Wireless Sensor Network For Structural Health Monitoring

Wireless Sensor Network For Structural Health Monitoring

Snehal D. Mhaske, Pursuing M.E in E&TC (Embedded and VSLI),

P. R. E. C. Loni (MH), India-413736

Prof. Shaikh S. A. Associate Prof. Dept. of E&TC,

P. R. E. C. Loni (MH), India-413736

Prof. Galande S. G. Associate Prof. Dept. of E&TC,

P. R. E. C. Loni (MH), India-413736

Prof. Turkane S. M. Associate Prof. & HOD

Dept. of E&TC,

P. R. E. C. Loni (MH), India-413736

Abstract

Structural Health Monitoring (SHM) strategies measure structural response and aim to effectively detect, locate, and assess damage produced by severe loading events and by progressive environmental deterioration. Structural response reflects the structural condition as well as the excitation force. By analyzing the response data, SHM strategies are expected to reveal structural condition, such as the damage existence. SHM has seen intense research efforts in mechanical, aerospace, and maritime, as well as civil engineering applications. The idea struck into mind that a SHM system should be implemented so that it can monitor structure (two story building) using different surface mounting sensors, these systems can collect various parameters of the structure. The rapid development of wireless sensor network (WSN) technology provides us a novel approach to real-time data acquisition, transmission and processing. Our aim is to monitor and measure the acceleration, strain, humidity and temperature of the building.

Index Terms- Structural health monitoring, wireless sensor network, FBG (Fiber Bragg Grating).

1. Introduction

   Structural Health Monitoring (SHM) strategies measure structural response and aim to effectively detect, locate, and assess damage produced by severe loading events and by progressive environmental deterioration. Structural health

   monitoring calls for sensors that are low-cost, low- profile, and power-constraint. It also requires the sensors to form a network to accurately monitor the low-frequency response that often occurs in many civil structures such as long-span bridges. However, the existing sensors are either not practice wireless implementation, does not have enough accuracy, or are not cost-effective. This project presents a multi-function sensor that can easily form a smart sensor network by the merit of the ZigBee mesh networking function integrated in the sensor. The radar sensor, integrated with a micro-controller, works in the arctangent- demodulated interferometric mode to monitor the structures displacement with an accuracy of sub- millimeter. Experimental results show that the smart sensor network using the multi-function radar sensors serves as a good alternative for monitoring structural health.

2. System Architecture

   The idea struck into mind that a SHM system should be implemented so that it can monitor structure (two story building) using different surface mounting sensors, these systems can collect various parameters of the structure. The rapid development of wireless sensor network (WSN) technology provides us a novel approach to real- time data acquisition, transmission and processing. In a system of this kind, there are several nodes and a base station. Each node contains a group of sensors and the nodes are distributed on both the floors of the building. Data collected by sensors is sent to the base station via WSN channel. The base station is usually a PC with Graphic User Interface (GUI) for users to analyze current status and alarm

   automatically when parameters detected is below preset standards. The recorded data can be analyzed using various simulation tools for future correspondence and actions. Structural health monitoring (SHM) can prevent these tragic incidents. For civil engineers, wireless sensor networks (WSNs) are an attractive technology: compared to traditional wired systems, they consistently reduce the installation time and costs and are not subjected to wires wear and tear or breakage caused by harsh weather conditions or other extreme events.

   Our aim is to monitor and measure the acceleration, strain, humidity and temperature of the building. The remote access of structure quality measurement parameters using wireless communication facilitates quality control, record keeping and analysis using simulation software at base station. Acceleration, humidity, strain and temperature are the parameters will be analyzed and control. Following will be the steps of idea implementation. Accelerometer sensor measures acceleration and Radar sensor measures displacement by taking double integration of the acceleration data it is possible to obtain displacement and that displacement can be compared with displacement of radar sensor.

