Robot fish with two-DOF pectoral fins and a wire-driven caudal fin

This paper presents a robot fish with a wire-driven caudal fin and a pair of pectoral fins. First, the design of the robot fish is presented. The caudal fin is driven through wire-driven mechanism. The pectoral fins can perform two degrees-of-freedom motions, i.e. flapping (roll) and feathering (pitch). The pectoral fins can move in labriform mode for propulsion, or for other purposes such as turning and diving. Second, the propulsion analysis models for caudal fin propulsion and pectoral fins propulsion are derived. Finally, three types of experiments are conducted. Experiment results show that the swimming speed of caudal fin propulsion and pectoral fin propulsion match the model predictions. Moreover, with the caudal fin propulsion alone, the robot fish can swim up to 0.66 BL/s (body length/second); with the pectoral fin propulsion alone, the robot fish can swim up to 0.26 BL/s. The pectoral fins can significantly improve the maneuverability of the robot fish. Without using the pectoral fins, the turning radius of the robot fish is 0.6 BL; with the pectoral fins, the turning radius is reduced to 0.25 BL.     

胸鳍推进机器鱼俯仰稳定性分析

胸鳍推进机器鱼的胸鳍在通过扑动产生推力的同时,也会产生纵向扰动,引起机身的俯仰运动,对应用产生一系列的影响.本文在传统潜艇稳定性概念的基础上建立了胸鳍推进机器鱼的俯仰稳定性模型,证明了机器鱼的俯仰运动系统是一个二阶线性系统;分析了由胸鳍扑动引入的扰动,证明其中包含常量分量、扑动频率的一倍频分量和二倍频分量.最后进行了样机的游动实验,实验结果间接证明了俯仰运动模型和胸鳍扑动扰动模型的正确性.     

Design Optimization of a Bionic Fish with Multi-Joint Fin Rays

This paper aims to design a novel bionic fish propelled by oscillating paired pectoral fins. Flapping motion deformation of the nature sample, the cow-nosed ray, is realized with simple mechanical structure through optimization. Locomotion analysis of the nature sample under linear cruise swimming conditions is carried out. Simplified mathematical models of the pectoral fin are obtained to be the design foundation of the bionic fin rays and the bionic fish. The number of fin rays is decided according to the passing kinematic wave shape and number. Distance and structure parameters are optimized, and determined by the minimum area error method. A novel two-stage slide–rocker mechanism is designed to fulfill the driving requirements with only one servo motor. System design of a new bionic fish robot is presented, including the mechanical design and the control method. Main bionic characteristics extracted from the cow-nosed ray are fulfilled by the prototype and verified by experiments.     

仿生机器鱼艏向摆动动力学仿真及分析

由尾鳍拍动产生侧向力导致的机器鱼的艏摇能够影响航行器的推进效率。该文首次运用Adamas软件埘北京航空航天大学机器人研究所“SPC—Ⅱ”仿生机器鱼进行了尾鳍受力分析和动力学仿真。从鱼体和尾鳍推进机构质阜比、拍动频率以及对尾鳍攻角的影响三个方面对仿真结果进行了分析，得出以下结论：随着鱼体和尾鳍推进机构质量比的增大以及频率的增大。艏摇不断减小；鱼体和尾鳍推进机构质量比小于78，没有出现共振现象；艏摇的存在会明显的衰减尾柄主臂和尾鳍攻角的角位移。     

仿生魟鱼环形胸鳍波动推进的流场仿真

针对自主设计的仿生魟鱼水下机器人环形胸鳍波动推进过程进行了流场仿真研究。基于魟鱼前进运动时的胸鳍波动特征,建立了仿生环形胸鳍三维波动运动模型。利用CFD对胸鳍波动推进过程进行数值计算,分析了波动胸鳍产生的拉力以及前向运动的速度等推进性能。研究了周期波动过程中鳍面的周向压力分布,进行鳍面附近核心涡以及切面二维涡分量的计算,分析了涡的产生、发展以及尾迹涡的相关特性。结果表明,稳定后的拉力系数以近似正弦波形式进行波动,鳍面波动前后缘分布的高压和低压区域随波动沿周向从前往后传播,环形波动长鳍最终在尾迹处形成卡门涡,流场分析为仿生魟鱼水下机器人的运动控制及性能优化提供理论基础。     

