CN100460841C - On-line test method and test system for differential temperature-compensated bridge cable force - Google Patents

Abstract

The differential temperature compensation bridge cable force online testing method and testing system based on the magnetoelastic effect of the present invention uses the bridge cable as a ferromagnetic material, puts the bridge cable in a specific magnetic field, the bridge cable will be magnetized, and the bridge cable will be magnetized. The magnetic permeability will change with the change of stress state and temperature. The sensor is composed of a working magnetic circuit and a reference magnetic circuit. In each magnetic circuit design, the bridge cable is only a part of the magnetic circuit, not as the iron core of the exciting coil and the measuring coil. The reference magnetic circuit of the sensor only senses changes in temperature, while the working magnetic circuit senses changes in temperature and cable force at the same time. The output signals of the working magnetic circuit and the reference magnetic circuit are differentially calculated to eliminate the influence of temperature. The corresponding relationship between force changes can be used to test the magnitude of the cable force. The cable force testing method of the present invention has the advantages of high precision, good dynamic response, small influence of temperature, low sensor price, convenient installation and debugging, long service life, strong overload protection ability, suitable for static and dynamic cable force measurement, and can be done at any time in all weathers Sampling, the anti-corrosion layer on the surface of the bridge cable and the protective plastic casing have no effect on the measurement results.

Description

On-line test method and test system for differential temperature-compensated bridge cable force

technical field

The invention relates to magnetic physics, magnetoelastic effect of ferromagnetic materials and sensing technology, in particular to magnetoelastic effect sensing and cable force testing of bridge cables.

technical background

At present, there are mainly the following types of methods for testing bridge cable force.

1. Pressure gauge method

When the bridge cable is stretched with a jack, the cable force can be obtained by measuring the hydraulic pressure of the oil cylinder through a precision pressure gauge or a hydraulic sensor. This method is simple and easy to implement, and it is the most practical method to control the cable force in construction. It can be used to adjust the cable force during the construction of cable-stayed bridges. However, due to some characteristics of the pressure gauge itself, there are disadvantages such as easy misalignment of the pointer, severe pointer vibration under high pressure, large reading error, and the need to convert the load indication value. It cannot be used for dynamic cable force monitoring after the bridge is completed.

2. Pressure sensor method

Add a backing plate and a bearing ring between the fixed anchor head of the bridge cable and the concrete of the bridge body, the tension on the bridge cable will all act on the bearing ring, and the bearing ring will produce strain. The strain can be used to calculate the cable force. At present, the sensors used to measure the strain of the pressure ring at home and abroad mainly include resistance strain sensors, vibrating wire strain sensors, optical fiber strain sensors and so on.

The resistance strain sensor is the most widely used pressure sensor. The resistance strain gauge is pasted on the outer surface of the pressure ring. Under the action of the cable force, the pressure ring produces elastic deformation, and the resistance value of the resistance strain gauge will change accordingly. It is connected to the Wheatstone bridge circuit, and under the action of the excitation voltage, the output terminal has an electrical signal output proportional to the cable force. But its biggest problem is the adhesive problem, which restricts the accuracy, linearity and application range of the resistance strain type pressure sensor.

The vibrating wire strain sensor aims at the shortcomings of the resistance strain gauge type, and replaces the strain gauge with a vibrating wire. 3, 4 or 6 high-precision vibrating wires are built in the pressure ring, and the vibrating wires are placed in the magnetic field. When the vibrating wires vibrate under the excitation signal, they will cut the magnetic force lines and generate induced electromotive force. The frequency of the induced electromotive force is the vibration of the vibrating wires frequency. When the pressure ring is under pressure, its deformation will change the tension state of the vibrating wire, thereby changing the vibration frequency and induced electromotive force frequency of the vibrating wire, so the cable force can be calculated by measuring the induced electromotive force frequency of the vibrating wire. However, the size is relatively large, the installation is inconvenient, the service life is not long, and it is easy to be interfered by electromagnetic fields. For example, electromagnetic field sources such as mobile phones, communication base stations, and power plants will obviously interfere with the test results, resulting in a decrease in the reliability of the measurement results; In addition, the vibrating wire sensor cannot Used in series, dynamic response and dynamic measurement cannot be performed, and it is not easy to form a detection network. If there is a network, there will be a lot of cables for transmitting signals, which will directly lead to a sharp increase in workload and affect the accuracy of measurement results.

