KR100669070B1 - Wireless telemetry system for monitoring structure - Google Patents

Abstract

The present invention relates to a wireless measurement system for measuring dynamic response for monitoring a structure. The method provides a wireless measurement system for acquiring dynamic data in a situation in which a real structure is constantly present, thereby enabling dynamic monitoring of the structure and distorting measurement data according to a conventional wired transmission. The present invention relates to a wireless measurement system that solves the problems of the present condition, high initial installation cost, and maintenance cost.

The wireless measurement system is configured to acquire, process and store dynamic data output as a vibration signal from the sensor system module at each position of the structure including the acceleration sensor for detecting the vibration of the structure and the acceleration sensor, and a control signal of the main computer. According to the present invention, a control and processing module for performing measurement system control and measurement situation determination and wirelessly transmitting dynamic data output from the control and processing module directly to the main computer and receiving various control signals output from the main computer And a wireless modem module comprising a sensor side modem and a main computer side modem provided to enable wireless transmission and reception with the sensor side modem for transmission and reception between the control and processing module and the main computer.

Sensor system module, acceleration sensor, control and processing module

Description

WIRELESS TELEMETRY SYSTEM FOR MONITORING STRUCTURE}

1 is a block diagram showing the configuration of a wireless measurement system according to the present invention.

2 is a block diagram showing an example of a wireless measurement system according to the present invention.

Figure 3 is an exemplary view showing a system for monitoring at all times by applying a wireless metrology system according to the invention to the structure.

4 is a view schematically showing the cantilever beam to explain the performance test of the system according to the present invention.

5 is a view showing the results of the free vibration experiment according to the present invention.

6 is a view showing a dynamic characteristic analysis result according to the present invention.

7 is a view showing the results obtained by analyzing the mode shape of the cantilever beam obtained by the experiment according to the present invention.

8 is a view showing a correlation between the mode obtained by the experiment of the cantilever beam according to the present invention and the mode obtained by the analysis.

<Description of the symbols for the main parts of the drawings>

1: wireless measurement system 10: sensor system module

11: acceleration sensor 20: control and processing module

21: microcontroller 22: external memory

30: wireless modem module 31: sensor side modem

32: main computer side modem 40: main computer

The present invention relates to a wireless measurement system for measuring dynamic response for monitoring a structure. More particularly, the present invention relates to a structure that enables dynamic monitoring of a structure at a remote location by wirelessly transmitting dynamic data after acquiring dynamic data in a situation in which a real structure is always present. The present invention relates to a wireless measurement system for dynamic response measurement for monitoring.

In general, a construction structure ages as time passes, and also receives a load unspecifically generated by wind, earthquake, vehicle, etc., and the behavior of the structure also changes with time and load applied.

However, when the state of the structure is kept constant, the natural frequency, attenuation coefficient, mode shape, etc. of the target structure, which are represented by the dynamic behavior of the structure, are kept constant, and such a structure is called an integrity structure.

However, aging and other damages result in changes in factors such as mass, stiffness, etc. that reflect the properties of the structure, and these changes cause changes in the dynamic properties of the circular structure.

Therefore, if a system that can monitor the dynamic characteristics of the structure at all times is built, it is possible to evaluate the state of the structure in real time and ensure the stability.

Recently, the role of the Structural Health Monitoring System (SHM) has become important as large civil structures such as skyscrapers and long bridges increase. In this regard, many studies have been attempted to implement a monitoring system. Such monitoring technology is a technology that can maximize the safety of structures and improve the safety of structures by measuring, analyzing, and diagnosing the dynamic behavior of structures such as buildings and bridges.

This monitoring technique is mainly classified into a process of acquiring data from sensors attached to the structure and converting the data to analyze data for evaluating damage of the structure.

However, designing an effective structure monitoring system requires a great deal of techniques. In particular, the structure damage identification technique and data acquisition and transmission techniques are the most important and basic elements. Such a system needs to generate artificial input excitation to the structure to excite the structure, and due to many problems, the condition is only conditional health monitoring.

