This document describes the design of a six-legged walking mechanism. It discusses designing each leg with six linkages that can convert rotational motion to walking motions. It also discusses using a tripod gait where three legs on each side move together in alternating triangular support patterns. The transmission system is designed with a single motor that drives three shafts connected by sprockets and chains to synchronize the six legs through their respective four-bar linkage designs.

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Chapter 1
Introduction
1.1 Movement: Wheeled, Tracked and Legged
Almost all animals and humans as well have legs for locomotion or movement. But
historically the very first vehicles developed by human were run with wheels. And even now
through the industrial revolution and technological progress wheeled locomotion has
remained the most widespread technology of transportation.
The wheeled locomotion is most advantageous in predetermined and plane surfaces.
However, it is disadvantageous in uneven and smooth terrains. The tracked locomotion has
been developed in order to cope with this problem. However, tracked locomotion is also
troublesome, since it destroys the terrain on which the vehicle is moving.
Legged locomotion is mechanically superior to wheeled or tracked locomotion over a variety
of soil conditions and certainly superior for crossing obstacles. This advantage of legged
locomotion is mostly due to the fact that legged systems use isolated footholds. Due to this
fact as an alternative to both wheeled and tracked forms, legged locomotion is being
developed by imitating the legged animals in nature.
1.2 Why Legged Mechanism?
The main advantage of legged robots or moving machine is their ability to access places
impossible for wheeled machines. US army investigation reports that about half the earth’s
surface is inaccessible to wheeled or tracked vehicles, whereas this terrain is mostly exploited
by legged animals.
Wheeled and tracked systems follow the surface in a continuous manner and consequently
their performance is spoiled by the worst parts on the terrain. A legged system, on the other
hand, can choose the best places for foot placement. These footholds are isolated from the
remaining terrain. Hence the performance of the legged system is boosted by the best
footholds. Besides using isolated footholds, the legged system can provide active suspension,
which does not exist in wheeled or tracked systems. A legged system can be arranged (leg
lengths lengthened and shortened) according to the level alteration and they can jump over
obstacles or holes. Therefore, the body can be moved in a desired course, for example

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horizontally, whatever the terrain is. The legged locomotion also inflicts the least damage to
the surface compared to wheeled and tracked systems.
The most forceful motivation for studying legged moving machine is:
• To give access to places which are dirty
• To give access to places those are dangerous
• To accomplish jobs which are highly difficult for wheeled or tracked vehicles
1.3 Multi-Legged Walking
Many of the animals in nature have adopted legs for various environmental conditions.
Centipedes, spiders, cockroaches, cats, camels, kangaroos, and human are among those,
either with different number of legs or with different kind of walking. People turned their
attention to these walking animals, after it was recognized that the wheeled and tracked
systems did not satisfy all the needs. The basic requirements of any walking mechanism can
be acquired from these biological examples. The plan of walking, namely the “gait pattern”,
determines the sequence of stepping of legs with their stance and swing durations in each
step. Gait pattern generation is the generation of rhythmic plan that determines which leg will
be in power or return stroke in any time. A coordination and control unit is also needed that
controls the legs according to the gait pattern. Another requirement is stability: both static
and dynamic.
There are different types of legged walking robots. They are roughly divided into groups
according to the number of legs they possess. Bipeds have two legs, quadrupeds four,
hexapods six and octopods have eight legs. Biped walking mechanisms are dynamically
stable, but statically unstable, they are harder to balance, and dynamic balance can only be
achieved during walking. Hexapods or six legged robots, on the other hand, have advantages
of being statically stable. During walking they can move three legs at a time, thus leaving
three other legs always on the ground forming a triangle.
1.4 Six Legged Walking Mechanism
The proposed Six Legged Walking Mechanism has three pairs of legs: three attached to the
front shaft and three more to the rear shaft. The mechanism is a lower pair mechanism with
only pin joints or revolute pairs. The legs are made by extending the couplers of a four bar
RRRR mechanism. All the four bar mechanisms are of crank-rocker type and the crank is
connected to the motor. A pair of legs (front and rear) share the same frame and a common

