基于LQR限宽水域中KVLCC2操纵运动控制研究

在航道宽度受限制的水域中,船舶会受到岸壁效应的影响,横向力与首摇力矩将发生变化,这会对船舶的航行安全产生不利的影响.鉴于此问题,本文应用现代控制理论最优控制LQR方法,对在限制水域中航行的超大型油轮KVLCC2的操纵运动进行控制研究.为便于LQR控制器的设计,采用线性状态空间形式的操纵运动方程,基于数值模拟获取的相应线性水动力系数,计算出使目标函数值最小的增益矩阵K,从而得到满足最优控制规律的时域舵角变化,实现对不同宽度水域中船舶运动的最优控制,并与极点配置控制法作比较,验证LQR控制器的优越性.结果表明,当船岸距离d/L≥1.2时,船舶基本不受岸壁效应的影响,控制幅度极小;当岸壁距离d/L=0.25时,摆舵角度将超过6°,同时船舶前进速度也将下降,下降幅度将超过前进速度的10%,岸壁效应明显.

Control study of KVLCC2 maneuvering in restricted water based on LQR

To investigate the hydrodynamic characters of a large ship in laterally restricted water, In restricted waters, ships will be affected by bank effect, sway force and yaw moment will change, which will have adverse effects on the con-trol of ship navigation. In this paper, the LQR optimal control theory is applied to a large oil tanker KVLCC2 to achieve con-trol design of ship maneuvering in restricted waters. In order to permit the design of a linear quadratic (LQ) controller, the maneuvering equations of motion are cast in a linear state-space framework, and CFD numerical simulation methods are used to compute the corresponding hydrodynamic coefficients. Based on the above, the paper calculates gain matrix K to minim-ize cost function and obtains the time-domain rudder angle satisfying optimal control law, which achieves optimal control of ship maneuvering in restricted waters with different widths. Simulation results demonstrate the effectiveness and superiority of the LQR controller compared with traditional pole placement method under the same control parameters. The results show that when the largest non-dimensional separation distance is d/L=1.2 the ship is merely disturbed and control action is very small. And the case of d/L=0.25 sees steady rudder angles beyond 6° and also forward speed reduction is 10% of the forward speed.