Therefore, various studies have been reported to solve these problems and to monitor the health of structures. For example, many researchers have studied the natural techniques. In particular, Farrar and Caicedo have studied natural structures. Excitation techniques (NExT and ERA) have proven effective for monitoring the health of civil structures.

On the other hand, another important factor in the design of the structure monitoring system is the data acquisition system. Sensors widely used in conventional structure monitoring techniques include semi-permanent, reliable and easily attachable inclinometers, accelerometers and displacement meters, and strain gauges have a resistance value when strain is applied to a metal or semiconductor resistor. It is used to measure the actual stress of a structure by using the variable pressure resistance effect.

The safety diagnosis of the bridge using the above sensors is to receive the real-time measurement data of the bridge directly in real time in preparation for the collapse of the bridge structure that may occur in case of emergency, and to record it in a data analysis device connected by wire, and the bridge manager of the bridge control station Based on the recorded data, the safety status of the bridge is checked and carried out. Through this, the safety status of the bridge can be determined in advance.

As a result, when regular monitoring of the structure is carried out using the bridge safety diagnosis system, measures can be taken for each situation such as controlling the traffic volume for the bridges concerned with safety, and problems such as the occurrence of human accidents Can be prevented in advance.

However, in the conventional structure safety diagnosis system, signals measured from a plurality of sensors attached to a civil engineering structure are transmitted to a data analysis device through a local area network or a wire such as a dedicated line or a general public line of a telecommunication company.

When using a measurement system by wire in such a monitoring system, not only a high initial installation cost is required, but also a lot of cost and time for changing and adding a measurement system, and noise caused by the surrounding environment is a problem. It is pointed out.

In addition, the monitoring system mainly installed on large bridges is still a semi-automatic monitoring system, which has problems such as a large amount of data processing problems and data accuracy, and also due to the inaccurate prototype of the structure for evaluating the condition of the structure. There has been no monitoring of health in its essential sense.

In particular, in order to effectively evaluate the aging progress and soundness of civil structures, it is necessary to acquire dynamic characteristic values through dynamic data analysis. Therefore, it is possible to apply to real structures and commercialize them. There is an urgent need to develop dynamic data acquisition system that can identify dynamic characteristics of civil engineering structures and to develop new wireless measurement system that can process data on its own.

The present invention has been made to solve the above problems, the object of the present invention is to enable dynamic monitoring of the structure by wireless transmission after acquiring dynamic data in the situation of the real structure of the real structure, and to the conventional wired transmission The present invention provides a wireless measurement system for dynamic response measurement for monitoring a structure in which distortion of measurement data, high initial installation cost, and maintenance cost can be eliminated.

In order to achieve the above object, the present invention, in the measurement system for transmitting the measured data after the measurement of the behavior characteristics of the structure in the structure monitoring system to the main computer,

A sensor system module including an acceleration sensor for detecting vibration of the structure, the plurality of sensors being installed at each position of the structure to measure the behavior of the structure;

A control and processing module for acquiring, processing, and storing dynamic data output from the acceleration sensor as a vibration signal, and performing measurement system control and measurement situation determination according to a control signal of a main computer; And

A sensor-side modem for wirelessly transmitting dynamic data output from the control and processing module to the main computer and receiving various control signals output from the main computer, and for transmitting and receiving between the control and processing module and the main computer. And a wireless modem module configured as a main computer side modem provided to enable wireless transmission and reception with the sensor side modem.

In addition, the acceleration sensor is characterized in that the acceleration sensor of the MEMS (Micro-Electro Mechanical System: MEMS) type.

The control and processing module may further include a microcontroller having a flash memory in which a program for performing the above functions is dumped, a data controller for storing data generated or required when a program is executed, and an external memory for providing additional data storage space. Characterized in that it comprises a.

According to the present invention, in the implementation of monitoring for measuring dynamic response of a structure by using a wireless measurement system for dynamic response measurement for monitoring of a structure, distortion of measurement data generated during wired transmission can be eliminated. In addition, initial installation and maintenance costs can be reduced and convenient system management can be achieved.

