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Study on the hydrodynamics and kinematics of a biomimetic fin propulsor actuated by SMA wires
Abstract
A flexible noiseless and high-efficient propulsor plays a prominent role in the performance of underwater vehicles. This paper presents a micro flexible caudal fin propulsor actuated by shape memory alloy (SMA) wires. To improve the responding frequency and fatigue of the SMA wires, a pair of slots is designed. So the SMA wires can be heated in the protection of silica ~ellayer and cool in the other status, i.e. flowing water. Then the propulsive performance of the biomimetic propulsor is evaluated through thrust measurement experiments. Note that higher undulating frequency does not mean stronger thrust force because the undulating amplitude descends along with the undulating frequency increase for this kind SMA propulsor. Further, the kinematics of the propulsor is analyzed and the corresponding equation of motion is obtained. At last, a three-dimensional numerical simulation on the biomimetic fin was conducted by CFD to investigate the interaction of the propulsor with surrounding water and the thrust production. The CFD results consist with the experimental results well, which verify the kinetic model and the numerical simlation.
... With the increased number of motors, on the other hand, the system becomes complicated and difficult to control. The wave motion can also be realized by using simple mechanism with smart materials such as Ionic Polymer Metal Composites (IMPC) [8], piezoelectric (PZT) [9] and Shape Memory Alloy (SMA) [4]. Using these smart materials, the propulsor structure is simple. ...
... is the ending point of line segment , is the length of line segment , is the bending angle between line segment and i-1, is the length of the propulsor, is the generalized coordinate denoting the distance to the origin along the backbone curve, i is the index of vertebras, ranging from 1 to 12. The lateral displacement of each line ending point is described by equation (4). According to the previous description, the joint rotation in each segment is the same. ...
This paper presents a robot tadpole which is actuated by a novel biomimetic wire-driven flapping propulsor. The propulsor has a 12-vertebra serpentine backbone and each pair of adjacent vertebras forms a spherical joint. The vertebras are divided into two groups and each group is controlled by a set of wires. By controlling the two sets of wires, the propulsor can generate oscillatory motion (C-Motion) and undulatory motion (S-Motion). A prototype is built. Experiment results show that the design is effective. Its maximum cruise speed of is 0.288 BL/s, and the turning radius is 0.8 BL.
... Also, the propulsion efficiency is impaired. The waving motion can also be realized by using simple mechanism with smart materials such as Ionic Polymer Metal Composites (IPMC),[8] piezoelectric (PZT) [9] and Shape Memory Alloy (SMA).[4] Using these smart materials, the propulsor structure is simple. ...
This paper presents a robot fish actuated by a novel biomimetic wire-driven flapping propulsor. The propulsor is composed by a flexible backbone and two sets of controlling wires. The backbone has 13 vertebras. They are articulated by cylindrical joints and an elastic fin plate. These vertebras are divided into two groups. Each group is controlled by one pair of wires and one actuator. By controlling the two sets of wires, the propulsor can generate oscillatory motion (C-Motion) and undulatory motion (S-Motion). The motions well resemble the fish swimming body curve. A prototype is developed and four swimming tests were conducted, i.e. ‘Big-C-Motion’ forward, ‘Small-C-Motion’ forward, ‘S-Motion’ forward and turning. Only two actuators are used in this prototype. Experimental results validated the effectiveness of the wire-driven design. Results show that the robot fish’s swimming performance is satisfactory. The forward swimming speed is influenced by the flapping amplitudes, waving frequency, the phase lag of the two segments and the swimming stability. In the experiments, the maximum cruise speed is 300.75 mm/s (0.608 BL/s) (BL/s is Body Length/s) in ‘C-Motion’ and 333.33 mm/s (0.673 BL/s) in ‘S-Motion’. The turning radius of the robot fish is around 0.7 BL, and the truning speed is 51.4 °/s.
The utility of unmanned Micro Underwater Vehicles (MUVs) is paramount for exploring confined spaces, but their spatial agility is often impaired when maneuvers require burst-propulsion. Herein we develop high-aspect ratio (150:1), multi-walled carbon nanotube microarray membranes (CNT-MMs) for propulsive, MUV thrust generation by the decomposition of hydrogen peroxide (H2O2). The CNT-MMs are grown via chemical vapor deposition with diamond shaped pores (nominal diagonal dimensions of 4.5 × 9.0 [µm]) and subsequently decorated with urchin-like, platinum (Pt) nanoparticles via a facile, electroless, chemical deposition process. The Pt-CNT-MMs display robust, high catalytic ability with an effective activation energy of 26.96 [kJ mol-1] capable of producing a thrust of 0.209 ± 0.049 [N] from 50% [w/w] H2O2 decomposition within a compact reaction chamber of eight Pt-CNT-MMs in series.
