CN114518067B - Data acquisition instrument and monitoring system based on carbon nanotube composite sensor - Google Patents

Data acquisition instrument and monitoring system based on carbon nanotube composite sensor Download PDF

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CN114518067B
CN114518067B CN202210386905.1A CN202210386905A CN114518067B CN 114518067 B CN114518067 B CN 114518067B CN 202210386905 A CN202210386905 A CN 202210386905A CN 114518067 B CN114518067 B CN 114518067B
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sensor
composite sensor
nano tube
carbon nanotube
carbon nano
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CN114518067A (en
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郭健
胡山
傅宇方
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Southwest Jiaotong University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
    • G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/225—Measuring circuits therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2268—Arrangements for correcting or for compensating unwanted effects
    • G01L1/2281—Arrangements for correcting or for compensating unwanted effects for temperature variations
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/02—Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

The embodiment of the invention discloses a data acquisition instrument and a monitoring system based on a carbon nano tube composite sensor. Wherein, data acquisition instrument includes: the device comprises a constant current circuit, a filter circuit, an amplifying circuit, an A/D signal conversion circuit, a communication module and an acquisition port, wherein the acquisition port is used for connecting a carbon nano tube composite sensor so as to connect the carbon nano tube composite sensor in the constant current circuit in series; the carbon nano tube composite sensor is a piezoresistive pressure sensor; the filter circuit is electrically connected with two ends of the carbon nano tube composite sensor and is used for filtering voltage signals at two ends of the carbon nano tube composite sensor; the amplifying circuit is connected with the filtering circuit and used for amplifying the filtered voltage signals. The embodiment improves the monitoring precision and robustness of the carbon nanotube sensor.

Description

Data acquisition instrument and monitoring system based on carbon nanotube composite sensor
Technical Field
The embodiment of the invention relates to the field of structural health monitoring, in particular to a data acquisition instrument and a monitoring system based on a carbon nano tube composite sensor.
Background
In recent years, many bridge structure damage events occur at home and abroad, the reasons are various, and if the bridge is monitored, problems can be found in time, and many accidents can be avoided. Therefore, bridge structure health monitoring is gradually concerned by relevant departments and is greatly developed, and the bridge structure health monitoring has become an important field for research in academic and engineering circles at home and abroad.
Wherein the sensor and the corresponding measurement and acquisition system are used as an important ring for monitoring the health of the bridge structure, and a set of system is also developed: in the prior art, the most widely applied strain gauge piezoresistive sensors and fiber bragg grating sensors are used, and a dynamic and static strain acquisition system is used for data acquisition and processing in most cases; in the measurement process of the traditional strain gauge type dynamic strain acquisition system, factors such as bridge circuit resistance mismatch, strain gauge pasting technology, cable resistance testing and the like can cause great zero drift and temperature drift; the optical fiber strain acquisition system has the characteristics of strong anti-interference capability, high sensitivity, corrosion resistance and the like, but the measurement result is often inaccurate due to the influence of temperature in the measurement process, and the actual requirement cannot be well met.
With the continuous research in the material-related field, carbon nanotubes are used as a novel high-performance material, and are tried to be added into a cement-based material to manufacture a carbon nanotube sensor; however, as a new sensor with a wide application prospect, the prior art lacks a corresponding measurement and acquisition system. The carbon nanotube sensor essentially belongs to a piezoresistive sensor, and at present, aiming at the carbon nanotube sensor, a general method is to utilize a resistance tester to collect signals; and because the carbon nanotube sensor has the characteristics of changeable and changeful properties, the dynamic and static strain acquisition system used in the prior art is difficult to be suitable for the carbon nanotube sensor.
Disclosure of Invention
The embodiment of the invention provides a data acquisition instrument and a monitoring system based on a carbon nano tube composite sensor, which are used for improving the monitoring precision and robustness of the carbon nano tube sensor.
In a first aspect, an embodiment of the present invention provides a data acquisition instrument based on a carbon nanotube composite sensor, including: a constant current circuit, a filter circuit, an amplifying circuit, an A/D signal conversion circuit, a communication module and an acquisition port, wherein,
the collection port is used for connecting the carbon nano tube composite sensor so as to connect the carbon nano tube composite sensor in the constant current circuit in series; the carbon nano tube composite sensor is a piezoresistive pressure sensor;
the filter circuit is electrically connected with two ends of the carbon nano tube composite sensor and is used for filtering voltage signals at two ends of the carbon nano tube composite sensor;
the amplifying circuit is connected with the filter circuit and is used for amplifying the filtered voltage signal;
the A/D signal conversion circuit is connected with the amplifying circuit and is used for carrying out A/D conversion on the amplified signal to obtain a digital signal;
the communication module is connected with the A/D signal conversion circuit and used for sending the digital signal to the outside.
In a second aspect, an embodiment of the present invention provides a monitoring system based on a carbon nanotube composite sensor, including: the data acquisition instrument based on the carbon nanotube composite sensor and the upper computer are adopted; the upper computer is in communication connection with the communication module and is used for receiving the digital signals and converting the digital signals into the resistance of the carbon nano tube composite sensor.
The technical effects of the embodiment of the invention are as follows:
1. the embodiment provides a data acquisition instrument based on a carbon nano tube composite sensor, which is used for acquiring resistance data of the carbon nano tube composite sensor. The instrument realizes the conversion from a resistance signal to a voltage signal through a constant current source circuit, has a self-filtering function, and has higher monitoring precision than the traditional resistance tester.
2. The data acquisition instrument that this application provided has better robustness to temperature variation, and the collection system is whole need not to carry out temperature compensation or secondary filter, and the flow of measurationing is simple and the precision is higher, can be better satisfy the actual engineering demand.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a flowchart of an impact load automatic identification method based on a carbon nanotube sensor according to an embodiment of the present invention;
fig. 2 is a circuit diagram of a constant current circuit according to an embodiment of the present invention;
fig. 3 is a circuit diagram of an amplifying circuit according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a monitoring system based on a carbon nanotube composite sensor according to an embodiment of the present invention.
FIG. 5 is a schematic diagram of one arrangement of four carbon nanotube composite sensors provided by an embodiment of the present invention;
fig. 6 is a schematic diagram of a simplified structure provided by an embodiment of the present invention.
Fig. 7 is a schematic structural diagram of a carbon nanotube composite sensor according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of another arrangement of four carbon nanotube composite sensors provided by an embodiment of the present invention;
fig. 9 is a schematic diagram of a carbon nanotube composite sensor during a detection test according to an embodiment of the present invention;
FIG. 10 is a graph showing the pressure and displacement curves of the built-in carbon nanotube composite sensor of a concrete structure according to the present invention, as measured by a universal tester.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below. It is to be understood that the disclosed embodiments are merely exemplary of the invention, and are not intended to be exhaustive or exhaustive. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Fig. 1 is a circuit diagram of a data acquisition instrument based on a carbon nanotube composite sensor according to an embodiment of the present invention. The data collecting instrument is used for collecting resistance data of the carbon nanotube composite sensor, and as shown in fig. 1, the data collecting instrument includes: the device comprises a constant current circuit, a filter circuit, an amplifying circuit, an A/D signal conversion circuit, a communication module and an acquisition port. In the drawings of the present embodiment, the dotted line portion is only for the circuit connection relationship and is not an essential component of the main structure of the drawings.