The present inventors have relied on the wired measurement in the conventional structure monitoring system (SHM) and control system, so the research on the use of the wireless measurement system has been pointed out as a problem of high initial installation cost, maintenance difficulty, and noise due to the surrounding environment. Through this research, we develop and design an intelligent wireless measurement system for acquiring dynamic data that can identify dynamic characteristics of civil structures and self-processing data, and verify the performance of sensors through various performance experiments as well as indoors. Experiments and field tests verify the suitability for monitoring real structures.

Hereinafter, with reference to the accompanying drawings will be described in detail the characteristic configuration and effect of the present invention.

1 is a block diagram showing a configuration of a wireless measurement system according to the present invention, Figure 2 is a block diagram showing an example of a wireless measurement system according to the present invention, Figure 3 is a wireless measurement system according to the present invention Figure 4 is an exemplary view showing a system applied to the structure at all times monitoring, Figure 4 is a view showing a cantilever beam to explain the performance test of the system according to the present invention, Figure 5 is a view showing the results of the free vibration experiment according to the present invention 6 is a view showing the results of dynamic characteristics analysis according to the present invention, FIG. 7 is a view showing the results obtained by analysis of the mode shape of the cantilever beam obtained by the experiment according to the present invention, and FIG. Figure 4 shows the correlation between the mode obtained by the experiment of the cantilever beam and the mode obtained by the analysis.

1 to 8, the intelligent wireless measurement system 1 according to the present invention includes a sensor system module 10 installed at each position of the target structure 50 and sensing dynamic response data of the structure. The main computer of the monitoring system in which the control and processing module 20 for acquiring and processing the data sensed through the sensor system module 10 and the dynamic data output from the control and processing module 20 are characterized. It comprises a wireless modem module 30 for transmitting to 40 in real time or near real time.

First, in the sensor system module 10 of the present invention, an acceleration sensor 11 for detecting vibration at each position of a structure is used, and in this case, an acceleration sensor 11 having a sensitivity and resolution suitable for a structure monitoring system should be used. do.

The acceleration sensor 11 having the above-mentioned performance is used based on MEMS (Micro-Electro Mechanical System: MEMS), and the MEMS is a microelectromechanical system such as low-cost, high-performance, ultra-small, and ultra-lightweight semiconductor. Sensors and application systems with the advantages of integrated circuits.

The acceleration sensor 11 is manufactured to output a complete two-axis (X, Y) acceleration signal as digital cycle data (Duty Cycle) data to separate the microcontroller 21 of the control and processing module 20 It can be connected directly without going through A / D converter.

Table 1 shows the general performance of the acceleration sensor according to the present invention.

Table 1

In the acceleration sensor 11, the bandwidth (Bandwidth) can be adjusted by the capacity of a capacitor (not shown) connected to the X _FILT and Y _FILT terminals, the pulse length (T2) adjustment is reset terminal (Reset Terminal) It can be adjusted by the capacity of the resistor (not shown) connected to.

The control and processing module 20 controls the wireless measurement system 1 as a whole and determines a measurement situation. The control and processing module 20 includes a microcontroller having a built-in flash memory and a data memory (SRAM). 21 and an external memory 22 providing additional storage space.

The control and processing module 20 may be manufactured in the form of a circuit board equipped with the above components, such as a small CPU chip and an external memory. Basically, a self data acquisition function, a digital signal processing (DSP) function, and a temporary data storage function are provided. According to a control command input through the wireless modem module 30 from the main computer, a system control function is provided. In addition, it adjusts the collection rate, sampling rate, acquisition time, and acquisition method of the dynamic data measured by the sensor system module 10, and transmits the obtained dynamic data to the wireless modem module 30 in real time. This function is achieved by a program stored in a flash memory embedded in the microcontroller 21.

As a microcontroller 21 having the above-mentioned function, a suitable specification provides 128kbytes of flash memory and 4,000 instructions, and data generated or needed in program execution is stored in a 4kbytes data memory.

In addition, since the microcontroller 21 implements an effective embedded system, an external memory 22 is mounted in a module to overcome the limitation of the data memory because there is a limitation in the data memory provided in the microcontroller 21.

