A bridge overweight detection system based on electromagnetic oscillation

Abstract

The present invention discloses a bridge overweight detection system based on electromagnetic oscillation, which relates to the technical field of bridge overweight detection, and comprises an oscillation detection module and a data analysis module. The oscillation detection module generates a sampling signal based on the weight borne by the bridge; the data analysis module is used to determine the sampling frequency f of the sampling signal. s and by comparing the sampling frequency f of the sampled signal s With the overweight threshold frequency f t The bridge overload detection system proposed in the present invention can detect the bridge overload according to the sampling frequency f s Quickly and accurately determine whether the bridge is overloaded, with high detection efficiency, low cost and simple installation and maintenance.

Description

Technical Field

[0001] The invention relates to the technical field of bridge overweight detection, in particular to a bridge overweight detection system based on electromagnetic oscillation. Background Art

[0002] With the rapid development of social economy, the scale of urban construction is getting bigger and bigger, and the scale of urban population and vehicle ownership is also getting bigger and bigger, which has brought huge pressure on travel and transportation. Ordinary ground transportation can no longer meet the flow of high-density population and vehicles in cities, which inevitably promotes the construction of a large number of viaducts in cities. In the past 10 years, most cities have built complex urban viaduct networks. The construction of urban viaducts is generally aimed at the passage of small cars and cost control, so there are requirements for the load-bearing capacity of bridges during construction. Generally, the load-bearing capacity of urban viaducts is less than 50 tons.

[0003] However, due to the current complex transportation environment, there are many trucks with a load of more than 100 tons or even more than 200 tons running in the city, so it is difficult to avoid some overweight trucks on the viaduct. Although all places have issued regulations not to allow overloaded trucks to use the viaduct, due to the lack of some strong inspection and supervision measures, overweight trucks often use the viaduct, which will cause great safety hazards. For example, there have been cases of overturned and broken viaduct pavement in various parts of the country, resulting in car crashes and deaths; even if the viaduct pavement does not roll over or break, overweight trucks will greatly shorten the service life of the viaduct road, so it is very important to conduct overweight inspections on bridges.

[0004] At present, the overload detection methods for viaducts include:

[0005] (1) Static weighing method: electronic scales are set up at both ends of the bridge. When the vehicle is completely on the bridge, the weight data is recorded. The weight data minus the weight when there is no vehicle is the net weight of the vehicle, which can be used to determine whether it is overloaded. This method has high weight accuracy and is easy to obtain evidence. However, its disadvantages are that this method is difficult to construct, causes serious damage to the viaduct, requires high maintenance frequency and is troublesome to detect. The cost of construction and maintenance is also high. At the same time, this method is only suitable for use at individual points on the bridge deck and is not suitable for large-scale promotion.

[0006] (2) Dynamic weighing method: Install a weighing instrument on the elevated road and measure the weight of the vehicle by the gravity of the vehicle passing through the weighing instrument. This instrument has a wide range of applications and a fast vehicle weighing speed. It can weigh vehicles while they are moving. However, its disadvantage is that the installation and maintenance costs are high and it is difficult to promote its use on a large scale.

[0007] (3) Infrared ranging method: An infrared detector is installed at both ends of the bridge to detect the number of tires and distance of the vehicle, and obtain information such as the length, number of axles and wheelbase of the vehicle, so as to calculate the weight of the vehicle. The advantages of this method are low cost and simple maintenance, but its weighing error is large.

[0008] (4) Intelligent video recognition method: By installing a high-definition camera on the bridge deck, the overload condition of the vehicle can be judged by the deformation degree of the vehicle tire in the image. For example, the larger the contact area between the tire and the road, the heavier the vehicle. The advantages of this method are simple installation, moderate cost, and large-scale installation. However, the size and air pressure of the tire will affect the judgment result, resulting in inaccurate weighing.

[0009] In summary, the existing overload detection methods for elevated bridges cannot simultaneously meet the application requirements of simple installation, simple maintenance, low cost, high weighing accuracy, and suitability for large-scale promotion. Summary of the invention

[0010] In view of the above problems and technical requirements, the inventors have proposed a bridge overweight detection system based on electromagnetic oscillation. The technical solution of the present invention is as follows:

[0011] A bridge overweight detection system based on electromagnetic oscillation comprises an oscillation detection module and a data analysis module, wherein the oscillation detection module generates a sampling signal based on the weight borne by the bridge;

[0012] The data analysis module is used to determine the sampling frequency f of the sampling signal s and by comparing the sampling frequency f of the sampled signal s With the overweight threshold frequency f t Carry out bridge overload inspection.

[0013] A further technical solution is that the oscillation detection module includes an LC oscillation circuit, and the LC oscillation circuit includes a displacement capacitor C4;

[0014] The displacement capacitor C4 is arranged between the pier and the bridge deck of the detected bridge, and is used to convert the distance between the pier and the bridge deck into the capacitance value of the displacement capacitor C4;

[0015] The oscillation detection module generates a sampling signal based on the capacitance value of the displacement capacitor C4.