The working principle of the optical fiber strain sensor is: the fiber grating is rigidly pasted on the outer surface of the pressure ring (along the circumferential direction or the direction of the busbar) to form a through-heart sensor head, which is installed on the anchorage of the cable-stayed bridge Between the cable hole backing plate, the sensing head bears the cable force of the bridge cable. When the broadband light emitted by the light source is transmitted to the measured point through the optical fiber, the grating selectively reflects back a narrow-band light, which is transmitted to the wavelength discriminator or wavelength demodulator through the optical splitter, and then photoelectrically converted by the photodetector. When the sensing head is under pressure, the center wavelength of the FBG will move correspondingly, and the cable force of the stay cable can be calculated by monitoring the amount of wavelength shift. The sensor has a strong ability to adapt to harsh environments (moisture-proof, anti-temperature drift, anti-electromagnetic interference); light weight, small size, small impact on the structure, easy to arrange; can be distributed in series, easy to achieve distributed measurement; high sensitivity, high precision; It has the advantages of high spatial resolution of the measured value, but like the resistance strain type, there is an adhesive problem, and it is only suitable for newly installed anchor cables. For many anchor cables that have been installed and are being put into use, it is impossible to install the sensor And the anchor cable is removed and reinstalled.

3. Vibration method (frequency method)

Its measurement principle is to use the dynamic structure model of the cable to conduct modal analysis on the model, and the relationship between the cable force and the vibration frequency of the cable can be obtained, and the precision vibration pickup is used to pick up the vibration signal of the cable under the excitation of environmental vibration. After filtering, amplification and spectrum analysis, the nth-order natural frequency of the cable is determined according to the spectrum diagram, and the cable force is obtained according to the relationship between the cable force and the frequency.

Using the frequency method to measure the cable force can realize the online dynamic monitoring of the cable force, which is one of the effective methods for monitoring the health of the cable force after the bridge is completed. This method is an indirect measurement method, and the service life of the sensor is long, but the relationship between the cable force and the frequency must Affected by various factors such as the sag, slope and boundary conditions of the bridge cable, the establishment and solution of the model are very complicated, and all-weather monitoring cannot be realized.

4. Magnetoelastic effect method

Its basic principle is to use the bridge cable as a ferromagnetic material, put it in a magnetic field environment, and the cable will be magnetized. When the stress of the bridge cable changes, the hysteresis curve will change accordingly, and the magnetic permeability will change. Therefore, the small precision electromagnetic sensor placed in the cable can be used to measure the change of magnetic permeability, and the cable’s magnetic permeability can be calculated. stress changes.

The magnetoelastic effect method to measure cable force is still under discussion, and the research of this method is mainly concentrated in some research institutions such as Czechoslovakia, Japan, and the United States. The main representatives are Sunaryo SUMITRO from Research and Development Keisoku, Japan; Andrej JAROSEVIC from Div Fac.of Math.and Physics Dept.of Civil and Materials Eng.of Comenius University in Czech Republic; MingL.WANG from University of Illinois at Chicago, USA.

The magnetoelastic effect method has the advantages of good dynamic response, low price, long life, and the test result is directly the cable force. It can realize all-weather dynamic monitoring. It is the most potential method for bridge cable force health monitoring. However, the currently developed magnetoelastic The sensors are mainly concentrated in the sleeve-type magnetic circuit structure, which is characterized in that the measured bridge cable is used as the iron core of the excitation coil and the detection coil. Therefore, the installation of the sensor is more convenient before the bridge cable is built, but for the bridge cable After being fixed, the installation is very troublesome, and the field winding machine can only be used to complete the winding of the exciting coil and the measuring coil, which is not only technically difficult, the working environment is harsh, and the measurement accuracy is low. In addition, after the bridge cable on which the sensor is installed is fixed, the sensor cannot be disassembled, making maintenance particularly difficult. On the other hand, the method of eliminating the influence of temperature currently adopts the look-up table offset method, which not only requires the drawing of the magnetic permeability-temperature curve, but also requires a huge workload. Moreover, in a wide temperature range, the influence of temperature on magnetic permeability is different in the process of heating and cooling. If only a single curve is used for compensation, the compensation effect is very limited.

