一种有效的船舶混沌运动自适应控制方法

针对船舶航行中的混沌运动控制问题,对部分参数不确定的船舶操纵运动非线性模型,提出一种有效的自适应控制方法。基于Lyapunov稳定性理论,证明在本文所提控制器作用下,系统的平衡状态渐进稳定。仿真实验表明,采用本文所提方法能够对船舶转首操纵运动中出现的混沌状态进行有效控制,具有计算量小、方法有效、易于实现等优点。该方法不受系统不确定参数变化的影响,具有良好的应用价值。     

纵浪上基本参数共振对船舶稳性的影响

本文建立了在纵浪上航行船舶的非线参数激励横摇运动方程。     

船舶在纵浪中的运动稳性分析

基于非线性动力学理论，分析船舶在纵浪上的运动响应和运动的稳定性。首先建立描述船舶在纵浪上运动的垂荡—横摇耦合运动方程，利用多尺度法，求得垂荡—横摇耦合运动的亚谐共振解。其次，对船舶运动的稳态响应进行稳定性分析，得到亚谐共振情况下，船舶运动稳态响应的分布图，并揭示了船舶运动的某些非线性特征。     

规则纵浪中船舶参数激励横摇运动研究

考虑船舶横摇运动中恢复力矩及阻尼力矩的非线性,建立船舶在规则波浪中参数激励下的非线性横摇运动方程,并对规则纵浪中船舶参数激励横摇运动进行研究,探讨船舶发生参数激励横摇运动的条件及大幅横摇的动力学特征,分析船速、波高及波长等因素对参数激励横摇运动的影响。     

规则纵浪中船舶参数激励横摇运动的鲁棒控制

为有效控制船舶在参数横摇运动中的失稳状态,根据规则纵浪中船舶参数横摇系统的非线性数学模型,设计了一种具有鲁棒性的非线性控制器.采用精确反馈线性化方法将纵浪中船舶参数横摇系统的非线性模型线性化,然后用闭环增益成形算法设计出非线性鲁棒控制器.在考虑不同的干扰和模型摄动情况后进行了仿真试验.仿真结果表明该控制策略对于船舶参数横摇系统十分有效,且鲁棒性能令人满意.算法的设计过程简单,物理意义明显.     

船舶横摇混沌阈值的数值方法研究

为计算梅尔尼科夫函数的简单零点,文章比较分析了两种数值算法:类帕德逼近和高斯—勒让德积分,作为验证,计算了某激励频率下系统的李雅普诺夫指数谱。然后选取某型船,采用梅尔尼科夫函数方法计算了横摇动力系统的混沌阈值,观察了横摇系统的安全池随外激励增大而逐渐破损的过程,并追踪了破损域中某点的相轨迹。研究计算表明:类帕德逼近可以较精确地得到同(异)宿轨道的参数方程,但在方程的设解形式上需要一定的技巧性,且计算量较大;高斯—勒让德积分不关注参数方程具体形式,处理简单,便于工程计算。     

Backstepping的船舶运动RBF-NN稳定性控制研究

针对船舶运动的非线性模型,设计了一种船舶航行的稳定性控制算法。首先将被控系统分解成与系统阶数相同的子系统,然后利用Backstepping技术,分别为每个子系统设计虚拟控制律,迭代得出虚拟输入控制律,其中的非线性未知函数用RBF-NN逼近,随着迭代次数的增加利用一阶低通滤波器解决计算量膨胀问题。最后通过Lyapunov第二判断法分析验证控制系统的稳定性,基于MATLAB仿真试验,结果表明该方法能够实现船舶航行的稳定性控制。     

船舶在随浪中的运动与横甩预报

本文在水平的随船坐标系下,建立了船舶在波浪中的六自由度操纵运动方程。进行船舶在波浪中的回转运动和Z形操纵运动模型试验,验证数学模型的正确性。通过不同波浪和航速条件下船舶Z形操纵运动的模拟计算,预报船舶在随浪中的横甩,预报结果与试验结果比较一致。     

