Fish Prototype Research Articles

Design, simulation, and experimental investigation on a novel robot fish driven by piezoelectric bimorphs

The efficient swimming performance of fish is a miracle of nature, and the bionic robot fish powered by smart materials can replicate the movement pattern of fish to a greater extent. To achieve a simple, flexible, and controllable underwater robot, a novel robot fish driven by piezoelectric bimorphs is proposed in this study, which has similar swimming patterns to the body and/or caudal fin propulsion swimming mode and can achieve straight travel and steering underwater. The validity and feasibility of the principles were verified by wet mode simulation. A prototype is manufactured and tested for underwater vibration characteristics to confirm the motion pattern of the caudal fin of the robot fish. It weighs 13.3 g, a length of 150 mm. The maximum uniform speed of the robot fish prototype is 53 mm s−1, the thrust is 2.213 mN, and its maximum efficiency is 0.864%.

OLBIAN DOLPHIN PROTO-COINS: STURGEONS, SHARKS OR DOLPHINS?

Introduction. Olbian dolphin proto-coins is one of the most common and simultaneously unique serial metalworks of the early antiquity period. The question of biological prototypes, which, according to different researchers, could be either fish or dolphins, remains debatable. The absence of species affiliation analysis of the dolphin-like depictions does not allow to give a clear answer to this question. Objective. Determination of zoological prototypes of dolphin protocoins by comparative anatomical analysis. Results. Among the 36 anatomical feautures that can be identified on the coins, 25 are inherent in fish, in particular 21 are specific for sturgeons and 19 for sharks, and only 9 clearly belong to dolphins. The presence and distinctiveness of the traits creates a variety of types of proto-coins, and the combination of feautures from fish and dolphins causes the depictions to look whimsical. Archaic and primitive proto-currency herewith have a fish prototype. Diagnostic features of fish on the coins: big eyes on the sides of the head, operculum, lateral line, two dorsal fins, pressed to the body pectoral fin, truncated caudal fin. Some feautures (hypertrophied elongated snout, dorsal fin being closer to caudal fin, scutes on the body, heterocercal caudal fin) correspond to sturgeons, others (gill slits, location and shape of dorsal and pectoral fins, heterocercal caudal fin) to sharks. Bulging forehead should be considered as direct proof of a dolphin prototype for the coins, while other traits are either overlaped by fish feautures, or their interpretation is subjective. Conclusions. 1. The multiplicity of types and forms of dolphin-like coins, which combines traits of dolphins and different species of fish, indicates an absence of a single prototype. 2. The majority of the traits on anepigraphic coins is native to fish. The prototypes are sturgeons and possibly sharks. 3. By combinations of features it is possible to distinguish sturgeon- and shark-type proto-coins. 4. Some creations have bizarre depictions. 5. Heavyweight dolphins - whimsical representations with features of sharks as well as possibly other fish and dolphins. 6. Epigraphical dolphins with an «АРІХО» inscription bear signs of fish, whilst smaller ones with «ΘΥ» are rather bizarre depictions. 7. Predominance of fish traits on archaic and primitive items proves the primacy of the image of the fish.

Research and experiments on electromagnetic-driven multi-joint bionic fish

AbstractBased on the characteristics of high-frequency swing during fast swimming of fish, this paper designs a bionic fish-driven joint based on electromagnetic drive to achieve high-frequency swing. Aiming at the characteristic parameters of high-frequency swing control, the Fourier transform is used to separate the characteristic parameters and then compared the driving accuracy of the joints in open-loop and closed-loop. The comparison results show that the closed-loop control is performed after Fourier transform. Under the same driving conditions, the closed-loop control method can improve the joint driving accuracy. Then a bionic fish robot composed of three joints is designed according to this method and Kane method is used to model it dynamically and combined with the central pattern generator control method to complete model simulation and related experiments. The experimental results show that the bionic fish prototype can swim faster under high-frequency swing under electromagnetically driven joints.

