Biorobotic AUV maneuvering by pectoral fins: inverse control design based on CFD parameterization

Biologically inspired maneuvering of autonomous undersea vehicles (AUVs) in the dive plane using pectoral-like oscillating fins is considered. Computational fluid dynamics are used to parameterize the forces generated by a mechanical flapping foil, which attempts to mimic the pectoral fin of a fish. Since the oscillating fins produce periodic force and moment of a variety of wave shapes, the essential characteristics of these signals are captured in their Fourier expansions. Maneuvering of the biorobotic AUV in the dive plane is accomplished by periodically altering the bias angle of the oscillating fin. Based on a discrete-time AUV model, an inverse control system for the dive-plane control is derived. It is shown that, in the closed-loop system, the inverse control system accomplishes accurate tracking of the prescribed time-varying depth trajectories and the segments of the intersample depth trajectory remain close to the discrete-time reference trajectory. The results show that the fins located away from the center of mass toward the nose of the vehicle provide better maneuverability.     

仿生胸鳍的三维尾涡结构与参数影响分析

为研究仿胸鳍推进的机理和流体动力特性及缩小机器鱼与生物原型之间的性能差距,利用浸入边界法数值模拟了做耦合旋转运动胸鳍的非定常绕流问题。详细探讨胸鳍非定常运动的三维尾涡结构演化和推进机理,并开展胸鳍推进性能与尾涡结构的参数影响分析。结果表明:迎流面在背、腹侧边缘及鳍梢部显著涡旋结构的作用下所出现的低压力区,加之鳍表面和上游来流之间好的垂直度共同造成了在动力划水阶段的高推力;在恢复划水阶段的高升力与背侧边缘涡强度的持续增加,以及因鳍表面倾斜而引起的水动力被分解到竖直方向的比重提升有关;胸鳍尾流场被一个三维双环涡结构所支配;当前的模拟为仿胸鳍推进建立了一个最优的斯特劳哈尔数St范围(在0.55附近),在此之后平均推力仍随St的增大而增加,而推进效率则表现出一个缓慢降低的趋势;当前后拍动与纵倾运动之间的相位差为90度时,胸鳍同时取得最佳的推力和效率。     

波浪滑翔机推进装置翼片的启动阶段水动力学分析

波浪滑翔机直接利用波浪能实现大范围长距离的机动运动观测,在海洋环境观测中可以发挥重要的作用。本文对波浪滑翔机推进装置在启动阶段的翼片的水动力学行为进行了研究。以波浪滑翔机水下推进装置的翼片为研究对象,运用雷诺平均Navier-Stokes方程(RANS),对给定垂荡和摆动运动的翼片水动力学进行了水动力分析和仿真,模拟了单个翼片、纵向阵列多翼片的运动状况,得到推进装置翼片附近的压力分布和整体推进动力,分析翼片间距变化在启动阶段对推进力的影响作用。通过该研究工作为深入理解波浪滑翔机推进装置工作状态提供了理论依据。     

Structure, function, and neural control of pectoral fins in fishes

Fin-based propulsion systems perform well for both high-speed cruising and high maneuverability in fishes, making them good models for propulsors of autonomous underwater vehicles. Labriform locomotion in fishes is actuated by oscillation of the paired pectoral fins. Here, we present recent research on fin structure, fin motion, and neural control in fishes to outline important future directions for this field and to assist engineers in attempting biomimicry of maneuverable fin-based locomotion in shallow surge zones. Three areas of structure and function are discussed in this review: 1) the anatomical structure of the fin blade, skeleton, and muscles that drive fin motion; 2) the rowing and flapping motions that fins undergo for propulsion in fishes; and 3) the neuroanatomy, neural circuitry, and electrical muscle activity that are characteristic of pectoral fins. Research on fin biomechanics, muscle physiology and neural control is important to the comparative biology of locomotion in fishes and application of fin function for aid in aquatic vehicle design. Recommendations are made regarding fin propulsor designs based on the fin shape, activation pattern, and motion. Research on neural control of fins is a key piece in the puzzle for a complete understanding of comparative fin function and may provide important principles for engineers designing control systems for fin-like propulsors.     