In the present invention, the wireless modem module 30 is directly connected to the control and processing module 20 to wirelessly transmit dynamic data output therefrom to the main computer 40 and to receive various control signals output from the main computer 40. A sensor side modem 31 and a main computer side modem 32 provided to enable wireless transmission and reception with the sensor side modem 31 for transmission and reception between the control and processing module 20 and the main computer 40. To be effectively applied to a real structure, a wireless modem having a long communication distance and a communication speed capable of transmitting data in real time is essential.

Therefore, the sensor-side modem 31 and the main computer-side modem 32 use a modem with a high output and a high communication speed compared to the power consumption as shown in Table 2.

Table 2

In this way, the wireless metrology system 1 of the present invention consisting of the sensor system module 10, the control and processing module 20, and the radio modem module 30 is constituted, and in such a wireless metrology system 1, the sensor system. The acceleration sensor 11 of the module 10 detects the vibration of the structure 50 and outputs a vibration signal according thereto, and the control and processing module 20 receives the vibration signal from the acceleration sensor 11 and receives the dynamic data. The wireless modem module 30 receives the data signal output from the control and processing module 20 and transmits the data signal to the main computer 40.

In this case, the control and processing module 20 sets matters related to data acquisition by the microcontroller 21 and the external memory 22, and stores and processes the acquired data.

The wireless measurement system 1 of the present invention employs the MEMS-based acceleration sensor 11, the microcontroller 21, the external memory 22, and the wireless modems 31 and 32. The new Smart Wireless MEMS-based on Accelerometer System (SWMAS), which is adapted to the monitoring system of civil structures 50, measures dynamic response through MEMS-based accelerometers, especially in the presence of real structures. After transmitting the measured dynamic data wirelessly, the dynamic characteristics analysis in the main computer 40 can be performed.

The wireless measurement system 1 of the present invention can be controlled by two-way wireless communication through the wireless modems 31 and 32 installed between the main computer 40 and the structure 50 as shown in FIG. It is possible to configure the structure monitoring system in a one-to-multiple configuration between the wireless measurement system 1 and the main computer 40 installed at each position of).

On the other hand, after configuring the wireless measurement system of the present invention, in order to verify sensor performance, experiments of sensitivity, resolution, and noise were conducted. Also, after constructing a monitoring system to which the wireless measurement system of the present invention was applied, the cantilever beam was subjected to constant excitation. In order to calculate the dynamic characteristics of the structure due to the real-time random ambient excitation from the transmitted measurement data, the main computer uses NExT (Natural Excitation Techniques) and ERA (Eigensystem Realization Algorithm). Algorithm is used.

This is described as follows.

1. Design of wireless measurement system

The MEMS-based acceleration sensor 11, the microcontroller 21, the external memory 22, and the wireless modems 31 and 32 are used to design a wireless measurement system.

In order for the wireless measurement system including sensors to be used in the structure's monitoring system (wireless measurement system + main computer), the basic requirements such as resolution, bandwidth, and frame time are required. It must be satisfied.

These requirements help to determine the bandwidth of the acceleration sensor 11, the clock speed of the microcontroller 21, and the period of the pulse in designing the wireless metrology system 1, and the bandwidth setting of the acceleration sensor 11 Determine the resolution to be measured.

Filtering is necessary to reduce the noise floor and to improve the resolution of the acceleration sensor. The resolution of the acceleration sensor depends on the analog filter bandwidth of X _FILT , Y _FILT , the speed of the timer / counter of the microcontroller, and the pulse length. Is determined.

The duty cycle transducer has a resolution of 14 bits that is higher than the resolution of the acceleration sensor.

However, the bandwidth of the actual acceleration signal is determined by the counting device used to decode the duty cycle.

Even if the resolution of the acceleration sensor 11 is set by X _FILT and Y _FILT , the faster the counter clock of the microcontroller 21 is, the better the resolution is, and the period of the pulse can be set smaller.

Table 3 below shows the relationship between the counter speed of the microcontroller, the period of the pulse (T2), and the resolution of the duty cycle modulator.

Table 3

Relationship between counter speed of microcontroller, period of pulse (T2) and decomposition concentration

In this design, the acceleration sensor's performance is set to 0.10F for X _FILT and Y _FILT and 1.25M for Reset, so that the sampling cycle is 10msec, that is, sampling rate is 100Hz, bandwidth is 50Hz, and resolution is 4.3mg. Design in rms (g: gravitational acceleration).