[0016] A further technical solution thereof is that it further comprises a data preprocessing module, wherein the data preprocessing module is connected between the oscillation detection module and the data analysis module;

[0017] The sampling signal is a sine wave signal, and the data preprocessing module converts the sampling signal into a square wave signal, counts the number of square waves n of the square wave signal within a preset time, and transmits the counted number of square waves n to the data analysis module;

[0018] The data analysis module collects the oscillation frequency of the sampling signal according to the number n of square waves of the square wave signal within a preset time, and determines the sampling frequency f according to the oscillation frequency of the collected sampling signal. s .

[0019] A further technical solution is that the LC oscillation circuit further includes capacitor C2, capacitor C3, capacitor C5, capacitor C6, capacitor C7, power device Q3, inductor L1, resistor R7, resistor R8, resistor R9 and resistor R10, wherein:

[0020] The first electrode of the power device Q3 is connected to one end of the resistor R7 and one end of the capacitor C6, the other end of the resistor R7 is connected to the second electrode of the power device Q3 through the resistor R8 and connected to the power supply voltage VCC, the other end of the capacitor C6 is grounded through the capacitor C2 and connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the third electrode of the power device Q3;

[0021] The second electrode of the power device Q3 is grounded through the resistor R9, and the capacitor C7 is connected in parallel with the resistor R9; the third electrode of the power device Q3 is connected to one end of the resistor R10 through the displacement capacitor C4, and the other end of the resistor R10 is connected to the data preprocessing module; the capacitor C5 is connected in parallel with the capacitor C4, and the temperature coefficient of the capacitor C5 is opposite to the temperature coefficient of the displacement capacitor C4.

[0022] A further technical solution is that the sampling frequency f s satisfy:

[0023]

[0024] Among them, k is the oscillation coefficient, L1 is the inductance value of inductor L1, and C4 is the capacitance value of displacement capacitor C4.

[0025] A further technical solution is that the oscillation detection module further includes a reference circuit for providing a reference signal to the data preprocessing module, and the data preprocessing module converts the sampling signal into a square wave signal according to the reference signal;

[0026] The reference circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R6, a voltage stabilizing chip Z1 and a capacitor C1, wherein:

[0027] One end of the resistor R3 is connected to the power supply voltage VCC, the other end of the resistor R3 is connected to one end of the resistor R4 and one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the resistor R4 and the cathode end of the voltage stabilizing chip Z1 through the resistor R6, and the cathode end of the voltage stabilizing chip is also connected to one end of the inductor L1 and one end of the capacitor C1; the anode end of the voltage stabilizing chip Z1 and the other end of the capacitor C1 are grounded.

[0028] Its further technical solution is that the data preprocessing module includes a voltage comparator U4A, a resistor R11 and a digital counter U3;

[0029] The non-inverting input terminal of the voltage comparator U4A is connected to one end of the displacement capacitor C4 through the resistor R10, the inverting input terminal of the voltage comparator U4A is connected to one end of the resistor R5 and one end of the resistor R6, and the output terminal of the voltage comparator U4A is connected to the clock input pin of the digital counter U3.

[0030] A further technical solution is that the oscillation detection module further includes an enabling circuit, and the enabling circuit includes a power device Q1, a power device Q2, a resistor R1 and a resistor R2, wherein:

[0031] One end of the inductor L1 is connected to the first electrode of the power device Q1 and the third electrode of the power device Q2, the third electrode of the power device Q1 is connected to the first electrode of the power device Q2 and one end of the capacitor C4, the second electrode of the power device Q1 is connected to the data processing module through the resistor R1, and the second electrode of the power device Q2 is connected to the data processing module through the resistor R2.

[0032] Its further technical solution is that it also includes an alarm control module, and the data analysis module is connected to the alarm device through the alarm control module;

[0033] When performing bridge overload detection, the data analysis module compares the sampling frequency f s With the overweight threshold frequency f t , when the sampling frequency f s Less than the overweight threshold frequency f t When the data analysis module controls the alarm device to send out an alarm signal through the alarm control module;

[0034] The alarm control module includes a resistor R14, a resistor R15, a power device Q4, a diode D1 and a relay K1, one end of the resistor R15 is connected to the data processing module and one end of the resistor R14, and the other end of the resistor R14 is connected to the power supply voltage VCC;

[0035] The other end of the resistor R15 is connected to the second electrode of the power device Q4, the first electrode of the power device Q4 is grounded, the third electrode of the power device Q4 is connected to the anode of the diode D1 and one end of the relay K1, the other end of the relay K1 is connected to the cathode of the diode D1 and connected to the power supply voltage VCC; the normally open contact of the relay K1 is connected in series in the power supply circuit of the alarm device.

