CN114485735A - An adaptive swept-frequency excitation string-type wireless sensor - Google Patents

Abstract

The invention discloses a self-adaptive sweep frequency excited string type wireless sensor which comprises a sensor, an excitation system, a vibration pickup system and a wireless Lora receiving and transmitting system, wherein the sensor is attached to the surface of a measured object or embedded in the measured object, a main body vibration string in the sensor is excited by the excitation system to vibrate, when the vibration string is in a free vibration stage, the vibration pickup system is used for acquiring free vibration frequency information of the vibration string, the acquired frequency information is converted into corresponding physical quantity change, and finally, data acquired by the vibration pickup system is transmitted to a target server through the wireless Lora receiving and transmitting system. The invention integrates the string type sensor, the excitation system, the vibration pickup system and the wireless Lora receiving and transmitting system, integrates the algorithms of frequency band division, staged frequency sweep, vibration pickup optimization and the like, expands the sensor compatibility of the vibrating wire acquisition instrument and is convenient for large-scale integrated application of the vibrating wire type sensor in the engineering safety monitoring system.

Description

An adaptive swept-frequency excitation string-type wireless sensor

technical field

The invention belongs to the field of intelligent monitoring of civil engineering structure operation safety, and relates to a string-type wireless sensor with adaptive sweep frequency excitation.

Background technique

Vibrating wire sensors can be used to monitor physical quantities such as building pressure, settlement, seepage pressure, and deformation. They are a type of sensor that is widely used in engineering quality and health monitoring. The vibrating wire collector can amplify and convert the millivolt analog signal of the vibrating wire sensor, and store and analyze the converted frequency data in digital form.

Most of the existing vibrating wire acquisition instruments are designed with the working principle of low-voltage sweep frequency excitation. Compared with the traditional high-voltage plucked-string excitation working principle, the low-voltage sweep frequency has the advantages of simple circuit structure, safe operation voltage, and output analog signal amplitude. Compared with high-voltage strumming, which will accelerate the aging of the sensor coil, low-voltage sweeping can effectively protect the coil and prolong the service life of the chord-type sensor.

Existing vibrating wire collectors can often obtain satisfactory results when sweeping frequencies in a small range, but in the case of large sweeping frequency ranges, the collectors will have excessive acquisition errors or cannot acquire at all due to the long sweeping excitation time. Vibration signal. In addition, the existing acquisition instrument and the string sensor are of a separate design, which requires on-site connection and manual acquisition during acquisition, which is inconvenient to use.

SUMMARY OF THE INVENTION

In order to solve the problems of the existing string-type sensor, such as excessively long frequency sweep time, large acquisition error, and inconvenient use, the present invention provides an adaptive frequency-sweep excitation string-type wireless sensor. Adaptive frequency sweep excitation can divide the frequency sweep interval into multiple frequency sweep sections by setting the threshold value of the frequency sweep interval, and at the same time, by changing the incremental step size of the sweep frequency pulse sequence, the excitation process can be divided into pre-sweep frequency excitation and pre-sweep frequency excitation. The complex sweep frequency excitation has two stages, and the two-stage sweep frequency excitation realizes the adaptive sweep frequency excitation under the condition that the sensor operating parameters are unknown. In addition, the wireless sensor also optimizes the vibration pickup system, which improves the accuracy of frequency measurement data and shortens the measurement time. At the same time, it also integrates Lora wireless technology to realize remote data collection and transmission through Lora wireless network.

The purpose of this invention is to realize through the following technical solutions:

A string-type wireless sensor with adaptive sweep frequency excitation, comprising a sensor, a vibration excitation system, a vibration pickup system and a wireless Lora transceiver system, wherein:

The sensor is attached to the surface of the measured object or embedded in the measured object, and the vibration excitation system is used to excite the main body of the sensor to vibrate. Free vibration frequency information, and convert the obtained frequency information into corresponding physical quantity changes, and finally send the data obtained by the vibration pickup system to the target server through the wireless Lora transceiver system.