卵形鲳鲹胚后发育阶段的体色变化和鳍的分化

采集在池塘进行育苗的31天前的卵形鲳鲹Trachinotus ovatus仔稚幼鱼,对其早期发育阶段的体色变化和鳍的发生、发育进行了连续观察。在水温24.73±2.11℃、盐度20‰—24‰、pH8.0—8.2条件下,初孵仔鱼体表已具有黑色素,第2天眼点的褐色素增加,此时仔鱼未开口、眼点未有视物功能;第3天开口时,眼大而突出、布满黑色素,变为黑色的眼睛,具有视觉功能;第17天当仔鱼变态为稚鱼时,鱼体变得不透明;在第22天变态为幼鱼时,鱼体体表为褐色;30天的幼鱼体表为银白色,与成鱼的体色一致。各鳍开始分化和发育的顺序依次为胸鳍→尾鳍→背鳍→臀鳍→腹鳍。1天仔鱼胸鳍原基出现;2—3天仔鱼开始摄食,胸鳍为扇形;第17天各鳍发育基本完成,标志着稚鱼期的开始。体色的变化和鳍的形成和发育对仔稚鱼的摄食、行为、生长、变态和存活等生命活动有着至关重要的作用,也是仔稚鱼变态发育的重要特征之一,与人工育苗生产技术尤其是投饵、分池等密切相关。     

出现于南沙海域的黄带棘箱鲀的形态特征

2011年4月17日在南沙海域调查时,采集到2尾棘箱鲀属(Kentrocapros)标本,经鉴定为黄带棘箱鲀(Kentrocapros flavofasciantus),标本现保存在南海水产研究所标本馆.标本体长分别为108、135 mm.无鳍棘和腹鳍,背鳍和臀鳍各1个.背鳍鳍条数目为11,胸鳍鳍条数目为12,臀鳍鳍条数目为10,尾鳍鳍条数目为11.体长为体高的2.41～2.57倍,体宽的3.07～3.09倍,头长的3.38～3.48倍,吻长的4.35～4.70倍.头长为眼径的2.22～2.38倍,眼间隔的1.35～1.54倍,鳃孔长度的3.10～3.33倍.除尾柄、胸鳍基部、背鳍基部、臀鳍基部、肛门附近之外,体披硬体甲,体甲刚好在背鳍前方闭合,体甲为6棱形,无刺平滑,从肛门连续沿纵线到胸鳍基部下前方形成裸褶.体侧无侧线.上下颌每侧具8个小柱状切牙.胸鳍最上第一鳍条很短,长度约为第二鳍条的1/6.体为褐黄色,体甲有两条较宽的纵向黄带.唇为褐棕色,牙为红褐色.所有鳍条为黄色或略显褐黄色.     

Optimal measurement strategies for target tracking by a biomimetic underwater vehicle

This study presents a novel navigation and control system allowing a biomimetic-autonomous underwater vehicle (BAUV) to track a target. A Bayesian approach using an extended Kalman filter and combined localization and environmental mapping by a BAUV are implemented. This strategy selects the best sensor measurement by choosing one of several forward-looking directions. The body of the BAUV moves in a cyclical pattern; thus, an inexpensive echo sounder can be installed on the BAUV head to detect environmental features without the need for expensive scanning devices. The localization and environmental mapping problem is then transformed into a non-linear two-point boundary value problem. Optimal policies are to maintain the accuracy of predicted states and to approach minimal observation cost by solving the control problem. A line-of-sight guidance law is utilized that drives the BAUV to the target. An approach that controls the motion of the body/caudal fin and pectoral fins of the BAUV is utilized for target tracking. Estimation, measurement, and control processes are integrated to form a working system. Experiments using a test bed BAUV confirm the effectiveness of the proposed approach.     

