IRJET-Conceptual Design of Locomotion Mechanism of an Amphibial Robot

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 01 | Jan-2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 730
Conceptual design of locomotion mechanism of an amphibial robot
Devashish Panchal1, Vaibhav Paradkar2, Shashank Parkar3, Akshar Parmar4
1,2,3,4 Dept. of Electronics & Telecom. Engineering, Atharva college of Engineering, Maharashtra, India
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Abstract - This paper focuses on the locomotion aspect of
remotely controlled semi-autonomous amphibious robotwith
a primary aim of surveillance in aquatic and terrestrial
environments. The proposed system can beusedforunmanned
marine monitoring applications. The direction of motion can
be controlled by a wireless module. This paper discusses the
locomotion mechanism of the robot in both water and land. A
separate mechanism is also discussed which explains how the
system will move around at different depths underwater. For
terrestrial locomotion chassis is used which is controlled
wirelessly by the user. The emphasis is on the stability of the
system in underwater conditions.
Key Words: amphibial, surveillance,aquatic,terrestrial,
chassis, wheels, propeller
1. INTRODUCTION
Robotics is one of the most rapidly advancing domains in
technology. The significance of unmanned exploration and
surveillance cannot be undermined in the near future.
Autonomous robotic systems are rapidly and effectively
reducing the human element in surveillance programs. A
robot is an automated mechanical device. It can be
developed and programmed to function in hostile
environments. Variouskindsof robots have been developed
along with the advancements in computer and information
processing technology. There is a great need fortheserobots
in unfavorable environments especially underwater.[6]
Application of underwater robots and vehicleshasincreased
dramatically in recent times. Thoughmostoftheunderwater
robots and vehicles are developed for scientific underwater
explorations, there also commercial and military
applications. For instance submarine investigations are
performed with the help of these, the Gas and Oil industry
uses underwater robots for laying pipelines etc.[12]
To perform any sort of underwater robotic research, an
appropriate platform is necessary. First of all it must be
watertight. Even a single unit of water can stop the whole
system from operating.[7] So it must be shielded completely
to prevent the entry of water. Next the weight of the
platform is important. If it is too heavy, the platform will
sink, and if it is too light it will be hard to sink. Therefore
design of the device must be effectively water resistant.
Hence design of the outer chassis must be made
meticulously. In this design the emphasis is on the stability
of design. [1]
1.1 Need for Amphibial Surveillance robots
The needs for monitoring and surveillance have increased
enormously in the near past, motivated by the wide range of
application scenarios that can be realized practically and by
the level of maturity achieved by the main enabling
technologies. Underwater ROVs, or Remotely Operated
Vehicles, have become a significant underwater technology.[9]
These aquatic unmanned vehicles are widely used by the oil
and gas industry, researchers, enthusiasts and the military
and. ROVs enormously enhance the competence of
organizations for exploration and maintenance of
underwater environments and resources. They are looked
upon as cost-effective solutions and a safer option than
sending in people to work at depth. They aremajorlyutilized
for myriad underwater surveillance operations. There is no
surprise that ROVs operate in some of the harshest
environments conceivable. UGVs or Unmanned Ground
Vehicles are similar to what underwater ROVs can do; the
only difference is that they operate exclusively in the
terrestrial domain. UGVs are widely used for military
purposes, space rovers and such applications in the similar
vein.[10]
The idea of an amphibiousrobot is simply the amalgamation
of the features of both Underwater ROVs and Terrestrial
Unmanned Robotic vehicles. [15] This results in a robust
design that can operate in various situations and
environments. This provides a perfect solution for the
surveillance operations which are difficult to undertake
manually. However we need a design that stays untarnished
in both land and water domains.
1.2 Challenges faced
Most underwater robots have now achieved remarkable
amount of flexibility in their motion with superior
navigation, imaging, and sensing that enables them to
provide a superior performance. Still major problems exist
which limit their capabilities. Some of the significant
problems faced in underwater navigation and locomotion
are as follows:
1.2.1 Communication-
Underwater communication systems involve the
transmission of information in the form of sound or
electromagnetic waves. Sound waves operating in shallow
water can be severely affected by surface ambient noise and
temperature gradients. EM waves do not work flawlessly in

