Armless underwater manipulation using a small deployable agent vehicle connected by a smart cable

Conventional underwater manipulation is performed by a remotely operated vehicle (ROV) equipped with a rigidly connected multi-link arm. However, accurate manipulation requires the ROV to have excellent maneuverability, which limits the design flexibility and capabilities of the vehicle. This paper instead proposes the use of a small, deployable, and highly maneuverable agent ROV as an end effector, which is connected to the main vehicle by a flexible smart cable. This cable tracks the relative position of the agent, thus eliminating the need for additional positioning sensors and allowing significant size reduction for the agent. In addition, to compensate for the limited lifting capability of the small agent, it is equipped with active buoyancy control. The proposed system can be applied to common autonomous underwater vehicles (AUVs) with minimal modification for coarse station-keeping. The whole system is operated as a conventional AUV under normal operating conditions, but the agent is deployed when manipulation or precise monitoring is necessary. Numerical simulations were performed for dynamic analysis and prototype design of the agent vehicle, and this design was implemented as a model-scale system for experiments in a test tank. This implementation confirmed the feasibility and potential capabilities of the proposed manipulation system concept.