Sensors and Actuators A: Physical

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1 Sensors and Acuaors A 144 (2008) Conens liss available a ScienceDirec Sensors and Acuaors A: Physical journal homepage: A micro-robo fish wih embedded SMA wire acuaed flexible biomimeic fin Zhenlong Wang a, Guanrong Hang a,, Jian Li a, Yangwei Wang a, Kai Xiao b a School of Mecharonics Engineering, Harbin Insiue of Technology, PO Box 421, Harbin, Heilongjiang, China b Deparmen of Mechanical Engineering, The Hong Kong Universiy of Science and Technology, Clear Waer Bay, Kowloon, Hong Kong, China aricle info absrac Aricle hisory: Received 13 Augus 2007 Received in revised form 23 February 2008 Acceped 25 February 2008 Available online 6 March 2008 Keywords: Micro-robo fish Biomimeic fin Squid/culefish fin Shape memory alloy Elasic energy sorage and exchange mechanism A flexible biomimeic fin propelled micro-robo fish is presened. Fish muscle and he musculaure of squid/culefish fin are analyzed firsly. Since he laer one is easier o be realized in he engineering field, i is emulaed by biomimeic fin. Shape memory alloy (SMA) wire is seleced as he mos suiable acuaor of biomimeic fin. Elasic energy sorage and exchange mechanism is incorporaed ino he biomimeic fin for efficiency improvemen. Furhermore he bending experimens of biomimeic fin were carried ou o verify he original ideas and research conceps. Thermal analysis is also conduced o find a proper acuaion sraegy. Fish swimming mechanism is reviewed as he foundaion of he robo fish. A radio frequency conrolled micro-robo fish propelled by biomimeic fin was buil. Experimenal resuls show ha he micro-robo fish can swim sraigh and urn a differen duy raios and frequencies. Subcarangiformand carangiform-like swimming modes were realized. The maximum swimming speed and he minimum urning radius reached 112 mm/s and 136 mm, respecively Elsevier B.V. All righs reserved. 1. Inroducion Fish ail-like propeller is considered as an alernaive apparaus for hrus o commonly used roaor of underwaer vehicle (UV). As he propulsive efficiency of small UVs is usually below 40%, fish ail-like propeller is superior o roaor used in small UVs [1]. Anoher advanage of fish ail-like propeller is ha he seering radius can be small even a high swimming speed. Micro-robo fish have grea advanages in exploring complex, narrow underwaer environmens. They may even be used in blood vessels for microsurgery. Many micro-robo fish have been developed in recen years. Mos repored micro-robo fish are driven by shape memory alloys (SMAs) [2,3], Ionic exchange Polymer Meal Composies (IPMCs) [4 6] or piezoelecric (PZT) acuaors [7,8]. The swimming performances of some micro-robo fish were invesigaed. For insance, he IPMC acuaed adpole robo, which is 96 mm in lengh and 16.2 g in weigh, reached a maximum speed of 23.6 mm/s a 4 Hz driving frequency, and he IPMC acuaed micro-robo fish, which is 230 mm in lengh and 295 g in weigh, reached a peak speed of 6.3 mm/s a 2 Hz. The difficulies of developing a microrobo fish mainly lie in selecion of acuaors, sealing, compacness, wireless conrolling, reducing noise and improving propulsive efficiency. Corresponding auhor. Tel.: x601; fax: address: hanggr@163.com (G. Hang). In his paper he developmen of a micro-robo fish driven by an embedded SMA wire acuaed biomimeic fin is invesigaed. The flexible bending biomimeic fin simulaes he musculaure and flexible bending of squid/culefish fin, which is suppored and driven by a special skeleon muscular hydrosa [9,10]. SMA wires ac as ransverse muscles of he biomimeic fin. Elasic energy sorage and exchange mechanism [11] is incorporaed in he bending of he biomimeic fin. The radio frequency conrolled micro-robo fish can swim sraigh and urn noiseless a differen duy raios and a