Communication and localisation using underwater acoustics

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The routine inspection underwater storage facilities for nuclear materials is typically conducted by tethered vehicles or robots. The use of untethered vehicles offers a number of advantages, including: removing the hazard of the tether becoming entangled; greater freedom in the positioning of the vehicle; and the opportunity to reduce the inspection time through the use of multiple (swarms) of vehicles. Legacy underwater nuclear storage facilities present a particular challenge when using tethered vehicles due to them having cluttered or unstructured layouts. Untethered vehicles may be the only practical way to inspect these facilities in support of decommissioning activities.The navigation and inspection of underwater storage facilities using non-tethered vehicles requires a communication and localisation (positioning) infrastructure. Radio Frequency (RF) wireless technology has a very limited useful range underwater when required to transmit data at rates greater than 10 kbps, and optical wireless technology is limited by scattering from suspended solids and the requirement for direct line-of-sight between the transmitter and receiver. Across the distances encountered in typical underwater storage facilities, acoustic communication and localisation is a practical alternative. This project will develop an acoustic communication and localisation system that can be retrofitted to existing vehicles and integrated into new designs. In the case of existing tethered vehicles, where the tether provides a high bandwidth communication link, the acoustic system will provide valuable position information. The system will use a series of base-stations positioned underwater around the periphery of the storage facility. The base-stations receive/transmit data acoustically from/to the underwater vehicles, and provide a wired communication link to the operators. The base-stations also provide known reference positions (termed anchors) to enable the positions of the vehicles to be determined (localisation). Achieving reliable communication and accurate positioning in the unstructured environment of the legacy storage facilities will prove challenging, and the project will undertake an extensive experimental evaluation of the system in a representative, but benign, test environment.EPSRC Research Areas: Artificial intelligence technologies; Robotics; Sensors and Instrumentation;