The collection port is used for connecting the carbon nano tube composite sensor so as to connect the carbon nano tube composite sensor in the constant current circuit in series. The carbon nano tube composite sensor is a piezoresistive pressure sensor. After the carbon nano tube composite sensor is arranged in the surface of an object, the pressure applied to the surface of the object can be observed through the resistance of the carbon nano tube composite sensor.
Specifically, after the carbon nanotube composite sensor is formed, two electrodes are led out by using a copper mesh and are connected to two acquisition ports, so that the carbon nanotube composite sensor is connected to a constant current source circuit. Fig. 2 is a circuit diagram of a constant current circuit according to an embodiment of the present invention.
As shown in fig. 2, in the constant current source circuit, the voltage reference chip U1 supplies a reference voltage V1 (i.e., a voltage across U1) to the circuit. The V2 voltage is applied to the pin C of U1 and the operational amplifier U2 through an external power supply chip. The "virtual short" is set between pins 2 and 3, and the voltage difference is zero. At this time, the voltage across the resistor R2 is substantially the reference voltage V1 of the voltage reference chip. By adjusting the resistance value of R2, the current value of the constant current source circuit can be adjusted, where the current value I0= V1/R2. A Darlington system structure consisting of two triodes Q1 and Q2 is adopted, wherein Q1 is NPN type, Q2 is PNP type, the current amplification factor of the circuit is the product of the amplification factors Q1 and Q2, and the base current of the triode Q1 can be effectively reduced by the method. When the carbon nano tube composite sensor deforms to generate resistance change, the resistance-voltage conversion is completed through the constant current source circuit, and the voltage signal is sent to the filter circuit for further processing.
The filter circuit is electrically connected with two ends of the carbon nano tube composite sensor and is used for filtering voltage signals at two ends of the carbon nano tube composite sensor.
Specifically, a part of clutter is mixed in a voltage signal obtained by a constant current source circuit, and in order to reduce the interference of the clutter noise signal to an available signal and efficiently extract useful components in the signal, a filter circuit is adopted to process the voltage signal.
Optionally, the filter circuit is a butterworth filter. Compared with other filters, the Butterworth filter has nearly parallel amplitude characteristic curves in a pass band, no obvious fluctuation exists, and a useful signal can approximately pass through the filter without attenuation. The clutter signal with the frequency higher than the frequency has a strictly descending trend of an amplitude curve, is very suitable for the output signal of the carbon nano tube composite sensor, and the amplitude-frequency response function can be expressed as follows:
Figure 670666DEST_PATH_IMAGE001
wherein the content of the first and second substances,Nto represent the order of the butterworth filter,ω c representing the cut-off frequency, i.e. the frequency at which the amplitude drops to-3 dB. Preferably, a third order butterworth filter is employed.
The amplifying circuit is connected with the filter circuit and used for amplifying the filtered voltage signal.
Specifically, the resistance of the carbon nanotube composite sensor adopted in this embodiment fluctuates around 1500 Ω, and after passing through the constant current source circuit, the voltage value fluctuates slightly within 1.5V, and the voltage signal is weak. Therefore, in order to facilitate the acquisition of voltage, a pre-amplification circuit design is required before data acquisition. Fig. 3 is a circuit diagram of an amplifying circuit according to an embodiment of the present invention.
As shown in fig. 3, amplification is performed using an operational amplifier U, R4 is an input resistor, R5 is a feedback resistor, and the gain amplification of the amplifier is set by R4 and R5 together. After the input voltage of the front-end module is amplified, the voltage fluctuation range of the input voltage is converted into a voltage interval where the micro-control chip is located, and C3 in the circuit is a coupling capacitor and is used for separating the direct current component of the operational amplifier circuit from the direct current components of other amplifier circuits, so that interference is avoided.
The A/D signal conversion circuit is connected with the amplifying circuit and is used for carrying out A/D conversion on the amplified signal to obtain a digital signal. Optionally, the a/D signal conversion circuit takes a single chip microcomputer as a core, and can collect the voltage signal after passing through the amplifying circuit and temporarily store the voltage signal in the memory.
The communication module is connected with the A/D signal conversion circuit and used for sending the digital signal to the outside. Optionally, the communication module is a USB interface or a remote communication module.
In summary, the working mechanism of the data acquisition instrument includes: after the carbon nano tube sensor is connected in series in the constant current circuit through the acquisition port, the constant current circuit provides constant current for the carbon nano sensor, so that voltage signals at two ends of the carbon nano sensor are in direct proportion to the resistance; the filter circuit filters the voltage signal and filters noise in the voltage signal; the amplifying circuit amplifies the filtered voltage signal; the A/D signal conversion circuit converts the amplified signal into a digital signal; and the communication module sends the digital signal to the outside.
The technical effects of the embodiment are as follows:
1. the embodiment provides a data acquisition instrument based on a carbon nano tube composite sensor, which is used for acquiring resistance data of the carbon nano tube composite sensor. The instrument realizes the conversion from a resistance signal to a voltage signal through a constant current source circuit, has a self-filtering function, and has higher monitoring precision than the traditional resistance tester.
2. Indexes such as the size, the shape, the manufacturing materials and the like of the carbon nanotube sensor are variable and easy to change, so that various properties represented by resistance values of the sensor have a large change range, and the dynamic and static strain acquisition system is difficult to be applied to the carbon nanotube sensor; in the prior art, in the measurement process of the traditional strain gauge type dynamic strain acquisition system, factors such as bridge circuit resistance mismatching, a strain gauge pasting process, cable resistance testing and the like cause great null shift and temperature shift; the optical fiber strain acquisition system is susceptible to temperature in the measurement process, so that the measurement result is often inaccurate, and the actual requirement cannot be well met. The data acquisition instrument that this application provided has from the filtering function, and temperature variation is weak to carbon nanotube sensor self sensing effect influence, and the collection system is whole need not to carry out temperature compensation or secondary filter, and the flow of measurationing is simple and the precision is higher, compares the satisfying actual engineering demand that prior art can be better.
The embodiment of the invention also provides a monitoring system based on the carbon nano tube composite sensor, which is used for realizing the measurement and monitoring of the carbon nano tube composite sensor in the actual engineering. The system comprises: the data acquisition instrument based on the carbon nanotube composite sensor and the upper computer in any embodiment. The upper computer is in communication connection with the communication module and is used for receiving the digital signals and converting the digital signals into the resistance of the carbon nano tube composite sensor.
Optionally, when the carbon nanotube composite sensor is arranged inside an object, the upper computer converts the received digital signal into a resistance change rate which is easy to directly observe in a software programming mode, and the deformation state of the carbon nanotube composite sensor inside the object structure is reflected in real time and is automatically pre-warned by observing the fluctuation condition of the resistance change rate, so that the health monitoring of the structure is realized.
Optionally, the collection ports have a plurality of pairs, and each pair of collection ports is used for connecting two ends of one carbon nanotube composite sensor; at the moment, the upper computer is also used for displaying the resistors of the plurality of carbon nano tube composite sensors on the same screen.
Fig. 4 is a schematic diagram of a monitoring system based on a carbon nanotube composite sensor according to an embodiment of the present invention. Because there is no coupling or overlapping signal interference among a plurality of modules in the data acquisition instrument, the constant current circuit, the filter circuit, the amplifying circuit, the A/D signal conversion circuit, the communication module and the acquisition port are integrally copied in multiple copies in the data acquisition instrument shown in fig. 4, and the multi-channel multi-sensor simultaneous measurement and the same-screen multi-display function can be realized by processing channels during welding and matching with upper computer software.