differen frequencies. The paper is srucured as follows. In Secion 2, he musculaure of culefish fin and he srucure of biomimeic fin are invesigaed, furhermore he bending experimens of he biomimeic fin were conduced o verify he concep. In Secion 3, hermal analysis for conrol sraegy of biomimeic fin is applied. In Secion 4, he design of he micro-robo fish propelled by biomimeic fin is discussed in deail. In Secion 5, sraigh swimming and urning capabiliy of he micro-robo fish are invesigaed and discussed. Finally, he conclusions are given in Secion Embedded SMA wire acuaed flexible biomimeic fin 2.1. Musculaure of culefish fin The design of propulsor is he foundaion of micro-robo fish. Since evoluionary processes of millions of years have almos opimized he shape and srucure of aquaic animals, i is an effecive way o mimic he srucure and funcion of fins of aquaic animals /$ see fron maer 2008 Elsevier B.V. All righs reserved. doi: /j.sna

2 Z. Wang e al. / Sensors and Acuaors A 144 (2008) Fig. 2. Schemaic diagram of he musculaure of squid/culefish fin. Fig. 1. Squid and culefish. direcly. The flexible bending fin like srucure is called biomimeic fin in his paper. Fish of body and/or caudal fin (BCF) propulsion modes bend heir propulsor flexibly by acivaing alernae sides of W-shaped segmened muscles in sequenial manner, o form a backward propulsive wave. Obviously, he mos direc way o realize flexible bending is o mimic he W shaped muscles, connecive issue and bones by using arificial maerials. However, i is difficul o realize his srucure because of he complexiy of segmened arranged W shaped muscles, especially for micro-robo fish. Besides fish, anoher wo kinds of aquaic animals wih excellen swimming capabiliy are squid and culefish (shown in Fig. 1), which belong o Cephalopoda. Squid and culefish swim by using a combinaion of je propulsion a high speed and fin undulaory/oscillaory propulsion a low speed [12,13]. Squid fins are shor while culefish fins are long, however heir srucures are similar. Therefore, he culefish fin srucure is seleced for explanaion. The frill-like culefish fins exend all along he manle and hey can bend flexible ino an undulaory moion for propulsion. If a shor segmen of culefish fin is aken, he movemen is flexible bending upward and downward only, which is similar o he movemen of fish. So he muscular srucure of culefish fin is worhy o be invesigaed o realize flexible bending. The culefish fins consis of a ighly packed 3-dimensional array of musculaure called muscular hydrosa, which can generae force and suppor movemen wihou bony skeleon suppor or fluid-filled caviies for hydrosaic skeleal suppor. Fig. 2 shows he muscular srucure of culefish fin. The fin exends from fin carilage (FC). The median connecive issue fascia (MF) divided he fin ino wo similar pars: dorsal par and venral par. Transverse muscle fibers (T) exend parallel o he fin surface from he fin base o he fin margin, some of hem inser on MF. Dorsalvenral muscle fibers (DV) exend from dorsal and venral connecive issue fascia (DF and VF) o MF. Longiudinal muscle fibers (L) lie adjacen o boh he dorsal and venral surface of MF. The connecive issue fibers (CT), which are oriened a 45 o he long axes of T and DV, are presened among he T and DV. L and DV conrol he lengh and hickness of he fin, respecively. Transverse muscle fibers conrol he curvaure of he fin, namely les he fin bend. CT provides skeleal suppor. There is lile fluid ino or ou of he fin and here are no compressible gas-filled caviies in he fin, so he fin volume almos remains consan. When he ransverse muscle fibers of dorsal par and venral par conrac and relax in sequence, he fin is laerally compressed and can bend dorsally and venrally. During bending, connecive issue fibers provide resisance o preven he fin