船舶运动控制中的非线性混沌及PID控制方法

本文从船舶运动控制的机理模型分析了系统可能出现混沌的条件,并介绍了种在恶劣海况下下出现混沌的有效的PID控制方法,仿真结果表明,该方法比只能稳定到混沌的不稳定轨道的方法有更实用的价值。     

基于随机Melnikov方法的甲板上浪船舶混沌运动研究

应用随机Melnikov方法和庞加莱截面研究甲板上浪时船舶的混沌运动。考虑甲板上浪对船舶静稳性的影响,建立随机横浪中船舶横摇运动方程。由随机Melnikov过程结合均方准则确定船舶产生混沌运动的参数域,计算不同参数域中船舶横摇响应的庞加莱截面和时间历程。结果表明,增加船舶阻尼将抑制混沌运动的发生。甲板上浪时船舶横摇响应的庞加莱截面上有两个吸引域,船舶运动过程有两个横摇中心。在非混沌参数域中,船舶只围绕其中的一个横摇中心运动;在混沌参数域中,发生由一个横摇中心到另一个横摇中心的随机跳跃。     

顶浪规则波中小水线面双体船纵向运动特性数值分析

基于RANS方程和VOF模型求解船体粘性兴波流场,采用Overset技术处理船体运动,开展了小水线面双体船(Small Waterplane Area Twin Hulls,SWATH)迎浪规则波中运动响应特性及其产生机理的研究.通过数值计算结果与模型试验结果的对比分析,验证了本文方法的有效性;在此基础上,分析了船体运动响应曲线中各峰值产生的原因及片体间相互干扰对SWATH船在波浪中运动响应的影响,发现其中一个峰值出现的原因为遭遇频率接近船体运动固有频率,由此发生共振;另一个峰值的出现则可能与SWATH特殊的船型及附体配置有关.由于SWATH船片体间的水动力干扰效应,SWATH船在波浪中运动响应峰值较单个片体响应峰值明显减小,且出现的位置向低频方向移动.     

Influence of varying restoring moment curve on parametric roll motion of ships in regular longitudinal waves

This paper examines the influence of stability characteristics on roll motion in the main parametric resonance region. For this purpose, parametrically exited roll motion was modeled as a single degree of freedom system considering heave and pitch effects by means of time varying restoring moment. In addition, restoring moment variations in waves with respect to time and instantaneous roll angle was modeled analytically using the restoring moment curves for the wave crest and wave trough conditions. Roll responses were evaluated in frequency domain by solving the model with an averaging method. Notable correlation between the stability of roll responses and moment curves were observed. The results revealed that, the ratio of metacentric height (GM)between the wave trough and wave crest affects the stability of the trivial solution. Furthermore, the shape of the restoring moment curves in wave trough and wave crest conditions affects the stability of the non-trivial solution or, in other words, the pitchfork bifurcations.     

Coupled motions of two ships in irregular waves in time domain

A three-dimensional time domain approach is used to study the coupled motions of two ships with forward speed in waves. In this approach, the boundary condition is satisfied on the mean wetted hull surface of the moving bodies and the free surface condition is linearized. The problem is solved by using a transient free-surface Green function source distribution on the submerged hulls. After solving the response amplitude operator, the method of spectral analysis is employed to clearly express the motion energy spectrum and significant amplitude of two ships. For verifying the code, two same circular cylinders at beam wave are selected to calculate coupled motions by comparison with the results obtained by 3D frequency method which has been proved to be efficient for solving such problems.Two Wigley ships of different sizes with the same forward speed are chosen for numerical calculation of the interaction effect, and some useful suggestions are obtained for underway replenishment at sea.     

