Discussion on: 'Identification of Multivariable Models of Fast Ferries'

摘要

The ultimate goal of the identification experiment described in this paper is to increase the maritime transport comfort of passengers and crew by reducing the motion sickness induced by heave and pitch. To design the actuator elements that control (reduce) heave and pitch motions, one needs the following dynamics: wave height to heave force G_(1H)(s), wave height to pitch moment G_(1P)(s), heave force to heave motion G_(2H)(s), and pitch moment to pitch motion G_(2P)(s). Since in situ measurements of heave force and pitch moments are difficult (or even impossible) and not very reliable, the wave height to heave force G_(1H)(s), and wave height to pitch moment G_(1P)(s) dynamics are obtained via a simulation program, called PRECAL, that solves numerically the physical nonlinear differential equations of the vertical dynamics of a high-speed ship. The wave height to heave motion G_H(s) = G_(1H)(s)G_(2H)(s), and wave height to pitch motion G_P(s) = G_(1P)(s)G_(2P)(s) dynamics can be obtained from real measurements on a full scaled ship in a model basin or via the simulator PRECAL. In this paper, all the data for identifying G_(1H)(s),G_(2H)(s), G_(1P)(s) and G_(2P)(s) are obtained via the simulator PRECAL using regular waves (single sine excitations) at different encounter frequencies.