Optionally, the upper computer is further configured to implement at least one of the following functions: the method comprises the steps of real-time display of resistance values and resistance change rates, setting of upper and lower lines, automatic early warning of exceeding of the upper and lower lines, playback of historical records, display of curve charts, curve comparison, range setting and storage of switches.
Specifically, the present embodiment implements functions such as data processing and data playback through upper computer software. The main functions realized are: the method comprises the steps of real-time display of resistance values, real-time display of resistance change rates, setting of upper and lower lines, automatic early warning of exceeding of the upper and lower lines, playback of historical records, display of curve charts, multi-display on the same screen, curve comparison, range setting, storage of switches and the like.
Through host computer software, in the deformation process of carbon nanotube composite sensor in the inside loaded emergence of structure, can carry out playback analysis through observing curve chart resistance change rate fluctuation range in real time or to historical data, combine carbon nanotube composite sensor resistance change and the characteristic that the deformation degree keeps linear positive correlation, real-time supervision, analysis carbon nanotube composite sensor are in the loaded condition of structure, deduce the healthy impaired condition of structure. And an upper line and a lower line can be arranged on the basis of a certain amount of research to automatically warn the damage of the structure.
On the basis of the above-described embodiment and the following-described embodiment, the present embodiment refines the use of the monitoring system. Optionally, the method for using the monitoring system comprises: connecting the carbon nanotube composite sensor with two acquisition ports of the data acquisition instrument provided by any one of the embodiments, so that the carbon nanotube composite sensor is connected in series in the constant current circuit; and starting an upper computer under the room temperature condition, starting the data acquisition instrument, and observing the resistance of the carbon nano tube composite sensor through the upper computer after the polarization resistance of the carbon nano tube composite sensor is stable.
Optionally, the using method further comprises: and setting the resistance up-down line setting and/or the resistance range of the carbon nano tube composite sensor through the upper computer.
In one embodiment, the performance of the monitoring system is verified by using two different carbon nanotube composite sensors, which comprises the following processes:
(1) two types of carbon nanotube composite sensors were fabricated, sensor a being a cube of 5cm x 5cm and sensor B being a prism of 4cm x 16 cm.
(2) Under the condition of room temperature, simultaneously connecting the sensor A and the sensor B with a carbon nano tube sensor acquisition instrument, opening the upper computer terminal software, starting the acquisition instrument, waiting for 6000s, enabling the sensor to be completely polarized and stable in resistance, and measuring that the resistance of the sensor A is 1587.81 omega and the resistance of the sensor B is 2650.97 omega.
(3) On an upper computer software interface, a lower line 1450.00 omega is set for the sensor A, the sensor A is loaded, the resistance indication value of the sensor A is changed rapidly, the lowest value is 1432.16 omega, in the process of changing the resistance value of the sensor, the software sends out an over-value alarm and refers to historical data, and the software alarms the over-value phenomenon 3ms after the resistance value of the sensor is reduced to 1450 omega.
(4) The carbon nanotube sensor and the multifunctional acquisition system are integrally moved to an environment with the temperature of 0 ℃, a curve chart is checked, and the acquired data has no obvious change.
According to the specific embodiment, after passing through the constant current source circuit, the filter circuit and the amplifying circuit, the resistance precision of the carbon nanotube sensor measured by measuring voltage is higher than that of a resistance tester. The acquisition system can simultaneously measure and read a plurality of sensors, and can successfully carry out early warning through up-down lines, and the response is rapid. After the environmental temperature changes, the effect of the acquisition system is still good, and the acquisition system is proved to have the advantages of various functions, strong anti-interference capability and the like, and has wide application prospect in the actual engineering structure.
In summary, the present embodiment provides a multifunctional monitoring system based on a carbon nanotube sensor. The system comprises a data acquisition instrument based on a carbon nano tube sensor and an upper computer, wherein the data acquisition instrument comprises: the device comprises a constant current circuit, a filter circuit, an amplifying circuit, an A/D signal conversion circuit, a communication module and an acquisition port. A resistance test wire is led out from the carbon nano tube sensor, the resistance signal constant current circuit, the filter circuit and the amplifying circuit are converted into a voltage signal which is easy to process by the singlechip, and then the A/D conversion is carried out by the singlechip; and finally, transmitting the digital signal to an upper computer in a USB communication mode or a remote transmission module. At the upper computer end, the voltage signal is converted into a resistance change rate numerical value which is easy to directly observe in a software programming mode, and the deformation state of the carbon nano tube sensor in the structure is reflected in real time and is automatically pre-warned by observing the fluctuation condition of the resistance change rate, so that the health monitoring of the structure is realized.
The technical effects of the embodiment are as follows:
1. the embodiment provides a multi-functional monitoring system based on carbon nanotube sensor, has multiple automatic function, can carry out data acquisition to the carbon nanotube sensor to can realize effects such as automatic analysis, storage, early warning to data, the special collection system who comprises collection instrument and host computer end software.
2. In an actual engineering structure, two or more carbon nanotube sensors are usually required to be built in to achieve an expected monitoring effect, however, in the resistance tester used for the carbon nanotube sensors in the prior art, under the condition of only one instrument, it is difficult to measure a plurality of sensors simultaneously, and the limitation causes that the carbon nanotube sensors have low monitoring efficiency, large limitation and high monitoring system cost in the application of the actual engineering structure. The multifunctional acquisition system based on the carbon nanotube sensor has the functions of multi-channel multi-point simultaneous measurement and multi-display on the same screen, and solves the problems that a resistance tester used in the prior art is difficult to measure and compare a plurality of sensors simultaneously under the condition of a single instrument, and the monitoring method is large in limitation.
3. The monitoring system that this embodiment provided has all reached good measuring effect to the carbon nanotube composite sensor of multiple type, compares resistance test instrument to the measurement of two kinds of carbon nanotube composite sensor resistance values in the embodiment and has appeared higher precision, has changed that prior art lacks the current situation that a performance is suitable for, the manifold carbon nanotube sensor collection system of function.
4. The monitoring system provided by the embodiment has the functions of real-time resistance value display, real-time resistance change rate display, setting of an upper line and a lower line, automatic early warning when the upper line and the lower line exceed, historical record playback, curve chart display and the like, in the embodiment, the lower line 1450 omega is set for the sensor and is loaded until the resistance value of the sensor exceeds the upper line and the lower line, the software indication value is accurate, and an alarm is given to an excessive value phenomenon within 3ms, so that the technical scheme is proved to be capable of effectively monitoring the loading condition of the carbon nanotube sensor, and the response is rapid and more intelligent; compared with a resistance tester used in the prior art, the resistance tester has the advantages of diversified functions, no need of manual inspection, high monitoring efficiency, good effect and low cost.
5. The monitoring system that this embodiment provided has the range and sets up and from the programming function, compares dynamic and static strain acquisition system, is applicable to the changeable carbon nanotube class sensor of attribute more, has better application prospect in actual engineering.
6. The monitoring system that this embodiment provided was provided to this embodiment is influenced weakly to the temperature variation, need not to carry out special filtering and compensation, has the self-filtering function to ordinary clutter simultaneously, makes whole flow of measurationing more simple than prior art, and the precision is higher, can be better satisfy the actual engineering demand.