[0036] A further technical solution is to determine the sampling frequency f of the sampling signal according to the oscillation frequency of the collected sampling signal. s It includes obtaining the vehicle-free frequency f0, filtering the oscillation frequency of the sampling signal according to the vehicle-free frequency f0, and using the filtered oscillation frequency as the sampling frequency f s The no-vehicle frequency f0 is the oscillation frequency of the sampling signal when there is no vehicle traveling on the detected bridge.

[0037] The beneficial technical effects of the present invention are:

[0038] The present invention provides a bridge overweight detection system based on electromagnetic oscillation, which can generate a sampling signal based on the pressure borne by the bridge, and the sampling frequency f of the sampling signal can be adjusted. s The system detects the load-bearing condition of the bridge. It has good detection accuracy, high detection efficiency, low cost, simple installation and maintenance, and can be flexibly set up on each section of the bridge deck, suitable for large-scale promotion and use. It makes the overload detection of the bridge deck simple and reliable, providing guarantee for safe traffic in the city. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a system block diagram of an embodiment of a bridge overweight detection system based on electromagnetic oscillation provided by the present invention.

[0040] Figure 2 It is a circuit schematic diagram of an embodiment of an oscillation detection module and a data preprocessing module provided by the present invention.

[0041] Figure 3 It is an equivalent AC model of an embodiment of the LC oscillation circuit provided by the present invention.

[0042] Figure 4 It is a waveform diagram of an embodiment of the sampling signal provided by the present invention.

[0043] Figure 5 It is a waveform diagram of an embodiment of the square wave signal provided by the present invention.

[0044] Figure 6 The present invention provides a pin diagram of a single chip microcomputer according to an embodiment of the present invention.

[0045] Figure 7It is an ideal square wave diagram of a square wave signal when performing overweight detection in one embodiment of the present invention.

[0046] Figure 8 It is a time division diagram of the sampling frequency when performing overweight detection in one embodiment of the present invention.

[0047] Fig. 9 The figure is a circuit diagram of an embodiment of the alarm control module provided by the present invention.

[0048] Fig.10 This is a pin diagram of an embodiment of the serial port chip provided by the present invention.

[0049] Fig.11 The present invention provides an overweight detection system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0051] A bridge overweight detection system based on electromagnetic oscillation comprises an oscillation detection module and a data analysis module, wherein the oscillation detection module generates a sampling signal based on the weight borne by the bridge;

[0052] The data analysis module is used to determine the sampling frequency f of the sampling signal s and by comparing the sampling frequency f of the sampled signal s With the overweight threshold frequency f t Carry out bridge overload inspection.

[0053] Specifically, the weight borne by the bridge includes the total weight of the vehicles traveling on the bridge. The oscillation detection module generates a sampling signal based on the weight borne by the bridge. The oscillation frequency of the sampling signal changes with the weight borne by the bridge. The specific relationship between the bridge load and the oscillation frequency of the sampling signal can be referred to the following description. When performing bridge overload detection, the data analysis module compares the sampling frequency f s With the overweight threshold frequency f t , when the sampling frequency f s Less than the overweight threshold frequency f t When the data analysis module determines that the load-bearing capacity of the bridge is in an overload state. Compared with the traditional bridge overload detection method, the bridge overload detection system proposed by the present invention can quickly and accurately determine whether the load-bearing capacity of the bridge is overloaded, with high detection efficiency, low cost and simple installation and maintenance. The specific form of the system can refer to the following description.

[0054] Furthermore, the oscillation detection module includes an LC oscillation circuit, which includes a displacement capacitor C4; the displacement capacitor C4 is arranged between the pier and the bridge deck of the detected bridge, and is used to convert the distance between the pier and the bridge deck into a capacitance value of the displacement capacitor C4; the oscillation detection module generates a sampling signal based on the capacitance value of the displacement capacitor C4.

[0055] Specifically, the displacement capacitor C4 is a displacement capacitor with self-recovery ability, generally composed of two flat electrodes and a medium arranged between the two flat electrodes. The displacement capacitor C4 is arranged between the bridge pier and the bridge deck, that is, one flat electrode of the displacement capacitor C4 is placed on the pier, and the other flat electrode is close to the bottom of the bridge deck.

[0056] The capacitance of the displacement capacitor C4 can be expressed as C4=ε*S / d, where S is the facing area of ​​the two flat electrodes, ε is the dielectric coefficient, and d is the distance between the flat electrodes. The distance between the bridge piers and the bridge deck decreases as the weight borne by the bridge increases, and the distance d between the flat electrodes of the displacement capacitor C4 decreases as the distance between the piers and the bridge deck decreases. It can be seen from the above-mentioned capacitance calculation formula of the displacement capacitor C4 that the capacitance of the displacement capacitor C4 increases as the distance d between the flat electrodes decreases. Therefore, the capacitance of the displacement capacitor C4 can reflect the change in the load-bearing capacity of the bridge, and the oscillation detection module generates a sampling signal based on the capacitance of the displacement capacitor C4, so that the oscillation frequency of the sampling signal changes with the weight borne by the bridge.

