Anti-pitching control of the catamaran based on low-high gain feedback control and extended state observer

Objectives The heave and pitch motions of the catamaran under severe sea state vary drastically and the amplitudes of the motions are too large, which seriously affects the seaworthiness, so an anti-pitching control by combining the low-high gain feedback control and high order extended state observer (HOESO) feed-forward compensation is proposed. Methods Firstly, the coupled catamaran vertical motion model is approximately decoupled, and the coupling of the heave and pitch motions, wave disturbance, etc. are regarded as lumped disturbance, which are extended into three virtual state quantities. HOESO is designed to improve the accuracy of the disturbance estimation, and the estimated values are used for feed-forward compensation. Secondly, a low-high gain feedback controller is proposed to achieve closed-loop stabilization of the anti-pitch and to reduce the conservatism of the low gain feedback control, while ensuring that attachment inputs of the T-foil and flap satisfy the constraints. Results MATLAB is used to build the anti-pitching control system of the catamaran for simulation, and the results show that the proposed control strategy can effectively suppress the amplitudes of the heave and pitch motions, and improve the stability of the vertical motion. The heave displacement is reduced by about 49%, and the pitch angle is reduced by about 53%. Conclusions The research results can provide reference value for the stability control of multihulls and have certain practical engineering significance.