On the basis of the above-described embodiment and the following-described embodiment, the present embodiment performs structural health monitoring using a monitoring system. Optionally, the monitoring system further comprises: the device comprises four carbon nanotube composite sensors, a monitoring unit and a monitoring unit, wherein the four carbon nanotube composite sensors are respectively arranged at four vertex angles of a square area on the surface of an object to be monitored; the data acquisition instrument is electrically connected with the four carbon nano tube composite sensors respectively and is used for transmitting digital signals generated by the four carbon nano tube composite sensors at the four vertex angles of the square area in real time; and the upper computer is used for receiving the digital signal and determining the position of the impact load received in the square area in real time according to the digital signal.
The structure to be monitored is an object structure which is to be used for remotely monitoring the impact load on the structure to be monitored in real time. The square areas are areas of the structure surface that may be subjected to impact loading. This embodiment will monitor the impact load experienced by this area.
The carbon nanotube composite sensor used in the present embodiment includes: a cement-based composite material, and carbon nanotubes dispersed in the cement-based composite material. The carbon nanotube composite sensor is a piezoresistive pressure sensor, and the resistance of the sensor changes along with the pressure acting on the sensor. Therefore, the present embodiment has the carbon nanotube composite sensor built inside the structure, and the resistance of the carbon nanotube composite sensor is used to reflect the pressure applied to the surface of the structure.
Optionally, the determining, in real time, the position of the impact load received in the square area according to the digital signal specifically includes the following steps:
step one, the digital signals are converted into the resistance of the four carbon nano tube composite sensor in real time.
And secondly, when the resistances of the four carbon nano tube composite sensors are changed at the same moment, identifying the position of the impact load on the square area at the moment according to the resistance change of the four carbon nano tube composite sensors.
Wherein, every carbon nanotube composite sensor is piezoresistive pressure sensor, includes: a cement-based composite material, and carbon nanotubes dispersed in the cement-based composite material; the size of each carbon nano tube composite sensor is determined according to the Poisson ratio of the sensor, and the size enables the response of the carbon nano tube composite sensor to the impact load in one direction to be more prominent in other directions.
If the resistance of the four carbon nanotube composite sensors is greatly changed at the same moment, the structural surface is subjected to impact load at the moment. At this time, the position of the impact load applied to the square area at the moment is identified according to the resistance change of the four carbon nanotube composite sensors.
The basic principle of position recognition is explained below. The size of each carbon nanotube composite sensor in the embodiment is determined according to the Poisson ratio of the sensor, and the size enables the response of the carbon nanotube composite sensor to the impact load in one direction to be more prominent in other directions. This characteristic of the carbon nanotube composite sensor is referred to as a one-way response characteristic in this embodiment, and the one-way response characteristic is a basis for identifying the impact load position by using the carbon nanotube composite sensor in this embodiment.
As shown in fig. 5, four carbon nanotube composite sensors are respectively disposed at four vertex positions of the square region. Carbon nano tube composite sensor opposite edgexResponse to shock loads in the axial direction is exceptionally sensitive toy、zThe response by the impact load in the axial direction is extremely weak. Based on the characteristic, when impact load acts on the structure surface in practical engineering, each carbon nano tube composite sensor pair arranged inside transmits to the edge of the sensor pairxThe load part of the shaft responds sensitively, but the load part of the shaft responds weakly to the load part of the shaft transmitted to other directions of the shaft, and the response can be ignored.
Thus at the edgexUnder the action of impact load in the axial direction, the structure among the four carbon nanotube composite sensors (including other carbon nanotube composite sensor sensors inside the structure) can be simplified and eliminated. The structure between the four carbon nanotube composite sensors and the surface subjected to impact load is similar to a concrete slab, and the four carbon nanotube composite sensors are taken as a support, as shown in fig. 6.
Optionally, when the resistances of the four carbon nanotube composite sensors all change at the same time, first, according to the resistance change of the four carbon nanotube composite sensors, an influence coefficient of an impact load received by the square area at the time on each carbon nanotube composite sensor is calculated. The influence coefficient represents the load of the impact load applied to the square area at the moment and transferred to each carbon nano tube composite sensor.
The influence coefficient is essentially a dimensionless coefficient and is related to the load transmitted by the impact load to each carbon nanotube composite sensor. Since the load causes a change in resistance of the carbon nanotube composite sensor, the influence coefficient can be calculated from the change in resistance.
In addition, according to the influence line theory of the common simply supported beam, the influence coefficient is related to the position relation between the impact load and each carbon nanotube composite sensor, so that the influence coefficient can be used for determining the position of the impact load.
Optionally, after obtaining the influence coefficient of each carbon nanotube composite sensor, calculating the position of the impact load according to the following formula:
F 1 =[(L 12 - d 12 )/L 12 ] ∙ [(L 13 - d 13 )/L 13 ]（1）
F 2 =[(L 21 - d 21 )/L 21 ] ∙ [(L 24 - d 24 )/L 24 ]（2）
F 3 =[(L 34 - d 34 )/L 34 ] ∙ [(L 31 - d 31 )/L 31 ]（3）
F 4 =[(L 43 - d 43 )/L 43 ] ∙ [(L 42 - d 42 )/L 42 ]（4）
wherein, the first and the second end of the pipe are connected with each other,F i respectively representing the impact load to the fourth carbon nano tube composite sensoriA sensor (iCoefficient of influence of =1,2,3, 4),L ij represents from the firstiPosition of the sensor tojLength of vector of position of sensor: (j=1,2,3,4，jIs not equal toi），d ij Represents from the firstiVector of position of sensor to position of said impact loadL ij Length of the projection of (a).
Specifically, in this embodiment, the structure of fig. 6 is regarded as a simple beam structure, and each carbon nanotube composite sensor is a support of the simple beam structure. Applying the influence line theory of a common simple supported beam to the structure of fig. 6, an influence equation of the moving impact load on the carbon nanotube composite sensor at different positions is established, as shown in equations (1) (2) (3) (4).
In addition, in the positive direction region, the following equation is also satisfied:
d ij +d ji =L ij （6）
L 12 =L 34 =L 13 =L 24 （7）
L ij =L ji （8）
in conclusion, the calculation resultsF 1 、F 2 、F 3 AndF 4 then, equations (1) - (4), (6) - (8) are simultaneously solvedd ij And thereby the location of the impact load.
Optionally, calculating an influence coefficient of the impact load applied to each carbon nanotube composite sensor by the square region at the time according to the resistance change of each carbon nanotube composite sensor, including the following steps:
step one, obtaining a basic form of the relationship between the resistance change and the influence coefficient of each carbon nano tube composite sensor:
μ i F i = ΔR i / R i （5）
wherein the content of the first and second substances,ΔR i is shown asiThe resistance of the carbon nanotube composite sensor changes,R i is shown asiThe initial resistance of the carbon nanotube composite sensor,F i is shown asiInfluence coefficient of the carbon nanotube composite sensor;μ i is shown asiSensor coefficient of carbon nanotube composite sensor for reflectingiThe relationship between the influence coefficient of the carbon nanotube composite sensor and the rate of change of resistance.
Step two, passing throughiThe resistance change of the carbon nano tube composite sensor under different impact loads is calibratediSensor coefficients of the carbon nanotube composite sensor.
