Modal Analysis Using a UAV-Deployable Wireless Sensor Network

In structural health monitoring, wireless sensor networks are favorable for their minimal invasiveness, ease of deployment, and passive monitoring capabilities. Wireless vibration sensor nodes have been implemented successfully for frequency domain analysis in ambient vibration detection. To leverage advances in structural damage quantification techniques, which require modal information, nodes in a wireless sensor network must operate with a near-synchronous clock to enable the collection of the signal phase. The non-deterministic timing nature of wireless systems raises a significant challenge when trying to accurately determine the phase of a signal. In particular, the trigger time delay of the various nodes on the structure cannot be differentiated from a true phase caused by the examined system. This study investigates the reliability and error-handling capabilities of the ShockBurst 2.4 GHz wireless protocol in triggering and data transfer. Building on an open-source UAV-deployable sensor node, mode shapes from a 2-meter test specimen are experimentally determined. An optimization technique that enhances time domain accuracy for non-deterministic wireless triggers is presented. This work quantifies latency and error management effects that contribute to enhancing the modal extraction capabilities of wireless systems in structural health monitoring applications.