approach the resonant frequency, if , indicating that it is close to the resonance frequency, then , is the step size of the last adjustment, the initial step size At the same time, in order to reduce the influence of noise interference on the calculation of phase difference change rate, sliding average filtering is used to process the phase difference change rate. The sliding window size is set to Phase difference change rate after filtering , establish a historical database of phase difference-frequency relationship curves, and calculate the similarity between the current phase difference-frequency curve and the historical curve ,like , re-evaluate the frequency adjustment direction, where is the similarity threshold, The correlation coefficient method is used for calculation, and the formula is:

[0039] ;

[0040] in and are the average values ​​of historical frequency and phase difference, is the number of historical data groups;

[0041] S32. Excitation frequency setting: according to the adjusted frequency step , assuming the initial excitation frequency is , with the initial excitation frequency Based on this, a series of excitation frequency sequences are generated. ,in , used to excite the vibrating wire strain gauge during the frequency sweep process; Excitation and signal acquisition: For each excitation frequency , output amplitude is 8V low voltage excitation signal And keep it for 30ms to ensure that the vibrating string can produce stable vibration under this excitation, turn off the output switch, turn on the input switch, read the frequency of the induced signal through the capture circuit, and get a set of frequency sequence data , is the number of data points collected;

[0042] S4. Frequency data processing and judgment:

[0043] S41. Data preprocessing: removing frequency series data The first 10 and last 10 data of the sequence are used to reduce the impact of unstable factors that may exist in the starting and ending stages on the final result, and the remaining sequence is obtained. ;

[0044] S42. Intermediate value calculation: for the remaining sequence To sort, if If it is an even number, take the middle value ,like is an odd number, then ;

[0045] S43. Stationarity calculation: Calculate the difference between each value in the remaining sequence and the middle value , statistical difference exist arrive The number of data in the range , calculate the stationarity percentage ;

[0046] S44. Frequency value judgment and storage: If the stability percentage , then save the frequency value of this channel ,like , mark the channel frequency sweep failure, set ,Will stored in the storage location of the corresponding channel;

[0047] S5. Channel switching and end condition judgment: After completing the detection of a channel, the channel index Increment by 1, that is , prepare to test the next channel, if , then return to the channel detection loop step and continue to detect the next channel; if , indicating that all channels have been detected. At this time, the frequency values ​​of each channel collected this time are stored, except for those that failed to sweep, and these values ​​are used as the initial values ​​of the excitation frequency for the next sweep, ending the entire sweep process.

[0048] The excitation circuit and the acquisition circuit are shared by multiple channels, and the connection with different vibrating wire strain gauges is realized through the channel switch; the frequency sequence data During the acquisition process, the number of data points collected is determined according to the actual measurement requirements and accuracy requirements; the sliding window size of the sliding average filter is Adjust according to the measurement environment and vibrating wire strain gauge characteristics.

[0049] The phase difference change rate threshold and similarity threshold According to the specific model and application scenario of the vibrating wire strain gauge, the initial excitation frequency During the first operation, the frequency range and experience value of the vibrating-wire strain gauge can be used as the setting. The excitation signal amplitude is 8V and is maintained for 30ms. The parameter setting is determined based on the excitation requirements and measurement stability of the vibrating-wire strain gauge. In the frequency value judgment and storage step, the stability percentage Threshold It can be adjusted according to the measurement accuracy requirements and the stability of the vibrating wire strain gauge.

