胸鳍/尾鳍协同推进的机器海豚动力学建模与仿真

动力学模型是机器海豚研究的一个重点和难点.基于胸鳍/尾鳍协同推进模式,采用"叶片单元法"建立2自由度胸鳍动力学模型,根据伯努利原理和大展弦比机翼平衡理论提出尾鳍动力学模型.通过MATLAB进行数值仿真,获取胸鳍、尾鳍的运动规律和不同模式下的游动速度;进一步分析机器海豚的游动模式和运动参数对直游性能的影响,为机器海豚的设计提供理论依据.该研究有助于进一步认识和研究海豚的运动机理,从而提高机器海豚的游动性能.     

新型两关节机器鱼的研制及实验研究

以鲹科加新月形尾鳍推进模式鱼类的仿生学研究成果为基础,采用模块化设计思想,设计了新型两关节仿生机器鱼"HRF-Ⅱ",其尾部模块采用单电机驱动,易于实现尾部运动参数的调整;其升潜模块采用吸排水实现机器鱼升潜.对仿生机器鱼直线推进、转向、升潜和逆向游动的动作进行了水下实验.实验结果表明"HRF-Ⅱ"具备良好的推进特性和升潜特性,并且实现了逆向游动.     

仿生机器鱼胸尾鳍协同推进的水动力学分析

利用CFD技术对仿箱鲀科胸尾鳍协同推进机器鱼的水动力学特性进行分析,将整个机器鱼放入流场,对其胸鳍推进模式、尾鳍推进模式和胸尾鳍协同推进模式的水动力学特性进行对比,得出不同模式下机器鱼水动力学的变化规律。分析得出,在压力变化云图中,胸尾鳍协同推进产生的压力变化最为复杂;在速度涡量变化图中,胸尾鳍协同推进产生最为复杂的涡量变化,胸鳍运动产生的涡会逐渐脱落向后移动,与尾鳍产生的涡互相作用,增加尾鳍的推力,从而证明胸尾鳍协同推进模式是一种高效的推进机制。     

展向刚度对拍动式仿生胸鳍水动力性能影响的实验研究

[目的]旨在研究拍动式胸鳍沿翼展方向结构设计刚度对其水动力性能的影响。[方法]提出一种柔性仿生胸鳍的非均匀展向刚度设计方法。通过搭建的胸鳍水动力性能实验平台,测试0.3～1.0 Hz驱动频率下不同展向刚度仿生胸鳍拍动时产生的平均推进力与平均侧向力,并结合高速摄像机采集的胸鳍运动图像序列,分析仿生胸鳍展向变形对其产生推进力的影响。[结果]实验结果表明,在测试的拍动频率范围内,柔性仿生胸鳍产生的平均推进力及平均侧向力均与鳍条的展向刚度大小及分布情况相关。通过优化机器鱼样机（XJmanta）柔性仿生胸鳍的展向刚度可使其最大游动速度提升约45%。[结论]研究成果可用于指导拍动式柔性仿生胸鳍的设计,优化胸鳍输出水动力性能,提升仿生机器鱼本体游动时的机动性。     

一种柔性胸鳍仿生鱼的初步设计和开发

设计开发一种以胸鳍作为动力推进系统的仿生机器鱼.该仿生鱼具有效率高、机动性好、噪音低,对环境扰动小的优点,并能利用柔性胸鳍摆动方式实现推进及水平面内的机动运动.所设计的仿生机器鱼具有一定的工程应用价值.     

多关节仿鱼运动推进机构的设计与实现

鱼类效率高、机动性强、持久力长的游动方式为人类水中运输设备提供了极佳的设计思路.通过模仿鱼类的运动方式,可设计出新颖的水下运输、作业装备.本文以仿鱼推进机构的设计和实现为目标,根据鱼类游动的特点,对其运动方式进行数字模拟,分析影响其游动性能的关键参数,并建立鱼类游动的数学模型.据此给出了一种多关节仿鱼推进机构的设计方案,完成了辅助这种仿生推进机构设计的仿真软件.借助可视化的鱼类游动及控制的仿真,给出仿鱼推进机构的关键参数,并研制了采用鱼类游动方式运动的仿生机器鱼.     