   1. Measurement of acceleration, humidity, strain, temperature using available sensors, at remote place.

   2. To collect data from various the sensor nodes and send it to base station by wireless communication.

   3. To control data communication between source and sink nodes (Synchronization using time division).

   4. To simulate and analyze quality parameters for quality control. (Graphical and numerical record using MATLAB)

   5. To publish the corresponding record over web for public information and further assessment of resource.

      Structural Health Monitoring (SHM) strategies measure structural response and aim to effectively detect, locate, and assess damage produced by severe loading events and by progressive environmental deterioration. Structural response reflects the structural condition as well as the excitation force. By analyzing the response data, SHM strategies are expected to reveal structural condition, such as the damage existence. SHM has seen intense research efforts in mechanical, aerospace, and maritime, as well as civil engineering applications. Buildings are subjected to natural hazards such as severe earthquakes and strong winds, as well hazards such as fire, crime,

      and terrorism, during their long-term use [1]. To mitigate these hazards, monitoring various risks in a building by an intelligent sensor network is necessary. The sensor network could measure acceleration, displacement, strain, etc. The risk to buildings includes aging of structural performance, fatigue, damage, gas leak invasion, fires, etc. The risk to buildings includes aging of structural performance, fatigue, damage, gas leak invasion, fires, etc. According to the results of risk monitoring, appropriate risk control measures such as structural control, maintenance, evacuation guidance warning, alarm, fire fighting, rescue, security measures, can be applied [2].

      Figure 1. Building Risk Monitoring

3. Literature survey and technological survey

   Only within the past century have scientists used electronic devices to verify the behavior of materials used to construct our societys infrastructure. As electronics technology has evolved, it has become more commonly available, and useful, to structural engineers in both the research and professional arenas. Today, it would be almost impossible to find a consultant who does not use computers as a design aide. Increasingly, monitoring the health of structures will not be solely a function of an annual physical, or visual, inspection by structural engineers. Engineers now, and in the future, will need to use technology in the field to help them verify the behavior of that which they have learned to analyze and design. As more structures are instrumented, we will learn more about their behavior and this can lead to more economical waysto build and maintain them [3].

   As an outcome of the combination of computer technology, communication technology and sensor network technology, it is regarded as the first of 21st century top 10 new technologies that changed world. With strong data capture and process abilities, it has very expansive application foreground in the fields of military, environment monitoring, disaster prevention and biomedicine, especially in some special fields such as environment monitoring and disaster rescue with nobody on duty, it has advantages that traditional technologies could never compare.

   Zigbee is a newly rising short-distance, low- complexity, low-speed-rate, low-cost and low- consumption two-way wireless communication technology or wireless net technology that applies direct serial spread spectrum technology. The working frequencies bands include 868MHz (for Europe), 915 MHz (for the U.S.A) or 2.4 GHz (Global) ISM Frequency Bands. Comparing with other wireless network technologies, it is easily- applicable, low-consumption, strong-networking ability, high-reliability and low cost. This technology is based on high security IEEE 802.15.4 protocol that uses 128 bit security [4].

   An accelerometer is an electromechanical device that measures acceleration forces [5]. These forces may be static, like the constant force of gravity pulling at our feet, or they could be dynamic – caused by moving or vibrating the accelerometer. There are many types of accelerometers developed and reported in the literature. Fiber Bragg gratings are formed by a periodic perturbation of the core refractive index of an optical fiber. Coupling between modes of the fiber may thus be achieved. A popular FBG couples a forward-propagating mode into its contra directional propagating version. With an adequate design this reflective coupling may be limited to a narrow spectral range, typically to a few hundred picometers [6].Humidity of the building can be measured by using HS220 sensor by mounting the sensor on the surface of the building[7].

4. Theoretical Details and Analysis

   Structural Heath Monitoring (SHM) is the term applied to the process of periodically monitoring the state of a structural system with the aim of diagnosing damage in the structure. Over the course of the past several decades there has been ongoing interest in approaches to the problem of SHM. This attention has been sustained by the belief that SHM will allow substantial economic and life-safety benefits to be realized across a wide range of applications. Several numerical and

   laboratory implementations have been successfully demonstrated. However, despite this research effort, real-world applications of SHM as originally envisaged are somewhat rare. Numerous technical barriers to the broader application of SHM methods have been identified, namely: severe restrictions on the availability of damaged-state data in real-world scenarios; difficulties associated with the numerical modeling of physical systems; and limited understanding of the physical effect of system inputs (including environmental and operational loads) [8].