[0057] Figure 2 FIG. 4 shows a circuit schematic diagram of the oscillation detection module in this embodiment, as shown in FIG. Figure 2 As shown, the LC oscillation circuit further includes capacitor C2, capacitor C3, capacitor C5, capacitor C6, capacitor C7, power device Q3, inductor L1, resistor R7, resistor R8, resistor R9 and resistor R10, wherein,

[0058] The first electrode of the power device Q3 is connected to one end of the resistor R7 and one end of the capacitor C6, the other end of the resistor R7 is connected to the second electrode of the power device Q3 through the resistor R8 and is connected to the power supply voltage VCC, the other end of the capacitor C6 is grounded through the capacitor C2 and connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to the third electrode of the power device Q3; the second electrode of the power device Q3 is grounded through the resistor R9, the capacitor C7 is connected in parallel with the resistor R9; the third electrode of the power device Q3 is connected to one end of the resistor R10 through the displacement capacitor C4, the other end of the resistor R10 is connected to the data preprocessing module; the capacitor C5 is connected in parallel with the capacitor C4.

[0059] In this embodiment, the power device Q3 is a PNP type triode. Corresponding to the PNP type triode, the first electrode of the power device Q3 is the emitter, the second electrode is the base, and the third electrode is the collector. The resistors R7 and R8 are bias resistors of the power device Q3, and the resistor R9 is the base protection resistor of Q3 during the power period. Since the capacitance value of the displacement capacitor C4 may be offset due to the influence of the ambient temperature, the temperature coefficient of the capacitor C5 is opposite to the temperature coefficient of the displacement capacitor C4 to achieve temperature compensation. In addition, the size of the capacitor C5 is about 1% of the capacitance value of the displacement capacitor C4, and its influence on the oscillation frequency of the LC oscillation circuit can be ignored.

[0060] Figure 3 The equivalent AC model of the LC oscillation circuit is shown, and only the connection relationship of the key components in the LC oscillation circuit is retained. The power device Q3 provides an amplification effect for the oscillation detection circuit, and the capacitors C2 and C3 have the same capacitance value, and the size is more than 10 times that of the displacement capacitor C4, so that the size of the equivalent capacitance formed by the capacitors C2, C3 and the displacement capacitor C4 is determined by the displacement capacitor C4. Since the displacement capacitor C4 is used as a sampling capacitor to determine the oscillation frequency of the sampling signal, the size of the equivalent capacitance formed by the capacitors C2, C3 and the displacement capacitor C4 is determined by the displacement capacitor C4, which can improve the sensitivity of the LC oscillation circuit.

[0061] Furthermore, the overweight detection system further comprises a data preprocessing module, and the data preprocessing module is connected between the oscillation detection module and the data analysis module;

[0062] In this embodiment, the sampling signal output by the LC oscillation circuit is a sine wave signal, and the data preprocessing module is used to convert the sampling signal into a square wave signal, count the number of square waves n of the square wave signal within a preset time, and transmit it to the data analysis module. The data analysis module collects the oscillation frequency f of the sampling signal according to the number of square waves n of the square wave signal within the preset time, and determines the sampling frequency f according to the collected oscillation frequency f of the sampling signal. s .

[0063] Specifically, due to errors in the hardware circuit and the influence of factors such as different installation environments and humidity, the oscillation frequency f of the sampling signal calculated by the microcontroller based on the number of square waves n may deviate from the theoretical oscillation frequency of the sampling signal actually output by the LC oscillation circuit. At the same time, there may be other sudden interference factors in practical applications, which will cause interference frequency in the oscillation frequency of the sampling signal collected by the data analysis module.

[0064] Therefore, before the system performs overweight detection, the data analysis module needs to obtain the oscillation frequency of the sampling signal when there is no vehicle traveling on the detected bridge as the vehicle-free frequency f0, and filter the oscillation frequency f of the collected sampling signal according to the vehicle-free frequency f0 when performing overweight detection to filter out interference frequencies. The common methods used by technicians in this field can be used to filter out interference frequencies.

[0065] The sampling frequency f obtained after filtering out the interference frequency s satisfy:

[0066]

[0067] Where k is the oscillation coefficient, L1 is the inductance of the inductor L1, and C4 is the capacitance of the displacement capacitor C4. The oscillation coefficient k is a constant value. The oscillation coefficient k is related to the values ​​of the components in the LC oscillation circuit. For a certain LC oscillation circuit, the oscillation coefficient k can be calculated and determined. The calculation method of the oscillation coefficient k can be consistent with the prior art. From the above formula, it can be seen that the sampling frequency f s As the capacitance of displacement capacitor C4 increases, the sampling frequency f s As the weight of the bridge increases, it decreases, so it can be measured by sampling frequency f s With the overweight threshold frequency f t The overload condition of the bridge can be determined by comparison.

