Design Requirements for Autonomous Multivehicle Surface-Underwater Operations

Future autonomous marine missions will depend on the seamless coordination of autonomous vehicles: unmanned surface vehicles (USVs), unmanned underwater vehicles (UUVs) and unmanned aerial vehicles (UAVs). Such coordination will enable important inter-vehicle applications such as autonomous refueling, high-throughput data transfer and periodic maintenance to extend the mission length. A critical enabling capability is the autonomous capture, retrieval and deployment of a UUV from a USV platform. As a first step toward solving this problem, we propose a performance specification that quantifies the necessary motion compensation required to safely and reliably operate a USV and UUV in concert in the dynamic marine environment. To accomplish this, we use a model-based approach to predict the motion of typical vehicles under the influence of the same sea conditions. We summarize the predictions succinctly using a scalar performance metric, the peak-to-peak vertical displacement, as a function of vehicle type, sea-state and vehicle formation.To substantiate this model-based approach experimentally, we present sea-trial data and compare the empirical observations to model predictions. The results show that although simple three degree-of-freedom models do not capture the full complexity of an actual six degree-of-freedom ship motion, they can prove expedient in an engineering context for quantifying the design requirements of a USV-UUV capture, deployment and retrieval system.