[0050] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0051] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A multi-channel vibrating wire strain gauge low-voltage sweep frequency detection method, characterized in that: The following steps are involved: S1. Program initialization: Read the number of channels configured by the user from the storage unit FLASH and the initial value of the excitation signal If the program is not running for the first time, the initial value of the excitation signal The frequency value obtained from the last frequency sweep; S2. Channel detection cycle: through the channel switch A vibrating wire strain gauge is connected to the excitation circuit and the acquisition circuit, where As the channel index, the initial value is 1, which is incremented after each cycle to read the resistance of the excitation coil of the vibrating wire strain gauge ,judge Is it established? and is the preset reasonable range of resistance. If it is not true, the channel detection is marked as failed and the channel frequency value is set to 0. If it is true, the adaptive excitation frequency adjustment and frequency sweep steps are performed; S3. Adaptive excitation frequency adjustment and frequency sweep: S31. Set the initial excitation frequency according to the rules , and determine the excitation frequency sequence based on the adaptive adjustment strategy , the adaptive adjustment strategy includes frequency adjustment based on phase difference, specifically: Frequency adjustment based on phase difference applies excitation signal to the excitation coil At the same time, another set of induction coils is used to measure the induced electromotive force generated by the vibration of the vibrating string. , using phase-locked loop technology to accurately measure ,in is the excitation signal amplitude, is the angular frequency, is the excitation frequency, is the amplitude of the induced electromotive force; Calculate the phase difference change rate , and adjust the excitation frequency step size according to the comparison result between the phase difference change rate and the preset threshold At the same time, the sliding average filter is used to process the phase difference change rate, establish a historical database of the phase difference-frequency relationship curve, and calculate the similarity between the current phase difference-frequency curve and the historical curve , determine whether to re-evaluate the frequency adjustment direction based on the similarity; S32. For each excitation frequency Output a low-voltage excitation signal with specific parameters and keep it for a certain period of time, turn off the output switch, turn on the input switch, read the frequency of the induction signal through the capture circuit, and obtain a set of frequency sequence data ; S4. Frequency data processing and judgment: Process the frequency sequence data, including removing some data, calculating the intermediate value and judging the data stability, and determine the frequency value of the channel based on the stability judgment result. and store; S5. Channel switching and end condition judgment: After completing the detection of a channel, the channel index Increment by 1, that is , prepare to test the next channel, if , then return to the channel detection loop step and continue to detect the next channel; if , indicating that all channels have been detected. At this time, the frequency values ​​of each channel collected this time are stored, except for those that failed to sweep, and these values ​​are used as the initial values ​​of the excitation frequency for the next sweep, ending the entire sweep process.

2. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 1, characterized in that: The calculated phase difference change rate The method is: Assume that the excitation frequencies of two consecutive measurements are and , the corresponding phase difference is and , then the phase difference change rate is approximately .

3. A multi-channel vibrating wire strain gauge low-voltage sweep frequency detection method as claimed in claim 2, characterized in that: The preset threshold includes a phase difference change rate threshold ,like , adjust the excitation frequency step , to quickly approach the resonant frequency, if , indicating that it is close to the resonance frequency, then , is the step size of the last adjustment, the initial step size .

4. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 3, characterized in that: The sliding window size of the sliding average filter Adjust according to the measurement environment and the characteristics of the vibrating wire strain gauge, the phase difference change rate after filtering .

5. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 4, characterized in that: Similarity The correlation coefficient method is used for calculation, and the formula is: ； in and are the average values ​​of historical frequency and phase difference, is the number of historical data sets, if , re-evaluate the frequency adjustment direction, where is the similarity threshold.

6. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 1, characterized in that: The specific parameters of the excitation signal are an amplitude of 8V and a duration of 30ms, which are determined based on the excitation requirements and measurement stability of the vibrating-wire strain gauge.

7. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 1, characterized in that: The detailed steps of the frequency data processing and judgment step of step S4 are as follows: S41. Data preprocessing: removing frequency series data The first 10 and last 10 data of the sequence are used to reduce the impact of unstable factors that may exist in the starting and ending stages on the final result, and the remaining sequence is obtained. ; S42. Intermediate value calculation: for the remaining sequence To sort, if If it is an even number, take the middle value ,like is an odd number, then ; S43. Stationarity calculation: Calculate the difference between each value in the remaining sequence and the middle value , statistical difference exist arrive The number of data in the range , calculate the stationarity percentage ; S44. Frequency value judgment and storage: If the stability percentage , then save the frequency value of this channel ,like , mark the channel frequency sweep failure, set ,Will Stored in the memory location of the corresponding channel.

8. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 1, characterized in that: The excitation circuit and the acquisition circuit are shared by multiple channels, and the connection with different vibrating-wire strain gauges is achieved through channel switches.

9. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 1, characterized in that: The frequency series data During the data collection process, the number of data points collected is determined according to the actual measurement needs and accuracy requirements.

10. A multi-channel vibrating wire strain gauge low voltage sweep frequency detection method as claimed in claim 1, characterized in that: The initial excitation frequency During the first operation, it can be set according to the nominal frequency range of the vibrating wire strain gauge and the empirical value.

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