【作者】 章永华；

【导师】 杨杰；

【作者基本信息】 中国科学技术大学 ， 精密仪器及机械， 2008， 博士

【摘要】 随着社会的不断发展,人类对陆地资源的开发需求日益膨胀,势必将导致资源的逐步耗竭。约占地球总面积71%的海洋蕴藏着巨大的潜力和无穷的奥妙,因此,设计高性能的水下推进器去探索海底的未知世界和丰富的资源已成为各国关注的热点和核心问题之一。鱼类作为海洋的主要“居民”经过上亿年的进化和自然选择,形成了适合海洋环境的独特形态和运动方式。其中波动鳍推进模式具有高效、高机动性和低流体扰动并且易于向水下推进器移植等显著优点,为未来水下推进器的仿生设计提供了新的选择,具有重要的理论研究价值和广阔的应用前景。本文以蓝点魟鱼类为研究对象,在详细观察分析其生物形态和波动运动特征以及生理结构的基础上,基于蓝点魟胸鳍结构、运动特征及推进功能开展仿生波动鳍的研究。论文主要围绕仿生波动鳍的结构设计、数值计算和实验验证三方面展开,并在如何利用新型智能材料作为驱动源研制仿生鱼鳍方面做了初步尝试和探讨,为仿生水下推进器的发展方向抛砖引玉,主要研究内容如下:1.仿生鱼鳍波动推进系统的设计与分析。结合实验室早期对仿生对象蓝点魟的定性观察和引用了L.J.Rosenberger等人大量的相关研究结论,深入开展了仿生对象生物形态、胸鳍波动运动特征以及生理结构等方面的研究,给出了这些参数随着游速变化的定量趋势,为仿生鱼鳍波动推进机构的设计和控制提供了客观依据和科学指导。根据仿生对象研究启示,基于模块化设计理念,在国内率先研制成功仿生蓝点魟模型。深入分析了仿生蓝点魟鱼鳍鳍条的运动学和动力学特性,与此同时建立了鱼鳍波动推进的运动学与动力学模型,并对鱼鳍波动推进力和推进速度进行了理论推导。针对仿生蓝点魟推进系统与控制系统一体化设计的技术特点,提出了蓝点魟胸鳍用于推进与姿态控制的控制方法,通过主动调节多个设计参数实现推进器的巡游、转弯、沉浮等基本运动方式,结合水下红外传感器阵列实现避障功能。2.仿生鱼鳍波动推进的数值计算。建立了以仿生蓝点魟为样本的简化二维及三维胸鳍波动运动模型,以不可压缩非稳定的N-S方程为主控方程,基于有限体积法与非结构网格的SIMPLE算法的控制方程离散,结合动网格技术,对仿生鳍条摆动过程和鱼鳍波动过程进行数值计算,综合分析了运动学参数、波动模式、波动鳍鳍面形状、鳍条刚度和倾角对游动性能的影响。给出了鱼鳍波动游动时流场信息以及总体受力情况,显示出了反卡门涡街的形成,并从涡动力学角度揭示了推力产生的流体力学机理。数值计算结果的正确性在随后的实验研究得以验证。3.仿生鱼鳍波动推进的实验研究。根据测试对象和测试内容的不同,分为鳍条摆动过程实验测试和仿生波动鱼鳍测量实验。鳍条摆动过程实验测试系统由运动机构及其控制系统、流场显示系统和测力系统组成。运动机构及其控制系统能模拟鳍条摆动的运动过程,流场显示系统能获得摆动运动流场涡结构的演化过程,测力系统能正确测量摆动运动过程中鳍条所受升阻力的变化规律。仿生鱼鳍波动实验系统则包括游速测量系统、推进力测量系统和功率测量系统组成,采用正交试验设计方案,分别使用极差分析和方差分析对波频、波幅、波长等运动学参数,波动模式,鱼鳍鳍面形状以及他们之间交互作用对游动速度、推进力、效率的影响进行详细的分析。同时还进行了鳍条刚度对游动性能影响的对比实验。实验结果较好地验证了理论推导和数值计算结论的可信性和正确性。4.仿生鱼鳍装置的初步改进。机电系统在工作原理、外形和性能等方面都与动物肌肉存在很大区别,尤其是缺乏类似动物“肌腱”的高性能储能元件。因此,本文在利用更接近肌肉驱动特征的智能材料作为驱动源的柔性仿生鱼鳍研究上做了一些探讨性工作。通过分析比较目前常见和相对比较成熟的几种智能材料的性能,最终选定N_iT_i形状记忆合金材料。同时针对柔性仿生鱼鳍的结构特点以及形状记忆合金材料本身的特性,提出了以一对差动方式安装的具有单向形状记忆效应的薄板状形状记忆合金作为鳍条基本单元,以应变传感器检测和反馈形状记忆合金薄板弯曲形变量,以模糊控制作为基本运动控制算法,实现了柔性鱼鳍的摆动和波动运动。通过实验给出了形状记忆合金鳍条弯曲输出力与薄板厚度的关系,鳍条最大偏转角度与厚度的关系以及加热电流占空比与鳍条最大偏转角度的关系,对仿生鱼鳍的设计进行了初步的优化。更多还原