conracing wholly, and hey may sore elasic energy ogeher wih skin and oher muscles. During he subsequen moion of unbending, he sored elasic energy is released o suppor he movemen. The elasic energy sorage and exchange mechanism, which can increase efficiency and improve locomoor performance, is also commonly exised in oher animals. There are wo kinds of ransverse muscle fibers: aerobic and anaerobic fibers. The former one is for genle movemens while he laer one is for vigorous fin movemens Srucure of biomimeic fin To realize flexible bending by emulae he srucure of a shor segmen of culefish fin, some simplificaions mus be done. When he fin segmen is shor enough, dorsalvenral and longiudinal fibers can be negleced. Then he problem urns o find proper acuaors o imiae he ransverse muscle fibers. Moors, PZT and IPMCs are apparenly no suiable. SMA is he alloy being able o reurn o a predeermined shape and i can be processed ino wires. The mos sophisicaed SMA is TiNi, he advanages of which are noiseless acuaion, large recovery srain (<8%), high recovery sress (>500 MPa) [14], low acuaion volage, operaional frequency similar o ha of animal muscles, long life (up o 10 6 acion cycles under a srain of 1%) [15]. The efficiency of SMA is low, bu i is no a primary concern for he prooype. When SMA wire is hin, he acivaed elecric value is similar o ha of small DC moors. These consideraions deermined our choice of hin SMA wires as he mos suied acuaor o mimic he ransverse muscle fibers. In he sressfree sae, he four ransiion emperaures are Marensie Finish (M f ), Marensie Sar (M s ), Ausenie Sar (A s ) and Ausenie Finish (A f ). Fig. 3 shows he srucure and bending movemen of biomimeic fin. Elasic subsrae divides he biomimeic fin ino wo symmeric pars. Skins are adhered o elasic subsrae, one or more SMA wires are embedded in he skin, lying adjacen o boh sides of he elasic subsrae. The maerials for elasic subsrae and skins are plasic and rubber/silicone, respecively. SMA wires serve as ransverse muscle fibers, providing laeral compressing force. Elasic subsrae is used o provide resisance and sore elasic energy ogeher wih he skins. When he SMA wires of wo sides are resisan heaed by pulse and cooled alernaively in sequence, he biomimeic fin can

3 356 Z. Wang e al. / Sensors and Acuaors A 144 (2008) Fig. 4. Experimenal resuls of bending of biomimeic fin. Fig. 3. The srucure and he schemaic of bending movemen of biomimeic fin. bend o boh sides flexibly. During he process of bending movemens, elasic energy is sored and relaxed jus like i does during he movemens of real fin. The sored elasic energy during bending is he key issue since i is he energy o le he biomimeic fin reurn o he sraigh sae. Fish caudal fin like componen can be aached a he ip of he biomimeic fin o enlarge conrol surface and hrus Iniial experimens of bending A biomimeic fin was buil and esed in waer environmen o validae he concep. Table 1 illusraes he specificaions of he biomimeic fin. TiNi (52 a% Ni) SMA wires are employed. In he sress-free sae, he four ransiion emperaures are M f = C, M s = C, A s = C, A f = C, respecively. The maerials for subsrae and skin are polypropylene and silicone, respecively. The emperaure of waer (T 0 )was21 C. The volage and pulse widh of he pulse are deonaed by U and on, respecively. The wo kinds of pulse sequences employed were (1) U = 4.7 V, on = 0.5 s and (2) U =11.0V, on = 0.06 s. Afer each pulse of he pulse sequence, an inerval of 1.8 s was added o cool he SMA wires prior o he heaing of he anagonisic SMA wires. Fig. 4 shows he curves of pulse widh, bending angle and reurn ime of he biomimeic fin acivaed by he wo kinds of pulses. The angle of firs bending of each bending sequence is defined as posiive value. Fig. 5 shows he saus of maximum bending angles o boh