design, fabrication and thrust drag analysis of improved fish robots actuated by piezoceramic composite actuators

Design, Fabrication and Thrust/Drag
Analysis of Improved Fish Robots Actuated
by Piezoceramic Composite Actuators



Nguyen, Quang Sang





Thesis of the Doctor of Philosophy
Department of Advanced Technology Fusion
Graduate School of Konkuk University
Design, Fabrication and Thrust/Drag
Analysis of Improved Fish Robots Actuated
by Piezoceramic Composite Actuators



Nguyen, Quang Sang





Thesis of the Doctor of Philosophy
Department of Advanced Technology Fusion
Graduate School of Konkuk University
Design, Fabrication and Thrust/Drag

Analysis of Improved Fish Robots Actuated
by Piezoceramic Composite Actuators

Nguyen, Quang Sang

A Dissertation Submitted to the Department of Advanced Technology Fusion
and the Graduate School of Konkuk University
in partial fulfillment of the requirements
for the degree of Doctor of Philosophy

August 2010

Approved by
Park, Hoon Cheol
Major Advisor
i

Table of Content
List of Figures v

List of Tables ix

ABSTRACT x

1.

Introduction 1

1.1

Understanding fish swimming 1

1.1.1

Reynolds number 5

1.1.2

Froude number: 6

1.1.3

Strouhal number 6

1.2

Overview of research on fish 7

1.3

Overview of research on fish robot driven by electromagnetic motor 8

1.4

Overview of fish robot driven by smart material 14

1.5

Objective and approach 21

2.

A fish robot driven by piezoceramic actuators 24

2.1

Description of the fish robot 24

2.1.1

Actuator 25

2.1.2

Linkage design 26

2.1.3

External power supply 27

2.1.4

Miniaturized power supply 31

2.2

Swimming test 33

2.2.1

Linkage analysis 33

ii

2.2.2

Thrust measurement 36

2.2.3

Wired-swimming test 38

2.2.4

Free-swimming test 38

2.3

Experimental result 39

2.3.1

Tail-beat angle 39

2.3.2

Thrust 40

2.3.3

Swimming speed 41

2.4

Summary 43

3.

An improved fish robot driven by piezoceramic actuators 44

3.1

Design and fabrication of the actuation system 44

3.1.1

Actuator 44

3.1.2

Design and working principle of the linkage system 46

3.1.3

Linkage analysis 48

3.1.4

Fabrication of the actuation system 51

3.2

Fish robot configuration 52

3.2.1

Tail fin of the fish robot 52

3.2.2

Description of the improved fish robot 53

3.3

Evaluation of the improved fish robot 53

3.3.1

Tail-beat angle of the fish robot in water 54

3.3.2

Swimming test of the fish robot 55

3.3.3

Thrust of the fish robot 58

3.3.4

Thrust coefficient 62

3.3.5

Turning swimming radius of the fish robot 63

iii

3.4

Parameter study 68

3.4.1

Reynolds number 68

3.4.2

Froude number 68

3.4.3

Strouhal number 70

3.5

Summary 70

4.

Thrust improvement by using Compressed LIPCAs 71

4.1

Fish robot 71

4.1.1

Actuator 71

4.1.2

Actuation mechanism 72

4.1.3

Fish body 72

4.2

Experiment 73

4.2.1

Swimming experiment 73

4.2.2

Thrust Measurement 77

4.2.3

Drag Estimation 77

4.3

Result 79

4.3.1

Swimming speed 79

4.3.2

Thrust of the Fish Robot 80

4.3.3

Drag of the Fish Robot 80

4.3.4

Drag coefficient 85

4.4

Summary 86

5.

CFD simulation 87

5.1

Simulation model 87

5.2

Model validation 90

iv

5.3

Results and discussions 92

6.