The characteristics of the carbon nanotube composite sensor are refined as follows. Alternatively, in the carbon nanotube composite sensor (hereinafter, simply referred to as a composite sensor), the cement-based composite material includes a dispersant, a water reducing agent, cement, sand, and deionized water. The carbon nano-tubes are uniformly dispersed in the cement-based composite material. The composite sensor has pressure-sensitive sensing capacity, can be placed in a concrete structure for long-term service without generating great influence on the structure, can perform special response to the direction load needing to be monitored due to the structural characteristics, and can also perform real-time monitoring on the impact load and the pressure load of the structure in a targeted manner.
In some embodiments, the carbon nanotubes are 0.2 to 1 part by weight, and the cement-based composite material comprises 0.2 to 1 part by weight of a dispersant, 0.3 to 1 part by weight of a water reducing agent, 99 to 100 parts by weight of cement, 200 to 300 parts by weight of sand and 35 to 60 parts by weight of deionized water.
In some embodiments, the carbon nanotubes are 0.4 to 0.7 part by weight, and the cement-based composite material comprises 0.4 to 0.7 part by weight of a dispersant, 0.5 to 0.8 part by weight of a water reducing agent, 99 to 100 parts by weight of cement, 230 to 280 parts by weight of sand, and 45 to 50 parts by weight of deionized water. In some embodiments, the ratio of parts by weight of the carbon nanotubes to the dispersant is 1: 1.
the carbon nanotube is a one-dimensional quantum material. The carbon nano tube mainly comprises a coaxial circular tube with several layers to tens of layers formed by carbon atoms arranged in a hexagon shape. The layers are kept at a certain distance, such as 0.3-0.4 nm. The carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes, depending on the number of layers of the coaxial circular tubes.
The radial dimension (pipe diameter) of the carbon nano tube is in nanometer magnitude, the axial dimension (pipe length) is in micrometer magnitude, and two ends of the pipe are basically sealed. In some embodiments, the carbon nanotubes have tube diameters of 2-20 nm, tube lengths of 10-40 um, and specific surface areas of 230-280 m/g. In some embodiments, the carbon nanotubes have tube diameters of 3-15 nm, tube lengths of 15-30 um, and specific surface areas of 250-270 m/g.
In some embodiments, the carbon nanotubes are aminated multi-walled carbon nanotubes. The aminated multi-walled carbon nanotube is prepared from multi-walled carbon nanotubes. For example, the aminated multi-walled carbon nanotube is prepared by carrying out radical reaction on multi-walled carbon nanotubes to prepare cyano-modified multi-walled carbon nanotubes, and then adopting Al-NiCl 2 ∙6H 2 Reducing the system with 0-THF to produce aminated multi-wall carbon nanotube. Compared with other materials, the aminated multi-walled carbon nanotube has stronger dispersibility and is not easy to agglomerate in the cement-based material, and the aminated multi-walled carbon nanotube is uniformly dispersed in the cement-based material due to the characteristic, so that the high consistency of the performance of the sensor in all aspects during the large-scale production is possible. Meanwhile, compared with the added materials in the prior art, the aminated multi-walled carbon nanotube has better enhancement effect on the mechanical property of the cement-based composite material, and the compressive strength of the composite sensor manufactured in the technical scheme isAbout 35MPa, the compressive strength is higher than 32.5MPa of the common 42.5 silicate cement mortar block, and the problem that the sensor strength is reduced due to an external material and the structure strength is negatively influenced when the sensor is arranged in the structure in the prior art is solved.
The dispersing agent is used for dispersing the carbon nano tubes and preventing the carbon nano tubes from agglomerating and depositing. The dispersant may include, but is not limited to, carbon nanotube water dispersant (TNWDIS), carbon nanotube alcohol dispersant (TNADIS), carbon nanotube ester dispersant (TNEDIS), and the like.
The water reducing agent is used for reducing the concrete admixture for mixing water consumption under the condition of maintaining the slump constant of concrete basically. The water reducing agent can increase the fluidity, the dispersion effect and the like of concrete mixtures. The water reducing agent can be lignosulfonate, naphthalene sulfonate formaldehyde polymer and the like.
The cement may be portland cement, alumina cement, etc. The cement may be numbered 32.5, 32.5R, 42.5R, 52.5R, etc.
The composite sensor further includes an electrode. The electrodes are arranged at two ends of the composite sensor in the form of grids formed by conductive materials. The conductive material is a conductive metal material such as copper, aluminum, silver and the like and/or a conductive non-metal material such as graphite and the like. In some embodiments, the electrodes are two pieces of copper mesh, respectively located at both ends of the composite sensor. The copper grid and the cement-based composite material have good compatibility, low contact resistance, low cost and easy acquisition.
Optionally, each carbon nanotube composite sensor is a cuboid; the sizing process of each carbon nanotube composite sensor includes the following operations: determining that the width and the height of a carbon nano tube composite sensor are equal; and determining the ratio of the length and the width of the carbon nano tube composite sensor according to the Poisson ratio of the sensor, wherein the product of the Poisson ratio and the ratio is larger than or equal to a set threshold (for example, larger than or equal to any constant of 10). Preferably, the threshold =10 is set.
Fig. 7 is a schematic structural diagram of a carbon nanotube composite sensor according to an embodiment of the present invention. The composite sensor has a profile, for example, with an aspect ratio of 1 and an aspect ratio of greater than 2. The copper grids are arranged in the cement-based composite material in a semi-insertion mode perpendicular to the long sides, and the arrangement mode is parallel arrangement. The carbon nano tube is an aminated multi-wall carbon nano tube. The dispersant is a carbon nano tube water dispersant. The weight ratio of the carbon nano tube to the dispersing agent is 1: 1.
originally, the common cement-based composite material is almost non-conductive, and when the conductive carbon nano tube (such as the aminated multi-wall carbon nano tube) is doped, the P electrons of the carbon atoms on the carbon nano tube form a large-range delocalized pi bond, so that the conjugation effect is obvious, and the carbon nano tube has good conductivity. The conductive carbon nanotubes are dispersed in the cement-based composite material, wherein the connected carbon nanotubes form a conductive channel like a wire, so that electrons can pass through, and the conductive channel (the conductive channel is not as effective as the conductive channel generated by the direct connection of the carbon nanotubes) is formed between the adjacent but unconnected carbon nanotubes due to the tunneling effect.
As shown in fig. 7, it is assumed that the initial dimensions of the carbon nanotube composite sensor are: long and longL x Wide, wideL y High, highL z At the receiving edgexAfter axial pressure in the axial direction, the geometrical dimension becomes:
Figure 587806DEST_PATH_IMAGE002
wherein the content of the first and second substances,
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、
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and
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respectively indicate the length, width and height after change,ε x to strain the sensor in the x-direction after stretching,υ xy 、υ xz the cement-based composite material has a Poisson ratio of 0.1-0.2.