Although the above-mentioned methods can test the cable force of the bridge cable, for the built bridge, the magneto-elastic effect method cannot be installed, and the on-site winding accuracy is low. The commonly used frequency vibration method for detection, because the model establishment and solution of this method is very complicated, the test accuracy is affected by many factors, and it is controlled by whether the bridge cable is vibrating, so it cannot realize all-weather detection. Therefore, none of the above methods can meet the requirements of remote health monitoring of modern bridges.

Contents of the invention

In view of the deficiencies in the prior art above, one of the purposes of the present invention is to propose a differential temperature-compensated bridge cable force online testing method based on the magnetoelastic effect, and the second purpose is to propose a testing system for realizing the method. To solve two problems: one is to solve the problem of difficult installation and maintenance, and the other is to solve the problem of temperature compensation.

The purpose of the present invention is to realize by following technical scheme:

The main idea of the differential temperature-compensated bridge cable force online test method proposed by the present invention is to use the material of the bridge cable as a ferromagnetic material, place the bridge cable in a magnetic field environment, the bridge cable will be magnetized, and the magnetic permeability of the bridge cable The rate will change with the stress state and temperature of the bridge cable. The specific method is: put the tested bridge cable in the magnetic field as a part of the working magnetic circuit, not as the iron core of the exciting coil and the measuring coil, and feel the change of temperature and cable force at the same time, and take another one of the same quality as the tested bridge cable A bridge cable is used as a reference bridge cable, placed in another magnetic field with the same ambient temperature as a part of the reference magnetic circuit, and only feels the temperature change. The working magnetic circuit and the reference magnetic circuit form a symmetrical differential magnetic circuit structure; use the excitation power supply to provide the same excitation signal to the two magnetic circuits, and perform signal conditioning on the output signals of the working magnetic circuit and the reference magnetic circuit before differential operation to eliminate temperature Influence, perform frequency spectrum analysis or integral calculation to obtain the change of magnetization characteristics of the bridge cable, and use the corresponding relationship between the change of magnetic permeability and the change of cable force to test the magnitude of the cable force. In the above method, the signal source of the excitation power supply can be a sinusoidal AC signal or a pulsed DC cross-current source.

The test system further proposed by the present invention to realize the on-line test method of bridge cable force is composed of an excitation power supply, a sensor, a processing circuit, a differential operation amplifier circuit and a processing computer. The sensor is composed of a working magnetic circuit and a reference magnetic circuit. The tested bridge cable, iron core, magnetic tile and yoke form a working magnetic circuit. A section of homogeneous cable with the same material as the tested bridge cable is used as a reference bridge cable, and the reference bridge cable, iron core, magnetic tile and yoke iron form a reference magnetic circuit. The two pairs of magnetic tiles of the working magnetic circuit and the reference magnetic circuit embrace the working bridge cable and the reference bridge cable respectively, with a certain distance between them; one iron core is equipped with an excitation coil, and the other iron core is equipped with a measuring coil; the reference magnetic circuit and the reference magnetic circuit The structural dimensions of each part of the working magnetic circuit are exactly the same, the only difference is that the length of the measured bridge cable and the reference bridge cable are different, and the length of the reference bridge cable is determined by the appearance size of the sensor. The output induced voltages of the working magnetic circuit and the reference magnetic circuit are respectively preprocessed by amplification, filtering, etc., and then sent to a differential operational amplifier for differential operation. Since the output induced voltage of the reference magnetic circuit is only caused by temperature, while the output induced voltage of the working magnetic circuit is caused by both the cable force and temperature, the result of the differential operation will eliminate the influence of temperature on the cable force. The differential output voltage is integrated to obtain the dynamic change of the magnetic flux caused by the cable force. When the external excitation magnetic field strength is constant, the change of the magnetic permeability of the working bridge cable can be known, and the cable force can be obtained.

The advantage of adopting the present invention is:

1. Good dynamic response. Since the force of the cable force directly affects the change of the magnetic flux of the magnetic circuit, the measuring coil senses the change of the magnetic flux through magnetic field coupling, so the dynamic response is good.

