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Wireless Sensor Network for Guided Wave Propagation with Piezoelectric Transducers



Guided waves are widely used for structural health monitoring (SHM) applications especially for the observing of width structures. For exciting guided waves into structures piezoelectric transducers are common used. But for an effective observing of structures a network of piezoelectric transducers is needed and normally the connection between the different transducers is done with wires. For short distances between the nodes (e.g. 5 to 10 cm) this works well, but for longer distances the influence of the cables capacitance is quiet high. Also the more on weight is a drawback of wired sensor networks. Because of the above mentioned disadvantages of such wired sensor networks, researchers developed wireless sensor network systems for SHM. In this paper we present a wireless sensor network system which is designed for SHM application with piezoelectric transducers and guided waves. First, the different hardware components of the wireless sensor network system are described in detail. The hardware mainly consists of a PC connected via USB hub which remotely controls wireless the actuator – sensor nodes. Each node in the sensor network can be used as actuator with an excitation voltage of about 60 V peak-to-peak, as well as sensor with a variable amplification to measure signals in the range between 0.5 and 100 mV. The frequency range covers 30 – 300 kHz. Powered by the integrated battery, the nodes operate completely autonomously. The main novelty of this system is its simple handling because of the Graphical User Interface (GUI). The GUI enables the choice between the actuator or sensor mode for each device in few seconds. Also the number of active nodes in the network (up to 8 nodes) or the excitation frequency can be selected by a mouse click. After every measurement cycle the measured data from each sensor node is diagramed on the screen. Finally, the paper presents a laboratory test on an aluminum/foam sandwich plate with a removable artificial defect to accurately assess the performance merits and weaknesses of the integrated hardware and software.

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