sides. Over 90 of maximum bending angles o boh sides were obained. Experimenal resuls show ha he biomimeic fin can bend flexibly o boh sides. When his biomimeic fin was acivaed by pulse sequence (1), small bending angle was obained even using long pulse widh. This indicaes ha he emperaure of SMA arises slowly wih ligh elecric curren. When he biomimeic fin was acivaed by pulse sequence (2), he bending speed was much higher and large maximum bending angle could be obained in very shor ime. The reurn speed was lower han he corresponding bending speed in experimens. In accordance o he experimenal resuls, we know ha shor pulse wih heavy curren could be applied o acivae he biomimeic fin in order o achieve high frequency acuaion, and he reurn speed would resric he bending frequency of he biomimeic fin driven by he Ø 0.2 mm TiNi wires. 3. Theory analysis of he biomimeic fin Since shape memory effec is induced by emperaure, heaing speed and cooling speed are he major influencing facors. SMA wires are embedding in he skin, so he emperaure of SMA wires is difficul o measure direcly. Therefore, he hermal analysis is used o esimae he emperaure of SMA wires and o find proper acuaion sraegy. In order o simplify he analysis, several simplificaions are made: (1) radiaion effec is ignored; (2) here is no hea ransfer beween SMA wires and elasic subsrae; (3) he skin is simplified as hea sink of SMA wires, so hea convecion is considered as he only way of hea ransformaion, an equivalen hea ransmission coefficien, h W (W/(m2 K)), is used o replace he original hea ransmission coefficien; (4) h, specific elecric resisance e ( m) and specific hea c (J/(kg K)) are assumed o be W consan. Table 1 Specificaions of biomimeic fin for iniial experimens Widh (mm) 14 Diameer of SMA wire (mm) 0.2 Lengh of SMA wire (mm) 48 Numbers of SMA wires 2 Lengh of bending segmen (mm) 50 Thickness of he skin (mm) Thickness of he subsrae (mm) 0.36 Fig. 5. Maximum bending angles of biomimeic fin.

4 Z. Wang e al. / Sensors and Acuaors A 144 (2008) Fig. 6. Simulaion curves of he biomimeic fin used in Secion 2.3. When SMA wires are heaed, he equaion describing he energy inpu, hea ransfer and he emperaure of SMA wires is given as: ( ) d 2 d 4 e l U()2 d = h 2 W dl[t() T 0]d + c l dt() 4 (1) where U() is he volage supplied o SMA wires (V), d is he diameer of SMA wires (m), l is he oal lengh of SMA wires of one side (m), T() is he emperaure of SMA wires (K or C), is he densiy of SMA wires (kg/m 3 ) and is he ime (s). When SMA wires are cooled, he equaion describing hea ransfer and emperaure of SMA wires is given as: ( ) d h 2 W dl[t() T 0]d + c l dt() = 0 (2) 4 The equivalen hea ransmission coefficien h can be obained by W experimens. Simulaion is carried ou o he biomimeic fin used in Secion 2.3 (shown in Fig. 6). The resul shows ha he corresponding h W was abou 2300 W/(m2 K). From he simulaion curves we can see ha in order o increase operaional frequency, shor pulse widh wih heavy elecric curren (or high volage) should be supplied o SMA wires. Furhermore, SMA wire wih smaller diameer could be applied o achieve higher frequency as long as he conrac force is enough. 4. The design of micro-robo fish 4.1. Fish swimming mechanism According o he momenum heorem, when fish swim by pushing waer away behind hem, momenum is ransferred from he fish o he surrounding waer and hrus is generaed. Oher kinds of forces acing on a swimming fish are drag, weigh, buoyancy and hydrodynamic lif in he verical direcion. Swimming drag consiss of viscous drag and pressure drag. Viscous drag is skin fricion beween he fish and he boundary layer of waer, and i depends on he weed area and swimming speed of he fish and he propery of he surrounding fluid. Pressure drag is caused by disorions of flow around fish body and energy