2. Sensor performance test

The purpose of this experiment is to examine whether a system consisting of a microcontroller and a wireless modem fully exhibits the inherent components of the acceleration sensor.The purpose of this experiment is to evaluate the sensitivity and resolution of the acceleration sensor constituting the wireless measurement system. Data Sheet) Performance is evaluated by comparing the values with each other.

The test acceleration sensor according to the present experiment includes a tilt sensor. When the acceleration sensor is positioned horizontally with the ground, it is equal to 0g (g: gravitational acceleration), and when it is perpendicular to the ground, + 1g is rotated 180 ° in this state. If it is, it becomes -1g

By using the characteristics of the test acceleration sensor, the sensitivity and resolution of the acceleration sensor can be easily obtained.

In addition, the trend of noise distribution was analyzed by acquiring the time history acceleration signal in the steady state, and the acceleration signal at 0 g was acquired for 20 seconds at a sampling rate of 100 Hz in real time.

As an experimental result for the designed wireless metrology system (1), as shown in Table 4, the sensitivity is 4.49% / g, the resolution is 4.4mg rms, the sensitivity of the data sheet is 4.0 ± 0.8% / g, the resolution is 4.3mg rms. Compared with, it showed close agreement.

Table 4

3. Performance evaluation experiment

Experimental equipment

As shown in Figure 4, cantilever beams are fabricated so that the analysis and measurement, and the analysis is easy, and the overall behavior characteristics of the structure is determined by the bending mode in the axial direction of the structure.

Using such a cantilever beam, dynamic characteristics analysis by constant excitation is performed to evaluate whether the wireless metrology system of the present invention is applicable to real-time monitoring of civil engineering structures. The cantilever beam was manufactured using structural steel, and the total length of the model structure was manufactured to 0.94 m.

The width and thickness of the cantilever beam were 6 cm and 0.5 cm so that the transverse dynamic response was not affected by the dynamic response occurring in the main axis direction.

Free vibration test

There are two methods of data acquisition in wireless measurement system: real time mode and quasi-real time mode. In real time mode, data is stored in data logger when data acquisition is completed and stored in memory. Therefore, the size of the data frame that can be acquired at one time is limited.

However, there is almost no limit on the sampling rate, and in the present wireless measurement system 1, the limitation of the frame size in the quasi-real time mode with the external memory is improved.

In order to use the wireless measurement system 1 as a real-time system, it is necessary to program by determining the optimal sampling rate and the amount of data to be transmitted at one time in consideration of all the time taken to transmit data. The rate is 100 Hz for one-to-one communication.

In order to investigate the performance of the wireless measurement system 1, an experiment for acquiring the acceleration signal of the cantilever beam in the free vibration state is performed, and a test acceleration sensor and a reference acceleration sensor are installed at the end of the cantilever beam of FIG. 4. .

5 shows the data obtained from the test acceleration sensor and the reference acceleration sensor at the end of the cantilever beam through the experiment. The data acquisition by the test acceleration sensor was performed for a total of 30 seconds at 100 Hz sampling rate in real time mode. .

As shown in FIG. 5, the response obtained by the test acceleration sensor showed a very good agreement with the response measured by the reference acceleration sensor.

Dynamic Characteristic Analysis

In this experiment, NExt and ERA were used to analyze the dynamic characteristics of the structure from constant vibration in order to evaluate the performance of the wireless metrology system of the present invention.

Using a wireless measurement system set in the quasi-real time mode, the output signal generated from the cantilever beam was obtained by averaging 10 times of 1024 data for about 10 sec, and the reference channel was set as the free end of the beam.

The data was analyzed using Modal analyis software package developed at Los Alamos National Lab (DAIMOND).

FIG. 6 shows representative signal processing results converted from a cross power spectrum analyzed in this way to a cross correlation function.

The first two modes of response of the present structure can be easily identified in FIG. 6 at 4.482 Hz and 28.002 Hz.