复合驱动仿生胸鳍机构设计与水动力研究

针对仿鱼型海洋探测机器人低速时的机动性问题,受鹞鲼鱼类依靠胸鳍摆动实现各种水下运动的启发,设计出一种基于共融理论的复合驱动刚-柔多体耦合仿生鱼胸鳍机构。通过构建基于三维非定常湍流控制方程组的柔性鳍摆动系统水动力学模型,研究仿生胸鳍柔性鳍面摆动时周围压力和速度场的变化情况,分析不同摆动幅度和频率下鳍面的水动力学特性,揭示仿生鹞鲼机器鱼的水下运动机理,对摆动胸鳍的水动力进行仿真。结论表明:鳍面摆动时周围的漩涡能够引起胸鳍面上推力、升力及侧向力按类似正弦变化,而推进力和侧向力的大小随摆动幅值和摆动频率增加而增大。     

双尾鳍组合仿生UUV的研制及其特性研究

提出"组合仿生"的设计思想,集自然界飞行与鱼游动物之所长,研制出组合仿生UUV模型.模型突破生物的生理局限,采用双尾鳍推进方式,不仅有效抑制了常规尾鳍推进所带来的本体晃动问题,改进了潜航器巡游的稳定性,而且显著提高了推进速度;此外,借鉴飞行动物拍翼的机动灵活之所长,为潜航器研制增设了强化功能的二自由度胸鳍机构,实现了高机动性.该模型的研制成功不仅验证了组合仿生概念的可行性,还初步揭示了其优势,为仿生UUV提供了一条新的发展思路.     

鲆鲽鱼型双驱动仿生机器鱼水动力研究

为了分析仿生机器鱼的推进模式并预测水下推进性能,对其水动力特性开展研究。基于鲆鲽鱼型双驱动仿生机器鱼和波动推进理论,研究入流速度和波动频率对自推进性能的影响。对胸鳍在不同攻角下的升阻比进行数值计算,最佳攻角为20°。通过研究掌握了影响运动性能的主要因素,确定了计算自推进速度的数值方法,改进了机器鱼波动推进模型。研究结果显示,尾部波动频率是最关键参数,对仿生机器鱼的推力和启动响应速度有直接影响。     

仿生机器鱼的运动规律研究

仿生机器鱼技术为研究高效、高机动性和低噪声的水下运载器提供了新的思路，是近几年水下机器人领域的研究热点之一。基于仿生机器鱼的运动模型，研究了它的运动规律，并进行了计算机仿真研究。仿真结果表明，尾鳍摆动频率和两关节相位差对推进速度有较大的影响。     

Locomotion by mechanical pectoral fins

The objectives of this study were the development of a new device for maneuvering an underwater vehicle using the mechanism of a fish swimming, an experimental and theoretical analysis of the hydrodynamic characteristics of the device, and its application to maneuvering a fish robot. Observations and experimental analysis of the pectoral fins of a black bass (Micropterus salmoides) revealed that the locomotion of the fish, such as swimming forward at low speed, swimming backward, and turning in a horizontal plane is generated by using a combination of a feathering motion and a lead-lag motion of the pectoral fins. A mechanical pectoral fin making a feathering motion and a lead-lag motion generates a thrust force in a range of phase differences between both motions. The unsteady vortex lattice method, including the effect of viscosity, can express fairly well the unsteady forces acting on the mechanical pectoral fin in the range of phase differences where it exerts the thrust force. The fish robot, consisting of a model fish body and a pair of mechanical pectoral fins, can not only swim forward and turn in almost the same position, but can also swim in a lateral direction without changing the yaw angle. Translation of an article that appeared in the Journal of The Society of Naval Architects of Japan, vol. 182 (1997): The original article won the SNAJ prize, which is awarded annually to the best papers selected from the SNAJ Journal, JMST, or other quality journals in the field of naval architecture and ocean engineering.     

水下滑翔机器鱼机构设计与运动性能分析

本文设计了一种具有仿生尾鳍的水下滑翔机器人混合驱动机构,通过内部质量块的平移、旋转、仿生尾鳍的偏置以及外部皮囊的伸缩可实现滑翔机器人的小半径三维螺旋运动。同时,建立了水下滑翔机器鱼的水动力学模型,得到了稳态螺旋运动方程,给出了俯仰调节机构质心位置、尾鳍角、横滚调节机构质心旋转角与转弯半径和垂直速度之间的关系,以及每种稳态螺旋运动所对应的输出变量初值的取值范围。所得结果表明,在俯仰调节、浮力调节、横滚调节和尾鳍驱动的共同作用下,水下滑翔机器鱼可以获得更小的转弯半径,因而机动性更好。所设计的水下滑翔机器鱼在河流和湖泊等环境的水质监测、水下柱形区域取样等领域具有潜在的应用价值。     

Hydrodynamics study of a BCF mode bioinspired robotic-fish underwater vehicle using Lighthill’s slender body model

This paper investigates the hydrodynamic characteristics of the rectilinear motion of a robotic fish underwater vehicle. This 2-joint, 3-link multibody vehicle model is biologically inspired by a body caudal fin carangiform fish propulsion mechanism. Navier–Stokes equations are used to compute the unsteady flow fields generated due to the interaction between the vehicle and the surrounding incompressible and Newtonian fluid (water) environment. The NACA 0014 airfoil aerodynamic profile has been designed to boost the swimming efficiency by reducing drag as the vehicle undergoes an undulatory/oscillatory motion. Using the Lighthill slender body model, a traveling wave mathematical function is defined to undulate the robotic fish posterior (caudal) region while the motion tracking is carried out by dynamic meshing technique. The results obtained show that though the net lift force approaches to zero, the net thrust or negative drag coefficient maintains a finite value dependent on kinematic parameters like tail beat frequency (TBF) and amplitude span (AS) at a given propulsive wavelength and the forward velocity of the vehicle. The results reveal the effects of TBF and AS on the coefficient of drag friction and the thrust force. Drag coefficients obtained from the simulations are compared and validated with the experimental results. The hydrodynamic results are found to be similar to the kinematic study results and suggest that TBF and AS play the most effective roles in the bioinspired propulsion technique. Relation of these parameters with propelling thrust force and forward velocity is also in conjunction over a given range of TBF and AS values.     