los in he vorices formed by he fins as hey generae lif or hrus. Precision calculaion of hrus is complex, so simplificaion by assuming seady or quasiseady flow is usually used. When a fish swim forward a a consan speed, he oal hrus is equal o he oal drag. On a small scale, hrus is defined as follows: F T = C D W AV 2 (3) 2 Where F T is hrus (N), C D is drag coefficien, W is waer densiy (kg/m 3 ), A is weed surface area (m 2 ) and V is swimming speed (m/s). When fish is swimming, i can narrow he wake by ensuring no vorex shed from he body bu one or wo vorices shed from he ail ip every fin ail bea. By doing his, reverse Karman vorex sree is formed and a je can be induced o increase hrus (shown in Fig. 7). The wake also sore energy and fish can recapure energy from he vorices o enhance swimming performance and o save energy. Two imporan nondimensional parameers which affec he swimming are Reynolds number (Re) and Srouhal number (S, reduced frequency). Reynolds number is he raio of inerial over viscous forces, defined as Re = LV (4) where L is a characerisic lengh (of eiher he fish body or he propulsor) (m), is he kinemaic viscosiy of waer (m 2 /s). When Re is larger han 1000, inerial forces are dominan and viscous forces are usually negleced and when Re is smaller han 1. Viscous forces are dominan. Inerial forces and viscous forces mus be boh considered when Re is beween 1 and 1000 [16]. Srouhal number can be approximaed as S = fa pp (5) V where f is ail-bea frequency (Hz) and A pp is he wake widh (approximaely as ail-bea peak-o-peak ampliude) (m). When S lies in he range , he swimming and hrus generaion are considered as opimal. Froude number is used o define he propulsive efficiency. I is he raio of he useful propulsive power over he oal power expended by he fish Srucure of he micro-robo fish Since he micro-robo fish is propelled by biomimeic fin, here are no radiional componens like gears, bearings and joins. In order o acivae he biomimeic fin, conrol circui and baeries should be required. As a resul, he micro-robo fish consiss of body and biomimeic fin based propulsor (shown in Fig. 8). The micro-robo fish prooype is 146 mm in lengh, 17 mm in widh and 34 mm in heigh. The weigh is abou 30 g. The propulsor consiss of a biomimeic fin (acive componen) and a caudal fin (passive componen). The caudal fin is used o enlarge he conrol surface and he hrus. Subcarangiform swimming can be formed by sofer caudal Fig. 7. The reverse Karman vorex sree.

5 358 Z. Wang e al. / Sensors and Acuaors A 144 (2008) Fig. 9. Subcarangiform-like swimming. in he body by shell and sealing skin. The conrol circui consiss of radio frequency remoe conrol module and MCU (PIC16F877A) based open-loop driving module. The propulsor is conneced o he conrol circui direcly Swimming modes Fig. 8. Micro-robo fish prooype. fin while carangiform swimming can be obained by harder caudal fin. To decrease he elecriciy value of driving he biomimeic fin and increase frequency, TiNi (50.2 a% Ni) wires wih he diameer of mm are used. In he sress-free sae, he four ransiion emperaures are M f = 43.4 C, M s = 52.2 C, A s =51.4 C, A f = 58.8 C. The conrol circui and wo 310 mah Li-polymer baeries are enveloped The micro-robo fish can swim forward and urn wih only one biomimeic fin. When he robo fish swims forward, he biomimeic fin bend back and forh, jus as illusraed in Fig. 3. When he robo fish urns, here are hree urning modes [17]: (1) The biomimeic fin bends only o one side. The body is equivalen o a rudder and he propulsor are equivalen o a roaor of he ship. I is he mos fundamenal and imporan urning mode as he robo fish can change he urning radius and speed in his mode, and i is he simples one. Fig. 10. The speed of swimming forward, urning radius and speed of urning of he micro-robo fish.

