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.
In order to enhance the suppression ability of high-speed multihulls against wave disturbance and reduce the amplitude of vertical motion, it is necessary to use two types of appendages, active T-foil and flap, to implement closed-loop anti-pitching. Aiming at the problems of sea wave disturbance and appendages input constraints, an anti-pitching scheme based on incremental predictive control is proposed. First, the vertical coupled motion model of the high-speed multihull ship is established, the frequency-domain and time-domain characteristics of random wave disturbance are analyzed, and the wave disturbance force and moment are estimated based on the integral disturbance model. On this basis, the incremental model of multihull vertical motion that includes the change rate of wave disturbance is used as the prediction model to reduce the influence of the average wave disturbance force and disturbance moment on vertical motion, improve the model prediction accuracy, and introduce the amplitude and change rate of heave and pitch into the objective function to minimize both. At the same time, in order to solve the input constraints of the anti-pitching appendages and reduce the amount of online calculation, the Lagrange multiplier method and the stair-like parameterization strategy are used to derive the analytical anti-pitching predictive control law and analyze the stability of the closed-loop system. The simulation results show that the proposed incremental predictive control effectively reduces the change rate and amplitude of heave and pitch, the heave displacement is reduced by 43.51%, and the pitch angle is reduced by 50.88%.
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