Development of Subcarangiform Bionic Robotic Fish Propelled by Shape Memory Alloy Actuators

In this paper, a shape memory alloy (SMA) actuated subcarangiform robotic fish has been demonstrated using a spring based propulsion mechanism. The bionic robotic fish developed using SMA spring actuators and light weight 3D printed components can be employed for under water applications. The proposed SMA spring-based design without conventional motor and other rotary actuators was able to achieve two-way shape memory effect and has reproduced the subcarangiform locomotion pattern. The positional kinematic model has been developed and the dynamics of the proposed mechanism were analysed and simulated using Automated Dynamic Analysis of Mechanical Systems (ADAMS). An open loop Arduino-relay based switching control has been adopted to control the periodic actuation of the SMA spring mechanism. The undulation of caudal fin in air and water medium has been analysed. The caudal fin and posterior body of the developed fish prototype have taken part in undulation resembling subcarangiform locomotion pattern and steady swimming was achieved in water with a forward velocity of 24.5 mm/s. The proposed design is scalable, light weight and cost effective which may be suitable for underwater surveillance application.

Locomotion control of a biomimetic robotic fish based on closed loop sensory feedback CPG model

ABSTRACT This paper presents mechatronic design and hierarchical locomotion control of a biomimetic robotic fish for three-dimensional swimming modes. Inspired by biological features of Lamprey, a closed loop sensory feedback Central Pattern Generator (CPG) model is adapted to hierarchical control mechanism in order to provide robust and effective biomimetic control structure. A sensory feedback mechanism plays an important role to react external stimuli from environment. In addition, a closed loop fuzzy logic control structure is developed as a brain model to decide adaptive swimming modes according to sensory information. In order to provide three-dimensional motion abilities, the Centre of Gravity (CoG) control mechanism is designed and controlled by a back-forth proportional control structure. Experimental results are obtained to prove the CPG-based closed loop sensory feedback control structure with the developed robotic fish prototype.

Mechatronic Design and Manufacturing of the Intelligent Robotic Fish for Bio-Inspired Swimming Modes

This paper presents mechatronic design and manufacturing of a biomimetic Carangiform-type autonomous robotic fish prototype (i-RoF) with two-link propulsive tail mechanism. For the design procedure, a multi-link biomimetic approach, which uses the physical characteristics of a real carp fish as its size and structure, is adapted. Appropriate body rate is determined according to swimming modes and tail oscillations of the carp. The prototype is composed of three main parts: an anterior rigid body, two-link propulsive tail mechanism, and flexible caudal fin. Prototype parts are produced with 3D-printing technology. In order to mimic fish-like robust swimming gaits, a biomimetic locomotion control structure based on Central Pattern Generator (CPG) is proposed. The designed unidirectional chained CPG network is inspired by the neural spinal cord of Lamprey, and it generates stable rhythmic oscillatory patterns. Also, a Center of Gravity (CoG) control mechanism is designed and located in the anterior rigid body to ensure three-dimensional swimming ability. With the help of this design, the characteristics of the robotic fish are performed with forward, turning, up-down and autonomous swimming motions in the experimental pool. Maximum forward speed of the robotic fish can reach 0.8516 BLs-1 and excellent three-dimensional swimming performance is obtained.

A dual caudal-fin miniature robotic fish with an integrated oscillation and jet propulsive mechanism

This paper presents the development of a biomimetic robotic fish that uses an integrated oscillation and jet propulsive mechanism to enable good swimming performance for small robotic fish. The designed robotic fish is driven by two caudal fins that flap oppositely, which are equipped in parallel at the fish tail. The propulsive mechanism of dual caudal fins is characterized by using numerical analysis, in which the distance between the two caudal fins is a key factor to the integrated mechanism and plays an important role to swimming performance. This finding has been further verified by experiments performed on a miniature robotic fish prototype with 100 mm length and 30 mm diameter. Experimental results have demonstrated the influence of the distance between the two caudal fins to swimming performance. The designed miniature robotic fish can swim stably and efficiently while exhibiting good motion maneuverability such as turning and braking. The developed robotic fish, with advantages of excellent swimming performance and small size, can be potentially used for monitoring and exploration in the underwater environment.

