No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Design and Performance Testing of a Micro Flexible Caudal Fin-Like Propulsor
Abstract
Inspired by caudal fin used for propulsion in most bony fishes, a micro flexible caudal fin-like propulsor actuated by shape memory alloy (SMA) wires is designed and presented. Bending experiment of the caudal fin-like propulsor is done to verify the concept. Then the propulsive performance of the caudal fin-like propulsor is evaluated through thrust force measurement experiments. Meanwhile, the variation of the thrust force with respect to the driven parameters of the caudal fin is studied. At last, a micro robot fish based on the propulsor is fabricated and the swimming capability was evaluated.
This study proposed an advanced micro-imprint lithography (MIL), which integrates electromagnetic field-aided hot imprinting and polydimethylsiloxane (PDMS) gray-scale curved surface magnetic flexible soft mold imprinting techniques, to imprint and replicate the microstructure. The
study results reveal that PDMS compounded with magnetic iron powder and electromagnetic disk-controlled even pressure by magnetic force can accurately duplicate microstructure on the large-area, curved surface, glass based material and effectively achieve the full and complete duplication
of a resist microstructure. Meanwhile, the PDMS flexible mold can be employed to achieve the conformal contact with the base material surface, the effective imprinting area and the duplicated representation are dramatically improved. In addition, as magnetic PDMS gray-scale curved surface
soft mold is easily produced and fast in recasting, the costs can be effectively reduced, and the gray-scale curved surface soft mold is evenly controlled by electro-magnetic disk for imprinting duplication.
Lithography is achieved by far-field diffraction. With this technology, we can obtain the feature pattern in the wavelength of sub-micron. Meanwhile, it has all the advantages of mask-less technology: no expensive cost of traditional mask, shortened process time, fast generation of
mask pattern, easy mask design modification, and capability of small quantity or experimental production. In this study, a wafer mold is made by semiconductor processing. Then, we try to produce a transparent phase shift mask by innovative gas-assisted nano-imprint technology. Finally, a study
and simulation analysis is carried out on the process of near-field contacted phase shift lithography. MATLAB is adopted in the calculation and simulation. After comparing the experimental results with the simulations, we find that the length of explosion has a direct influence on diffraction.
The distribution of the diffraction energy may impact the entire explosion region and result in the energy differences accumulated in the region. It's proved that diffraction component utilizing far-field diffraction simulation has a similar effect of phase shift lithography with near-field
simulation.
The hydrodynamic forces due to the motion of a flexible foil in a large amplitude curved path in an inviscid incompressible flow are analysed. A parametric study of large amplitude oscillatory propulsion, with special emphasis on the effect of chordwise flexibility of the fin, is presented. This flexibility was found to increase the propulsive efficiency by up to 2% while causing small decreases in the overall thrust, compared with similar motion with rigid foils.
Several physico-mechanical designs evolved in fish are currently
inspiring robotic devices for propulsion and maneuvering purposes in
underwater vehicles. Considering the potential benefits involved, this
paper presents an overview of the swimming mechanisms employed by fish.
The motivation is to provide a relevant and useful introduction to the
existing literature for engineers with an interest in the emerging area
of aquatic biomechanisms. The fish swimming types are presented,
following the well-established classification scheme and nomenclature
originally proposed by Breder. Fish swim either by body and/or caudal
fin (BCF) movements or using median and/or paired fin (MPF) propulsion.
The latter is generally employed at slow speeds, offering greater
maneuverability and better propulsive efficiency, while BCF movements
can achieve greater thrust and accelerations. For both BCF and MPF
locomotion, specific swimming modes are identified, based on the
propulsor and the type of movements (oscillatory or undulatory) employed
for thrust generation. Along with general descriptions and kinematic
data, the analytical approaches developed to study each swimming mode
are also introduced. Particular reference is made to lunate tail
propulsion, undulating fins, and labriform (oscillatory pectoral fin)
swimming mechanisms, identified as having the greatest potential for
exploitation in artificial systems
A two-dimensional time-domain constant potential panel method was used for analysis of chordwise flexible oscillating hydrofoils as oscillating propulsors. The oscillatory motions as well as the chordwise deflections were of large amplitude. Results are presented of propulsive thrust coefficient and efficiency over ranges of motion parameters including varied reduced frequency; pitch amplitude and feathering parameter; heave amplitude/chord ratio; pitching axis position; phase between pitching and heaving motions; and deflected shape. The ranges were taken about a favourable operating point for a flexible oscillating NACA 0012 foil. A peak in propulsive efficiency was found for each motion parameter variation studied. Propulsive efficiency varied strongly with changes in heave amplitude/chord ratio, pitch amplitude and phase between heaving and pitching motions, but less strongly for variations in pitching axis position and flexibility.