an aquatic environment, specifically due to the conducting
nature of the medium, especially in the case of seawater.
1.2.2 Positioning-
Aquatic navigation has always faced the challenge of
obtaining precise positioning, and this is especially true in
underwater environments. On land the geo-referenced
positioning is facilitated by the use of GPS.
In Underwater environments, GPS fails to provide location
which affects the positioning of the device.
1.2.3. Unpredictable disturbances-
Disturbances caused due to weather changes, winds, waves,
and ocean currents have a drastic impact on underwater
robot locomotion and stability. Such environmental
disturbances play a vital role in determining the degree of
autonomous behavior in underwater robots. The odds of
facing a totally new problem in the underwaterenvironment
are extremely high.
2. PROPOSED METHODOLOGY
In this project we are interested in the amphibious nature of
the robot. Certain additional attributes are included in this
overall project. However the locomotion mechanism is the
backbone of the entire model. So there arises a need to
formulate a proper method to navigate the model in both
land and water domains. Simple and practical solutions are
proposed in the following sections. These formulated
solutions can be implemented albeit in an advanced manner
for the high power, heavy duty systems. This model being
just at the prototype stage is unable to solve all the issues
faced at the advanced levels. Hence only thebasicunderlying
issues are considered.
To simplify the understanding let us look at the underwater
and terrestrial locomotive mechanisms separately. In the
underwater system we need to navigate the object in two
dimensional axes. In other words the model can move up
and down in one axis, and in the other axis it can move
forward, backward, left or right. This is the most basic
concept which is required before we see that how we
actually realize this model. Being in the aquatic domain, we
need such system which will push the water backwards so
that the device moves forward in the required direction.
Thus we need something to constantly push the water
backwards to ensure that the model moves forward and we
get uniform motion. To go down, the model designed must
be heavy and bulky enough so that it goes down in water as
per our requirements. To bring the model upwardswe need
to push the water down such the resulting force will propel
the model up. For lateral and forward backward movement
an identical method is used.
For the terrestrial locomotion, we need wheels or legged
locomotion, whichever is feasible as per our requirements.
The legged locomotion follows a different mechanism
altogether, which is not discussed in this paper. The wheels
are the simplest option for land movement. The motion of
Fig-1: Diagrammatic representation of the proposed
methodology
the wheelscan be controlled by connecting themto a motor,
which will provide the revolutions to move the device
forward.[4] Now for both the cases the common aspect is
application of the force to move the device ahead. The
energy required for performing suchactionscanbeprovided
as per the requirement and the application of the specified
device.
2.1 Terrestrial locomotion
The most popular locomotion mechanism in vehicles is
wheeled locomotion; so it is not surprising that it is
consistently used in robotics.[11] Reason for this is thesimple
mechanical implementation of the wheel and there is no
need for balance control if the vehicle has at least three or in
some case two wheels. Wheeled locomotion is significantly
power efficient, even at high operating speeds.[8]
However there are various factors that affect the wheel
locomotion. The starting point of considering wheeled
locomotion is the wheel itself. There are four major types of
wheels used for locomotion. They are as follows
i) Standard wheel – It has two degrees of freedom, these are
rotation around the wheel axle and around the contact