As can be seen from the formulas (9) to (11), the followingxWhen one compressive strain is generated in one direction, only 0.1-0.2 tensile strain is generated in other directions, so that the tensile strain is generated along the directionxThe space between the carbon nano tubes in the axial direction is obviously reducedyShaft andzthe increase of the distance between the carbon nano tubes in the axial direction is relatively not obvious; such a change increases the number of contact points between the carbon nanotubes, which macroscopically indicates that the overall resistance of the carbon nanotube composite sensor is reduced, and when a load F acts on the yz plane of the sensor, there are, according to the mechanics of materials:
Figure 609976DEST_PATH_IMAGE006
when the same load is acting on the xy-plane of the sensor, there are:
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wherein the content of the first and second substances,Ein order to be the modulus of elasticity,A 0 、A 1 respectively the cross-sectional areas of yz surface and xy surface,νin order to be the poisson's ratio of the sensor,ε 0 、ε 1 respectively along the x-axis and along the z-axis,ε 2 as a strain in the x-axis direction when a force acts on the xy-plane.
Taking Poisson's ratioνIs 0.2, sensor widthL y Height ofL z Ratio of 1, then longerL x Width ofL y When the ratio is more than 2, it can be obtainedε 2 Is less thanε 0 An order of magnitude.
Optionally, the structure to be monitored is a pier, the impact load is from ship collision, and the four-carbon-nanotube composite sensor is installed in the pier; determining a square area to be detected on the surface of a structure to be monitored, comprising: determining the area range of the ship collision on the bridge pier according to the navigation environment of the bridge pier; and determining the square area according to the area range.
In this embodiment, the condition that the bridge pier is collided by a ship is remotely monitored by adopting the identification method provided by any one of the above embodiments, the basic region where the ship is collided is determined at first, the carbon nanotube composite sensors are installed at the four vertex angles of the region, and then the position where the ship is collided is automatically identified, so that the health remote real-time monitoring of the bridge pier structure is realized.
The technical effects of the embodiment are as follows:
1. in the embodiment, the size of each carbon nanotube composite sensor is determined according to the Poisson ratio of the sensor, and the size enables the response of the carbon nanotube composite sensor to the impact load in one direction to be outstanding to other directions, so that the response to the load in other directions can be ignored, the sensor is prevented from generating sensitive response to multi-directional complex loads to generate high coupling in all directions, and a foundation is provided for the automatic identification of the impact load position by applying the influence line theory of a simply supported beam.
2. In the embodiment, the carbon nanotube composite sensor with the one-way response characteristic is adopted to establish an analysis model of the structure to be detected subjected to the impact load, the structure among the four carbon nanotube composite sensors is simplified and eliminated, so that the region to be monitored is similar to a simply supported beam structure with four supports, and therefore the influence equation of the moving impact load on the carbon nanotube composite sensors at different positions is established by utilizing the influence line theory of the simply supported beam, and the position of the impact load on the region to be monitored is determined; the positioning method is simple and easy to implement and high in accuracy.
3. The sensor at the four vertex angles of the square area can be remotely monitored, so that the impact load condition of the structure to be monitored can be acquired in real time, and the field real-time monitoring is not needed.
4. In the prior art, a response signal of a structure is measured by using a centralized or distributed piezoelectric strain measurement method to identify an impact load, but a piezoelectric sensor reflects pressure change through current generated by the piezoelectric sensor, is easily interfered by an electromagnetic environment, and has poor and unstable monitoring and identifying precision on the impact load in a large-scale structure with a large number of devices arranged in a complicated wiring way. This application adopts carbon nanotube composite sensor, receives the load to take place deformation production resistance change reflection pressure variation through the sensor, and essence is a piezoresistive sensor, and output signal is the resistance variation value, is difficult for receiving external electromagnetic environment interference, utilizes this characteristic to come discernment monitoring to the impact load, has solved the unstable problem of prior art sensing effect in electromagnetic environment.
5. In the prior art or by using a fiber grating sensing mode, in practical application, because the sampling frequency of a demodulator is low and the impact load is often instantaneous, a large amount of effective information for representing the impact response characteristic is lost, the time difference positioning principle cannot be met, and the positioning precision of the impact load is greatly reduced. The time difference positioning principle is not required to be met, the frequency requirement on the acquisition instrument is low, and the problem that ultra-high frequency acquisition time-range data are required to perform positioning in the prior art by using a fiber grating sensing mode is solved; in addition, the carbon nanotube composite sensor has good sensitivity and almost synchronously responds to the load, so that the technical scheme overcomes the defect that a large amount of effective information of the impact response characteristic of the fiber grating sensing mode is lost under the conditions that the frequency of a demodulator is low and the impact load instantaneously occurs.
6. The sensor used in the traditional monitoring technology is easily interfered by the external environment, particularly the temperature, and multiple times of filtering are specially needed to eliminate the influence of the interference on the monitored data, and the problems of complex flow and large workload exist in the prior art due to the multiple times of filtering. The sensor is insensitive to temperature, cement and the carbon nano tube are insensitive to the interference of the external environment, particularly the temperature, and can be used in the structure for a long time in the monitoring process, so that the problems that the prior art needs to filter for many times in order to eliminate the environmental interference, the compatibility is poor and the durability is poor in a concrete structure are avoided.
7. The traditional sensor has the problems of high manufacturing cost, poor durability, poor compatibility with a concrete structure and the like, and the formed monitoring method is difficult to meet the requirements of high durability, good compatibility and long service life of a large structure during service; the sensor is made of high-strength materials and is good in durability; the cement-based material is also one of concrete, and has good compatibility with the concrete; and the concrete is arranged in the concrete, is not easy to damage and can be used in the structure for a long time, thereby avoiding the problems of poor compatibility and poor durability in the concrete structure in the prior art.
On the basis of the above-described embodiment and the following-described embodiment, the present embodiment optimizes the identified impact load position. Optionally, when the resistances of the four carbon nanotube composite sensors all change at the same time, after identifying the position of the square area under the impact load at the time according to the resistance change of the four carbon nanotube composite sensors, the method further includes: and inputting the identified position into a trained deep learning model, and predicting the final position of the impact load.
The trained deep learning model is used for reducing an error between the actual position of the impact load and the identified position. Since a certain error inevitably exists between the identified position of the impact load and the actual position, and the error has certain randomness and is difficult to eliminate through theoretical derivation, the embodiment adopts a form of a deep learning model to compensate the error, so that the predicted final position is closer to the actual position of the impact load.
Optionally, the deep learning model is trained by:
step one, sequentially loading multiple impact loads in the square area.
And sequentially applying impact loads for multiple times in the multiple square areas, and recording the actual position of each impact load action.
And step two, acquiring the resistances of the four carbon nanotube composite sensors in real time.
And thirdly, when the resistances of the four carbon nanotube composite sensors are changed at the same moment, identifying the position of the impact load on the square area at the moment according to the resistance change of the four carbon nanotube composite sensors.
By the identification method provided by the embodiment, the position of each impact load is automatically identified. The specific process is the same as any of the above embodiments, and is not described herein again.
And step four, inputting a deep learning model for training by taking the recognized position as a training sample, so that the output of the deep learning model approaches to the actual position of the impact load received at the moment.
According to the embodiment, the error is reduced by selecting a deep learning network form according to the error characteristic between the identified impact load position and the actual position, so that the position error is reasonably reduced, and the positioning precision is improved.