Concluding remarks and recommendations future work 100

6.1

Concluding remarks 100

6.2

Academic contribution 102

6.3

Recommendation for future work 103

REFERENCE 104

APPENDIX 107

요약문
요약문요약문
요약문 108



v

List of Figures
Figure 1-1: Fish configuration [2] 3

Figure 1-2: Swimming mode associated with (a) BCF propulsion and (b) MPF
propulsion [3] 3

Figure 1-3: Diagram showing the relation between swimming propulsors and
swimming functions [4] 4

Figure 1-4: (a) The forces acting on a swimming fish; (b) Pitch, yaw, and roll
definitions. [5] 4

Figure 1-5: Typical velocity of the largest possible variety of swimmers as a
function of the Reynolds number [1] 6

Figure 1-6: Flow visualization of velocity field in the x-y planes [13] 10

Figure 1-7: Viscous flow around a swimming fish: (a) mesh around the fish
model; (b) detail of a cut through the mesh [14]. 10

Figure 1-8: Schematic view of the eight internal links of the MIT’s Robot Tuna
mechanism [18] 11

Figure 1-9: Draper Lab’s hydraulic-actuated Vorticity Control Unmanned
Undersea Vehicle’s configuration [19] 11

Figure 1-10: RoboPike [20] 12

Figure 1-11: Design of Boxybot fish robot [21] 12

Figure 1-12: Prototype of the experimental robot fish [22] 13

Figure 1-13: Apparatus of pectoral fin motion [23] 13

Figure 1-14: Pressure sensor and its location on the fish body [24]. 15

Figure 1-15: Drag measurement apparatus [25] 15

Figure 1-16: Geometry and position of neutral axis of LIPCA [28] 17

Figure 1-17: An IPMC strip under a low voltage [29] 17

Figure 1-18: Large actuation displacement and actuation force of SMA with low
responsiveness [31] 18

Figure 1-19: Lamprey robot actuated by SMA [32] 18

vi

Figure 1-20: Two type robots driven by IPMC [33] 19

Figure 1-21: The tadpole robot: (a) configuration of the microrobot; (b)
miniaturized of the battery, electrode and embedded controller located inside the
body [34]. 19

Figure 1-22: The floating boat driven by THUNDER [35] 20

Figure 1-23: Fish robot actuated by two LIPCA: (a) Configuration of the fish
robot; (b) Linkage system 20

Figure 2-1: Assembly of the fish 25

Figure 2-2: Geometry and position of layers in a LIPCA 25

Figure 2-3: Linkage system of the fish robot 27

Figure 2-4: Function generator (Agilent 33220A) 29

Figure 2-5: Voltage amplifier (MATSUSADA model AML-1.5B40-LC) 29

Figure 2-6: Oscilloscope (Tektroniks TDS 2024) 29

Figure 2-7: The schematic of the MIPAD 30

Figure 2-8: Hardware implementation of the MIPAD. 32

Figure 2-9: MIPAD response to square wave command 32

Figure 2-10: Tail-beat angle analysis by vector calculus 34

Figure 2-11: Tail-beat angle measurement apparatus 35

Figure 2-12: Load cell (Nano 17 Transducer) 36

Figure 2-13: The apparatus of the thrust measurement 37

Figure 2-14: Schematic diagram of the wired-swimming test 37

Figure 2-15: Fish robot in the free-swimming test 38

Figure 2-16: Tail-beat angle by vector calculus 40

Figure 2-17: Tail-beat angle of the fish robot in water 40

Figure 2-18: The average thrust of the fish robot 42

Figure 3-1: Fabricated LIPCA. 45

Figure 3-2: Design of the actuation mechanism. 45

Figure 3-3: Working principle of the actuation mechanism. 47

Figure 3-4: Configuration of linkage system. 49

vii

Figure 3-5: The tail-beat angle by vector calculus. 50

Figure 3-6: Fabricated actuation mechanism. 50

Figure 3-7: The limited tail-beat angle. 51

Figure 3-8: Comparison of the linkage systems. 52

Figure 3-9: The four scaled tail fins. 54

Figure 3-10: The fish robot. 54

Figure 3-11: Schematic diagram of the tail-beat angle measurement. 56

Figure 3-12: The tail-beat angle in water. 56

Figure 3-13: Schematic diagram of the swimming test. 57

Figure 3-14: The swimming speed of the fish robot. 59

Figure 3-15: Measured thrust of a rigid connection 59

Figure 3-16: Effect of LIPCA’s inertial force 60

Figure 3-17: Schematic diagram of the thrust measurement. 61

Figure 3-18: The average thrust of the fish robot. 62

Figure 3-19: The thrust data of the fish robot at a tail beat frequency of 3.7 Hz.62

Figure 3-20: Thrust coefficient of the fish robot (see Appendix for more detail).
63