形状记忆合金驱动仿生蝠鲼机器鱼的设计

研究了一种采用鳐科模式游动、柔性胸鳍摆动方式推进的形状记忆合金（SMA）丝驱动型仿生蝠鲼机 器鱼．首先,对双吻前口蝠鲼游动动作进行了分析,建立了蝠鲼胸鳍柔性摆动的简化运动模型．然后对能够模仿蝠 鲼肌肉动作的智能材料进行了分析．最后设计了SMA 丝驱动的柔性仿生胸鳍和仿生蝠鲼机器鱼,并分析了SMA 丝 的热力学特性,确定了控制规律．该机器鱼外形与双吻前口蝠鲼外形相似,身体呈现扁平形状,有一对三角形的柔 性仿生胸鳍,直线游动速度达到79 mm/s,最小转弯半径为118 mm．该机器鱼游动稳定性好,无噪声．     

Dynamic modeling of a CPG-governed multijoint robotic fish

This paper is devoted to the formulation of a dynamic model of a serially connected multijoint robotic fish with a pair of wing-like pectoral fins, in which the whole robot is treated as a moving multilink rigid body in fluids. Considering that the thrust of fish mainly results from the force of trailing vortex, added lateral pressure, and leading edge suction force, the dynamic equations of the swimming fish have been derived by summing up the longitudinal force, lateral force, and yaw moment on each propulsive component in the context of Lagrangian mechanics. Along with the bio-inspired central pattern generators (CPGs) as the locomotor controller, the overall dynamic propulsive characteristics of the swimming robot are then estimated in a mathematical environment (i.e. Mathematica). Finally, simulations and experiments are carried out to validate the effectiveness of the built dynamic model. Results demonstrate that the CPG-coupled dynamic model provides a fairly good guide to seeking pragmatic backward swimming patterns for a carangiform robotic fish.     

超磁致伸缩薄膜驱动仿生游动微型机器人

研制了以超磁致伸缩薄膜为驱动器的仿生游动微型机器人，其作业原理是以超磁致伸缩薄膜驱动器为尾鳍，通过改变时变振荡磁场的驱动频率，在超磁致伸缩薄膜的磁机耦合作用下,将时变振荡磁场能转换成驱动器的振动机械能，振动的超磁致伸缩薄膜驱动器再与液体耦合，便产生了机器人的推力．由于超磁致伸缩薄膜为非接触式驱动，因此机器人不需要电缆驱动．基于仿生游动原理，提出一种计算推力的数学模型，以建立的超磁致伸缩薄膜受迫振动模型的前三阶谐振频率模态为尾鳍的摆动，对振动薄膜产生的推力进行了计算．实验验证了理论分析的正确性，表明仿生游动微型机器人的方案切实可行．     

3-D Locomotion control for a biomimetic robot fish

This paper concerns with 3-D locomotion control methods for a biomimetic robot fish. The system architecture of the fish is firstly presented based on a physical model of carangiform fish. The robot fish has a flexible body, a rigid caudal fin and a pair of pectoral tins, driven by several servomotors. The motion control of the robot fish are then divided into speed control, orientation control, submerge control and transient motion control, corresponding algorithms are detailed respectively. Finally, experiments and analyses on a 4-link, radio-controlled robot fish prototype with 3-D locomotion show its good performance.     

基于仿脊髓网络的咽颌模式仿生胸鳍协调控制

根据所研制的咽颌模式仿生胸鳍的结构和驱动特点以及操纵运动的特征,构建了咽颌模式仿生胸鳍的仿脊髓控制网络.首先,根据咽颌模式推进时左右胸鳍的协调运动特点,构建左右仿生胸鳍仿脊髓控制网络之间的拓扑连接关系,实现左右仿生胸鳍的协调控制.然后,利用Matlab对仿脊髓控制网络在咽颌模式仿生胸鳍推进运动形态产生和左右胸鳍协调控制方面的性能进行仿真分析,并对比仿真结果与观测结果,发现两者非常吻合,从而证明了所构建的咽颌模式仿生胸鳍的结构和驱动方式及其仿脊髓控制网络是合理的,能够反映硬骨鱼胸鳍的操控机理,并且左右胸鳍的协调控制也具有较好的仿生性能.这些研究为高性能咽颌模式推进系统的研制、咽颌模式推进机理和神经肌肉控制机理等方面的研究提供了基础.     

