Motion response control of a single spar using linear quadratic regulator (LQR) method

Cargo-transfer and underway replenishment are essentially important in long-term naval operations. The Office of Naval Research (ONR) initiated a technology development program in 2007 called STLVAST (Small to Large Vessel At-Sea Transfer). The goal of this program is to develop 'enabling capabilities' in the realm of logistic transfer (i.e. stores, equipment, vehicles) between a large transport vessel (e.g., the USNS Bob Hope) and a smaller T-craft ship, using a Deep Water Stable Crane (DWSC) spar between them. The DWSC spar consists of two entities, a catamaran craneship and a detachable spar. In this paper, a new numerical scheme to simulate time-domain motion responses of floating systems has been successfully proposed and applied to the motion response control of the DWSC spar. The equation of motions using the Impulse Response Function (IRF) is initially discretized into a new state-space model, where the first order and second order waves loads transfer functions are calculated from WAMIT. Two time steps affect the construction of this state-space model: the time step t used to estimate the IRF, and simulation step t. The LQR method is selected in this study. Firstly, the effects of both time step on the controlling efficiency is studied. Then various weighting factors (Q,R) for the LQR controller are further considered to study the robustness of the LQR method. Copyright 2012 by the International Society of Offshore and Polar Engineers (ISOPE).

Motion response control of a single spar using linear quadratic regulator (LQR) method Conference Paper