Figure 3-21: Changes in the duty ratio. 64

Figure 3-22: Schematic diagram of the turning experiment. 65

Figure 3-23: Fish robot in the turning experiment. 65

Figure 3-24: The turning radii of the fish robot. 66

Figure 3-25: The Reynolds number of the fish robot 66

Figure 3-26: The Froude number of the fish robot 69

Figure 3-27: The Strouhal number of the fish robot 69

Figure 4-1: Deformation of LIPCA under compressive mechanical load 74

Figure 4-2: The actuation mechanism using four CLIPCAs 74

Figure 4-3: (a) Configuration of the CLIPCA fish robot, (b) The CLIPCA fish
robot can be excited by LIPCA and compressed LIPCA. 75

Figure 4-4: Schematic diagram of drag measurement. 76

viii

Figure 4-5: Schematic diagram of bearing friction measurement. 76

Figure 4-6: The computation domain of the CLIPCA fish robot: (a) a view of
meshed domain; (b) detail of this mesh near the fish robot. 81

Figure 4-7: The boundary condition of the computation model. 81

Figure 4-8: The swimming speed of the CLIPCA fish robot actuated by LIPCAs.
82

Figure 4-9: The swimming speed of the CLIPCA fish robot actuated by
CLIPCAs. 83

Figure 4-10: The average thrust of the CLIPCA fish robot for 0.6A tail fin. 83

Figure 4-11: The drag of the LIPCA fish robot. 84

Figure 4-12: Comparison of drags of the CLIPCA fish robot and the LIPCA fish
robot (without electric wires). 84

Figure 4-13: Drag coefficient of fish robots. 85

Figure 5-1: Tail fin kinematic 91

Figure 5-2: Tail-beat angle 91

Figure 5-3: Simulation model 94

Figure 5-4: Thrust comparison between analysis and measurement at 3.7 Hz tail-
beat frequency 94

Figure 5-5: Position of the cross section 95

Figure 5-6: Thrust analysis of the fish robot at 3.7 Hz tail-beat frequency 95

Figure 5-7: Velocity, vortex, and pressure at the cross-section of tail fin 97

Figure 5-8: Average thrust comparison between analysis and measurement 98

Figure 5-9: Thrust analysis comparison 98

Figure 5-10: Vortex comparison 99

ix

List of Tables
Table 1-1: Reynolds numbers of fish 2

Table 2-1: Material properties of LIPCA’s layers. 26

Table 2-2: Dimension of linkages of the fish robot 35

Table 3-1: Dimension of linkages of the improved fish robot 46



x

ABSTRACT

Design, Fabrication and Thrust/Drag Analysis of Improved Fish

Robots actuated by Piezoceramic Composite Actuators
Quang-Sang Nguyen
Department of Advanced Technology Fusion
Graduate School of Konkuk University
This dissertation focuses on the design, fabrication and thrust/drag analysis of
fish robots actuated by Lightweight Piezoelectric Composite Actuator (LIPCA).
In the first model, four LIPCAs were utilized in the actuation system. The
linkage system was composed of links and two gears to amplify actuation
displacement produced by LIPCAs. The tail-beat angle by means of vector
calculus to evaluate the actuation mechanism was estimated. The calculated tail-
beat angle was compared with the measured tail-beat angle in air at a low
frequency (about 0.5 Hz). Tests of the first model in water were carried out to
measure the tail-beat angle, thrust, and swimming speed for various tail-beat
frequencies from 0.5 Hz to 2 Hz. They were compared with those of the fish
robot actuated by two LIPCAs in the previous study. The best tail-beat frequency
of the fish robot was 1.4 Hz and the maximum average thrust force was 0.0048
N. A miniaturized power supply, which was developed to excite the LIPCAs,
was installed inside the fish robot body for free swimming. The maximum free-
swimming speed was 3.2 cm/s due to the increased size.
In the second model, a new actuation mechanism was developed which was
simple to fabricate because it works without gears. With the new mechanism, the
second model has a 30% smaller cross section than that of the fist model. A
xi

series of tests of the second model in water were carried out to measure the tail-
beat angle, thrust, swimming speed for various tail-beat frequencies from 1 Hz to
5 Hz, and turning radius. The maximum swimming speed of the fish robot was
7.7 cm/s at a best tail-beat frequency of 3.9 Hz. A turning experiment at the best
frequency showed that the swimming direction of the second model could be
controlled by changing the duty ratio of the driving voltage; it showed a turning