[0068] Furthermore, combining the expression of the displacement capacitor C4 capacitance value and the sampling frequency f s The expression of can be obtained:

[0069]

[0070] According to the above formula, the sampling frequency f s The distance d between the plate electrodes of the displacement capacitor C4 is calculated. According to the above description, the distance d between the plate electrodes of the displacement capacitor C4 is proportional to the distance between the bridge pier and the bridge deck. Therefore, the system can also be used to determine the degree of inclination of the bridge deck. Specifically, the system is installed on the piers on both sides of the bridge, that is, a displacement capacitor C4 is installed on the piers on both sides of the bridge, and the displacement capacitor C4 on each side is connected to other modules of the system accordingly. The piers on both sides determine a sampling frequency according to the above method, that is, the sampling frequency f s1 and sampling frequency f s2 , according to the sampling frequency f s1 and sampling frequency f s2 The distance d1 between the flat plate electrodes and the distance d2 between the flat plate electrodes are calculated and uploaded to the host computer. When the difference between d1 and d2 is too large, an alarm signal indicating that the bridge is tilted can be issued accordingly.

[0071] Specifically, the data preprocessing module counts the number of square waves of the square wave signal per unit time as n1, and the oscillation frequency of the sampling signal is 1 / n1. The data preprocessing module converts the sampling signal into a square wave signal according to a reference signal, and the reference signal is provided by a reference circuit in the oscillation detection module. Figure 2 As shown, the reference circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R6, a voltage stabilizing chip Z1 and a capacitor C1, wherein one end of the resistor R3 is connected to a power supply voltage VCC, the other end of the resistor R3 is connected to one end of the resistor R4 and one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the resistor R4 and the cathode end of the voltage stabilizing chip Z1 through the resistor R6, and the cathode end of the voltage stabilizing chip is also connected to one end of the inductor L1 and one end of the capacitor C1; the anode end of the voltage stabilizing chip Z1 and the other end of the capacitor C1 are grounded. The voltage stabilizing chip Z1 provides a reference voltage vref, and the resistors R5 and R6 divide the voltage across the resistor R4 to form a reference signal com that is transmitted to the data preprocessing module, and the reference signal com is a fixed voltage value.

[0072] Figure 2 Also shown is a circuit diagram of an embodiment of a data preprocessing module, such as Figure 2 As shown, the data preprocessing module includes a voltage comparator U4A, a resistor R11 and a digital counter U3. The in-phase input terminal of the voltage comparator U4A is connected to one end of the displacement capacitor C4 through the resistor R10, the inverting input terminal of the voltage comparator U4A is connected to one end of the resistor R5 and one end of the resistor R6, and the output terminal of the voltage comparator U4A is connected to the clock input pin of the digital counter U3.

[0073] The non-inverting input terminal of the voltage comparator U4A receives the sampling signal det, and the inverting input terminal of the voltage comparator U4A receives the reference signal com. Figure 4 1 shows a waveform diagram of the sampling signal det in this embodiment, and the sampling signal det is a sine wave signal biased on the reference voltage vref. It should be noted that: Figure 4 The waveform of the sampling signal det shown is the waveform when the displacement capacitor C4 is fixed. In specific implementation, when the capacitance value of the displacement capacitor C4 changes with the load-bearing value of the bridge, the oscillation frequency of the sampling signal det will also change accordingly. The oscillation frequency of the sampling signal det decreases as the load-bearing value of the bridge increases. The specific change logic can refer to the above description.

[0074] The data preprocessing module converts the sampling signal det into a square wave signal of the same frequency, that is, the voltage comparator is used to compare the voltage of the sampling signal det with the reference signal com. When the sampling signal det is greater than the reference signal com, the voltage comparator U4A outputs a high-level signal (VCC) to the clock input pin of the digital counter U3; conversely, when the sampling signal det is less than the reference signal com, the voltage comparator U4A outputs a low-level signal (0V) to the clock input pin of the digital counter U3 to convert the sampling signal det into a square wave signal. Figure 5 Square wave signals of the same frequency as shown.

[0075] In this embodiment, the model of the digital counter U3 may be CD4017, and the clock input pin of the digital counter U3 is the CLK pin. The digital counter U3 counts the number of pulses input to the CLK pin within a preset time, i.e., the number of square waves n, and outputs it to the data processing module in parallel through the D0-D9 pins. The counting range of the digital counter U3 is 0-1023.

