Low Power Wireless Sensor Network for Monitoring Civil Infrastructure

• Forschungsstelle: ASTRA SBT
• Projektnummer: ASTRA2005/008
• Projekttitel Englisch: Low Power Wireless Sensor Network for Monitoring Civil Infrastructure

Schlüsselwörter (Deutsch)

Drahtlos, Sensor-Netzwerk, Infrastruktur, Zustandsüberwachung

Schlüsselwörter (Englisch)

Structural Health Monitoring, Low Power, Wireless Sensor Network, Civil Infrastructure

Kurzbeschreibung (Deutsch)

Für die Zustandsüberwachung von Bauinfrastrukturen wird ein universelles, drahtloses Sensornetzwerk entwickelt. Das Netzwerk wird für permanente Langzeit und temporäre Kurzzeit Überwachungsaufgaben ausgelegt. Das Netzwerk besteht aus einer beliebigen Anzahl Knoten und einer zentralen Einheit. Die einzelnen Knoten sind modular aufgebaut und bestehen aus einer drahtlosen Kommunikationseinheit (auf niedrigen Energieverbrauch optimiert), einem digitalen Datenverarbeitungsblock, einem oder mehreren Sensoren und einer Batterie als Energiequelle. Bezüglich Energieverbrauch wird eine Überlebensdauer eines Knotens von 2 bis 5 Jahre zum Ziel gesetzt. Die zentrale Einheit sammelt alle Daten der einzelnen Sensorknoten und analysiert diese hinsichtlich möglicher Sicherheitsmängel der Struktur. Diese zentrale Einheit soll in der Lage sein, autonom Sicherheitsprobleme zu erkennen und in angemessener Weise reagieren, z.B. schliessen des Verkehrsträgers, Besitzer kontaktieren, ...
Die Kapazität des Netzwerkes wird an einer Labor- und einer Feldanwendung demonstriert:
1) Kontinuierliche Überwachung der Kabelkräfte der Schrägseilbrücke in der Bauhalle der Empa.
Aufgrund der grossen Datenmenge und dem hohen Rechenaufwand (Kraftbestimmung aus
ambienten Schwingungsmessungen), stellt diese Anwendung höchste Anforderungen an das
System.
2) Kontinuierliche Überwachung von Kabelkräften einer extern vorgespannten Brücke.

Kurzbeschreibung (Englisch)

A general purpose smart wireless sensor network to monitor civil infrastructure is developed. The network will be design for permanently long-term and for temporarily mid-term continuous structural health monitoring. The network consists of an arbitrary number of motes and one central unit. The motes consist of a low power wireless communication unit, a digital signal processing unit, one or several sensors and a state of the art battery as power supply. The targeted mote lifetime ranges between 2 to 5 years. The central unit gathers all the data from the motes. The collected structural data is analyzed globally in order to detect negative trends regarding structural safety. The central unit is able to autonomously react in an adequate way, e.g. closing the road, getting in contact with the owner, etc..
The network will be demonstrated on one laboratory and on one field application:
1) Monitoring the cable forces of the indoor cable stayed bridge at Empa. Due to the high amount of
signal processing (ambient vibration measurements and force estimation), this application will show the ultimate capability of the system.
2) Continuously monitoring of cable forces of externally pre-stressed bridges

Projektbeschreibung (Englisch)

Appendix 1

Methoden (Englisch)

The key point of this project is the collaboration of micro-electronic experts (CSEM) and experts in structural health monitoring (Empa). The monitoring network is based on the wireless communication platform developed at CSEM. This system will be adapted and optimized for civil infrastructure monitoring.
1) Define the technical requirements for the sensor network (sampling frequency, maximal power consumption, amount of data processing, data through put ...).
2) CSEM: Adaptation and enhancement of the motes and network communication protocol;
Empa: development of a procedure to estimate cable forces based on vibration measurements and its optimization for low power consumption; integrating sensors on the motes.
3) Implementing this measurement technique into a 'one mote network'. Validation and demonstration of the functionality.
4) Assembling a first multi-mote network in the laboratory of Empa. The objective is to permanently monitor the cable forces of the laboratory bridge.
5) First field application: transferring the laboratory setup to a real bridge. The monitoring objective is to survey the cable forces of an externally pre-stressed bridge.

Spezielle Geräte und Installationen (Englisch)

One existing, externally pre-stressed bridge for short-term monitoring cable forces.

Stand der eigenen Forschung (Englisch)

Structural Health Monitoring is one of the core activities of the Structural Engineering Research Laboratory of Empa since many years. Beside services for infrastructure owners, the main focus is on research in monitoring of civil infrastructure. Damage detection and structural integrity assessment is investigated based on experimental modal analysis and modal updating. Regarding safety and serviceability issues, identifying crucial structural parameters and monitoring these values is an approach we follow. External cables, mostly stayed cable, are investigated in terms of non-destructive testing, semi-active vibration mitigation and theoretical analysis of the dynamic behavior. The Structural Engineering Research Laboratory is workpackage leader in the project ‘Sustainable Bridges’ of the 6th framework program of the European Union. The objective of the workpackage is to establish a wireless monitoring sensor network.