radius of 0.41 m for a left turn and 0.68m for a right turn.
Actuation force of the LIPCA can be improved by applying a compressive force
on the LIPCA. Thrust measurement was conducted for two fish robots with the
same tail fin areas to investigate the thrust force improvement by using the
compressed LIPCA. One fish robot was actuated by the compressed LIPCAs,
and the other one was actuated by the original LIPCAs. The results showed that
the use of compressed LIPCAs could increase the best tail-beat frequency of fish
robot from 3.7 Hz to 4.2 Hz, resulting in 10% increase in hydrodynamic force.
However, when springs were utilized to apply the compressive force on LIPCAs,
the cross section became slightly larger than that of the fish body actuated by
original LIPCAs. To evaluate effect of the larger cross section, drag of the fish
robots was estimated by measurement and computational fluid dynamics (CFD)
analysis with the ANSYS-CFX software package. The CFD analysis and
measurement showed about 4.9% and 8.7% increment of drag, respectively, due
to about 8.4% larger cross section.
To identify the mechanism to produce a highest thrust, a three-dimensional CFD
simulation with the ADINA software was carried out by implementing the tail-
beat motion captured by using a high speed camera (Photron Ultima APX 120K).
The thrust simulation was done for the 0.6A tail fin at 3.7 Hz tail-beat frequency
which can create the fastest swimming speed. The calculated time history of the
thrust agreed well with that acquired from experimental with about 14%
difference. This means the force measurement apparatus worked properly
xii

providing fairly reliable data. Besides, based on velocity, vortex, and pressure
images at a cross section of the tail fin, peak thrust generation progress was
explained. To confirm the best frequency, which was found out from thrust
experiment, thrust was calculated for the 0.6 A tail fin at three tail-beat
frequencies: 3.2 Hz, 3.7 Hz and 4 Hz. The simulation result showed that highest
average thrust was produced at 3.7 Hz tail-beat frequency.

This work may provide a guideline for the design, analysis, and experimentation
of fish robots propelled by artificial muscle-type actuators.
1

1. Introduction
1.1 Understanding fish swimming
After million years of evolution, fish became master of art of propulsive
interaction with water with more than 22,000 fish species [1]. Due to high
density of water, force of gravity on fish body is mostly close to its buoyancy.
Therefore, some fish pieces are very good in maneuvering or hovering. On the
other hand, fish easily transfer its momentum into water surrounding it due to
incompressibility characteristic of water. Hence, some others pieces are
fanta1stic cruise swimmers [2].
Figure 1-1 shows configuration of fish. Fishes swim by transferring momentum
from the fish to surrounding water. To create thrust, fish bends their bodies into
backward-moving propulsive wave from their caudal fin which is called body
and/or caudal fin (BCF) locomotion mode. On the other hand, fish uses median
and pectoral fins for maneuvering and stabilization which is called median
and/or paired fin (MPF) locomotion mode as shown in Figure 1-2. Figure 1-3
clearly shows about the relationship between propulsors and swimming
functions.
During swimming, as shown in Figure 1-4 (a), there are four main forces acting
on the fish body such as via buoyancy plus hydrodynamic lift, weight, thrust,
and resistance. For balancing the vertical forces, fish can create supplement lift
force by using their pectoral fins extended. For forward swimming, thrust
created by fish can be larger than resistance which was called sometime drag.
Drag has three main components: viscous (or friction drag), form drag, vortex
(or induced drag). Viscous drag is skin friction between the fish and the
boundary layer of water. It depends on the wetted area and swimming speed of
2

the fish and property of layer water around the fish. Form drag is generated by
the distortion of flow around solid bodies and depends on their shape. Induced
drag is energy lost in the vortices formed by the caudal and pectoral fins when
they generate lift or thrust. On the other hand, pitch, roll, and yaw motions as
shown in Figure 1-4 (b) are also important terms when the hydrodynamic
stability and direction of fish movement are considered.

