Robust anti-pitching control for high-speed multihull without velocity measurements

Abstract

Considering the excessive vertical motion amplitude of high-speed multihull, and the difficulty of measuring heave velocity and pitch angular velocity directly, a robust anti-pitching control method without velocity measurements is proposed in this paper. The vertical motion model of the high-speed multihull is established with the used anti-pitching appendages, that is, T-foil and flap. The uncertainty of the vertical control model, and the coupling between heave and pitch motions are analyzed. Only using the output feedback of heave displacement and pitch angle, a stable second-order dynamic system is constructed to realize the anti-pitching control, avoiding the observation of heave velocity and pitch angular velocity during the process of control design. Furthermore, the regional pole assignment theory is adopted to select the parameters, so as to ensure the dynamic performance. On this basis, an extended state observer (ESO) is designed to estimate the stochastic disturbance and the coupling between heave and pitch motions online, and the bandwidth of the ESO is chosen based on the wave power spectrum, such that the robust anti-pitching performance can be further improved due to the real-time feedforward compensation. The stability of the closed loop system is theoretically proved using Lyapunov theory, and the effectiveness of the proposed algorithm is also verified by numerical simulations.