An experimental testbed for mobile offshore base control concepts

The concept of a mobile offshore base (MOB) reflects the need to stage and support military and humanitarian operations anywhere in the world. A MOB is a self-propelled, modular, floating platform that can be assembled into lengths of up to 2 km, as required, to provide logistic support to US military operations where fixed bases are not available or adequate. It accommodates the take-off and landing of C17 aircraft, and can be used for storage, as well as to send resources quickly to shore. In most concepts, the structure is made of three to five modules, which have to perform long-term station-keeping in the presence of winds, waves, and currents. This is usually referred to as dynamic positioning (DP). In the MOB, the alignment is maintained through the use of thrusters, connectors, or a combination of both. In this paper, we consider the real-time control of scaled models of a MOB. The modules are built at the 1:150 scale, and are kept aligned by rotating thrusters under a hierarchical hybrid control scheme. This paper describes a physical testbed developed at the University of California, Berkeley, under a grant from the US Office of Naval Research, for the purpose of evaluating competing MOB control concepts.