A method for using the above-mentioned string-type wireless sensor to perform adaptive frequency sweep excitation based on a feedback strategy, comprising the following steps:

Step 1: When the sensor is powered on for the first time, according to the length of the set frequency sweep interval, intelligently select the full frequency sweep frequency or the sub frequency band sweep frequency; Perform pre-sweep frequency excitation; after the pre-sweep frequency is over, use a small step size to perform a fast re-sweep frequency near the resonance point to obtain more accurate measurement results, where:

The step size of the pre-sweep frequency is between 1Hz and 10Hz, and the step size can be adjusted intelligently according to the actual measurement situation. During the initial pre-sweep frequency excitation, the frequency can be swept from 1Hz step size to 10Hz step size according to 1Hz increments, and the main body can be detected. The maximum vibration amplitude of the vibrating wire, so as to determine the optimal pre-sweep frequency step size of the sensor;

The step size of the complex sweep frequency is fixed at 0.1Hz;

Step 2: After the frequency sweep excitation in step 1 is completed and the vibration is successfully excited, the main control chip controls the excitation system to be turned off, the vibration pickup system is turned on, and the vibration waveform information is continuously obtained through the vibration pickup system, and the vibration is found according to the optimized vibration pickup algorithm. In the free vibration stage of the process, the vibration frequency is calculated and stored in the onboard flash memory chip;

Step 3: Realize the wireless networking of the sensor through wireless Lora technology, remotely collect data according to the instructions of the Lora gateway, and finally send the collected data to the Lora gateway through the wireless Lora transceiver system;

Step 4: When it is necessary to measure again, the sensor first reads the frequency information in the flash memory chip, and assumes that the current frequency is not much different from the storage frequency, and performs small-step fast frequency sweep excitation within the range of 10Hz above and below the taken frequency value. Control the step size of fast frequency sweep to 0.1Hz. If the excitation can be effectively performed, operations such as frequency band division, pre-sweep and re-sweep are omitted, and the measurement results can be obtained quickly. If the excitation cannot be effectively performed, repeat step 1.

Compared with the prior art, the present invention has the following advantages:

The string-type wireless sensor of the present invention integrates the string-type sensor, the excitation system, the vibration pickup system and the wireless Lora transceiver system, and integrates algorithms such as frequency band division, frequency sweeping in stages, and vibration pickup optimization, etc. Under the circumstance, the adaptive frequency sweep excitation algorithm is adopted, and the accurate data of the sensor is obtained by using multi-band and two-stage sweep frequency excitation, which expands the sensor compatibility of the vibrating wire acquisition instrument, and facilitates the large-scale vibrating wire sensor in the engineering safety monitoring system. Scale integration applications. At the same time, by optimizing the vibration pickup system, the data acquisition time is shortened and the measurement accuracy is improved. Using Lora wireless technology, the integration of sensor and acquisition instrument is realized, which can effectively improve the quality and work efficiency of string sensor data acquisition.

Description of drawings

FIG. 1 is a schematic structural diagram of a string-type wireless sensor with adaptive frequency sweep excitation;

Fig. 2 is the working flow chart of the string-type wireless sensor of adaptive sweep frequency excitation;

Fig. 3 is the actual use diagram of the string-type wireless sensor of the adaptive sweep frequency excitation.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be included in the present invention. within the scope of protection.

The present invention provides a string-type wireless sensor with adaptive frequency sweep excitation. As shown in FIG. 1 , the string-type wireless sensor includes a sensor, a vibration excitation system, a vibration pickup system and a wireless Lora transceiver system, wherein:

The sensor is a chord sensor, which can be used to measure physical quantities such as building body pressure, settlement, seepage pressure, deformation, etc. According to different measurement requirements, different types of chord sensors are selected;

The vibration excitation system is used for triggering the main body vibrating wire vibration of the sensor through adaptive sweep frequency excitation;

The vibration pickup system is used to obtain the free vibration frequency information of the main body vibrating wire of the sensor, and convert the obtained frequency information into corresponding physical quantity changes;

The wireless Lora transceiver system is used for the collection and transmission of remote control data;

The sensor is attached to the surface of the measured object or embedded in the measured object, and the vibration excitation system is used to excite the main body of the sensor to vibrate. Free vibration frequency information, and convert the obtained frequency information into corresponding physical quantity changes, and finally send the data obtained by the vibration pickup system to the target server through the wireless Lora transceiver system.

A method for using the above-mentioned string wireless sensor to perform adaptive frequency sweep excitation based on feedback strategy, as shown in Figure 2, the method includes the following steps:

Step 1: When the sensor is powered on for the first time, according to the length of the set frequency sweep interval, intelligently select the full frequency sweep frequency or sub-band frequency sweep frequency; after the frequency sweep interval is determined, select the pre-sweep frequency step size The frequency is between 1Hz and 10Hz, and the step size can be intelligently adjusted according to the actual measurement situation. During the initial pre-sweep frequency excitation, the frequency can be swept from 1Hz step to 10Hz step according to 1Hz increments, and the maximum vibration amplitude of the main vibrating wire can be detected. , so as to determine the optimal pre-sweep frequency step size of the sensor; after the pre-sweep frequency is over, use a small step size to perform a fast re-sweep frequency near the resonance point, and the re-sweep frequency step size is fixed at 0.1Hz to obtain more accurate measurement results.

