基于CFD的减摇水舱流体仿真

研究海洋救助船水舱稳定性优化问题,减摇水舱是最有效的减摇装置之一,可在全航速下实现船舶横摇减摇,通常是在台架和实船实验中验证水舱性能的直接有效性,但是耗时长,造价高,针对以上实验的局限性,提出采用CFD流体软件分析水舱的特性.减摇水舱内气体和液体运动是一种典型的VOF气液两相模型,通过对海洋救助船水舱模型建模,分析了水舱内阻尼板布置不同对水舱产生的最大对抗力矩调节,对抗力矩与横摇运动之间相位差以及水舱固有周期的动特性进行仿真.仿真结果表明,减摇水舱流体优化准确性能够满足平衡性要求,为水舱的设计提高有效的依据.     

减摇水舱试验台架横荡系统研究

船舶减摇水舱试验台架是研究和设计减摇水舱的重要实验设备,准确模拟船舶在海浪中的运动是设计试验台架的关键。目前试验台架研究的仅是单纯横摇,如果考虑了横荡的基本轨圆运动,以及相应的横摇与水舱内液体加速度的耦合,则船的横摇运动更符合实际情况．本文对横荡运动进行了理论分析,并将PID控制方法应用于模拟横荡运动的电液位置伺服控制系统中,仿真结果表明系统具有良好的跟踪性能．符合设计要求．     

减摇水舱试验台架横摇阻尼系数的试验研究

针对某型船舶横摇运动数学模型,依据缩尺比通过硬件和软件相结合的方法在减摇水舱试验台架装置上实现对该船舶横摇运动的模拟。应用角度传感器数据对台架摇摆的机械摩擦阻尼进行计算,并结合角速度传感器数据来模拟台架横摇阻尼力矩;通过台架横摇试验,绘制了力矩和角度试验曲线。对试验曲线的分析可知,应用传感器确定的台架阻尼系数能够满足台架模拟船舶横摇运动的要求。     

H∞回路整形在减摇水舱摇摆台中的应用

减摇水舱摇摆台是实现位置随动控制的液压伺服系统,其功能是模拟船舶运动姿态和验证减摇水舱的性能。摇摆台运动时,在横摇和横荡2个自由度上存在着相互耦合,且水舱内流体晃荡产生很大的干扰力和力矩,导致建模时参数不确定,对系统精度造成很大影响。为此建立摇摆台耦合运动模型,运用力学理论分析并进行解耦控制,求解流体产生的干扰力和力矩,引入H∞回路整形控制策略设计控制器,最后进行仿真分析和实验验证。结果表明,系统能够准确快速跟踪动态输入的横摇和横荡位移信号,实现了对干扰的估计和补偿,提高了系统的跟踪速度和鲁棒性,更为精确地验证水舱的性能。为模拟船舶运动姿态和其他领域中同类型的液压系统控制问题提供有效的解决方法。     

大型舰船综合减摇系统无模型自适应控制

针对减摇鳍单独控制,减摇水舱单独控制和鳍/被动水舱综合控制3种减摇系统设计了无模型自适应控制方案,并对相应的减摇效果进行仿真研究.仿真研究结果表明:大型舰船采用基于无模型自适应控制的鳍/被动水舱联合减摇方案,其工作性能好于单独使用减摇鳍或减摇水舱等减摇装置的性能,在各种航态下都能满足系统设计要求.另外,无模型自适应控制仅用系统I/O数据,不必事先建立系统精确的数学模型,可适应海况的变化,且参数调整少,计算量小,还能适应系统对快速性的要求.     

可控被动式减摇水舱气阀控制规律仿真研究

可控被动式减摇水舱是世界上成功使用的减摇装置之一,气阀控制规律是决定可控被动式减摇水舱减摇效果的关键因素.本文推导了最佳控制相位的理论依据,对气阀开启和关闭时刻的选取进行了详细研究.对不规律波作用下的"船舶-可控被动式减摇水舱"系统进行仿真研究,结果表明控制规律是行之有效的,在各种浪向和航速下都能够获得较好的减摇效果,从而最大限度地发挥了可控被动式减摇水舱的减摇能力.     