[0076] The data processing module in this embodiment adopts a single chip microcomputer of model STC12C5410AD, which has the advantages of low price, low power consumption, high processing speed, etc. Figure 6 The pin diagram of the single-chip microcomputer is shown. As shown in the figure, the 18th to 27th pins of the single-chip microcomputer are connected to the D0-D9 pins of the digital counter U3 in a one-to-one correspondence, and are used to receive the counting data of the number of square waves n. The 9th pin of the single-chip microcomputer is connected to the RESET pin of the digital counter U3, and the output CLR signal is used to control the switch of the digital counter U3. The RESET pin of the digital counter U3 is also grounded through a resistor R12. When the CLR signal is at a high level, the digital counter U3 is turned on and counts from zero; when the CLR signal is at a low level, the digital counter U3 is turned off and stops counting. A 12MHz passive crystal oscillator is connected between the 6th and 7th pins of the single-chip microcomputer to provide a clock reference. The single-chip microcomputer operates in a 12MHz single-cycle mode. The 6th pin of the single-chip microcomputer is also grounded through a capacitor C8, and the 7th pin of the single-chip microcomputer is also grounded through a capacitor C9.

[0077] The oscillation detection module further includes an enabling circuit, which includes a power device Q1, a power device Q2, a resistor R1 and a resistor R2, wherein:

[0078] One end of the inductor L1 is connected to the first electrode of the power device Q1 and the third electrode of the power device Q2, the third electrode of the power device Q1 is connected to the first electrode of the power device Q2 and one end of the capacitor C4, the second electrode of the power device Q1 is connected to the data processing module through the resistor R1, and the second electrode of the power device Q2 is connected to the data processing module through the resistor R2.

[0079] Specifically, the 11th pin of the single chip microcomputer is connected to one end of the resistor R1 and one end of the resistor R2, and is used to output an EN signal. The conduction state of the power device Q1 and the power device Q2 can be controlled by the EN signal, thereby controlling the on-off state of the LC oscillation circuit in the oscillation detection module. The power device Q1 and the power device Q2 described in this embodiment both use NPN type transistors, and the definitions of the first electrode, the second electrode and the third electrode of the power device Q1 and the power device Q2 are consistent with the above-mentioned definitions of the first electrode, the second electrode and the third electrode of the PNP type transistor, and are not repeated here. When the EN signal is at a high level, the power device Q1 and the power device Q2 are turned on, and the oscillation detection module outputs a sampling signal.

[0080] In specific implementation, it is necessary to select appropriate inductance and capacitance values ​​in the LC oscillation circuit so that when there is no vehicle on the bridge, the oscillation frequency of the sampling signal is between 500-1000kHz. When there is a vehicle on the bridge, the oscillation frequency of the sampling signal will decrease accordingly. For ease of understanding, Figure 7 The ideal square wave diagram of the square wave signal during detection is shown by Figure 7 It can be seen that the frequency of the square wave signal is relatively large when there is no vehicle on the bridge, and relatively small when there is a vehicle on the bridge. In fact, the frequency of the square wave signal is a continuous change process. This is because when vehicles are pressed onto the bridge, the load-bearing capacity of the bridge is a continuous change process. For a vehicle, when all vehicles are pressed onto the bridge, the weight of the bridge reaches the maximum value, and the frequency of the square wave signal reaches the minimum value. This value is maintained until the vehicle starts to drive off the bridge. After the vehicle completely drives off the bridge, the frequency of the square wave signal returns to the frequency when there is no vehicle. When there are multiple vehicles on the bridge, the frequency of the square wave signal changes continuously with the total weight of the bridge.

[0081] As an example of an application of this system, Figure 8 The sampling frequency f is shown for three vehicles of different weights when vehicles V1-V3 respectively pass through the detected bridge. s From the above description, we can see that for each vehicle sampling frequency f s It is at its minimum value when the vehicle is completely on the bridge deck. Figure 8 It can be seen that the sampling frequency f corresponding to vehicles V1-V3 is s The minimum value of the vehicle V1-V3 decreases, that is, the weight relationship of the vehicle V1-V3 is V1>V2>V3. If the specified overweight threshold frequency f t Set the sampling frequency f corresponding to vehicle V1 s The minimum value of vehicle V2 corresponds to the sampling frequency f s The system can determine that the vehicle V1 is overweight when the vehicle V1 is traveling toward the bridge deck.

[0082] Furthermore, due to reasons such as vehicle engine vibration, vehicles passing through the bridge may cause vibration to the bridge structure, and the vibration of the bridge is reflected at the sampling frequency f s When the vehicle is traveling on the bridge, the sampling frequency f s Therefore, this system can also be used to calculate and determine the vibration frequency f of the bridge. z , which can provide reference for bridge maintenance, etc. The vibration frequency of the bridge is f z The calculation method can be as follows: When the vehicle is driving on the bridge, the sampling frequency f is obtained s The time t0 when the minimum value appears and the time t1 when the maximum value appears in a fluctuation cycle, f z =1 / t1-t0.