In this step, the full-band frequency sweep and the sub-band frequency sweep are divided, and the specific operation steps of the two-stage frequency sweep excitation are as follows:

Step 11: When the frequency sweep interval of the sensor is too long, if the frequency sweep excitation with a large step size is used, it is very likely that the resonance point will be missed during the frequency sweep because the step size is too long, so that the vibrating wire cannot be reliably excited. If the frequency sweep excitation is adopted with a small step size, the frequency sweep time may be too long because the step size is too small, and the vibrating wire cannot be reliably excited. In order to reduce the sweep time, the system automatically selects the full-band sweep and sub-band sweep according to the set sweep threshold: the sweep section length threshold is set to 2000Hz, when the sweep section length is less than or equal to 2000Hz, you can Pre-sweep and re-sweep are performed in the entire interval. When the length of the sweep interval is greater than 2000Hz, the sweep interval is divided into multiple 2000Hz sections, and the section less than 2000Hz becomes a separate section, according to the divided sections. If the resonance point is found, perform a re-sweep in this interval, obtain the frequency value and end the measurement operation; if no resonance point is found in the pre-sweep, do not perform a re-sweep in this interval, and continue to sweep frequency to the next interval.

Step 1 and 2: Each interval is swept in two stages. The first stage is the pre-sweep frequency excitation stage. First, set the parameters such as the increment step size of the pre-sweep frequency pulse sequence, and pick up after sending the pre-sweep frequency excitation pulse sequence. Measure the frequency, and check whether the vibrating wire is reliably excited according to the frequency measurement data. If there is no reliable excitation, adjust the pulse sequence step size. The step size can be adjusted from 1Hz to 10Hz, and the step size increment is 1Hz. The second stage is the complex-sweep frequency excitation stage. According to the frequency measurement data of the pre-sweep frequency excitation, parameters such as the complex-sweep frequency excitation range and pulse sequence increment step size are set. After the complex-sweep frequency excitation pulse sequence is sent, the Frequency measurement, and check whether the vibrating wire is reliably excited according to the frequency measurement data. If the two inspection results are reliable excitation, the vibration measurement frequency will be returned; otherwise, an error message will be returned.

The pre-sweep frequency excitation stage adopts the 1-10Hz frequency sweep pulse sequence increment step size, which can be intelligently adjusted according to the start-up situation, greatly shortening the frequency sweep excitation time, and maximizing the working time of vibration pickup and frequency measurement; In the frequency sweep stage, the frequency sweep working range is set on the basis of the approximate resonance frequency of the vibrating wire measured in the pre-sweep frequency stage, and the frequency sweep pulse increment step size of 0.1 Hz is used to sweep the frequency excitation in a small frequency range to ensure the sensor The amplitude of the induced electromotive force at the output of the vibrating wire is the largest, and the measurement accuracy is improved.

Step 2: After the frequency sweep excitation in step 1 is completed and the vibration is successfully excited, the main control chip controls the excitation system to be turned off, the vibration pickup system is turned on, and the vibration waveform information is continuously obtained through the vibration pickup system, and the vibration is found according to the optimized vibration pickup algorithm. In the free vibration stage of the process, the vibration frequency is calculated and stored in the on-board flash memory chip.

In this step, the specific operations of optimizing the vibration pickup algorithm and the structure of the vibration pickup system, and storing the measurement data in the onboard flash memory chip are as follows:

Step 21: Adaptive frequency sweep excitation After each stage of frequency sweep, the sensor turns off the vibration excitation system and turns on the vibration pickup system. The vibration pickup system collects the weak electromotive force generated by cutting the magnetic field line during the vibration process of the vibration wire of the sensor, and passes the amplifier circuit. , Filter circuit and shaping circuit convert millivolt-level sinusoidal vibration wave into volt-level square wave. Use the pins of the main control chip to continuously monitor the vibration period of the square wave, and judge whether the vibrating wire enters the free vibration stage according to the period change. When the difference between adjacent periods of five consecutively collected periodic signals is less than 1us, it can be considered that the vibrating wire has entered the free vibration stage. At this time, the vibration data of ten periods are continuously collected, and the average value of the period is calculated, and finally the vibration frequency is obtained.

Step 22: A flash memory chip is integrated in the vibration pickup system. When the vibration pickup system obtains an effective vibration frequency, the frequency value is stored in the flash memory chip to provide a reference for the next frequency sweep.