This paper attempts to emulate the great study by Goldstein (1929) ‘On the vortex wake of a screw propeller’, by looking for a dynamical theory of how another type of propulsion system has evolved towards ever higher performance. An ‘undulatory’ mode of animal propulsion in water is rather common among invertebrates, and this paper offers a preliminary quantitative analysis of how a series of modifications of that basic undulatory mode, found in the vertebrates (and especially in the fishes), tends to improve speed and hydromechanical efficiency.
The fins of fishes are remarkable propulsive devices that appear at the origin of fishes about 500 million years ago and have
been a key feature of fish evolutionary diversification. Most fish species possess both median (midline) dorsal, anal, and
caudal fins as well as paired pectoral and pelvic fins. Fish fins are supported by jointed skeletal elements, fin rays, that
in turn support a thin collagenous membrane. Muscles at the base of the fin attach to and actuate each fin ray, and fish fins
thus generate their own hydrodynamic wake during locomotion, in addition to fluid motion induced by undulation of the body.
In bony fishes, the jointed fin rays can be actively deformed and the fin surface can thus actively resist hydrodynamic loading.
Fish fins are highly flexible, exhibit considerable deformation during locomotion, and can interact hydrodynamically during
both propulsion and maneuvering. For example, the dorsal and anal fins shed a vortex wake that greatly modifies the flow environment
experienced by the tail fin. New experimental kinematic and hydrodynamic data are presented for pectoral fin function in bluegill
sunfish. The highly flexible sunfish pectoral fin moves in a complex manner with two leading edges, a spanwise wave of bending,
and substantial changes in area through the fin beat cycle. Data from scanning particle image velocimetry (PIV) and time-resolved
stereo PIV show that the pectoral fin generates thrust throughout the fin beat cycle, and that there is no time of net drag.
Continuous thrust production is due to fin flexibility which enables some part of the fin to generate thrust at all times
and to smooth out oscillations that might arise at the transition from outstroke to instroke during the movement cycle. Computational
fluid dynamic analyses of sunfish pectoral fin function corroborate this conclusion. Future research on fish fin function
will benefit considerably from close integration with studies of robotic model fins.
This paper describes the unmanned underwater remotely operated vehicle (UROV) THETIS, an easy to operate vehicle suitable for exploiting water environments. The subsystems composing our system, as compared to conventional ROVs, are discussed and evaluated. The vehicle's primary use, at the present stage of development, is to perform underwater observations as well as temperature, pH/dissolved O2 and suspended sediment measurements for underwater pollution studies. Using simple components, the ROV's high reliability and efficient performance offer a versatile and cost-effective work system.
This paper addresses the design of a biomimetic fish robot actuated by piezoceramic actuators and the effect of artificial caudal fins on the fish robot's performance. The limited bending displacement produced by a lightweight piezocomposite actuator was amplified and transformed into a large tail beat motion by means of a linkage system. Caudal fins that mimic the shape of a mackerel fin were fabricated for the purpose of examining the effect of caudal fin characteristics on thrust production at an operating frequency range. The thickness distribution of a real mackerel's fin was measured and used to design artificial caudal fins. The thrust performance of the biomimetic fish robot propelled by fins of various thicknesses was examined in terms of the Strouhal number, the Froude number, the Reynolds number, and the power consumption. For the same fin area and aspect ratio, an artificial caudal fin with a distributed thickness shows the best forward speed and the least power consumption.
Biomimetic robots replicate their senses and structures from animals, such as insects, fishes and human. Development of underwater vehicles is one of the areas where biomimetic robots can potentially perform better than conventional robots in some application. In this paper, an Asian Arowana robot with a caudal fin mechanism has been developed. The performance of the fin design is evaluated through a series of experiments. The experiments conducted in the laboratory setting aim to study the variation of robotic fish's velocity with respect to fin's angular displacements and velocities. The testing also enables us to understand the effects of fin size and fin materials. Field trials were conducted in an outdoor pool to evaluate the swimming capability of the carangiform robot fish.
This study investigates the potential for incorporating the elastic mechanisms found in fish propulsive systems into mechanical systems for the development of underwater propulsion. Physical and kinematic information associated with the steady swimming of the bonito and other scombrid species was used for the design. Several electroactive materials were examined for simulating muscle behavior and their relative suitability was compared. A dynamic analysis method adapted for muscle, which is a work-loop technique, would provide valuable information. However, the lack of such information on engineering materials made any direct comparison between the biological and mechanical systems difficult. Based on available information, nickel-titanium shape memory alloy (SMA) was better suited to produce relatively slow and powerful steady swimming of scombrid species. The simplified geometry of muscular systems and axial tendons was adapted. These arrangements alleviate the limited strain of the SMA by trading force for distance and provide an effective force transmission pathways to the backbone.