Design and validation of a smartphone based wireless structural vibration monitoring system

Traditional structural health monitoring (SHM) system usually uses expensive professional sensors, data transmission and data acquisition systems. Thus, only very important structures are affordable to install a SHM system. In recent years, smartphones become very popular, which not only integrate high-performance vibration sensors, but also have powerful data acquisition, processing, storage and transmission capabilities, making it possible to utilize smartphones to carry out some SHM tasks. In this paper, the authors developed a software that can easily convert several android based smartphones into a wireless structural vibration monitoring system. The software consists of a server program and a client program. The smart phone installing the server program can remotely control the smartphones installing the client program via local WIFI network to perform the tasks of network timesynchronization and measuring structural responses. First, the architecture of this program is introduced in detail. Then, the time synchronizing algorithm for all client nodes in the software is discussed. Next, the accuracy of time synchronization of the smartphone based wireless sensing system is validated through an experiment. Finally, a shaking table experiment is conducted, the results of which demonstrate that the smartphone based wireless structural vibration monitoring system can quite accurately identify the modal parameters of the tested structure.