【Abstract】 With the development of our society, the resource of the earth is gradually exhausted. The ocean which occupies more than 70% of surface area of our earth contains huge potential and infinite profound. Therefore, the development of high performance Automatic Underwater Vehicle (AUV) to explore the unknown areas and rich resource of the undersea environment has become one of the popular voice recently all over the world. Fishes, the main residents of the ocean with billions of years’ evolution and nature selection, have grown special characteristics of shapes and motion modes that are suitable for ocean condition. Among them the undulatory fin propulsion mode has the special advantages on high swimming efficiency, high maneuverability, less disturbance and convenience of being transplanted to underwater vehicles. Generally speaking, such a bio-propulsion mode provides a novel scheme for the development of future aquatic robots, it possesses values of both theoretical research and prospective for wide applications.This thesis takes Bluespotted stingray as a research object. After detailed investigations on its morphology, kinematics character and inner physiology structure, we propose a bionic undulatory fin based on pectoral fin structure, kinematics as well as propulsive function, including bionic design scheme, computational fluid dynamic (CFD) and the corresponding experimental validation. Furthermore, a new actuator driven by smart material is initially investigated, which provides an innovative idea and another choice for the bionic design of underwater vehicles. Through this research work, we may draw the following four points:1. Bionic design and analysis of the undulatory fin propulsion system.According to our qualitative observation combined with research work done by Rosenberger et al on Bluespotted stingray, we present morphology, undulatory kinematics character and inner physiology structure of its widely expanded pectoral fin as well as some quantitive conclusions of the variation of these parameters with propulsion velocity. It provides adequate guidance for bionic design and control of undulatory mechanical fin. Inspired by Bluespotted stingray and modular design motivation, we build a Bluespotted stingray model. According to our knowledge, it’s the first Rajiform underwater robot in China. Hereby, the kinematical and dynamic performance of a single fin ray together with the whole fin is in-depth studied, followed by the analysis on thrust and velocity generated by undulatory motion of the mechanical fin. On the integrative design of the propellant system and the control system of our bionic Bluespotted stingray, a novel control method has been proposed for propulsion and gesture control. By actively modulating multi design parameters combined with infrared sensor array, we finally achieve several locomotion behaviors including: cruising, turning, depth control and obstacle avoidance.2. Computational Fluid Dynamic analysis of the undulatory fin propulsion system. Set up both 2D and 3D simplified undulatory kinematical equations. The governing equations are the incompressible, unsteady Navier-Stokes equation that is discretized using the finite volume method (FVM) with an implicit segregated solver approach. The pressure velocity coupling of the continuity equation was achieved using the SIMPLE algorithm. By combining with unstructured mesh and adaptive re-meshing, we implement the numerical analysis on oscillatory motion of fin ray and undulatory motion of bio-fin. The flowing aspects have been investigated to reveal the contribution to the propulsion performance: kinematical parameters, undulatory modes, fin shapes, stiffness and obliquity of fin rays. The field information around swimming fin and the force coefficient are obtained from the calculation. With these results, we analyze the forming mechanism of reverse Karman vortex streets and producing of thrust of fin during its motion by vortex dynamics. To be more important, these computational results of the undulatory fin model have been validated by experimental tests.3. Experimental tests on the undulatory fin propulsion system. The experiment is divided into two main parts: the tests on fin ray with oscillatory motion and the tests on fin with undulatory motion according. The equipment for the fin ray tests consists of motion control system, digital particle image velocimetry (DPIV) system and force measurement system. The motion control system can imitate the oscillatory motion of fin rays, the DPIV can display the vortex structure in the wake, while the force measurement system is used for lift and drag testing during oscillating. The equipment for the fin tests consists of velocity measurement system, propulsion force measurement system and power measurement system. We adopt orthogonal experimental design and use both range analysis and variance analysis to make a detailed study on the influence of kinematics parameters (such as frequency, amplitude, wavelength), undulatory modes, fin shapes as well as their correlations on propulsion velocity, thrust and efficiency. In addition, we test the influence of fin stiffness on propulsion performance. The experimental tests show the feasibility and creditability of the theoretic and computational conclusions.4. Improvement of the undulatory fin propulsion system. There exists great difference between electro-mechanical system and animal muscle on driven principle, form, performance, etc., particularly lacks efficient energy storage element that similar to the muscle tendon of animals. Therefore, we further carry out research on smart material driven bio-fin, the character of which is much close to muscles. After comparing the performance of several recently available smart materials, we finally choose N_iT_i Shape Memory Alloy (SMA). According to the structure of flexible bio-fin along with the characteristic of SMA, a couple of differentially equipped SMA plates with single Shape Memory Effect (SME) act as the function of fin ray. The deformation information is detected and feedback by strain transducer, and then achieve both oscillatory and undulatory motion of the flexible fin through Fuzzy Logic Control (FLC) algorithm. The preliminary experiments present the relationship between the bending force and the thickness of SMA plate, the relationship between the maximal bending angle and the thickness of SMA plate, and the relationship between the maximal bending angle and the heating current. This is meant for an initial optimal design of SMA bio-fin.更多还原