Role of Pectoral Fin Flexibility in Robotic Fish Performance

Pectoral fins play a vital role in the maneuvering and locomotion of fish, and they have become an important actuation mechanism for robotic fish. In this paper, we explore the effect of flexibility of robotic fish pectoral fins on the robot locomotion performance and mechanical efficiency. A dynamic model for the robotic fish is presented, where the flexible fin is modeled as multiple rigid elements connected via torsional springs and dampers. Blade element theory is used to capture the hydrodynamic force on the fin. The model is validated with experimental results obtained on a robotic fish prototype, equipped with 3D-printed fins of different flexibility. The model is then used to analyze the impacts of fin flexibility and power/recovery stroke speed ratio on the robot swimming speed and mechanical efficiency. It is found that, in general, flexible fins demonstrate advantages over rigid fins in speed and efficiency at relatively low fin-beat frequencies, while rigid fins outperform flexible fins at higher frequencies. For a given fin flexibility, the optimal frequency for speed performance differs from the optimal frequency for mechanical efficiency. In addition, for any given fin, there is an optimal power/recovery stroke speed ratio, typically in the range of 2–3, that maximizes the speed performance. Overall, the presented model offers a promising tool for fin flexibility and gait design, to achieve speed and efficiency objectives for robotic fish actuated with pectoral fins.

Design and characterization of a miniature free-swimming robotic fish based on multi-material 3D printing

Research in animal behavior is increasingly benefiting from the field of robotics, whereby robots are being continuously integrated in a number of hypothesis-driven studies. A variety of robotic fish have been designed after the morphophysiology of live fish to study social behavior. Of the current design factors limiting the mimicry of live fish, size is a critical drawback, with available robotic fish generally exceeding the size of popular fish species for laboratory experiments. Here, we present the design and testing of a novel free-swimming miniature robotic fish for animal-robot studies. The robotic fish capitalizes on recent advances in multi-material three-dimensional printing that afford the integration of a range of material properties in a single print task. This capability has been leveraged in a novel design of a robotic fish, where waterproofing and kinematic functionalities are incorporated in the robotic fish. Particle image velocimetry is leveraged to systematically examine thrust production, and independent experiments are conducted in a water tunnel to evaluate drag. This information is utilized to aid the study of the forward locomotion of the robotic fish, through reduced-order modeling and experiments. Swimming efficiency and turning maneuverability is demonstrated through target experiments. This robotic fish prototype is envisaged as a tool for animal-robot interaction studies, overcoming size limitations of current design.

Autonomous Sampling of Water Columns Using Gliding Robotic Fish: Algorithms and Harmful-Algae-Sampling Experiments

Gliding robotic fish, which is a hybrid of underwater gliders and robotic fish, is energy efficient and highly maneuverable and holds strong promise for long-duration monitoring of underwater environments. In this paper, a novel scheme is proposed for autonomously sampling multiple water columns using gliding robotic fish. The scheme exploits energy-efficient spiral-down motion to sample each water column, followed by sagittal-plane glide-up toward the direction of the next water column. Once surfacing, the robot uses Global Positioning System guidance to reach the next column location through swimming. To enhance the path-tracking performance, a two-degree-of-freedom controller involving $H_\infty$ control is used in the spiral motion, and a sliding-mode controller is employed to regulate the yaw angle during glide-up. The sampling scheme has been implemented on a gliding robotic fish prototype, “Grace,” and verified first in pool experiments and then in field experiments involving the sampling of harmful algae concentration in the Wintergreen Lake, Michigan.

A Survey on Undulatory Motion Based Robotic Fish Design

A B S T R A C T Robotic fish design (Biomimetic) is an upcoming research area in which undulation motion has its own set of parameters to decide its efficiency. To analyse its swimming efficiency several existing robotic models using undulation motion have been thoroughly studied and few critical parameters such as fin size, shape, flexibility of material, fin flapping rate etc., have been identified. After simulating the above critical parameters using a MATLAB based CFD tool, mainly to design prototypes for research purpose which concentrates on optimizing its swimming efficiency. Several combinations of critical parameters are discussed for robotic fish prototype design by identifying critical parameters and maximizing the swimming efficiency of robotic fish based on the above properties. The fin models have been tested using Matlab based CFD tool through simulation and the swimming speed, direction have also been tested for various models. An improved benchmark for designing robotic fish model is proposed in order to simplify selection of components, architecture, and cost involve.