6 Z. Wang e al. / Sensors and Acuaors A 144 (2008) In he case of swimming forward, he peak speed a 16.7% duy raio was obained a 2.1 Hz, meanwhile he speed a 25% duy raio decreased wih he increase of frequency. The urning radii of boh duy raios increased firsly and hen decreased wih he increase of frequency. The speed of urning a 33% duy raio decreased wih he increase of frequency while a 25% duy raio, he peak value appeared a 3.13 Hz. A maximum speed of swimming forward of 112 mm/s was obained a a 25% duy raio, 2.5 Hz. A minimum urning radius of 136 mm was obained a a 33% duy raio, 3.7 Hz. Fig. 11 shows he saus of swimming forward and urning righ a a 25% duy raio, 2.78 Hz. The Srouhal number a he maximum swimming speed was As he robo fish is open-loop conrolled, he bending of biomimeic fin may be influenced by he waer flow and he emperaure inequaliy of waer. The bending angles o each side may be differen and i would resul in course deviaion. 6. Conclusions Fig. 11. Synheic images of he saus of swimming forward and urning righ of micro-robo fish a 2.78 Hz, 25% duy raio. (2) The biomimeic fin bends o one side and keeps he posure afer he robo fish swims forward a a cerain speed. The robo fish urns by hydrodynamics force. Smaller urning radius can be obained by using his mode. This mode is difficul o achieve by an open-loop conrol mehod. (3) The biomimeic fin bends o one side rapidly from saionary sae. Ineria force and fricion force of he propulsor and he body are changed o he momen of roaion. Turning from a saionary sae can be achieved by his urning mode. The urning radius is he smalles among he hree urning modes. 5. Experimens Swimming forward and urning capabiliies were invesigaed. Square wave volage was applied. Duy raio is defined as he raio of power on ime of a period over he periodic ime. Because he biomimeic fin is open-loop conrolled, longer power on ime means larger bending angle. Fig. 9 shows he subcarangiform-like swimming saus while swimming forward a a 25% duy raio, 2.5 Hz. The average swimming speed was abou 58 mm/s. More experimens were conduced on carangiform-like swimming. The bending angle of he biomimeic fin increases wih decreasing he driving frequency a a cerain duy raio. Turning mode (1) was applied. Prior o urning, he robo fish swam forward for 8 cycles a 25% duy raio wih he same pulse widh as he urning o ge an iniial forward speed. Fig. 10 illusraes he speed of swimming forward and urning radius a differen duy raios and frequencies. In he case of swimming forward, a maximum frequency of 8.33 Hz was esed a a 25% duy raio. For urning, a maximum frequency of 11.1 Hz was esed a a 33.3% duy raio. When swimming a he same frequency, swimming speed and urning curvaure (1/uring radius) of he higher duy raio are larger han heir values a lower duy raio. A micro-robo fish propelled by a biomimeic fin is presened in his paper. The micro-robo fish has no radiional componens such as gears and bearings, and i can swim noiseless and flexibly. The embedded SMA wire acuaed biomimeic fin imiaes he srucure of squid/culefish fin. Simplificaions are made for he squid/culefish fin o build up he biomimeic fin. The biomimeic fin consiss of elasic subsrae, skin, and ransverse muscle-liked SMA wires. Elasic energy sorage and exchange mechanism is incorporaed during he bending of biomimeic fin. Iniial experimens of bending were conduced o verify he concep of biomimeic fin. Thermal analysis is also applied o find proper acuaion sraegy. Then a radio frequency conrolled microrobo fish prooype was buil based on he biomimeic fin. Wih differen ail fin, subcarangiform- and carangiform-like swimming movemens were realized. Experimenal resuls show ha he micro-robo fish can swim forward and urn wih a biomimeic fin. A maximum swimming speed of 112 mm/s and a minimum urning radius of 136 mm were obained. Furher research on he srucure, maerial, and conrol sraegy would be made o improve he performance of biomimeic fin. We believe ha using biomimeic fin, robo fish wih smaller size could be buil. Acknowledgemen This work is suppored by Naional Naural Science Foundaion of China under No Appendix A. Supplemenary daa