Table 1-1: Reynolds numbers of fish
Species Velocity
(ms
-1
)
Length
(m)
Re
Blue whale 10.00 30 3 × 10
8

Tuna 10.00 3 3 × 10
7

Human 1.70 1.8 3 × 10
6

Mackerel 3.30 0.3 1 × 10
6

Herring

Adult 1.00 0.2 2 × 10
5

Larvae 0.50 0.1 5 × 10
4

0.16 0.04 6 × 10
3

0.06 0.02 1 × 10
3

0.02 0.01 2 × 10
2

Copepods 0.002 0.001 2 × 10
0


Sea urchin sperm 0.0002 0.00015 3 × 10
-2


3


Figure 1-1: Fish configuration [2]


Figure 1-2: Swimming mode associated with (a) BCF propulsion and (b) MPF

propulsion [3]
dorsal fin
caudal fin
(tail)
median
anal fin
pectoral fin
paired
pelvic fin
caudal peduncle
fin-base
main axis
4


Figure 1-3: Diagram showing the relation between swimming propulsors and
swimming functions [4]

Figure 1-4: (a) The forces acting on a swimming fish; (b) Pitch, yaw, and roll
definitions. [5]
Swimming Propulsors
BCF
propulsion
MPF
propulsion
Oscillations Undulations Fin Oscillations Fin Undulations
Transient
movements
Periodic
swimming

ACCELERATING CRUISING MENOEUVRING
resistance
boyancy plus hydrodynamic lift
weight
(a)
(b)
thrust
roll
pitch
yaw
5

To evaluate locomotion of fish such as cruise, and maneuvering, researchers
considered fish in terms of some dimensionless numbers: Reynolds number,
Strouhal number, and Froude number.
1.1.1 Reynolds number
The Reynolds number (Re) is a dimensionless number which shows ratio of
inertial forces to viscous forces [1]. The Reynolds number is used to characterize
different flow regimes, such as laminar or turbulent flow. When Re is low which
means the viscous forces were dominant, laminar flow occurs and flow is
characterized by smooth, constant fluid motion. On the contrary, turbulent flow
occurred at high Reynolds numbers. The inertial force is domination at this time
and produces random eddies, vortices and other flow instabilities. The Reynolds
number for a fish is calculated as follows:
Re

ൌ

U
.

L
.
ρ
µ
.

(1)

where U is velocity of fish, L is length of the fish, ρ is the density or weight of
fresh water (which is about 1000 kgm
-3
at 1 atm and 15
o
C), and µ is viscosity of
water.
In fish research field, the Reynolds number is used to evaluate cruise
performance of the fish. The Reynolds number of aquatic animals is from less
than 1 for bacteria to 10
8
for the blue whale as shown Table 1-1 [1]. Depending
on value of the Reynolds number, there are two groups: plankton and nekton as
shown in Figure 1-5. In plankton group, animals are too small and have slow
speed. Therefore, their main concern is to avoid sinking. Their weight and
buoyancy are the important forces. While, aquatic animals in nekton group are
larger than plankton, they have powerful enough for fast swimming for example
whales, dolphins and squid.
6


Figure 1-5: Typical velocity of the largest possible variety of swimmers as a

function of the Reynolds number [1]
1.1.2 Froude number:
The Froude number is used to evaluate maneuverability of fish [1]. The Froude
number is high for long and light strip for example dolphin, whales. Burst speed
of the fish is generated when Fr > 1 and Re > 10
5
. The Froude (Fr) is a ratio
between inertial forces and the forces of gravity that act on a flow. The inertia
force of the flow is represented by U
2
/L, and the gravity force is the acceleration
due to gravity, g. The Froude number can be used to quantify the resistance of an
object moving through water, and compare objects of different sizes. The Froude
number of a fish is defined as follows:
Fr
ൌ
U
ඥ
g
.
L
.

(2)

1.1.3 Strouhal number
Plankton
Blue
whale
Nekton

Fishes
Copepods
Sperm
Bacteria
10
6
10
9
Re
10
3
10
0
10
-3
10
-6
10
-5
10
-3
10
0
10
3
Velocity (ms
-1
)
Viscosity
Inertial

7

In fluid analysis, the Strouhal number (St) is a dimensionless number describing
oscillating flow mechanisms and is essentially ratio of unsteady force to inertial
force. The Strouhal number is related how fast vortices are being generated and
the space between them. Based on experimental studies, Triantafyllou et al.
concluded that maximum spatial amplification and optimum creation of thrust lie
in a narrow range of St which was from 0.25 to 0.35 with peaking at 3.0 [6]. The
Strouhal number of a fish is defined as follows:
St
ൌ
A
.
f
U
,