Influence on the propulsive performance due to the difference in the fin shape of a robotic manta

This paper experimentally investigates the influence on the propulsive performance by the difference in the fin shape of a robotic manta. Five kinds of fin shapes, i.e., a rectangle, a triangle, a trapezoid, and two right triangles, are used in experiment to measure the forward speed of the robot, where two types of right triangle are discriminated, depending on the arrangement of the right angle part and each fin area is assumed to be approximately equal, and the number of fin rays is the same at all the fins. It is proved that a significant difference in propulsive speed arises depending on the difference in the fin shape. Some experiments are additionally conducted to examine the influence on the propulsive speed and its efficiency, due to the parameter change of a progressive wave in the fin.     

Microautonomous Robotic Ostraciiform (MARCO): Hydrodynamics, Design, and Fabrication

Boxfish with multiple fins can maneuver in confined spaces with a near zero turning radius, and it has been found that its unusual boxy shape is responsible for a self-correcting mechanism that makes its trajectories immune to water disturbances. The microautonomous robotic ostraciiform aims to apply these features in a novel underwater vehicle design. Miniature underwater vehicles with these characteristics have a variety of applications, such as environmental monitoring, ship wreck exploration, inline pipe inspection, forming sensor networks, etc. This paper presents the research leading to the design and fabrication of a robotic ostraciiform. Tail fin hydrodynamics have been investigated experimentally using robotic flapper mechanisms to arrive at a caudal fin shape with optimal-shape-induced flexibility. Fluid simulation studies were utilized to arrive at the body shape that can result in a self-correcting vorticity generation. Finally, the robotic ostraciiform prototype was designed based on the previous results. The ostracifform locomotion is implemented with a pair of 2 DOF pectoral fins and a single DOF tail fin. The finalized body shape of the robot is produced by 3-D prototyping two separate halves.     

基于CPG模型的仿生机器鱼运动控制

仿生机器鱼的研究已经成为一个富有挑战性的热点问题.为了控制机器鱼自身的运动和姿态,本文研究了胸鳍对机器鱼运动的影响,并且基于CPG模型,提出了一种运动控制方法.采用的控制模型由4个振荡器构成,可根据反馈的信息产生节律信号以控制机器鱼胸鳍和尾鳍的运动.根据CPG模型参数与反馈输入之间的关系,设计了机器鱼俯仰和转弯反馈控制方法,利用反馈的信息自主调节CPG参数,达到控制胸鳍运动模式的目的.仿真实验验证了控制模型和反馈策略的有效性.     

仿生机器鱼S形起动的控制与实现

给出一种仿生机器鱼S形起动的控制方法.结合北美狗鱼S形起动的形态特征及水动力学知识, 建立了多关节链式结构仿生机器鱼的S形起动模型.整个过程设计为两个阶段: 1)弯曲阶段:以转向速度最大化为目标.在鱼体S形变保证重心稳定平移的前提下, 增大较长转向力臂处的转向力矩,提高转向速度,使鱼体迅速转向目标方向. 2)伸展阶段:以增大前推力为目标.始终保持部分将要伸展的鱼体垂直前进方向,以L形滑动方式打开鱼体. 同时,为保证转向精度,采用模糊控制调节已展开鱼体关节的小角度转动,实时纠正鱼体展开所引起的游动方向偏离. 在S形起动末期,采用变幅值——频率的中枢模式发生器(Central pattern generator, CPG)实现向稳态游动方式的过渡:前期为保证游动方向及获取较大推进力,采用小幅值——高频率的CPG信号, 后期则进入大幅值——低频率的稳态游动.最终,采用四关节仿生机器鱼验证了该方法的有效性, 实现了峰值转速为318.08±9.20°/s、转向误差为1.03±0.48°的较好结果, 对提升水下游动机器人的机动性能具有指导意义.     

NiTi形状记忆合金驱动的仿生鱼鳍的研究

为了提高仿鱼型推进器在水中运动的灵活性，选择了典型的依靠腹部绸带状鱼鳍波动运动产生推进力的黑色魔鬼刀鱼进行研究，对此绸带状鱼鳍的形态和运动机理进行了分析，同时对鱼鳍的结构进行简化．基于绸带状鱼鳍的这种简化模型设计了形状记忆合金驱动的仿生鱼鳍．介绍了鱼鳍的机械结构和相应的控制电路．重点推导了仿生鱼鳍波状运动时理论上能到达的推进速度和产生的推进力；并采用数值仿真给出了波动推进时仿生鱼鳍表面的压力分布以及推进力随时间的周期变化规律．将数值仿真结论和先前的实验结果进行了比较，验证了数值仿真的合理性和正确性．通过上述分析，说明基于形状记忆合金驱动的仿生鱼鳍的研究是很有意义而且可行的．     