Step 3: Realize the wireless networking of sensors through wireless Lora technology, collect data remotely according to the instructions of the Lora gateway, and finally send the collected data to the Lora gateway through the wireless Lora transceiver system.

In this step, the wireless networking of the sensor is realized through the wireless Lora technology, and the specific operations of the remote control acquisition are as follows:

The string wireless sensor is equipped with a wireless Lora transceiver system, and cooperates with the wireless Lora gateway to realize remote data collection. When the device starts, the wireless Lora transceiver system establishes a communication connection with the Lora gateway, and the Lora gateway controls the behavior of the sensor uniformly. When the Lora gateway sends a collection command, the sensor performs the collection operation according to the received command, and finally transmits the collected frequency data to the Lora gateway wirelessly through the wireless Lora transceiver system.

Step 4: When it is necessary to measure again, the sensor first reads the frequency information in the flash memory chip, and assumes that the current frequency is not much different from the storage frequency, and performs small-step fast frequency sweep excitation within the range of 10Hz above and below the taken frequency value. The frequency sweep step is 0.1Hz. If the excitation can be effectively performed, operations such as frequency band division, pre-sweep and re-sweep are omitted, and the measurement results can be obtained quickly. If the excitation cannot be effectively performed, repeat step 1.

In this step, the specific operation of fast frequency sweep through the onboard flash memory chip is as follows:

When the device needs to perform frequency sweep excitation again, first read the frequency value recorded in the on-board flash memory chip, perform a fast frequency sweep in small steps of 0.1Hz within the range of 10Hz up and down, obtain the current frequency information, and update the memory chip value in . This operation can save frequency band division, pre-sweep and re-sweep and other operations, and quickly obtain frequency information. When the excitation cannot be effectively performed, the two-stage frequency sweep needs to be performed again, and the value in the storage chip is updated.

In the present invention, the actual use diagram of the string-type wireless sensor with adaptive frequency sweep excitation is shown in FIG. 3 , and the measurement results are shown in Table 1. Among them, A represents the measurement time, and the system collects data every ten minutes; B represents the sensor number; C represents the frequency value obtained through adaptive frequency sweep excitation and vibration pickup measurement, the unit is Hertz; D represents the current ambient temperature, the unit is Celsius.

Table 1

Claims (8)

1. The utility model provides a string formula wireless sensor of self-adaptation sweep frequency excitation which characterized in that string formula wireless sensor includes sensor, excitation system, picks up system and wireless Lora receiving and dispatching system that shakes, wherein:

the sensor is attached to the surface of a measured object or embedded in the measured object, the vibration exciting system is used for exciting a main vibrating wire in the sensor to vibrate, when the vibrating wire is in a free vibration stage, the vibration pickup system is used for acquiring free vibration frequency information of the vibrating wire, the acquired frequency information is converted into corresponding physical quantity change, and finally, data acquired by the vibration pickup system is sent to a target server through the wireless Lora receiving and sending system.

2. A self-adaptive swept frequency excited chordal wireless sensor as claimed in claim 1, wherein the sensor is a chordal sensor.

3. A method for feedback strategy based adaptive swept frequency excitation using the chordal wireless sensor as claimed in any one of claims 1-2, the method comprising the steps of:

the method comprises the following steps: when the sensor is powered on for the first time, intelligently selecting full-band frequency sweeping or frequency-dividing band frequency sweeping according to the length of a set frequency sweeping interval; after the sweep frequency interval is determined, selecting a pre-sweep frequency step length, and performing pre-sweep frequency excitation in the sweep frequency interval; after the pre-sweep frequency is finished, carrying out fast repeated sweep frequency by using a small step length near a resonance point so as to obtain a more accurate measurement result, wherein:

step two: after the sweep frequency excitation in the first step is finished and the excitation is successfully carried out, the excitation system is controlled to be closed through the main control chip, the vibration pickup system is opened, the waveform information of the vibration is continuously obtained through the vibration pickup system, the free vibration stage in the vibration process is found according to the vibration pickup algorithm, the vibration frequency is calculated, and the vibration frequency is stored in an onboard flash storage chip;

step three: the wireless networking of the sensor is realized through a wireless Lora technology, the data acquisition work is remotely carried out according to the instruction of the Lora gateway, and the acquired data are finally sent to the Lora gateway through a wireless Lora transceiver system;

step four: when re-measurement is needed, the sensor firstly reads frequency information in the flash memory chip, and supposing that the difference between the current frequency and the stored frequency is not large, small-step-length fast frequency sweep excitation is carried out within the range of 10Hz above and below the taken frequency value, the fast frequency sweep step length is controlled to be 0.1Hz, if effective excitation can be achieved, operations such as frequency band division, pre-frequency sweep, frequency re-sweep and the like are omitted, measurement results are obtained quickly, and if effective excitation cannot be achieved, the step one is repeated.

