Impact and near failure detection using digital spatial domain multiplexing technique

Impact and near failure detection is very important for the monitoring of structure health in many industrial sectors, especially aerospace and civil engineering. Such problems are normally indicated by an unusually fast change of strain in localised areas. The sensor system for these applications has to have a large dynamic range, a wide detection bandwidth and a capacity to located the position of the problem in a large area. The digital spatial domain multiplexing (DSDM) technique provides sufficient multiplexing capacity and gauge length to cover a large structure area. In addition, it is a fringe interpretation plus fringe counting technique, thus possessing a huge dynamic range. In this paper, we present a dual wavelength coding technique to increase the detection bandwidth of the system. Furthermore, a novel position coding scheme is proposed to located the positions where the problems occur.