横向规则波作用下的船舶倾覆

运用安全池理论研究了某近海干货船在横向规则波作用下的船舶倾覆问题.用阿当姆斯预估-校正法数值求解时域内单自由度非线性横摇方程.采用三维格林积分方程法计算水动力系数的频域特性.分析了非线性横摇方程中势流阻尼、非线性阻尼以及在横向规则波作用下波高和频率对安全池的影响.     

数值波浪水池中船舶顶浪运动模拟研究

文献[1,2]进行了数值波浪水池波浪环境的模拟、规则波顶浪中船舶水动力的计算以及船舶辐射问题的模拟.文章在其基础上,基于N-S方程,对规则波中顶浪前进的Wigley船模运动进行了模拟.数值模拟的船模运动结果与DUT(Dem University of Technology)的试验数据进行了比较,分析,二者符合较好.文中与文献[1,2]的研究工作一起,初步构建了真正意义上的基于N-S方程的数值波浪水池.     

三维波对船舶运动响应影响研究

通常情况,实际海况的波浪更接近三维波,而在船舶运动预报时,目前主要考虑二维波(长峰波)中的响应,不能真正反映船舶在实际海浪中的运动.文中利用不同方法(频域方法、时域方法以及模型)研究了三维波的方向扩散性对船舶运动响应的影响.三种方法得到的三维波对船舶运动的影响是一致的.结果显示,在研究实际海况中的船舶运动时,考虑三维波的方向扩散性是非常重要的.     

A unified seakeeping and maneuvering analysis of ships in regular waves

The behavior of a ship in regular waves during maneuvering was studied by using a two-time scale model. The maneuvering analysis was based on Söding’s (Schiffstechnik 1982; 29:3–29) nonlinear slender-body theory generalized to account for heel. Forces and moments due to rudder, propeller, and viscous cross-flow follow from the state-of-the-art procedures. The developed unified theory of seakeeping and maneuvering was verified and validated for calm water by comparing it with experimental and calculated zigzag and circle maneuvers. Linear wave-induced motions and loads were determined by generalizing the Salvesen-Tuck-Faltinsen (Trans SNAME 1970; 78:250–287) strip theory. The mean second-order wave loads in incident regular deep water waves in oblique sea conditions were estimated by the potential flow theories of Faltinsen et al. (Proc 13th Symp Naval Hydrody 1980), Salvesen (Proc Intl Symp Dynam Mar Vehicl Struct Wave 1974), and Loukakis and Sclavounos (J Ship Res 1978; 22:1–19). The considered theories cover the whole range of important wavelengths. Comparisons between the different mean second-order wave load theories and available experimental data were carried out for different ship hull forms when the ship was advancing forward on a straight course. The mentioned methods have been incorporated into the maneuvering model. Their applicability from the perspective of the maneuvering ability of the selected types of ships was investigated in given wave environments. The wave conditions are valid for realistic maneuvering cases in open coastal areas. It was demonstrated that the incident waves may have an important influence on the maneuvering behavior of a ship. The added resistance, mean second-order transverse force, and yaw moment also play important roles.     

纵向规则波中参数横摇的数值模拟

基于ITTC推荐的参数横摇运动方程,采用估算方法确定方程中的阻尼系数和复原力矩系数,数值模拟出船舶在规则波中的参数横摇情况,将上述方法具体应用于一艘滚装船船模的参数横摇预报,并与试验数据进行对比,验证了所采用方法的有效性。     

船舶参数激励非线性随机横摇运动分析

研究了随机纵浪中船舶的参数激励横摇运动。将船舶初稳性高作为时变的随机参数激励,应用随机平均法和FPK方程,分析了船舶的参数激励横摇运动微分方程。考虑航速、船舶瞬时湿表面积及随机波浪,建立了船舶横摇幅值概率密度、概率分布函数及其均值的计算方法。以某渔政船为例,计算了不同航速时船舶随机横摇幅值的概率密度、概率分布函数及其均值。结果表明,参数激励谱峰频率为横摇固有频率的2倍时,发生主参数共振,船舶横摇严重,船舶倾覆发生的概率增加。