北部湾出现苏门答腊金线鱼及其形态特征

2008年1月在北部湾调查时,采集到1金线鱼科标本,经鉴定为苏门答腊金线鱼．渔获总尾数156尾,带回5尾到实验室作进一步鉴定,标本现保存在南海水产研究所标本馆．体长范围为50mm-126mm,背鳍X-9;臀鳍Ⅲ-7;胸鳍15;腹鳍I-5;尾鳍21．体适度延长,侧扁,体长为体高的3．5～3．8倍,体高在躯干中部背鳍第七鳍棘处为最高．上下颌几等长,仅上颌前端具较大犬牙．眼眶下缘处于吻端与胸鳍基部上端连线的上方,眼眶下缘顶端微凹,后缘几呈直线．前鳃盖骨裸露（无鳞）宽度是有鳞宽度的1．4～1．7倍．体被薄栉鳞,背鳍与侧线间具鳞4～7行,有腋鳞．侧线完全,位高,近似与背缘平行．眼下至上颌骨呈倾钭的金黄色带,体上部略带桃色,下部银白色,体侧有明显的金黄色带,并延至尾鳍叉端附近鳍条．体侧有一红斑,红斑位于背鳍起点与胸鳍基部之间的侧线下缘．背鳍边缘黄色,中间有明显的黄色带,臀鳍粉红色并有2条黄色带,尾鳍粉红色,近叉端鳍条呈金黄色．背鳍第一鳍棘与第二鳍棘由隔膜分开,第一鳍棘和第二鳍棘其长度短于其他鳍棘,无丝状延长．背鳍鳍棘部与鳍条部连接完全,中间无缺刻．胸鳍伸达肛门上方,胸鳍长度为头长的1．1～1．5倍．腹鳍中等长,约与胸鳍等长,不伸达臂鳍起点．臂鳍最后鳍条不明显长于其他鳍条．尾鳍呈叉形,上叶末端呈锐角或钝圆,上叶末端略呈丝状延长或延长不明显．     

Experimental Study of a Command Governor Adaptive Depth Controller for an Unmanned Underwater Vehicle

Unmanned Underwater Vehicles (UUVs) are increasingly being used in advanced applications that require them to operate in tandem with human divers and around underwater infrastructure and other vehicles. These applications require precise control of the UUVs which is challenging due to the non-linear and time varying nature of the hydrodynamic forces, presence of external disturbances, uncertainties and unexpected changes that can occur within the UUV’s operating environment. Adaptive control has been identified as a promising solution to achieve desired control within such dynamic environments. Nevertheless, adaptive control in its basic form, such as Model Reference Adaptive Control (MRAC) has a trade-off between the adaptation rate and transient performance. Even though, higher adaptation rates produce better performance they can lead to instabilities and actuator fatigue due to high frequency oscillations in the control signal. Command Governor Adaptive Control (CGAC) is a possible solution to achieve better transient performance at low adaptation rates. In this study CGAC has been experimentally validated for depth control of a UUV, which is a unique challenge due to the unavailability of full state measurement and a greater thrust requirement. These in turn leads to additional noise from state estimation, time-delays from input noise filters, higher energy expenditure and susceptibility to saturation. Experimental results show that CGAC is more robust against noise and time-delays and has lower energy expenditure and thruster saturation. In addition, CGAC offers better tracking, disturbance rejection and tolerance to partial thruster failure compared to the MRAC.     

Description of the larval development of Galaxies maculatus in landlocked lentic and lotic systems in Western Australia

The larvae and larval development of Galaxias maculatus are described from a freshwater lake and a saline river in southwestern Western Australia. The size at hatching (7.0 mm total length) was similar to that recorded elsewhere for G. maculatus and the sequence of fin development (i.e., caudal, dorsal, anal, pectoral, and pelvic fins) was identical to that recorded for galaxiids generally. There were relative increases in the proportions of head length and body depth with larval growth and a decrease in proportion of pre‐anal length. Larvae from river habitats were smaller throughout larval stages of development than those from the lake. Fins of riverine fish began and completed development at a smaller size of fish than the lacustrine population, presumably as a response to the need for great motility at a smaller fish size in lotic environments.     