Bio-inspired flexible joints with passive feathering for robotic fish pectoral fins

In this paper a novel flexible joint is proposed for robotic fish pectoral fins, which enables a swimming behavior emulating the fin motions of many aquatic animals. In particular, the pectoral fin operates primarily in the rowing mode, while undergoing passive feathering during the recovery stroke to reduce hydrodynamic drag on the fin. The latter enables effective locomotion even with symmetric base actuation during power and recovery strokes. A dynamic model is developed to facilitate the understanding and design of the joint, where blade element theory is used to calculate the hydrodynamic forces on the pectoral fins, and the joint is modeled as a paired torsion spring and damper. Experimental results on a robotic fish prototype are presented to illustrate the effectiveness of the joint mechanism, validate the proposed model, and indicate the utility of the proposed model for the optimal design of joint depth and stiffness in achieving the trade-off between swimming speed and mechanical efficiency.

Dynamic simulation model of a biomimetic robotic fish with multi-joint propulsion mechanism

In this paper, a biomimetic carangiform robotic fish is analysed based on dynamic and kinematic models. The carangiform fish can swim with features like high mobility, fast swimming and changing direction suddenly. Because it has these amazing features, a carangiform swimmer is modelled. Dynamic and kinematic models are analytically obtained to design a biomimetic carangiform robotic fish. The designed robotic fish consists of two parts: an anterior rigid body and a flexible tail, which is modelled as a four-joint propulsion mechanism, and each joint is driven by a servo motor. The dynamic model is developed in the MATLAB/Simulink environment using a Lagrange function and the state-space model is performed to linearize the obtained model. Each joint is controlled with conventional PID controller in the simulation. Furthermore, a solid model of the robotic fish prototype is drawn in SolidWorks and transferred to the MATLAB/Simmechanics environment, and the motion of the robotic fish is simulated using joint angles. Finally, experimental studies and simulation results show that a carangiform motion for autonomous swimming is developed and verified using controlled joint angles.

Effect of freezing and frozen storage on restructured FISH prototypes made with glucomannan and FISH mince

This paper examines the physicochemical and rheological properties to determine the freezing and frozen stability of restructured fish prototypes made with glucomannan (GM) and fish mince lacking any protein functionality. The effect of adding salt and fish oil to the fish prototype formulae is also examined. Three prototype fish gels at 1.25% final GM concentration were made: control lot (C); oil lot (O): control gels with 5% added fish oil, and salt lot (S): control gels were made with 0.8% NaCl. The analyses were performed after 24 h refrigerated storage (5 °C) and 30, 90 and 150 days frozen storage at −20 °C.Freezing produced hardening of gels due to partial dehydration caused by ice crystal formation, particularly in Lot S where the gels were more rigid with less water binding capacity (WBC) and more cooking loss (CL) after 30 days storage. Conversely, lot C exhibited some synergy between GM and protein molecules, giving time-stable networks with higher WBC after freezing. Lot O showed less CL and a more regular trend in mechanical and viscoelastic parameters between 90 and 150 days frozen storage, demonstrating the stabilizing effect of the “oil–protein–water” complex in a GM matrix.

A dynamic model for tail-actuated robotic fish with drag coefficient adaptation

In this paper we present a dynamic model for a tail-actuated robotic fish by merging rigid-body dynamics with Lighthill’s large-amplitude elongated-body theory. The model is validated with extensive experiments conducted on a robotic fish prototype. We investigate the role of incorporating the body motion in evaluating the tail-generated hydrodynamic force, and show that ignoring the body motion (as often done in the literature) results in significant overestimate of the thrust force and robot speed. By exploiting the strong correlation between the angle of attack and the tail-beat bias, a computationally efficient approach is further proposed to adapt the drag coefficients of the robotic fish, and its effectiveness is supported by experimental results.

Bio-inspired aquatic robotics by untethered piezohydroelastic actuation

This paper investigates fish-like aquatic robotics using flexible bimorphs made of macro-fiber composite (MFC) piezoelectric laminates for carangiform locomotion. In addition to noiseless and efficient actuation over a range of frequencies, geometric scalability, and simple design, bimorph propulsors made of MFCs offer a balance between the actuation force and velocity response for performance enhancement in bio-inspired swimming. The experimental component of the presented work focuses on the characterization of an elastically constrained MFC bimorph propulsor for thrust generation in quiescent water as well as the development of a robotic fish prototype combining a microcontroller and a printed-circuit-board amplifier to generate high actuation voltage for untethered locomotion. From the theoretical standpoint, a distributed-parameter electroelastic model including the hydrodynamic effects and actuator dynamics is coupled with the elongated-body theory for predicting the mean thrust in quiescent water. In-air and underwater experiments are performed to verify the incorporation of hydrodynamic effects in the linear actuation regime. For electroelastically nonlinear actuation levels, experimentally obtained underwater vibration response is coupled with the elongated-body theory to predict the thrust output. The measured mean thrust levels in quiescent water (on the order of ∼10 mN) compare favorably with thrust levels of biological fish. An untethered robotic fish prototype that employs a single bimorph fin (caudal fin) for straight swimming and turning motions is developed and tested in free locomotion. A swimming speed of 0.3 body-length/second (7.5 cm s−1 swimming speed for 24.3 cm body length) is achieved at 5 Hz for a non-optimized main body-propulsor bimorph combination under a moderate actuation voltage level.