On the basis of the above-described embodiment and the following embodiments, the present embodiment verifies the validity of the identification method provided by the embodiment of the present invention. In a specific embodiment, an aminated multi-walled carbon nanotube composite sensor is adopted, the content of carbon nanotubes is 0.25%, the specification of the sensor is 4cm × 4cm × 16cm, the number of electrodes 2 is copper electrodes, and the number of sensors is 4. Fig. 8 is a schematic diagram of another arrangement of four carbon nanotube composite sensors according to an embodiment of the present invention. In the arrangement shown in fig. 8, a specific verification method includes the following steps:
(1) the side length of a square monitoring area is defined to be 110cm on a structure to be monitored, the thickness of the monitoring area structure is 20cm, and the structure in the specific embodiment is poured by plain concrete in consideration of the problem of material anisotropy; the carbon nano tube composite sensors are poured into the structure together in the structure manufacturing process, all the sensors are vertically arranged in the structure by the long edge (16 cm) and the surface of the structure, the embedding depth is 2cm, the sensors are arranged in four corners in a monitoring area in a plane arrangement mode, the central distance between the sensors is 96cm, the numbers of the sensors are respectively 1,2,3 and 4, the sensors are connected with electrodes of the sensors and led out by using wires in the pouring process, and the structure is subjected to standard maintenance for 28 days subsequently.
(2) After the maintenance is finished, all the sensors are connected with a data acquisition instrument through a lead in a room temperature environment, and the acquisition instrument can acquire the resistance and the resistance change of each carbon nano tube composite sensor. Because the cement-based composite material of the carbon nanotube composite sensor belongs to a colloid composite material, the resistance of the cement-based composite material can drift due to the dielectric property, and 6000s of polarization needs to be carried out on the sensor to reach stable resistance value after a power supply of a data acquisition instrument is turned on in order to obtain stable sensor resistance.
(3) After the resistance values of all sensors are stabilizedy-zAnd (3) applying impact load at the coordinates (20, 30) in the plane, and remotely acquiring the resistance of the four carbon nanotube composite sensors in real time.
(4) And selecting a resistance change peak value of each sensor, wherein the value represents the response of the sensor to the impact load, substituting all sensor data and positions into an influence equation according to a coefficient calibrated in the manufacturing process of the sensor, and calculating to obtain the identified load positions (21.3 and 28.5) which are close to the actual load action position.
(5) And (3) in the environment of 0 ℃, applying impact load with the same position and size in the process (3) to the structure, and identifying the load position through the process (4), wherein the positions are (21.3, 28.5) and are the same as the positions identified at room temperature.
The impact load detection method has the advantages that the identified load position is close to the actual load position, the identified position is the same under the condition of changing the ambient temperature, the ambient temperature interference resistance is high, and the impact load detection method is suitable for positioning and monitoring of impact loads in actual engineering.
On the basis of the above-described embodiment and the following embodiments, this embodiment refines the method of manufacturing a composite sensor (exemplarily, the content of carbon nanotubes is 0.25%). Optionally, the preparation method of the composite sensor comprises the following steps:
s1, 2.5g of dispersing agent is fully dissolved in 450ml of deionized water, the water dispersing agent is viscous liquid, the dispersing agent is added into water to form transparent colloid, the dispersing agent is slowly and uniformly stirred and is completely dissolved in the water, 2.5g of aminated multi-wall carbon nano tube is weighed and added into a dispersing agent water solution, an ultrasonic crushing device is used for dispersing the carbon nano tube, the ultrasonic is suspended for 3 seconds(s) after being started every 3 seconds(s), the total dispersion time is 10 minutes (mins), a large amount of foam can be generated to influence the dispersion effect due to the fact that the dispersing agent is a surfactant, and 0.3ml of defoaming agent can be dripped into the dispersing agent for defoaming.
S2, pouring the dispersed carbon nanotube liquid into a stirring pot, pouring 1000g of portland cement, starting the stirring pot to stir for 2mins, pouring 2000g of standard sand, stirring for 4mins, turning off the stirring equipment, standing for 2mins, and starting the equipment to stir for 4 mins.
S3, pouring cement mortar into a standard mortar mould with the size of 40mm multiplied by 160mm, inserting a metal grid, wherein the metal grid used in the embodiment is a copper grid, the grid specification is a square grid with the size of 4mm multiplied by 5mm, inserting two pieces into a test piece, the arrangement mode is parallel arrangement, the distance between the two pieces is 14cm, vibrating the mould for 60 times, and after 36 hours (h) of room temperature maintenance, removing the mould and performing standard maintenance for 28 days (d).
The prepared composite sensor was tested, as shown in fig. 9, and the specific test process included:
s1, attaching strain gauges to two surfaces, perpendicular to a loading direction (for example, the loading direction is the length direction), of the composite sensor after maintenance is finished, and measuring a strain value of the composite sensor in a loading process;
s2, connecting the electrode of the composite sensor with a signal acquisition instrument, a strain gauge and a strain gauge respectively by using a lead, wherein the resistance of the composite sensor is drifted due to dielectric properties because the composite sensor is made of a colloid composite material, and in order to obtain stable sensor resistance, a power supply of the signal acquisition instrument is turned on after connection is finished, and the composite sensor is polarized for 6000s until the resistance value is stable;
s3, placing the composite sensor in a universal testing machine, loading, wherein the loading rate is 250N/s, the maximum loading force is 8MPa to ensure that the loading is in an elastic range, and recording strain data and a resistance change value in the loading process;
s4, calibrating the sensitivity of the composite sensor through data of the strain gauge and resistance change data to obtain a strain factor in the elastic range of the sensor;
s5, monotonously loading the composite sensor until a test piece is damaged to obtain the compressive strength of the composite sensor, wherein the pressure and displacement curve of a universal testing machine is shown in a graph 10, the maximum value of the pressure is 87.9KN, the test piece starts to be damaged, the obtained compressive strength is 35.16MPa, and the electrical property, the mechanical property and the strain factor test data of the composite sensor are as follows:
content of carbon nanotube% Rate of change of resistance Strain factor Compressive strength after 28 days
0.25% 34% 1600 35.16MPa
From the data, the mechanical property of the composite sensor is improved compared with that of common cement mortar only by using the carbon nano tube with the content of 0.25%, and meanwhile, the strain factor of 1600 is achieved.
In the scheme, excellent effect can be realized only by adding special materials (carbon nano tubes and the like) with the mass less than two orders of magnitude (0.2% -1%) of the cement material, and the problems that in the prior art, the special materials with higher content need to be added, the effect is general and the cost is higher are solved.
In the scheme, the aminated multi-walled carbon nanotube is used as a functional component, the compressive strength of the prepared composite sensor reaches 35.16MPa, is higher than the compressive strength of 32.5MPa of common 42.5 cement mortar, and the strain factor of the sensor reaches 1600.
In addition, in the scheme, the resistance value difference among a plurality of composite sensors manufactured based on the method is very small, experimental data show that the maximum difference value of the resistance among 3 groups of sensors is only 13 omega, the fact that the carbon nano tubes are uniformly dispersed in the composite sensors is proved, according to the characteristic that aminated multi-wall carbon nano tubes are not easy to agglomerate and disperse easily, water dispersing agents and ultrasonic dispersing methods are selected to prepare carbon nano tube dispersing liquid, the resistance values of a plurality of groups of manufactured composite sensors are almost consistent, the fact that the carbon nano tube dispersing liquid prepared by the method is uniformly dispersed in the carbon nano tube dispersing liquid is proved, compared with the prior art, the manufactured sensors have quicker and better response to the change of external load (accurate response can be realized under the frequency of a signal acquisition instrument 2 HZ) due to the better dispersing effect, the operation process of dispersing is safer and more convenient, and the aminated carbon nano tubes have stable performance, this allows the sensor resistance fabricated from such carbon nanotubes to be very reversible, i.e., the sensor resistance will recover toward the pre-load resistance during unloading.