Studies on an algorithm to control the roll motion using active fins

The very purpose of attaching fins to the hull is to reduce the roll motions of a ship. Roll minimization is a requisite for various operations in the seas. The presence of fin system provides enhanced state of stabilization especially when the vessel is performing a fast maneuvering amidst rough environmental disturbance. The fins in turn are activated by electro-hydraulic mechanism based on the in-built intelligence as per control theory like proportional–integral–derivative (PID) or fuzzy logic. As per this paper, fin system is activated using PID control algorithm. A frigate-type warship is considered for the demonstration purpose. Nonlinear roll motions are controlled using active fins. Lift characteristics of the fins in hydrodynamic flow were studied using CFD package fluent.Good amount of reduction in roll amplitude is achieved from various simulations in random sea. The approach can be used for any irregular sea conditions.     

The optimum control of thruster system for dynamically positioned vessels

An offshore vessel with a dynamic positioning system (DP system) needs fast response to produce thrust to counteract the environmental forces acting on it for the purpose of maintaining its position and heading as close as possible to the working position. Therefore, quick and effective modulation of the thrust is the problem to determine the thrust and the rotation angle of the thruster devices of the ship. This paper presents an effective optimum control for a thruster system, using the sequential quadratic method to achieve economical and effective modulation of the thrust and the direction of the thruster. An optimum control study of a 2280 tons DP coring vessel with five rotary azimuth thruster marine positioning is studied in detail, which can quickly and exactly estimate the thrusts and angles of direction of all the thrusters. The results can provide a valuable thruster system for a dynamically positioned vessel.     

Effect of free surface and strut on fins attached to a strut

An extensive experimental and computational investigation of the combined and separate effects of free surface and body on the lift characteristics of a pair of fins attached to a strut and fin alone is conducted. The results reveal that the free-surface effect becomes significant when the depth of submergence to chord ratio (H/c) is less than three. The effect of the strut is also realized for shallower depth of submergence of the fins through free-surface deformation leading to a significant change in the incidence angle of the flow to the fins. The numerical results based on the Higher Order Boundary Element Method with the linearized free-surface condition show good agreement with the experimental results for fin (foil) alone even at shallow submergence, but some discrepancies appear for the fin attached to the strut at higher speeds mostly due to the neglect of the nonlinear free-surface effect.     

Adaptive input–output feedback linearizing yaw plane control of BAUV using dorsal fins

This paper presents the design of an adaptive input–output feedback linearizing dorsal fin control system for the yaw plane control of low-speed bio-robotic autonomous underwater vehicles (BAUVs). The control forces are generated by cambering two dorsal fins mounted in the vertical plane on either side of the vehicle. The BAUV model includes nonlinear hydrodynamics, and it is assumed that its hydrodynamic coefficients as well as the physical parameters are not known. For the purpose of design, a linear combination of the yaw angle tracking error and its derivative and integral is chosen as the controlled output variable. An adaptive input–output feedback linearizing control law is derived for the trajectory control of the yaw angle. Unlike indirect adaptive control, here the controller gains are directly tuned. The stability of the zero dynamics is examined. Simulation results are presented for tracking exponential and sinusoidal yaw angle trajectories and for turning maneuvers, and it is shown that the adaptive control system accomplishes precise yaw angle control of the BAUV using dorsal fins in spite of the nonlinearity and large uncertainties in the system parameters.     

中国大陆沿海鲆科新记录属——线鳍鲆属(Taeniopsetta)和新纪录种——眼斑线鳍鲆(Taeniopsetta ocellata)*

2016年10月采自北部湾海域的1尾鱼类标本经鉴定为线鳍鲆属Taeniopsetta Gilbert, 1905的眼斑线鳍鲆Taeniopsetta ocellata(Günther, 1880), 隶属于鲽形目Pleuronectiformes鲆科Bothidae, 这是该属和种首次在中国大陆海域的报道。线鳍鲆属的主要形态特征包括: 体长卵圆形; 双眼位于头左侧; 口小; 有眼侧和无眼侧均有1行小尖牙; 鳞细小, 仅体左侧有1条侧线; 雄鱼有1枚强吻棘和2或3枚眼棘, 雌鱼吻棘和眼棘很钝或无; 无眼侧腹鳍始于有眼侧第2根腹鳍鳍条基部右侧; 腹鳍基较短; 背鳍和臀鳍的部分鳍条延长成丝状。眼斑线鳍鲆的主要形态特征为: 两侧胸鳍不等长; 雄鱼背鳍的第13~17根鳍条及臀鳍的第1~6根鳍条延长成丝状; 体左侧背腹缘分别有2~4个不规则的“V”形或半圆形中空黑色斑块, 斑块内部具一黄色圆斑。     