In addition, in order to compare the results of this experiment with the numerical calculations by the FE model, the results are summarized as in Table 5, where the natural frequencies of the structures analyzed by the experiments are numerically calculated and the error range is 5%. A match was found within.

Table 5

7 shows the mode shape of the cantilever beam extracted by the experiment as shown in the analysis.

MAC is used to numerically analyze the correlation of the mode shapes obtained by the two methods.

According to the research results of Ewins et al., It is judged that the correlation is excellent when the MAC index value is 0.9 or more.

However, because the correlation index is heavily influenced by the number of nodes (measurement points), up to 0.8 is allowed if the number of measurement points is limited, such as experiments. [Ewins, DJ, Modal Testing: Practice and Application, RSP, 200].

Table 6 and FIG. 8 show correlations between modes obtained by experiments of cantilever beams and modes obtained by analysis, and the correlations of the first mode showed a high index of 0.9752, but the second mode. The correlation index of was 0.8747.

Table 6

In this way, a new wireless measurement system for the smart monitoring system of civil structures using MEMS type accelerometer, microcontroller, external memory, and wireless modem has been disclosed, and various verification experiments were conducted to evaluate its performance characteristics. First, a sensor performance experiment was conducted to evaluate the performance of the sensor. Second, real-time free vibration data acquisition and quasi-real time vibration tests were conducted to evaluate the overall performance of the wireless measurement system.

As a result of the sensor performance evaluation experiment, the sensor sensitivity of the wireless measurement system of the present invention described above is 4.49% / g and the resolution is 4.4 mg rms, which is almost in agreement with the values of 4.00 ± 8% / g and 4.3 mg rms, respectively. Showed.

In addition, the data obtained from the free vibration experiments are excellent in comparison with the data obtained from the conventional acceleration sensors.In the natural vibration analysis of the cantilever beam by constant excitation, A match was found within about 5%.

In addition, it was confirmed that an excellent correlation can also be obtained between the mode shape of the structure, and from the above results, it can be seen that the dynamic characteristics of the structure can be analyzed using the wireless measurement system according to the present invention.

As can be seen from the above description, according to the wireless measurement system for monitoring a structure, the present invention is composed of an acceleration sensor, a microcontroller, an external memory, and a wireless modem of a MEMS type, thereby providing dynamic data in a situation where a real structure is always present. After acquisition, wireless transmission in real time or near real time becomes possible, and thus, more effective structure monitoring through dynamic characteristics analysis becomes possible.

In particular, the wireless metrology system of the present invention can be applied to a real structure and commercialized, and it is possible to acquire, process, and transmit dynamic data capable of identifying dynamic characteristics of civil structures, rather than simply obtaining static data as in the prior art. Has

In addition, the distortion of measurement data generated in the conventional wired transmission can be eliminated, and the initial installation cost and maintenance cost can be reduced and convenient system management can be achieved.

When the wireless measurement system of the present invention is applied to the structure monitoring system, the maintenance of each structure such as a bridge or a building can be made more economically, and the reliability of the construction field can be restored by securing safety for social infrastructure facilities. And social anxiety.

Claims (3)

delete In the measurement system for transmitting the measured data after the measurement of the behavior of the structure in the structure monitoring system to the main computer, A sensor system module including a MEMS type acceleration sensor for detecting vibration of the structure, and a plurality of sensors installed at each position of the structure to measure the behavior of the structure; A control and processing module for acquiring, processing, and storing dynamic data output from the acceleration sensor as a vibration signal, and performing measurement system control and measurement situation determination according to a control signal of a main computer; And A sensor-side modem for wirelessly transmitting dynamic data output from the control and processing module to the main computer and receiving various control signals output from the main computer, and for transmitting and receiving between the control and processing module and the main computer. A wireless measurement system for dynamic response measurement for monitoring the structure consisting of a wireless modem module consisting of a main computer side modem provided to enable wireless transmission and reception with the sensor side modem. The method of claim 2, The control and processing module may include a flash controller in which a program for performing the above functions is stored, a microcontroller having a data memory in which data generated or necessary when the program is executed is stored, and an external memory for providing additional data storage space. Wireless measurement system for dynamic response measurement for monitoring the structure, characterized in that.

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