仿生机器鱼研究的进展与分析

介绍了仿生机器鱼具有效率高、机动性好、噪音低、对环境扰动小的特点和几种分类方法, 以及国内外在鱼类推进机理和仿生机器鱼研制方面的成果和现状, 在此基础上分析了机器鱼研究的主要内容: 鱼类推进理论模型、仿生机器鱼机械结构、仿生机器鱼游动的推进速度、运动方程、Q效率、Q功率等方面的客观规律, 特别是其控制性能和相关技术问题.     

仿生机器鱼俯仰与深度控制方法

提出一种基于重心改变法的仿生机器鱼俯仰姿态与深度控制方法, 用于实现机器鱼水中的浮潜运动. 该方法利用一种可调整位置的配重块结构, 改变机器鱼的重心位置, 进而实现机器鱼俯仰姿态的调节. 在对机器鱼内部配重块位置和机器鱼俯仰角的关系进行分析的基础上, 对一定速度下机器鱼的深度与俯仰角的关系进行建模, 提出由于尾部形变引起的俯仰姿态变化的补偿方法. 文中给出机器鱼原形样机的相关实验, 分析验证配重块位置变化和机器鱼重心及其姿态的调整, 深度控制等在多种情况下的结果.     

Locomotion and Depth Control of Robotic Fish with Modular Undulating Fins

This paper presents an environmental-friendly robotic system mimicking the undulating fins of a fish. To mimic the actual flexible fin of real fish, a fin-like mechanism with a series of connecting linkages is modeled and attached to the robotic fish, by virtue of a specially designed strip. Each link is able to turn and slide with respect to the adjacent link. These driving linkages are then used to form a mechanical fin consisting of several fin segments, which are able to produce undulations, similar to those produced by the actual fish fins. Owing to the modular and re-configurable design of the mechanical fin, we are able to construct biomimetic robotic fish with various swimming modes by fin undulations. Some qualitative and workspace observations by experiments of the robotic fish are shown and discussed.     

仿生机器鱼胸/尾鳍协同推进闭环深度控制

为改善机器鱼定深控制过程中的动态性能与稳态性能,根据深度误差的大小将定深控制过程分解为趋近阶段与巡游阶段,给出了一种基于中枢模式发生器（central pattern generator,CPG）与模糊控制相结合的闭环运动控制方法．为此,首先建立了以压力传感器信号为反馈输入,通过模糊控制器调节控制参数的CPG运动控制模型．在此基础上,针对误差较大的趋近阶段,采用胸/尾鳍协同方式,通过趋近模糊控制器改变摇翼关节的偏置量与幅值来使机器鱼快速到达期望深度;针对误差较小的巡游阶段,采用改变攻角方式,通过巡游模糊控制器改变胸鳍攻角来使机器鱼保持在期望深度．两阶段之间通过胸鳍CPG的启停实现切换．模糊控制器设计时利用了基于最小二乘法对实验数据拟合而得出的俯仰角变化率与控制参数的近似关系,提高了机器鱼趋向期望深度的速度并减小了在期望深度巡游时的稳态误差．仿真与实验结果验证了所提控制方法的有效性．     

Fluid–structure interaction study on the performance of flexible articulated caudal fin

In this paper, the propulsive performance of a flexible articulated caudal fin is investigated by fluid–structure interaction. The caudal fin is composed of two links which are connected by a hinge. One link is driven by pitching motion while the other one moves passively. Five cases of link flexibility are investigated, namely, the rigid–rigid case, the medium flexible–medium flexible case, the flexible–flexible case, the rigid–flexible case and the flexible–rigid case. Their fluid field and structure deformations are analysed and hydrodynamic forces are compared. It is found that the rigid–rigid caudal fin produces larger thrust force than other cases with a low-pitching frequency, while the rigid–flexible case performs better with a higher frequency. The mean thrust force increases with the frequency in our experiments, however, for the medium flexible–medium flexible case, an optimal frequency exists. Besides, the effect of the hinge stiffness is studied. It is seen that the medium flexible–medium flexible case exhibits a striking performance. When the hinge stiffness decreases, its mean thrust force increases and possesses larger amplitude while the forces of other cases decrease. These results can guide the design of flexible propeller with links and will be useful for the development of flexible underwater robots.