   1. Acceleration

      MEMS accelerometers are one of the simplest but also most applicable micro-electromechanical systems. They became indispensable in automobile industry, computer and audio-video technology. This seminar presents MEMS technology as a highly developing industry. Special attention is given to the capacitor accelerometers, how do they work and their applications. An accelerometer is an electromechanical device that measures acceleration forces [5]. These forces may be static, like the constant force of gravity pulling at our feet, or they could be dynamic – caused by moving or vibrating the accelerometer. There are many types of accelerometers developed and reported in the literature. The vast majority is based on piezoelectric crystals, but they are too big and too clumsy. People tried to develop something smaller, that could increase applicability and started searching in the field of microelectronics. They developed MEMS (micro electro mechanical systems) accelerometers.

   2. Strain and Temperature

      In recent years, FBG (Fiber Bragg Grating) has been accepted as a new kind of sensing element for temperature and strain measurement for structural health monitoring (SHM) in civil infrastructures. Cost of FBG fabrication, high-quality FBG demodulation system, practical encapsulation (package) techniques and indirect FBG-based sensors, and practical applications are the cores for FBG to be widely popularized in infrastructures. In this paper, firstly, the FBG fabrication and demodulation The optical fiber sensors for the measurement of strain have been under development for a number of years and a lot of are shapes to embed within the structural material for the purpose of feature of optical fiber sensors is their inherent ability to serve as both the sensing transmission medium.

      Dynamic Strain Measurement Using FBG Sensors:

      Recently, many researchers have demonstrated that the FBG sensors can be used to measure the strain of a Structure under static loadings. The resolution of FBG sensors also gives a reliable data while comparing with the traditional RSG sensors. Under this situation, applying the FBG sensors to the dynamic measurement becomes an interesting topic in civil engineering. Since the smart structure concept gradually rises up in civil engineering, there is a need of large amount of sensors in the structure. The main reason to use the FBG sensors is that they can solve the complex wire problems if there are hundreds of sensors on the structure. On the other hand, the FBG sensors have another advantage: sequential measurement.

   3. Humidity

      Humidity of the building can be measured by using HS220 sensor by mounting the sensor on the surface of the building.

      The structural monitoring system includes three parts, one is the collection of the parameters of the buildings, transmission using Zigbee module and the other is the monitoring centre system. The system components are showed in above Figure.

      • Sensor Node

        1. Accelerometer sensor.

        2. FBG strain sensor.

        3. FBG temperature sensor.

        4. Radar sensor.

        5. Humidity sensor.

      • Receiver Node

      1. PC with GUI (Simulation in MATLAB): visualizes data in real time

   4. Accelerometer Sensor

      SOURCE NODE

      SOURCE NODE

      ACCELEROMETER SENSOR

      ZIGBEE MODULE

      HUMIDITY SENSOR

      STRAIN SENSOR

      TEMPERATURE SENSOR

      SIGNAL CODITIONING

      ARM7 PROCESSOR

      RS232 COMMUNICATION

      Figure 3: Accelerometer Sensor

      SINK NODE

      SINK NODE

      ZIGBEE MODULE

      RADAR SENSOR

      ARM9 PROCESSOR

      PC WITH GUI

      dIGITEXX d110-U (uniaxial) or d110-U (triaxial) accelerometer sensors used in structural health monitoring for many applications. d110-U (uniaxial) or d110-U (triaxial) accelerometers are force balanced electro-mechanical capacitive accelerometers. They have wide dynamic range excellent bandwidth and ultra low noise floor while still operating at highest performance commercially available. Available as uniaxial or triaxial these sensors provide electrostatic feedback without magnetic components [5]. The accelerometers high resolution and accuracy make them ideal for structural health monitoring [9].

      Figure 2: Block Diagram of Structural Health Monitoring For Building

      Radar Sensor (D1S Radar Distance Sensor):

      Figure 4. Experimental setup for acceleration and distance measurement

      • D1S Radar Sensor is a rugged distance sensor for a wide range of applications.