Open-Loop Control of a Multifin Biorobotic Rigid Underwater Vehicle

This paper presents an open-loop control system for a new experimental vehicle, named the biorobotic autonomous underwater vehicle (BAUV). The rigid cylindrical hull of the vehicle is attached with six strategically located fins to produce forces and moments in all orthogonal directions and axes with minimal redundancy. The fins are penguin-wing inspired and they implement the unsteady high-lift principle found widely in swimming and flying animals. The goal has been to design an underwater vehicle that is highly maneuverable by taking the inspiration from nature where unsteady hydrodynamic principles of lift generation and the phase synchronization of fins are common. We use cycle-averaged experimental data to analyze the hydrodynamic forces and moments produced by a single foil as a function of its kinematic motion parameters. Given this analysis, we describe a method for synthesizing and coordinating the sinusoidal motion of all six foils to produce any desired resultant mean force and moment vectors on the vehicle. The mathematics behind the resulting algorithm is elegant and effective, yielding compact and efficient implementation code. The solution method also considers and accommodates the inherent physical constraints of the foil actuators. We present laboratory experimental results that demonstrate the solution method and the vehicle's resulting high maneuverability.      

黄海鲱鱼的人工孵化及胚胎发育的初步观察

对鲱科鱼类个体发育及早期形态特征的研究,国外早已进行过,尤以苏联和日本的资料最多。     

Morphological and molecular evidence supports the first occurrence of two fishes,Siganus sutor(Valenciennes, 1835)and Seriolina nigrofasciata(Rüppell, 1829)(Actinopterygii:Perciformes), from marine waters of Odisha coast,Bay of Bengal,India

Marine ecosystems provide a wide variety of diverse habitats that frequently promote migration and ecological adaptation. The extent to which the geographic distribution of marine organism has reshaped by human activities remains underappreciated. The limitations intrinsic to morphology-based identification systems have engendered an urgent need for reliable genetic methods that enable the unequivocal recognition of fish species,particularly those that are prone to overexploitation and/or market substitution. In the present study, however, an attempt has been taken to identify two locally adapted fish species, Siganus sutor(Valenciennes, 1835) and Seriolina nigrofasciata(Rüppell, 1829) of order Perciformes, which happens to be the first record in Odisha coast,Bay of Bengal. The diagnostic characteristics of Siganus sutor are: dorsal fin XIII-10, anal fin VII-9, pectoral fin 15,pelvic fin II-3, while that of Seriolina nigrofasciata dorsal fin VI-I-35, anal fin I-17, pectoral fin 16, pelvic fin 5. All COI barcodes generated in this study were matched with reference sequences of expected species, according to morphological identification. Bayesian and likelihood phylogenetic trees were drawn based on DNA barcodes and all the specimens clustered in agreement with their taxonomic classification at the species level. The phylogeographic studies based on haplotype network and migration rates suggest that both the species were not panmitic and the high-frequency population distribution indicates successful migration. The result of this study provides an important validation of the use of DNA barcode sequences for monitoring species diversity and changes within a complex marine ecosystem.     

多水下机器人系统水动力计算的多线程实现

介绍多水下机器人(UUV)数字仿真平台的硬件结构以及单体UUV和多UUV系统的水动力计算流程,在此基础上利用Windows多线程技术实现多UUV的水动力计算,该方法已经用于多UUV数字仿真平台虚拟环境节点的设计中.系统仿真实验表明该方法设计的应用程序具有良好的执行效率和实时响应能力,为以后多UUV半物理仿真平台的水动力计算和实体多UUV系统水动力系数的验证奠定了基础.