Development of a Nonlinear Simulation for Testing of Control Systems in a General Class of Lifting Body Vessels, SWATHs, and Hydrofoils

The demand for faster, more efficient ships has increased the use of non-traditional technologies such as hydrofoils, lifting bodies, and alternative hull forms, many of which use control systems for improved seakeeping and in some cases to ensure dynamic stability. High-fidelity time-domain methods available to simulate the motion of a ship in a seaway in support of control system design are often computationally expensive, so testing changes in control system parameters can be time consuming; obtaining statistically meaningful data sets can also be computationally prohibitive. Frequency-domain based codes allow the user to design control systems based on an assumed input wave spectrum, but they are very low fidelity and do not permit visualizing the time history of the ship and its actuators. A fast, medium-fidelity simulation would be extremely useful in control system design and testing. Such a simulation must be adaptable to varied ship configurations and compatible with all the non-traditional ships of interest. This paper presents such a simulation as developed for a general class of lifting body/foil borne ships, SWATHS, and mutlihulls; examines the methodology used as well as the assumptions made in development of this simulation; and presents an example of the simulation’s results