2. Easy installation and debugging. Since neither the excitation coil nor the measurement coil uses the bridge cable as the iron core, the bridge cable is only used as a part of the magnetic circuit, and the connection with other parts adopts a magnetic tile structure, so the use of this method is not affected by the bridge under construction or under construction. , can be easily tested for cable force.

3. Automatic temperature compensation. Since the magnetic circuit structure of the entire sensor is designed as a symmetrical differential structure, the structural parameters of the working magnetic circuit and the reference magnetic circuit are exactly the same, the output induced voltage of the reference magnetic circuit is only related to temperature, and the output induced voltage of the working magnetic circuit is The function of cable force and temperature, the result after difference operation will eliminate the temperature effect. That is, the voltage after the differential does not change with the change of temperature, achieving automatic temperature compensation.

4. Strong overload protection ability and long service life. The method is a non-contact measurement method, the sensor has strong overload protection ability and long service life.

5. The measurement result has high precision. Since the method and system use the relationship between the magnetic properties of the material and the cable force to measure the cable force, and have nothing to do with the protective layer and protective plastic casing on the surface of the bridge cable, or the vibration state of the bridge cable, the measurement result has high precision.

6. The present invention can also monitor the corrosion of the bridge cable, because the corrosion of the bridge cable will seriously affect the magnetization state of the bridge cable.

Description of drawings

Fig. 1 test system structural diagram of the present invention

Detailed ways

Below in conjunction with Fig. 1, the process of structure and method realization of this system is described further:

Cut a section of the bridge cable under test (or a bridge cable of the same quality and type as the bridge cable under test) with a suitable length as the reference bridge cable [12] to form a reference magnetic circuit. The third and fourth iron cores [33] [34] and the second yoke [42] in the reference magnetic circuit are fixed on the reference bridge cable [12] through the third and fourth magnetic tiles [23] [24] , the third and fourth magnetic tiles [23][24] hug the reference bridge cable [12], and fix them with fastening countersunk bolts [62], a certain distance should be reserved in the middle, wherein the third and fourth magnetic tiles Watt [23][24] and the 3rd, the 4th iron core [33][34] are a whole; The 4th iron core [34] of reference magnetic circuit installs the second exciting coil [53], the 3rd iron core The second measurement coil [54] is installed on [33], and the connection of the third and fourth iron cores [33] [34] and the second yoke iron [42] adopts interference shaft hole fit.

The first and second iron cores [31][32] and the yoke are installed on the tested bridge cable [11] with the first and second magnetic tiles [21][22] to form a working magnetic circuit. The first and second magnetic tiles [21][22] hug the working bridge cables [11] and fix them with fastening countersunk bolts [61]. After the magnetic tiles and the working bridge cables are fixed, a certain distance should be kept in the middle , wherein the first and second magnetic tiles [21][22] are integrated with the first and second iron cores [31][32], and the first excitation coil is installed on the first iron core [31] of the working magnetic circuit [51], the first measuring coil [52] is installed on the second iron core [32], and the connection between the first and second iron core [31] [32] and the fourth yoke [41] adopts interference shaft hole fit . The arrows in the figure indicate the lines of magnetic force.

In the above two magnetic circuits, the magnetic tile structure connected by the bridge cable should have a coaxiality requirement with the bridge cable. In practical applications, the working magnetic circuit and the reference magnetic circuit can be put together to work, or they can be separated. Work, as long as the ambient temperature of the working magnetic circuit and the reference magnetic circuit are the same.

The constant current applied by the excitation power supply acts on the first and second excitation coils [51][53] of the working magnetic circuit and the reference magnetic circuit at the same time, generating the same stable magnetic field strength in the two circuits. When the bridge cable is subjected to When the tension or temperature changes, the magnetic flux in the circuit will change, and the first and second measuring coils [52][54] will generate induced voltage. Because the reference bridge cable only senses the temperature, the induced voltage of the second measuring coil [54] is only related to the temperature, while the working bridge cable feels the change of temperature and cable force at the same time, the induced voltage of the first measuring coil [52] is related to temperature and cable force. related to changes in force.

The induced voltages output by the first and second measuring coils [52] and [54] are respectively amplified and filtered by the pre-processing circuit, and then sent to the two input ports of the differential operation amplifier circuit for differential operation to eliminate temperature fluctuations. Influence.