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pivot. The motion and the gait is obtained by keeping suitable angular lag between the cranks
connected to the various legs. While the mechanism is in motion, at any instant of time three
legs keep contact with the ground forming a triangle and making the mechanism dynamically
stable.
1.4.1 Applications
1. It would be difficult to compete with the efficiency of a wheel on smooth hard
surfaces but as condition increases rolling friction, this linkage becomes more viable
and wheels of similar size cannot handle obstacles that this linkage is capable of. Toys
could be developed that would fit in the palm of your hand and just large enough to
carry a battery and a small motor.
2. Six leg mechanical spiders can be applicable for the making of robots. It has a wide
range of application in the manufacturing of robots. A large version could use existing
surveillance technology to convert your television into a real-time look at the world
within transmitting range.
3. It would also relay commands from the remote to the spider bike additional
frequencies could be used to operate manipulators for retrieving the mail during
unfavorable weather or taking the dog out.
4. It can also be used for military purpose. By placing bomb detectors in the machines,
we can easily detect the bomb without harmful to humans. It can be used as heavy
tanker machines for carrying bombs as well as carrying other military goods.
5. It is also applicable in the goods industries for the small transportation of goods inside
the industry. The mountain roads or other difficulties where ordinary vehicles cannot
be moved easily can be replaced by our six-leg mechanical spider.
6. Heavy loads can be easily transported if we made this as a giant one. It has got further
application for the study of linkage mechanism and kinematic motions. The geometry
and conditions can be changed according to application needs. It can travel in rough
surfaces very easily, so this machine can be used in rough surfaces were ordinary
moving machine cannot travel.

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Chapter 2
Literature Review
2.1 History of Legged Mechanism
The scientific study of legged locomotion began just very a century ago when Leland
Stanford, then governor of California, commissioned Edward Muyridge to find out whether
or not a trotting horse left the ground with all four feet at the same time (). Stanford had
wagered that it never did. After Muybridge proved him wrong with a set of stop motion
photographs that appeared in Scientific American in 1878, Muybridge went on to document
the walking and running behavior of over 40 mammals, including humans. His photographic
data are still of considerable value and survive as a landmark in locomotion research. The
study of machines that walk also had its origin in Muybridge’s time. An early walking model
appeared in about. It used a linkage to move the body along a straight horizontal path while
the feet moved up and down to exchange support during stepping. The linkage was originally
designed by the famous Russian mathematician Chebyshev some years earlier. During the 80
or 90 years that followed, workers viewed the task of building walking machines as the task
of designing linkages that would generate suitable stepping motions when driven by a source
of power.
Many designs were proposed but the performance of such machines was limited by their
fixed patterns of motion, since they could not adjust to variations in the terrain by placing the
feet on the best footholds. By the late 1950s, it had become clear that linkages providing
fixed motion would not suffice and that useful walking machines would need control. One
approach to control was to harness a human. Ralph Mosher used this approach in building a
four-legged walking truck at General Electric in the mid-1960s. The project was part of a
decade-long campaign to build advanced operators, capable of providing better dexterity
through high-fidelity force feedback. The machine Mosher built stood 11 feet tall, weighed
3000 pounds, and was powered hydraulically. Each of the driver’s limbs was connected to a
handle or pedal that controlled one of the truck’s four legs. Whenever the driver caused a
truck leg to push against an obstacle, force feedback let the driver feel the obstacle as though
it were his or her own arm or leg doing the pushing. After about 20 hours of training, Mosher
was able to handle the machine with surprising agility. Films of the machine operating under

