Abstract
A robust H∞-type state feedback model predictive control (H∞-SFMPC) with input constraints is proposed to optimize the control performance during the ship sailing. Specifically, the approach employed in this paper is able to optimize the closed-loop performance with respect to an H∞-type cost function which predicts the system performance based on the actual model instead of the ideal model. As a result, the effect caused by disturbances is attenuated. The state feedback control gain for the control input of the rudder-fin joint roll/yaw control system is obtained by solving a constrained convex optimization problem in terms of linear matrix inequalities. Simulations are carried out, which reveal that the proposed approach has outstanding control performance. Furthermore, it is found that the approach also has significant robustness with respect to parameter uncertainties.
Highlights
For safe sailings and operations in the ocean, large ships often encounter uncertain situations, such as supply difficulties, unknown sea conditions and hidden risks in the operation of marine equipment, which may affect the ship safety during the sailing [1]
For the ship roll/yaw controller design, the discrete-time ship motion state prediction model is carried out according to H∞ -type cost function, the minimum value of cost function is treated as inequality constraint and the multiple input constraints are considered, including the saturation limitation of the rudder/fin stabilizers and the delay constraint of the fin stabilizers
It can be seen from (a) and (b) that the ship motion response based on two different models has good similar control effect, and from (c) and (d) it can (d) Rudder angle (c) Fin angle be seen that the H∞ -SFMPC has strong robustness to the parameter uncertainty model when the control inputs based on nominal/uncertain modelunder are not so different
Summary
For safe sailings and operations in the ocean, large ships often encounter uncertain situations, such as supply difficulties, unknown sea conditions and hidden risks in the operation of marine equipment, which may affect the ship safety during the sailing [1]. A significant feature of MPC is the receding horizon fashion, and the optimization problem is solved at each time instant to determine the control inputs Both fin roll reduction and rudder roll reduction are faced with the problems of complex modeling and controller failure caused by the change of sailing states. In the rudder-fin joint MIMO control system, the receding-horizon optimization strategy is implemented in real time, and the input constraints of rudder angle and fin angle are considered In such a way, ship roll/yaw motion control is handled with the minimized disturbance attenuation level.
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