The output data of the differential operational amplifier is collected by the high-speed data acquisition card and sent to the processing computer, and the cable force value is obtained by using the signal processing software. Among them, the signal acquisition and processing equipment preferably includes a dynamic signal analysis and processor with a high-impedance dynamic signal acquisition card.

The present invention has been described above using examples. But those improvements and modifications that become obvious to those skilled in the art after reading the disclosure document still belong to the scope of the present application

Claims (7)

1. based on the differential type temperature compensating type bridge cable force on-line testing method of magnetoelastic effect, it is characterized in that: with the bridge rope is ferromagnetic material, place magnetic field to form work magnetic circuit on detected bridge rope as the part of magnetic circuit, experience the variation of temperature and Suo Li simultaneously, other gets one section bridge rope with detected bridge rope homogeneity as reference bridge rope, place the part formation reference magnetic circuit of the magnetic field of another equivalent environment temperature as magnetic circuit, only experience variation of temperature, work magnetic circuit becomes the magnetic structure of symmetrical differential type with reference magnetic circuit; Provide identical excitation signal with field power supply to two magnetic circuits, the output signal of work magnetic circuit and reference magnetic circuit is carried out behind the signal condition calculus of differences again eliminate temperature effect, carry out spectrum analysis or integral operation, obtain the variation of bridge rope magnetization characteristic, utilize the variation of magnetic permeability and the corresponding relation that Suo Li changes, the size of test Suo Li.

2. according to the described bridge cable force on-line testing of claim 1 method, it is characterized in that: the signal source of field power supply is selected sinusoidal ac signal for use, or selects pulse direct current constant current source signal for use.

3. realize the test macro of claim 1 or 2 described bridge cable force on-line testing methods, it is characterized in that being made up of field power supply, sensor, treatment circuit, calculus of differences amplifying circuit and process computer, wherein sensor is made up of work magnetic circuit and reference magnetic circuit;

Work magnetic circuit is made up of service bridge rope (11), first, second magnetic shoe (21) (22), first, second iron core (31) (32) and first yoke (41); First, second magnetic shoe (21) (22) of work magnetic circuit is embraced service bridge rope (11), the middle spacing that keeps; First iron core (31) is gone up first field coil (51) is installed, and second iron core (32) is gone up the first measurement coil (52) is installed;

Reference magnetic circuit is made up of reference bridge rope (12), the 3rd, the 4th magnetic shoe (23) (24), the 3rd, the 4th iron core (33) (34) and second yoke (42); The the 3rd, the 4th magnetic shoe (23) (24) of reference magnetic circuit will be embraced with reference to bridge rope (12), the middle spacing that keeps; The 4th iron core (34) is gone up second field coil (53) is installed, and the 3rd iron core (33) is gone up the second measurement coil (54) is installed;

First, second measures the signal wire difference connection processing circuit of coil (52) (54), carry out filtering, amplify pre-service by the signal condition module, the output of two-way treatment circuit connects the calculus of differences amplifying circuit again signal is carried out calculus of differences rejecting temperature effect, the output signal connection processing computing machine of calculus of differences amplifying circuit carries out spectrum analysis or integral operation, obtains the result of variations of bridge rope magnetization characteristic.

4. test macro according to claim 3 is characterized in that: the iron core of work magnetic circuit and reference magnetic circuit is connected employing interference axis hole and cooperates with yoke; The magnetic shoe of work magnetic circuit and reference magnetic circuit and iron core are an integral body; The work of putting together of work magnetic circuit and reference magnetic circuit, or separately work.

5. test macro according to claim 3 is characterized in that: first field coil (51) and first measures coil (52) and second field coil (53) and second is measured coil (54) shared iron core respectively, or independent separately not shared iron core.

6. test macro according to claim 3 is characterized in that: first, second field coil (51) (53) and first, second are measured coil (52) (54) and directly are wrapped on first, second, third, fourth iron core (31) (32) (33) (34).

7. test macro according to claim 3 is characterized in that: the material selection high permeability ingot iron or the A3 mild carbon steel of first, second, third, fourth magnetic shoe (21) (22) (23) (24), first, second, third, fourth iron core (31) (32) (33) (34) and first, second yoke (41) (42).

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