[0083] Furthermore, the bridge overweight detection system further comprises an alarm control module, and the data analysis module is connected to the alarm device via the alarm control module;

[0084] When performing bridge overload detection, the data analysis module compares the sampling frequency f s With the overweight threshold frequency f s , when the sampling frequency f s Less than the overweight threshold frequency f t When the alarm is triggered, the data analysis module controls the alarm device to send out an alarm signal through the alarm control module.

[0085] Specifically, Fig. 9 As shown, the alarm control module includes a resistor R14, a resistor R15, a power device Q4, a diode D1 and a relay K1, one end of the resistor R15 is connected to the data processing module and one end of the resistor R14, and the other end of the resistor R14 is connected to the power supply voltage VCC; the other end of the resistor R15 is connected to the second electrode of the power device Q4, the first electrode of the power device Q4 is grounded, the third electrode of the power device Q4 is connected to the anode of the diode D1 and one end of the relay K1, and the other end of the relay K1 is connected to the cathode of the diode D1 and connected to the power supply voltage VCC; the normally open contact of the relay K1 is connected in series in the power supply circuit of the alarm device.

[0086] In this embodiment, the power device Q4 is an NPN transistor. The definitions of the first electrode, the second electrode and the third electrode of the power device Q4 are consistent with the above definitions of the first electrode, the second electrode and the third electrode of the NPN transistor, and are not repeated here. The base of the power device Q4 is connected to the 10th pin of the above-mentioned single-chip microcomputer through the resistor R12, and the 10th pin of the single-chip microcomputer outputs the JDQ signal to the base of the power device Q4. Sampling frequency f s Less than the overweight threshold frequency f tWhen the single chip microcomputer outputs a high level JDQ signal, the relay K1 is energized, so that the normally open contact of the relay K1 is closed, the power supply circuit of the alarm device is energized to power the alarm device, and the alarm device sends an alarm signal to the outside, indicating that the bridge is in an overweight state.

[0087] Optionally, the bridge overweight detection system further includes a serial port chip of model MAX232. Fig.10 The pin diagram of the serial port chip is shown. The T1in pin of the serial port chip is connected to the 4th pin of the single-chip microcomputer, the R1out pin of the serial port chip is connected to the 5th pin of the single-chip microcomputer, the VCC pin of the serial port chip is connected to the power supply voltage VCC, the C1+ pin is connected to the C1- pin through the capacitor C10, the C2+ pin is connected to the C2- pin through the capacitor C11, the V- pin is connected to the GND pin through the capacitor C12, and the GND pin is grounded. The T1out pin and R1in pin of the serial port chip are connected to the host computer through the interface J1, and the single-chip microcomputer can upload the detection results to the host computer through the serial port chip.

[0088] Fig.11 The working flow chart of the overweight detection system is shown. After the system is started, the overweight threshold frequency f is set in the single chip microcomputer. t And obtain the car-free frequency f0; obtain the oscillation frequency f of the sampling signal and filter it, and use the oscillation frequency f after filtering as the sampling frequency f s , the sampling frequency f s With the overweight threshold frequency f t For comparison, if the sampling frequency f s Less than the overweight threshold frequency f t , the single chip microcomputer outputs a high level JDQ signal to the alarm control module, controlling the alarm device to send an alarm signal.

[0089] It should be noted that the above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A bridge overweight detection system based on electromagnetic oscillation, characterized in that: It includes an oscillation detection module and a data analysis module, wherein the oscillation detection module generates a sampling signal based on the weight borne by the bridge; The data analysis module is used to determine the sampling frequency f of the sampling signal s and by comparing the sampling frequency f of the sampled signal s With the overweight threshold frequency f t Carry out bridge overload inspection.

2. The bridge overweight detection system based on electromagnetic oscillation according to claim 1 is characterized in that: The oscillation detection module includes an LC oscillation circuit, and the LC oscillation circuit includes a displacement capacitor C4; The displacement capacitor C4 is arranged between the pier and the bridge deck of the detected bridge, and is used to convert the distance between the pier and the bridge deck into the capacitance value of the displacement capacitor C4; The oscillation detection module generates a sampling signal based on the capacitance value of the displacement capacitor C4.

3. The bridge overweight detection system based on electromagnetic oscillation according to claim 1 is characterized in that: It also includes a data preprocessing module, which is connected between the oscillation detection module and the data analysis module; The sampling signal is a sine wave signal, and the data preprocessing module converts the sampling signal into a square wave signal, counts the number of square waves n of the square wave signal within a preset time, and transmits the counted number of square waves n to the data analysis module; The data analysis module collects the oscillation frequency of the sampling signal according to the number n of square waves of the square wave signal within a preset time, and determines the sampling frequency f according to the oscillation frequency of the collected sampling signal. s .