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.
The development of a wireless undulatory tadpole robot using ionic polymer–metal composite (IPMC) actuators is presented. In order to improve the thrust of the tadpole robot, a biomimetic undulatory motion of the fin tail is implemented. The overall size of the underwater microrobot prototype, shaped as a tadpole, is 96 mm in length, 24 mm in width, and 25 mm in thickness. It has one polymer fin tail driven by the cast IPMC actuator, an internal (wireless) power source, and an embedded controller. The motion of the tadpole microrobot is controlled by changing the frequency and duty ratio of the input voltage. Experimental results show that this technique can accurately control the steering and swimming speed of the proposed underwater tadpole robot.
This paper investigates the propulsive performance of the lunate tails of aquatic animals achieving high propulsive efficiency (the hydromechanical efficiency being defined as the ratio of the work done by the mean forward thrust to the mean rate at which work is done by the tail movements on the surrounding fluid). Small amplitude heaving and pitching motions of a finite flat-plate wing of general planform with a rounded leading edge and a sharp trailing edge are considered. This is a generalization of Chopra's (1974) work on model rectangular tails. This motion characterizes vertical oscillations of the horizontal tail flukes of some cetacean mammals. The same oscillations, turned through a right angle to become horizontal motions of side-slip and yaw, characterize the caudal fins of certain fast-swimming fishes; viz. wahoo, tunny, wavyback skipjack, etc., from the Percomorphi and whale shark, porbeagle, etc., from the Selachii. Davies’ (1963, 1976) method of finding the loading distribution on the wing and generalized force coefficients, through approximate solution of an integral equation relating the loading and the upwash (lifting-surface theory), is used to find the total thrust and the rate of working of the tail, which in turn specify the hydromechanical swimming performance of the animals. The physical parameters concerned are the tail aspect ratio ((span)2/planform area), the reduced frequency (angular frequency x typical length/forward speed), the feathering parameter (the ratio of the tail slope to the slope of the path of the pitching axis), the position of the pitching axis, and the curved shapes of the leading and trailing edges. The variation of the thrust and the propulsive efficiency with these parameters has been discussed to indicate the optimum shape of the tail. It is found that, compared with a rectangular tail, a curved leading edge as in lunate tails gives a reduced thrust contribution from the leading-edge suction for the same total thrust; however, a sweep angle of the leading edge exceeding about 30° leads to a marked reduction of efficiency. Another implication of the present analysis is that no negative work is involved in the actual oscillation of the tail.
A flexible biomimetic fin propelled micro-robot fish is presented. Fish muscle and the musculature of squid/cuttlefish fin are analyzed firstly. Since the latter one is easier to be realized in the engineering field, it is emulated by biomimetic fin. Shape memory alloy (SMA) wire is selected as the most suitable actuator of biomimetic fin. Elastic energy storage and exchange mechanism is incorporated into the biomimetic fin for efficiency improvement. Furthermore the bending experiments of biomimetic fin were carried out to verify the original ideas and research concepts. Thermal analysis is also conducted to find a proper actuation strategy. Fish swimming mechanism is reviewed as the foundation of the robot fish. A radio frequency controlled micro-robot fish propelled by biomimetic fin was built. Experimental results show that the micro-robot fish can swim straight and turn at different duty ratios and frequencies. Subcarangiform- and carangiform-like swimming modes were realized. The maximum swimming speed and the minimum turning radius reached 112 mm/s and 136 mm, respectively.
The paper seeks to determine what transverse oscillatory movements a slender fish can make which will give it a high Froude propulsive efficiency,The recommended procedure is for the fish to pass a wave down its body at a speed of around of the desired swimming speed, the amplitude increasing from zero over the front portion to a maximum at the tail, whose span should exceed a certain critical value, and the waveform including both a positive and a negative phase so that angular recoil is minimized. The Appendix gives a review of slender-body theory for deformable bodies.
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.
Steering mechanism of underwater micro mobile robot
- T Fukuda
- A Kawamoto
- F Arai
- H Matsuura