      • Works in harsh conditions such as vapor, dust, smoke, rain or other small particles.

      • Measurement signal is not affected by wind or temperature changes

      • Measure distance to objects down to 30 cm.

   5. FBG (Fiber Bragg Grating) Strainand Temperature Sensor (OS3155)

      Working principle

      Fiber Bragg gratings are formed by a periodic perturbation of the core refractive index of an optical fiber. Coupling between modes of the fiber may thus be achieved. A popular FBG couples a forward-propagating mode into its contra directional propagating version. This is achieved by adding a periodic variation to the refractive index of the fiber core, which generates a wavelength specific dielectric mirror. A fiber Bragg grating can therefore be used as an inline optical filter to block certain wavelengths, or as a wavelength-specific reflector. Fiber Bragg Gratings are made by laterally exposing the core of a single-mode fiber to a periodic pattern of intense ultraviolet light. The Braggs wavelength is given by: Bragg =2neff

      • FBG is a longitudinal periodic variation of the index of refraction in the core of an optical fiber.

      • The spacing of the variation is determined by the wavelength of the light to be reflected.

      Figure 5.Working Principle For FBG (Fiber Bragg Grating) Sensor

      The OS3155 is a rugged strain gage with integrated temperature compensation. Both strain and temperature compensation measurements are based on fiber Bragg grating (FBG) technology. Optimized for outdoor installations on steel structures, the os3155s stainless steel carrier holds the FBG in tension and protects the fiber during installation. Since there are no epoxies holding the fiber to the carrier, long term stability is ensured by design [6].

      Figure 6. FBG Sensor for Temperature And Strain Measurement

   6. Humidity Sensor HS220

   This module converts relative humidity intothe output voltage.

   Figure 7. Graph of Relative Humidity Vs Output Voltage

5. Conclusion

This Project describes a wireless sensor network for structural health monitoring. A wireless sensor node equipped with a 3-axis digital accelerometer and a temperature and humidity sensor, Radar sensor, strain sensor is presented. A Matlab program running on an external PC connected to the sink node processes and visualizes in real-time the data received from the sensor nodes by Implementing WSN for SHM to prevent tragic incidents.

References

1. Chen, B., and Tomizuka, M. 2008. Open SHM: open architecture design of structural health monitoring software in wireless sensor nodes. Proceedings of the IEEE International Conference on Mechatronic and Embedded Systems and Applications (MESA 2008), Beijing, China, October 12-15.

2. Takeya, H., Ozaki, T., and Takeda, N., Structural Health Monitoring of Advanced Grid Structure Using Multi-point FBG Sensors, Smart Structures and Materials 2008: Industrial and Commercial Applications of Smart Structures Technologies, Edited by E. V. White, Vol. 5762, pp. 204-211.

3. Changsha Gu, Jennifer A. Rice, and Changzhi Li A. Wireless Smart Sensor Network based on Multi- function Interferometric Radar Sensors for Strut, IEEE Transaction on structural Health Monitoring, 978-1-4577-1238-8/12 2012.

4. Bocca, M., Cosar, E. I., Salminen, J. and Eriksson, L.M., Helsinki University of Technology (TKK), Recon Figureurable Wireless Sensor Network for Structural Health Monitoring 4th International Conference on Structural Health Monitoring of Intelligent Infrastructure (SHMII-4), Switzerland, 22-24, July 2009.

5. http;//www.micronoptics.com FBG fiber optic sensors.

6. Paek, J., Chintalapudi, K., Cafferey, J., Govindan, R., and Masri, S., A wireless sensor network for structural health monitoring: Performance and experience. Proc., 2nd IEEE Workshop on Embedded Network Sensors (EmNetS-II), Sydney, Australia) 2005.

7. Quing ling, zhi tain, Yuejun yin, and yue li. Localised structural health monitoring using energy efficient wireless sensor networks, IEEE sensor journal, vol. 9, no-11, November 2009.

8. Glauco feltrin, olga saukh, jonas meyerand masoud motavalli structural monitoring with WSN: Experiences from field deployments first middle east conference on smart monitoring, 8-10 feb2011.

9. http;//www.mdpi.com/journal/sensors.