ii) Castor wheel – It has two degrees of freedom, rotation
around the wheel axle and the offset steering joint.
iii) Omni wheel – It has three degrees of freedom: rotation
around the contact point, around the wheel axle and around
the rollers.
iv) Spherical wheel - This wheel is omnidirectional [2]
The main advantages of the standard wheel are easy
implementation, high load capacity and high tolerance to
irregularities. But these wheels are not inherently
omnidirectional, therefore to make a vehicle using these
wheels steerable; the steerable wheel(s) must be steered
first along a vertical axis and then moved around a
horizontal axis.[16] Specifically in case of heavy vehicles and
when it is not moving during steering, this steering method
causes high friction and abrasion during steering as the
wheel is actively twisted around its vertical axis, this
increments the power consumption and reduces the
positioning accuracy of the vehicle. [14]
In this model we have used standard wheels astheyareeasy.
We have four wheels attached to the chassis which can be
used for changing the direction of the device.
In the figure 2.1.1 the smaller arrows indicate the direction
change of the wheels while the big arrow indicates the
direction change of the entire device.
Maneuverability of the device can be controlled accordingly
using the technique shown in Fig 2. To move right the upper
two wheels must be moved in the upper right direction
keeping the lower two wheels’ direction forward. Doing this
same procedure for the leftward movementwecanmovethe
device to the left. To make a reverse turn we need to move
either two of the left or the two right wheels in their
respective directions. By continuing to turn the wheels in
that direction the device can make a reverse turn. In this
manner we can use the wheels for terrestrial locomotion. It
must be noted that here only standard wheels are
considered for the proposed design.[3] A complete designfor
the terrestrial and aquatic locomotion will be discussed in a
different section.
Fig- 2: Terrestrial locomotion by maneuvering the wheels
Fig -3: Relation between Torque and power
An engine produces power by providing a rotating shaft
which can exert a given amount of torque on a load at a
given RPM. The amount of torque the engine can exert
usually varies with RPM. Here P stands for power, τ stands
for torque and ω stands for angular velocity. We can infer
that, greater the torque, greater is the power of the system.
2.2 Aquatic Locomotion
Locomotion in the underwater domain is always a
challenging prospect for an amphibial robot. The pushing
mechanism is utilized to push the water and to thrust the

device forward.[13] Ducted fans are used to push the waterin
this case. Alternatively a DC pump can also be utilized to
thrust the device forward.[5] This model is driven through
water using a propulsion mechanism that thrustsby moving
water at a certain velocity. Propulsion is one of the main
sources of power consumption. Therefore, selecting the
convenient mechanism depends on factors such as the size,
cost, power consumption and produced thrust.[10] Propellers
and jets are some of the options for underwaterapplications.
Fig -4: Aquatic locomotion by maneuvering the thrusters
Fig -5: Ducted fan propeller
Propellersuse motorswhile jets use a turbine. Wehaveused
motor based propulsion system due to its cost efficiency.
Degreesof freedom of the vehicle are affectedbythelocation
of the motors. Noise interference with onboard electronic
componentsis affected as well. Hence, special careshouldbe
taken deciding the number of motors to be used and their
positioning. Ballast tanks or thrusters pointing downwards
are two of the alternatives for submerging. Although the
implementation of thrusters is simple, it is not optimum for
greater depths. Propellers have specific features, which
indicate what should be the right combination for the task
and size of the device.
3. PROPOSED DESIGN
This project can be used to carry out undersea operations. A
pressure hull is also required to place the components, such
as electronic components and batteries. The pressure hull
must be able to provide a watertight environment. Also, it
should be made with special materials to handle the highly
corrosive and higher-pressure ocean environment. This
design collaborates both aquatic and land locomotion
mechanisms for the prototype level. The design of the
structure would be optimized with the following features:
 Buoyancy centered along the length of the ROV
 Minimal drag for forward travel
 Adequate buoyancy and room for batteries
 Accommodations for four thrusters (two
vertical/side thrusters and two horizontal
thrusters)
 Easy access to thrusters
 Thrusters protected from collisions by barriers
 Structurally stable
The diagrammatic representation of the proposed design is
as follows.
Fig-6: Conceptual working design

This design has four standard wheels for terrestrial
locomotion. The movement can be synchronized as
discussed in section 2.1. Four thrusters are used for aquatic
locomotion. The propeller design is as shown in Fig. -5. The
ducted fan is operated by a motor providing 300 RPM.
4. CONCLUSIONS
The project has been developed for surveillance. It can be
used to carry out underwater research and analysis.Itcanbe
sent to the places where human life cannot go. The extreme
environments, that cause a threat to human life, can be
studied by using this robot. The use of DC power supply for
both terrestrial and aquatic locomotion is a goodoption asit
meets the energy requirementsof the system. The proposed
system can work effectively on land and water, providedthe
controlling center of the device is shieldedandwellenclosed.
This model can be upgraded for further higher, heavy duty
applications.
REFERENCES
[1] Birk, A. and Carpin, S.: Rescue robotics: a crucial
milestone on the road to autonomous systems, Adv.
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“Design and Implementation of a System for Wireless
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Science Issues, Vol. 7, Issue 5, pg 191- 197, September
[3] Campion, G. and Chung, W.: Wheeled robots,in:Springer
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IRJET-Conceptual Design of Locomotion Mechanism of an Amphibial Robot

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