4. The bridge overweight detection system based on electromagnetic oscillation according to claim 3 is characterized in that: The LC oscillation circuit further includes capacitor C2, capacitor C3, capacitor C5, capacitor C6, capacitor C7, power device Q3, inductor L1, resistor R7, resistor R8, resistor R9 and resistor R10, wherein: The first electrode of the power device Q3 is connected to one end of the resistor R7 and one end of the capacitor C6, the other end of the resistor R7 is connected to the second electrode of the power device Q3 through the resistor R8 and connected to the power supply voltage VCC, the other end of the capacitor C6 is grounded through the capacitor C2 and connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the third electrode of the power device Q3; The second electrode of the power device Q3 is grounded through the resistor R9, and the capacitor C7 is connected in parallel with the resistor R9; the third electrode of the power device Q3 is connected to one end of the resistor R10 through the displacement capacitor C4, and the other end of the resistor R10 is connected to the data preprocessing module; the capacitor C5 is connected in parallel with the capacitor C4, and the temperature coefficient of the capacitor C5 is opposite to the temperature coefficient of the displacement capacitor C4.

5. The bridge overweight detection system based on electromagnetic oscillation according to claim 4 is characterized in that: The sampling frequency f s satisfy: Among them, k is the oscillation coefficient, L1 is the inductance value of inductor L1, and C4 is the capacitance value of displacement capacitor C4.

6. The bridge overweight detection system based on electromagnetic oscillation according to claim 4 is characterized in that: The oscillation detection module also includes a reference circuit for providing a reference signal to the data preprocessing module, and the data preprocessing module converts the sampled signal into a square wave signal according to the reference signal; The reference circuit includes a resistor R3, a resistor R4, a resistor R5, a resistor R6, a voltage stabilizing chip Z1 and a capacitor C1, wherein: One end of the resistor R3 is connected to the power supply voltage VCC, the other end of the resistor R3 is connected to one end of the resistor R4 and one end of the resistor R5, the other end of the resistor R5 is connected to the other end of the resistor R4 and the cathode end of the voltage stabilizing chip Z1 through the resistor R6, and the cathode end of the voltage stabilizing chip is also connected to one end of the inductor L1 and one end of the capacitor C1; the anode end of the voltage stabilizing chip Z1 and the other end of the capacitor C1 are grounded.

7. The bridge overweight detection system based on electromagnetic oscillation according to claim 6 is characterized in that: The data preprocessing module includes a voltage comparator U4A, a resistor R11 and a digital counter U3; The non-inverting input terminal of the voltage comparator U4A is connected to one end of the displacement capacitor C4 through the resistor R10, the inverting input terminal of the voltage comparator U4A is connected to one end of the resistor R5 and one end of the resistor R6, and the output terminal of the voltage comparator U4A is connected to the clock input pin of the digital counter U3.

8. The bridge overweight detection system based on electromagnetic oscillation according to claim 4 is characterized in that: The oscillation detection module further includes an enabling circuit, which includes a power device Q1, a power device Q2, a resistor R1 and a resistor R2, wherein: One end of the inductor L1 is connected to the first electrode of the power device Q1 and the third electrode of the power device Q2, the third electrode of the power device Q1 is connected to the first electrode of the power device Q2 and one end of the capacitor C4, the second electrode of the power device Q1 is connected to the data processing module through the resistor R1, and the second electrode of the power device Q2 is connected to the data processing module through the resistor R2.

9. The bridge overweight detection system based on electromagnetic oscillation according to claim 1 is characterized in that: It also includes an alarm control module, and the data analysis module is connected to the alarm device through the alarm control module; When performing bridge overload detection, the data analysis module compares the sampling frequency f s With the overweight threshold frequency f t , when the sampling frequency f s Less than the overweight threshold frequency f t When the data analysis module controls the alarm device to send out an alarm signal through the alarm control module; The alarm control module includes a resistor R14, a resistor R15, a power device Q4, a diode D1 and a relay K1, one end of the resistor R15 is connected to the data processing module and one end of the resistor R14, and the other end of the resistor R14 is connected to the power supply voltage VCC; The other end of the resistor R15 is connected to the second electrode of the power device Q4, the first electrode of the power device Q4 is grounded, the third electrode of the power device Q4 is connected to the anode of the diode D1 and one end of the relay K1, the other end of the relay K1 is connected to the cathode of the diode D1 and connected to the power supply voltage VCC; the normally open contact of the relay K1 is connected in series in the power supply circuit of the alarm device.

10. The bridge overweight detection system based on electromagnetic oscillation according to claim 3, characterized in that: Determine the sampling frequency f of the sampling signal according to the oscillation frequency of the collected sampling signal s The method includes obtaining the vehicle-free frequency f0, filtering the oscillation frequency of the collected sampling signal according to the vehicle-free frequency f0, and using the filtered oscillation frequency as the sampling frequency f s The no-vehicle frequency f0 is the oscillation frequency of the sampling signal when there is no vehicle traveling on the detected bridge.

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