航行状态下减摇水舱减摇能力仿真研究

本文根据“船舶-水舱”系统的运动模型,研究被动式减摇水舱在航行状态下的减摇能力。分别在不同海况、航速以及航向等条件下进行仿真,总结出水舱在不同航行状态下的减摇规律。并分析了可控被动式水舱的控制机理,为研究水舱的控制策略奠定了基础。     

U型减摇水舱实验研究

本文讨论U型减摇水舱模型的摇摆台实验。通过实验确定了水舱模型的重要特性参数,很好地解决了实现U型减摇水舱最佳控制的关键问题,并用实验结果验证了水舱模型的减摇效果。     

舵鳍联合控制参数优化及仿真

船舶上装置的舵和减摇鳍系统分别完成航向和横摇减摇控制,但是两者之间存在着耦合,因此提出了舵鳍联合控制,实现多翼面的协调控制.建立船舶运动系统横荡、艏摇和横摇的三自由度运动、舵和减摇鳍的驱动控制、海浪干扰等数学模型,构建仿真环境.利用线性二次型最优控制理论设计舵和减摇鳍的联合控制器,并采用多目标优化手段确定舵速和鳍速参数,仿真表明,在不同的海况,以及船体不同航行状态下,都取得了显著的减摇效率,效果较减摇鳍单独减摇效果更佳,且能够保证良好的航向控制精度,说明舵鳍联合减摇有效地协调舵和鳍控制水翼的控制力和控制力矩.     

减摇水舱试验台架系统PID控制算法的研究与实现

船舶减摇水舱试验台架是研究和设计减摇水舱的重要试验设备，准确模拟船舶在海浪中的运动是设计试验台架的关键。本系统用电液力矩伺服控制系统来模拟海浪力矩，采用PID算法进行控制，其仿真结果符合要求。     

基于CFD的船舶斜浪三自由度运动仿真研究

针对船舶在斜浪中的多自由度耦合运动问题, 建立了三维粘性流耐波性数值波浪水池, 采用边界条件造波法生成高精度的斜向规则波, 通过同时求解RANS方程和刚体运动学方程, 结合网格整体移动方法和滑移网格方法, 实现了船舶斜浪航行的垂荡、纵摇及横摇三自由度耦合运动数值模拟。给出了DTMB5512船模斜浪中的垂荡、纵摇及横摇的频率响应函数, 与线性切片理论计算结果进行比较, 吻合良好。该方法可为船舶斜浪航行的耐波性预报提供一种有效的途径。     

Iterative method based on CFD data for the assessment of seakeeping control effects,considering amplitude and rate saturation

An iterative procedure for the frequency domain evaluation of control effects in nonlinear loops is introduced. The article focuses on ship seakeeping control, to attenuate ship motions. There is no model of the ship, only CFD tabulated data. The proposed procedure could be used for design or empirical tuning of a controller. The actuators have angle and rate limits. In the case of a ship, the actuators are submerged moving wings: flaps, fins and T‐foil. The control evaluation procedure uses a describing function approach. The paper considers amplitude and rate saturation in series. The results are validated with experiments using a scaled ship in a towing tank facility. Copyright © 2010 John Wiley & Sons, Ltd.     

三维薄膜型FLNG储舱晃荡载荷的数值仿真

针对浮式液化天然气(Floating Liquefied Natural Gas,FLNG)船大型储舱内的液体晃荡问题,分别以薄膜型储舱的1∶20模型及原型为研究对象,采用CFD仿真方法分析百年一遇生存海况下液舱内晃荡载荷的基本规律和危险工况.结果表明:在真实海况下,现有FLNG储舱设计中的晃荡冲击载荷主要来源于船体纵向运动,可能出现的最大冲击载荷约为0.4 MPa,主要发生在纵舱壁与横向隔水舱的拐角位置,危险载液率为20%~30%及90%.     