In the scheme test, the resistance of the composite sensor is recovered to 1589 omega from an initial value of 1588 omega after the loading is finished, compared with the prior art, the weak drift is realized, the durability of the composite sensor is better due to the existence of strong reversibility, and the composite sensor has more outstanding performance when being in service in an internal structure for a long time.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims (5)

1. A monitoring system based on a carbon nanotube composite sensor, comprising:
the data acquisition instrument is based on the carbon nano tube composite sensor, and the upper computer is used for acquiring data;
wherein, the data acquisition instrument based on the carbon nano tube composite sensor comprises: a constant current circuit, a filter circuit, an amplifying circuit, an A/D signal conversion circuit, a communication module and an acquisition port, wherein,
the collection port is used for connecting the carbon nano tube composite sensor so as to connect the carbon nano tube composite sensor in the constant current circuit in series; the carbon nano tube composite sensor is a piezoresistive pressure sensor;
the filter circuit is electrically connected with two ends of the carbon nano tube composite sensor and is used for filtering voltage signals at two ends of the carbon nano tube composite sensor;
the amplifying circuit is connected with the filtering circuit and is used for amplifying the filtered voltage signal;
the A/D signal conversion circuit is connected with the amplifying circuit and is used for carrying out A/D conversion on the amplified signal to obtain a digital signal;
the communication module is connected with the A/D signal conversion circuit and used for sending the digital signal to the outside;
the monitoring system further comprises: a four-carbon nanotube composite sensor, wherein,
the four carbon nano tube composite sensors are respectively arranged at four vertex angles of a square area on the surface of an object to be monitored;
the data acquisition instrument is respectively electrically connected with the four carbon nano tube composite sensors and is used for transmitting digital signals generated by the four carbon nano tube composite sensors at the four vertex angles of the square area in real time; specifically, the collection ports are provided with a plurality of pairs, and each pair of collection ports is used for connecting two ends of one carbon nanotube composite sensor;
the host computer with communication module accessible communication is connected for receive the digital signal, and confirm according to the digital signal in real time the position of the impact load that receives in the square region, include:
converting the digital signal into the resistance of the four-carbon nano tube composite sensor in real time;
when the resistances of the four carbon nanotube composite sensors are changed at the same moment, identifying the position of the square area under the impact load at the moment according to the resistance change of the four carbon nanotube composite sensors;
wherein, every carbon nanotube composite sensor is piezoresistive pressure sensor, includes: a cement-based composite material, and carbon nanotubes dispersed in the cement-based composite material; the size of each carbon nano tube composite sensor is determined according to the Poisson ratio of the sensor, and the size enables the response of the carbon nano tube composite sensor to the impact load in one direction to be protruded out of other directions;
specifically, when the resistances of the four carbon nanotube composite sensors all change at the same time, firstly, according to the resistance change of the four carbon nanotube composite sensors, calculating an influence coefficient of an impact load received by the square area at the time on each carbon nanotube composite sensor, wherein the influence coefficient represents the magnitude of a load transmitted to each carbon nanotube composite sensor by the impact load received by the square area at the time;
after the influence coefficient of each carbon nano tube composite sensor is obtained, calculating the position of the impact load according to the following formula:
F 1 =[(L 12 - d 12 )/L 12 ] ∙ [(L 13 - d 13 )/L 13 ]（1）
F 2 =[(L 21 - d 21 )/L 21 ] ∙ [(L 24 - d 24 )/L 24 ]（2）
F 3 =[(L 34 - d 34 )/L 34 ] ∙ [(L 31 - d 31 )/L 31 ]（3）
F 4 =[(L 43 - d 43 )/L 43 ] ∙ [(L 42 - d 42 )/L 42 ]（4）
wherein the content of the first and second substances,F i respectively representing the impact load to the fourth carbon nano tube composite sensoriCarbon nanotube composite sensor (C)iCoefficient of influence of =1,2,3, 4),L ij represents from the firstiPosition of carbon nanotube composite sensor tojLength of vector of position of carbon nanotube composite sensor: (j=1,2,3,4，jIs not equal toi），d ij Represents from the firstiVector from the position of the carbon nanotube composite sensor to the position of the impact loadL ij Length of the projection on.
2. The monitoring system of claim 1, wherein the host computer is further configured to display the resistances of the plurality of carbon nanotube composite sensors on a screen.
3. The monitoring system of claim 1, wherein the host computer is further configured to perform at least one of: the method comprises the steps of real-time display of resistance values and resistance change rates, setting of upper and lower lines, automatic early warning of exceeding of the upper and lower lines, playback of historical records, display of curve charts, curve comparison, range setting and storage of switches.
4. The monitoring system of claim 1, wherein the filter circuit is a butterworth filter.
5. The monitoring system of claim 1, wherein the operating mechanism of the data collection instrument comprises: after the carbon nano tube composite sensor is connected in series in the constant current circuit through the acquisition port, the constant current circuit provides constant current for the carbon nano tube composite sensor, so that voltage signals at two ends of the carbon nano tube composite sensor are in direct proportion to resistance;
the filter circuit filters the voltage signal and filters noise in the voltage signal;
the amplifying circuit amplifies the filtered voltage signal;
the A/D signal conversion circuit converts the amplified signal into a digital signal;
and the communication module sends the digital signal to the outside.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005038468A1 (en) * 2003-09-22 2005-04-28 Brother International Corporation A method and apparatus for sensing applied forces
CN102620900A (en) * 2012-04-01 2012-08-01 长安大学 Method for detecting bridge impact coefficient based on dynamic load test
CN114137587A (en) * 2021-12-01 2022-03-04 西南交通大学 Method, device, equipment and medium for estimating and predicting position of moving object

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7536911B2 (en) * 2003-09-22 2009-05-26 Hyeung-Yun Kim Diagnostic systems of optical fiber coil sensors for structural health monitoring
KR20110099711A (en) * 2008-12-03 2011-09-08 메사추세츠 인스티튜트 오브 테크놀로지 Multifunctional composites based on coated nanostructures
CN103024940A (en) * 2012-12-26 2013-04-03 山东科技大学 Carbon nano tube cement based composite sensor testing system
CN107773784B (en) * 2017-10-30 2019-10-18 西南交通大学 A kind of magnetism bone cement and preparation method thereof
WO2020254909A1 (en) * 2019-06-21 2020-12-24 株式会社半導体エネルギー研究所 Semiconductor device and electronic apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005038468A1 (en) * 2003-09-22 2005-04-28 Brother International Corporation A method and apparatus for sensing applied forces
CN102620900A (en) * 2012-04-01 2012-08-01 长安大学 Method for detecting bridge impact coefficient based on dynamic load test
CN114137587A (en) * 2021-12-01 2022-03-04 西南交通大学 Method, device, equipment and medium for estimating and predicting position of moving object

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Smart damping of a simply supported laminated CNT-based hybrid composite plate using FE approach;M Gupta el.;《Elsevier Science》;20211231;全文 *
基于一阶剪切变形理论的CNTRC板的自由振动分析;薛婷 等;《机械工程学报》;20191231;全文 *

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