Effect of spanwise flexibility on propulsion performance of a flapping hydrofoil at low Reynolds number

Spanwise flexibility is a key factor influencing propulsion performance of pectoral foils. Performances of bionic fish with oscillating pectoral foils can be enhanced by properly selecting the spanwise flexibility. The influence law of spanwise flexibility on thrust generation and propulsion efficiency of a rectangular hydro-foil is discussed. Series foils constructed by the two-component silicon rubber are developed. NACA0015 shape of chordwise cross-section is employed. The foils are strengthened by fin rays of different rigidity to realize variant spanwise rigidity and almost the same chordwise flexibility. Experiments on a towing platform developed are carried out at low Reynolds numbers of 10 000, 15 000, and 20 000 and Strouhal numbers from 0.1 to 1. The following experimental results are achieved: (1) The average forward thrust increases with the St number increased; (2) Certain degree of spanwise flexibility is beneficial to the forward thrust generation, but the thrust gap is not large for the fins of different spanwise rigidity; (3) The fin of the maximal spanwise flexibility owns the highest propulsion efficiency; (4) Effect of the Reynolds number on the propulsion efficiency is significant. The experimental results can be utilized as a reference in deciding the spanwise flexibility of bionic pectoral fins in designing of robotic fish prototype propelled by flapping-wing.

Vision-Based Target Tracking and Collision Avoidance for Two Autonomous Robotic Fish

A new type of vision-based autonomous robotic fish capable of 3-D locomotion is developed in this paper. Based on our robotic fish prototype, the forces and moments acting on its fins and body are analyzed, and the governing motion equations are derived. We further investigate a decentralized control method in target-tracking and collision-avoidance task for two autonomous robotic fish. Most of previous work on the task strategies of autonomous robots is focused on terrestrial robots and seldom deals with underwater applications due to the uncertainties and complexity in a hydro environment. To address this challenge in such an underwater task, a situated-behavior-based decentralized control is employed on each robotic fish according to its visual data. On dealing with motion planning of the fish during target tracking and collision avoidance, a control law by a combination of an attractive force toward a target and a repulsive force for collision avoidance is utilized. Experimental results of the task performed by two autonomous robotic fish validate the effectiveness of the proposed method.

Gait Planning for Steady Swimming Control of Biomimetic Fish Robots

This paper is dedicated to the implementation of biological fish swimming motion onto biomimetic fish robots. By learning from different species of fish, the mechanism design and the motor control of swimming machines could be shaped in different forms. In general, they can be grouped into two major forms, from an engineering viewpoint: serial open-chain design and parallel mechanism design. The gait planning on both forms is then performed based on the well-established theory of fish swimming. By using the associated kinematics equations, the generic solution of the gait planning for multi-link fish robots in the two respective forms of mechanisms is derived. The solution is taken as the gait control input for the swimming testing of a six-link body and/or caudal fin fish prototype and an eight-link media and/or paired fin fish prototype. The experiments show that smooth steady swimming and forward/backward swimming are achievable by making use of the gait planning and control.

Coordinated Transport by Multiple Biomimetic Robotic Fish in Underwater Environment

This paper presents a coordination method for multiple biomimetic robotic fish in underwater transport task. Based on our robotic fish prototype, we further investigate the coordination problems of multiple robotic fish. Considering the kinematic constraints of the robotic fish, and the unstructured and dynamic characteristics of the water environment, we utilize the limit cycle approach to control the posture of the fish and realize collision avoidance. To control the transport orientation in the particular underwater environment, the fuzzy logic method is adopted. Experimental results of transportation performed by three robotic fish validate the effectiveness of the proposed method.