ABSTRACT

To estimate the response of small vessels to control inputs, a general parametric three degree of freedom mathematical model and dynamics simulation has been constructed. The general form of this model allows a variety of vessels with displacement hulls to be easily simulated. To verify the accuracy of this simulation, sea trials were conducted. During these sea trials, the test vessel was instrumented with shaft RPM sensors, a rudder angle sensor, a wind sensor, and a duel antenna GPS compass. Using the results from the sea trials and dynamics simulation, the response of the vessel to rudder and RPM inputs is quantified and the accuracy of the simulation is validated.

INTRODUCTION

The Navy and Marine Corps are pursuing a Sea Basing program in accordance with the Seapower21 initiative for the purpose of conducting logistics operations from sea. A Sea Base will consist of many vessels operating in close proximity to one another for the purpose of transferring cargo, personnel, and fuel between large intercontinental vessels and smaller littoral vessels, as well as to act as staging, supply, and reconstitution platforms. While many of these vessels will be large (>75 m), there will also be small vessels (<75 m) operating in the Sea Base. To effectively and safely come together, remain at a constant stand off distance, and separate, the vessels will need to dynamically position relative to each other. However, Dynamic Positioning, DP, systems are only used on large vessels and technology must be developed for small vessels if they are to dynamically position themselves. One challenge in converting DP technology from large to small vessels is that large and small vessels respond differently to environmental forces. Another challenge is that smaller vessels are typically underactuated, reducing the number of states which can be directly controlled.

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