Supplemenary daa associaed wih his aricle can be found, in he online version, a doi: /j.sna References [1] M.S. Trianafyllou, G.S. Trianafyllou, An efficien swimming machine, Scienific American 272 (1995) [2] J. Ayers, C. Wilbur, C. Olco, Lamprey robos, in: Inernaional Symposium on Aqua Biomechanisms, Hirasuka, Japan, 2000, pp [3] N. Shinjo, G.W. Swain, Use of a shape memory alloy for he design of an oscillaory propulsion sysem, IEEE Journal of Oceanic Engineering 29 (2004) [4] S. Guo, T. Fukuda, K. Asaka, A new ype of fish-like underwaer microrobo, IEEE/ASME Transacions on Mecharonics 8 (2003) [5] A. Punning, M. Anon, M. Kruusmaa, A. 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7 360 Z. Wang e al. / Sensors and Acuaors A 144 (2008) [6] B. Kim, D.-H. Kim, J. Jung, J.-O. Park, A biomimeic undulaory adpole robo using ionic polymer meal composie acuaors, Smar Maerials and Srucures 14 (2005) [7] T. Fukuda, A. Kawamoo, F. Ami, H. Masuura, Mechanism and swimming experimen of micro mobile robo in waer, in: Proc. IEEE Inernaional Conference on Roboics and Auomaion, New Orleans, LA, USA, 8 13 May, 1994, pp [8] T. Fukuda, A. Kawamoo, F. Arai, H. Masuura, Seering mechanism of underwaer micro mobile robo, in: Proc. IEEE Inernaional Conference on Roboic and Auomaion, Nagoya, Japan, May, 1995, pp [9] W.M. Kier, The fin musculaure of culefish and squid (Mollusca, Cephalopoda) morphology and mechanics, Journal of Zoology (London) 217 (1989) [10] W.M. Kier, J.T. Thompson, Muscle arrangemen, funcion and specializaion in recen coleoids, Berliner Paläobiol. Abh. 3 (2003) [11] M.H. Dickinson, C.T. Farley, R.J. Full, M.A.R. Koehl, R. Kram, S. Lehman, How animals move: an inegraive view, Science 288 (2000) [12] E.J. Anderson, M.E. Demon, The mechanics of locomoion in he squid Loligo pealei: locomoory funcion and unseady hydrodynamics of he je and inramanle pressure, The Journal of Experimenal Biology 203 (2000) [13] I.K. Barol, M.R. Paerson, R. Mann, Swimming mechanics and behavior of he shallow-waer brief squid Lolliguncula brevis, The Journal of Experimenal Biology 204 (2001) [14] G. Song, B. Kelly, B.N. Agrawal, Acive posiion conrol of a shape memory alloy wire acuaed composie beam, Smar Maerials and Srucures 9 (2000) [15] K. Ikua, Micro/miniaure shape memory alloy acuaor, in: IEEE Inernaional Conference on Roboics and Auomaion, Cincinnai, OH, USA, 1990, pp [16] C.E. Jordan, A model of rapid-sar swimming a inermediae reynolds number: undulaory locomoion in he chaeognah Sagia elegans, The Journal of Experimenal Biology 163 (1992) [17] K. Hiraa, Turning Modes for a Fish Robo, 2001, hp:// eng/khiraa/fish/general/urn/index e.hml. Biographies Zhenlong Wang graduaed from he Deparmen of Mechanical Manufacuring and Auomaion a Harbin Insiue of Technology (HIT), Heilongjiang, China, in 2000 wih a PhD. He is currenly a professor in he School of Mecharonics Engineering a HIT. Professor Wang is ineresed in biomimeic underwaer robos, non-radiional machining, micro-machining and precision machining. Guanrong Hang received bachelor degree in Deparmen of Mechanical Engineering and Auomaion a HIT, in He is currenly a PhD candidae in he Deparmen of Mechanical Manufacuring and Auomaion a HIT. His research ineres includes sudies of biomimeic underwaer robos, swimming mechanics of fish, squid, and culefish, and conrol mehods of shape memory alloy. Jian Li received bachelor degree in he Deparmen of Mechanical Manufacuring and Auomaion, Shandong Universiy, Shandong, China, in He is currenly a PhD candidae in he Deparmen of mechanical manufacure and auomaion a HIT. Yangwei Wang received bachelor degree in he machine design and manufacuring and auomaion, Nanjing Universiy of Aeronauics and Asronauics, Jiangsu, China, in He received MS in he Deparmen of Mechanical Manufacuring and Auomaion a HIT, in He is currenly a PhD candidae in he Deparmen of Mechanical Manufacuring and Auomaion a HIT. Kai Xiao received his bachelor and maser degree in Deparmen of Mechanical Manufacuring and Auomaion a HIT in 2002 and 2005, respecively. He is currenly a PhD suden in he Deparmen of Mechanical Engineering a The Hong Kong Universiy of Science and Technology.