To optimize power consumption, the Swiss Center for Electronics and Microtechnology (CSEM)
has developed WiseNET, an ultra low-power platform for the implementation of wireless sensor
networks that achieves low-power operation through a careful codesign approach. WiseNET
combines a dedicated duty-cycled radio with WiseMAC, a low-power MAC protocol designed for
low-duty-cycle wireless sensor networks. The WiseNET solution consumes about 100 times less
power than comparable solutions available today. A WiseNET node consists of a basic board with
mainly a low-power radio, a microcontroller and some IO interface connectors (I2C, UART, etc…).
The low-power WiseMAC multi-hop protocol is embedded in the microcontroller. Application specific
boards with sensors as well as a host processor running the main application software can be
stacked on the basic board. The host processor communicates with the “radio” microcontroller
through a serial interface using a packet based HCI (Host Controller Interface) protocol.

Projektziele (Deutsch)

Ein drahtloses Sensor-Netzwerk zur Zustandsüberwachung ziviler Infrastruktur wird entwickelt.
Das Design des Sensor-Netzwerkes wird so gewählt, dass nur ein kleiner Aufwand erforderlich ist, um das System für die meisten Bau-Infrastruktur Überwachungsaufgaben anzupassen.
In einer ersten Laboranwendung (Schrägseil Brücke, Empa) und in einer ersten Feldanwendung werden erste praktische Erfahrungen gesammelt. Darauf basieren, kann das Optimierungspotential dieses System eruiert werden, und in zukünftige Netzwerkgenerationen einfliessen. Zusätzlich können künftige Überwachungsstrategien, basierend auf solchen drahtlosen Netzwerken, entwickelt werden.

Projektziele (Englisch)

Development of a wireless sensor network for monitoring civil infrastructure.
The network will be designed in a general way. Therefore, it is adaptable to most monitoring applications in civil engineering with only minor expenditures.
First midterm (labratory) and short-term (field application) experience in wireless monitoring of civil infrastructures is attained. Based on this, the optimization potential of such systems can be explored and implemented in a next generation network. Additionally, future monitoring strategies can be developed.

Forschungsplan (Englisch)

See below in "Methodik" for a more detailed description.
07.2005 - 12.2005: Technical requirements (CSEM / Empa)
10.2005 - 09.2006: Mote adaption (CSEM) and information processing (Empa)
07.2006 - 12.2006: "One-mote network" (CSEM / Empa)
10.2006 - 03.2007: Network validation and demonstration in the laboratory (CSEM / Empa)
04.2007 - 05.2007: First field application (CSEM / Empa)
05.2007 - 06.2007: Writing Report

Abstract (Deutsch)

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Umsetzung und Anwendungen (Deutsch)

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Umsetzung und Anwendungen (Englisch)

The wireless sensor network is applied to one laboratory and one field structure within this project. The developed tools will be adaptable for any future monitoring application for civil engineering structures.
1) New infrastructure: embedded into structure during construction.
2) Existing infrastructure: attached to the structure for mid- and long-term monitoring purposes.

Berichtsnummer (Deutsch)

1232

Literatur (Englisch)

Chang, P.C. and S.C. Liu, Recent research in nondestructive evaluation of civil infrastructures. Journal of Materials in Civil Engineering, 2003. 15(3): p. 298-304.

Carden, E.P. and P. Fanning, Vibration based condition monitoring: A review. Structural Health Monitoring, 2004. 3(4): p. 355-377.

Aktan, A.E., et al., Issues in infrastructure health monitoring for management. Journal of Engineering Mechanics-Asce, 2000. 126(7): p. 711-724.

Huth, O., Feltrin, G., Maeck, J. Kilic, N., Motavalli, M., Damage Identifiation Using Modal Data: Experiences on a Prestressed Concrete Bridge. Structural Engineering ASCE, 2004(submitted).

Bergamini, A., Christen, R., Non-destructive inspection of steel cables with large diameters for cable-stayed bridges. Vol. 574 May 2004. 2004: ASTRA. 75.

Feltrin, G., Natural frequencies and mode shapes of taut cables with flexural rigidity and rotational constraint at the supports. Sound and Vibration Research, 2004: p. to be published.

Motavalli, M., Feltrin, G., Gsell, D., Meyer, J. Instrumentation of the Indoor Cable Stayed Bridge at EMPA.
in CSHM UIC 2004 North American Euro-Pacific Workshop. 2004. Sheraton Royal Hawaiian Hotel, Honolulu.

Enz C., El-Hoiydi A., Decotignie J.-D., Peiris V., WiseNET: An Ultralow-Power Wireless Sensor Network
Solution. IEEE Computer, Vol. 37, Nr 8, August 2004, p. 62-70