(3)

where A is width of the wake, which is approximated the amplitude of tail
oscillation; and f is the frequency of oscillation which is tail-beat frequency.
1.2 Overview of research on fish
To understand how fish swims, many theories have been developed to explain
the swimming mechanism of fish. Lighthill was highly successful with the best-
known theory for the hydrodynamics of undulatory fish swimming, in which the
curvature of the fish was assumed small and the effect on the fish of the vortex
wake was neglected [7, 8]. Treating the fish as an elastic plate, Wu developed a
two-dimensional waving plate theory [9] which formed the basis for Lighthill’s
elongated-body theory [7, 10]. To be able to consider carangiform swimming,
Lighthill developed the original theory to cater for fish motions of arbitrary

amplitude, leading to the large-amplitude elongated-body theory [11]. While,
Cheng et al. made assumption that fish was infinitely thin and the undulations of
small amplitude [12]. Base on those theories, researchers have used numerical
models to simulate fish swimming. Studies on simulation help researchers more
understand about the flow field around fish during its motion. Adkins et al.
proposed a CFD simulation to investigate fluid around the fish during motion
8

[13]. The flow around the fish can be examined by changing of amplitude and
frequency of the swimming motion (Figure 1-6). To estimate vorticity and thrust
produced by swimming motion, Z. Zhang et al. built a model (Figure 1-7) based
on the solution of the Navier-Stokes equations on unstructured meshes [14].
Kowalczyk et al. used a commercial software ANSYS (CFX-10.0) to model
undulatory and oscillatory fin movements [15]. The authors studied the
influences of different fin-like movements of the surrounding fluid such as
vortex and velocity.
1.3 Overview of research on fish robot driven by
electromagnetic motor
Propeller-driven designs have been developed and widely used for underwater
vehicles for a long time but it was not very efficient for small underwater vehicle.
Their efficiencies are no more than 40 percent and they show power
maneuverability [16]. Swimming speed and maneuverability of propeller driven
designs are inversely proportional to each other; a high-speed vehicle shows low
maneuverability. In addition, power efficiency of propeller is only optimal in a
range of operation swimming speeds. To overcome these restrictions, researchers
have been studying locomotion of aquatic animals. In addition, autonomous
underwater vehicles (AUV’s) missions require a variety of capabilities can be
mutually exclusive: high transit speed, long range and duration, maneuverability,
and station-keeping ability. Whereas, fish can cruise great distances at
significant, maneuver in tight space, and accelerate and decelerate quickly from

rest or low speed, especially highly efficient-fast swimming and silent
propulsion. For example, dolphins follow ships at 20 nautical miles per hour
(knots) with impressive grace and apparent ease, playfully bursting. Tuna, which
is one of the fastest swimming fish in the world, can swim at a speed of 40 knot
[17]. Therefore, research in the propulsion and maneuvering flow mechanisms
9

used by fish can potentially provide inspiration for a design of propulsors that
will outperform the thrusters currently in use.
There were a lot of models of fish robots presented by now. The most famous
one is MIT’s motor-actuated RoboTuna, which was used to study fish propulsion
mechanism [18]. Robot tuna is 1.25 m long, covered with a flexible skin and
equipped with a tail fin. The outer shape of the robot is the same with that of a
bluefin tuna. The caudal fin has maximum (vertical) span 0.32 m. Figure 1-8
shows the mechanism of the robot, which is assembled of eight links made of
anodized aluminium.
Another famous fish robot is Draper Lab’s hydraulic-actuated Vorticity Control
Unmanned Undersea Vehicle (VCUUV) [19]. This vehicle is the first mission-
scale, autonomous underwater vehicle that used vorticity control propulsion and
maneuvering. To study the energetic and maneuvering performance of fish-
swimming propulsion, the VCUUV mimicked the morphology and kinematics of
a yellowfin tuna. Figure 1-9 shows configuration of the VCUUV. The VCUUV
can swim at a stable speed of 1.2 m/sec and has maneuvering with turning rates
up to 75 degrees per second. In addition, there are two others famous fish robot:
RoboPike [20], Boxybot [21] as shown in Figure 1-10 and 1-11, respectively.
Wang presented a novel unmanned underwater vehicle biomimetic robot fish
which was able to carry out underwater mission [22]. The fish robot was
mimicked as carangiform swimmer. The fish robot has four links, which were
connected with four servomotors, the control system and battery, which were
equipped in the plastic fish head (Figure 1-12).