4. A feedback strategy-based adaptive swept frequency excitation method according to claim 3, wherein in the first step, the pre-sweep step size is between 1Hz and 10Hz, frequency sweeps can be respectively performed from the 1Hz step size to the 10Hz step size according to 1Hz increments during initial pre-sweep excitation, and the maximum vibration amplitude of the body vibrating wire is detected, so that the optimal pre-sweep step size of the sensor is determined.

5. A method for adaptive swept frequency excitation based on a feedback strategy according to claim 3, wherein in the first step, the step size of the complex sweep frequency is fixed at 0.1 Hz.

6. A method for adaptive swept frequency excitation based on a feedback strategy according to claim 3, wherein the specific steps of the first step are as follows:

the method comprises the following steps: the system automatically selects full-band frequency sweeping and frequency-dividing band frequency sweeping according to a set frequency sweeping threshold: setting the length threshold of the sweep frequency zone to be 2000Hz, when the length of the sweep frequency zone is less than or equal to 2000Hz, pre-sweeping and re-sweeping in the whole zone, when the length of the sweep frequency zone is greater than 2000Hz, dividing the sweep frequency zone into a plurality of 2000Hz zones, independently forming the zone with the frequency less than 2000Hz into one zone, pre-sweeping according to the divided zones, if a resonance point is found, re-sweeping in the zone, obtaining a frequency value and finishing the measurement operation; if no resonance point is found in the pre-sweep frequency, not performing repeated sweep frequency in the section, and continuing to sweep frequency in the next section;

the first step is: each interval is swept in two stages, the first stage is a pre-sweep excitation stage, firstly, a pre-sweep pulse sequence incremental step length parameter is set, vibration pickup and frequency measurement are carried out after the pre-sweep excitation pulse sequence is sent, whether the vibration string is reliably excited is checked according to frequency measurement data, if the vibration string is not reliably excited, the pulse sequence step length is adjusted, the step length is adjusted from 1Hz to 10Hz, and the step length increment is 1 Hz; the second stage is a complex frequency sweep excitation stage, a complex frequency sweep excitation range and a pulse sequence incremental step length parameter are set according to frequency measurement data of pre-frequency sweep excitation, vibration pickup and frequency measurement are carried out after a complex frequency sweep excitation pulse sequence is sent, whether a vibrating wire is reliably excited is checked according to frequency measurement data, and if the two checking results are reliable excitation, the vibration measurement frequency is returned; otherwise, an error message is returned.

7. A method for adaptive swept frequency excitation based on a feedback strategy according to claim 3, wherein the specific steps of the second step are as follows:

step two, firstly: after the self-adaptive frequency sweep excitation finishes each phase of frequency sweep, the sensor closes the excitation system, opens the vibration pick-up system, the vibration pick-up system collects the weak electromotive force generated by cutting the magnetic induction line in the vibrating process of the vibrating string of the sensor, and the millivolt-level sinusoidal vibration wave is converted into the volt-level square wave through the amplifying circuit, the filter circuit and the shaping circuit; continuously monitoring the vibration period of the square wave by using a pin of a main control chip, and judging whether the vibrating wire enters a free vibration stage according to the period change; when the difference values of adjacent periods of five continuously collected periodic signals are all smaller than 1us, the vibrating wire can be considered to enter a free vibration stage, vibration data of ten periods are continuously collected at the moment, the average value of the periods is calculated, and finally the vibration frequency is obtained;

step two: and a flash memory chip is integrated in the vibration pickup system, and when the vibration pickup system acquires the effective vibration frequency, the frequency value is stored in the flash memory chip to provide reference for the next frequency sweep.

8. A method for adaptive swept frequency excitation based on a feedback strategy according to claim 3, wherein the specific steps of the third step are as follows:

the string type wireless sensor is provided with a wireless Lora receiving and transmitting system and is matched with a wireless Lora gateway to realize remote data acquisition; when the equipment is started, the wireless Lora transceiving system and the Lora gateway establish communication connection, and the behavior of the sensor is uniformly controlled by the Lora gateway; when the Lora gateway sends the acquisition instruction, the sensor executes acquisition operation according to the received instruction, and finally transmits the acquired frequency data to the Lora gateway through the wireless Lora transceiver system.

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