减摇鳍与船体的适配性数值模拟

利用计算流体力学方法对减摇鳍与船体之间的适配性问题进行研究。利用零航速减摇鳍的参数以及某型驱逐舰的船型型值表,分别建立在敞水条件下的减摇鳍模型以及加上减摇鳍的船体模型。首先,仿真分析在中、高航速下敞水条件的减摇鳍与受船体约束减摇鳍的静态水动力特性。其次,利用动网格技术分别分析在中、高航速和低航速下敞水条件的减摇鳍与受船体约束减摇鳍的动态水动力特性。计算结果分析表明：静态仿真时,虽然受船体约束减摇鳍的失速角没有敞水条件下的减摇鳍大,但在同样的攻角下,其升力系数却有较大的提高;在动态仿真中,无论是在中、高航速还是低航速下,受船体约束减摇鳍拍击产生的升力都要比敞水条件下的减摇鳍大,但同时产生的阻力以及所需的转鳍力矩也有较大的提高。     

鳍对拖式吊舱推进器水动力性能的影响

为研究鳍的影响,建立了吊舱推进器的水动力性能的计算模型.计算了吊舱推进器安装和不安装鳍时的水动力性能,螺旋桨与吊舱及鳍之间的相互影响通过迭代计算加以考虑.采用基于速度势的基本积分微分方程,并采用双曲面元以消除面元间的间隙.采用Newton-Raphson迭代求解压力分布使得桨叶的随边满足压力库塔条件,用柳泽的方法求得物体表面的速度分布以避免数值求导的奇异性.无鳍.单鳍和双鳍的吊舱推进器水动力性能计算结果表明,附加鳍时吊舱推进器的螺旋桨推力增加,由于鳍上产生推力导致吊舱阻力减小.附加双鳍时的吊舱推进器水动力性能最好,附加单鳍时次之,无鳍时最低.     

仿胸鳍/尾鳍推进水下航行器方案设计与模型试验

针对小型水下航行器开展了系统方案设计,系统主要包括中央主体模块、胸鳍模块、尾部推进模块及控制模块。选用可编程序控制器(PLC)实施运动控制,完成了模型制作,编写了控制程序,并进行了初步的模型试验,探讨了仿生水下航行器运动的基本性能。     

Effects of longitudinal fins on dynamic stability of pipes conveying fluid made of functionally graded material

Dynamic behavior and instability of clamped-clamped pipes conveying fluid with longitudinal fins are studied in this paper. The analysis is done for pipes made of both homogeneous and functionally graded materials (FGM). In the FGM case, the materials of pipe and fins are assumed to be graded through the radial direction based on a power-law distribution. The Hamiltonian principle and Euler-Bernoulli beam assumptions are employed to derive the governing differential equations of the pipe system. Different fin configurations are investigated and the effects of several parameters including power‐law index, fluid velocity, number of fins, thickness and height of the fins are analyzed. Natural frequencies of the pipe and critical flow velocities are determined for various values of parameters. Numerical results show that the stability of the system is significantly affected by the power‐law index and fin dimensions. Among different fin configurations studied in this paper, the addition of non-horizontal fins provides significant improvement in the stability of both homogeneous and FGM pipes conveying fluid and consequently, can be considered as an effective “dynamic stabilizer” for the pipe system. In contrast to non-horizontal fins, the horizontal fins improve the stability of pipes conveying fluid, slightly.     

Control system design and performance evaluation of anti-pitching fins

We have investigated the usefulness of active stabilizing fins to reduce ship pitching under varying forward speeds, and in varying wave lengths. A 4-m self-propelled model ship and an electrohydraulically driven stabilizing fin system were used in our experiment. Pitch angles, pitch rates, and ship forward speeds were measured and fed back to a controller to calculate the deflection angle of the stabilizing fin. The effects of fin nonlinearity on achievable pitch reduction performance are discussed. It is shown that the desired pitch response can only be achieved when the fin is operated in the linear region. The overall dynamic response of the ship approaches open-loop behavior when the degree of nonlinearity is high. This simple analysis of the pitch stablizing system provides basic information to ship designers. Experimental results validate these design guidelines. Received for publication on Feb. 12, 1998; accepted on Dec. 8, 1999