Parallel unstructured multigrid simulation of 3D unsteady flows and fluid-structure interaction in mechanical heart valve using immersed membrane method

In this work, a second-order accurate immersed membrane method (IMM) is adopted to simulate the fluid-structure interaction phenomena in the mechanical heart valves (MHVs). The leaflets of the MHV are immersed in the fluid flows and move on top of the fixed fluid mesh. The blood flow is computed by a 3D parallel unstructured multigrid implicit finite-volume Navier-Stokes solver for incompressible flows. The opening and closing phases of a St. Jude 29 mm MHV are computed under pulsatile inflow to investigate the blood-leaflet interactions. The results show that the moment generated by the fluid pressure is the major cause for the valve motions, while the moment due to the fluid shear stresses is almost negligible. It is also observed that near the end of the opening phase the valve opening speed decelerates, so the valve leaflets have a cushioning effect and avoid a sudden impact on the hinges. For closing phase, jet flows are formed in the central channel and squeeze flows occur in the side channels near the fully closed positions.     

EMG control of a pneumatic 5-fingered hand using a Petri net

This article presents the control method for a 5-fingered artificial hand using electromyography (EMG) signals. Our targeted artificial hand is driven by pneumatic actuators to reduce its weight, and we use ON/OFF solenoid valves instead of electro pneumatic regulators to simplify the control system. The pneumatic hand has 15 degrees of freedom, and it seems difficult to reproduce all the finger motions from the EMG signals only. Therefore, we describe typical hand motions using a Petri net, and control the finger motions efficiently based on this model. Each state of the Petri net indicates one step in the hand posture to complete the intended motion. Simultaneously, this state corresponds to the ON/OFF pattern of the 15 solenoid valves. This enables the operator to control the 5-fingered dexterous hand smoothly, transiting the state in the Petri net according to the EMG motion signals. We conducted an experiment to verify the validity of the proposed method. In the experiment, five typical motions (spherical grasp, power grip, hook grip, key grip, precision grip) were successfully performed using the 6-channel EMG signals measured from the operator’s forearm.     

飞轮调速器反馈控制系统的混沌及控制

建立了飞轮调速器反馈控制系统的动力学方程,利用系统的相图和Poincar6映射图分析了系统的混沌形成过程．通过对飞轮调速器反馈控制系统增加一个比例微分反馈控制器,利用它控制系统从混沌运动转化为周期运动．数值仿真表明了该控制方法在飞轮调速器反馈控制系统的混沌控制中的有效性与可行性,可利用适当的控制强度镇定系统中不稳定的周期轨道．     

A ship motion simulation system

In this article, efficient computational models for ship motions are presented. These models are used to simulate ship movements in real time. Compared with traditional approaches, our method possesses the ability to cope with different ship shapes, engines, and sea conditions without the loss of efficiency. Based on our models, we create a ship motion simulation system for both entertainment and educational applications. Our system assists users to learn the motions of a ship encountering waves, currents, and winds. Users can adjust engine powers, rudders, and other ship facilities via a graphical user interface to create their own ship models. They can also change the environment by altering wave frequencies, wave amplitudes, wave directions, currents, and winds. Therefore, numerous combinations of ships and the environment are generated and the learning becomes more amusing. In our system, a ship is treated as a rigid body floating on the sea surface. Its motions compose of 6 degrees of freedom: pitch, heave, roll, surge, sway, and yaw. These motions are divided into two categories. The first three movements are induced by sea waves, and the last three ones are caused by propellers, rudders, currents, and winds. Based on Newton’s laws and other basic physics motion models, we deduce algorithms to compute the magnitudes of the motions. Our methods can be carried out in real time and possess high fidelity. According to ship theory, the net effects of external forces on the ship hull depend on the ship shape. Therefore, the behaviors of the ship are influenced by its shape. To enhance our physics models, we classify ships into three basic types. They are flat ships, thin ships, and slender ships. Each type of ship is associated with some predefined parameters to specify their characteristics. Users can tune ship behaviors by varying the parameters even though they have only a little knowledge of ship theory.     

船舶运动状态下风速风向测量补偿与数字仿真

为了研究船舶运动状态下的风速风向精确测量,设计了一种船舶风速风向动态测量及误差补偿的数字仿真系统。通过对船舶航行状态下的风速风向测量原理进行分析,建立了船舶平面运动的相对风速风向和真风风速风向的解算模型,并根据船舶空间运动的风速风向测量及其误差补偿算法,对船舶横摇、纵摇状态下的风速风向的动态测量和误差补偿进行了数字仿真。数字仿真结果表明,该方法能够消除船舶航行时的运动姿态对风速风向测量带来的影响,为船舶的操纵控制和航行安全提供了精确和可靠的风速风向数据信息。