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his control show it ambling along at about 5 MPH, climbing a stack of railroad ties, pushing a
foundered jeep out of the mud, and maneuvering a large drum onto some hooks. Despite its
dependence on a well-trained human for control, this walking machine was a landmark in
legged technology.
2.2 Different Types of Legged Mechanisms
Normally six bar mechanism is chosen for moving leg robot because of its superior force-
transmission angle and bigger oscillating angle in comparison with other types such as the
four-bar mechanism. Force transmission is very important for leg mechanisms, because of the
point contact with the ground. The leg mechanism itself has one DOF for lifting, whilst the
base of mechanism has another DOF for swinging. The body size and link dimensions are
determined from the maximum swing and lift angles. Each link is created by entering its
shape and reference coordinates. To mate the contact surfaces of the parts, the assembly bar
of the assembly mating menu is used. Then the component is rotated around an axis,
specifying the desired axis and rotation for the selected surfaces.
Yoseph Bar-Cohen, in his report named -Biomimetics: mimicking and inspired-by biology,
discussed that how the evolution of nature led to the introduction of highly effective and
power efficient biological mechanisms. Imitating these mechanisms offers enormous
potentials for the improvement of our life and the tools we use [2]. Shibendu Shekhar Roy,
Ajay Kumar Singh, and Dilip Kumar Pratihar, in their paper, highlighted the analysis of Six-
legged Walking Robots and the attempt made to carry out kinematic and dynamic analysis of
a six-legged robot. A three-revolute (3R) kinematic chain has been chosen for each leg
mechanism in order to mimic the leg structure of an insect [3]. Patil Sammed Arinjay and
Khotin developed Bio-Mimic Hexapod and explained Dynamic Modeling and Control in
Operational Space of a Hexapod Robot and comments the real times application of hexapod
robot for control. Based on an operational trajectory planner, a computed torque control for
the leg of hexapod robot is presented. This approach takes into account the real time force
distribution on the robot legs and the dynamic model of the hexapod. First, Kinematic and
dynamic modeling are presented. Then, a methodology for the optimal force distribution is
given. The force distribution problem is formulated in terms of a nonlinear programming
problem under equality and in equality on straits. The friction on strains is transformed from
nonlinear inequalities into a combination of linear equalities and linear inequalities.
Simulations are given in order to show the effectiveness of the proposed approach [4].

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Fig.2.2.1- ASV Six Legged Walking Machine
Fig.2.2.2- OSD Six Legged Walking Robot

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Fig.2.2.3- John Dear Walking Robot
Fig2.2.4- Forest Walking Machine

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Chapter 3
Methodology
3.1 Problem Statement
Literature review reveals that the main concern with the moving leg mechanism is the
number of links involved in the design of the structure. If there are more number of links it is
very tedious to design and operate. For the mechanism to move in a smooth manner the
dimensions of the pieces should be precise. More priority should be given to maintain the
exact lengths of the links which is determined by the position of the holes to be drilled. Also
the movement depends on the amount of power or motion which is transferred to the
locomotive parts with respect to the position of the drills. The key to success for this
mechanism is for the designer to make it locomotive even in the roughest of terrains. An
objective is set to develop a six- legged mobile robot in this project.
3.2 Methodology
The objective is to be achieved through the following steps which defines the methodology
adopted in this project work:
Literature Review
Problem
Design
Fabrication of Project
Testing and Alingment
Conclusion

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Chapter 4
Plan of Work
A work plan is an outline of a set of goals and processes by which a team and/or person can
accomplish those goals, and offering the reader a better understanding of the scope of the
project. Work plans, whether used in professional or academic life, help you stay organized
while working on projects. Through work plans, we break down a process into small,
achievable tasks and identify the things we want to accomplish.
In this semester, we have to learn about objectives and then determining the most effective
activities of our project Six Legged Walking Mechanism and draw a success full design of all
parts and components. So, that at first, we have a knowledge about mechanism and
principles.
Our concept of project based on the walking mechanism of six legged animal like Spider,
Crab etc. so we have to learn walking mechanism of six legged animal and construct a
mechanical design which can run using these mechanism. The working schedule of our
project are listed below step by step,
Step 1: Identify the purpose of our project.
Step 2: Making a knowledge about working mechanism.
Step 3: Draw some designs of parts and components.
Step 4: Purchase material and accessories.
Step 5: Construction of all parts.
Step 6: Assembling all parts and components.
Step 7: Testing of Product.
In this semester, we have to make on first three steps that gather a knowledge and make some
designs, it helps to done our project success fully.

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Chapter 5
Design of the Six Legged Walking Mechanism
5.1 Design of Leg
Leg structure is the core component of multi-legged walking machines which features
determine the basic properties of multi-legged walking machine. Leg structure of this
walking machine use six linkage. Crank is the antriebstange, bracing swing around sleeve.
When crank fixed to the shaft at one end, link 3 swings around the joint C and Joint D back
and forth, preparing the institution for preliminary leg open and contractile function. When
the joint B in the sleeve, joint B subject constraints from sleeve rather than turning, so joint D
and joint C hold up the machine body, link 3 ‘s swing make the body moving forward.
Crank rotating 360° around the drive shaft center completes an operation cycle. In the first
180° of crank rotation, as joint B in the sleeve, link 1 and 2 is equivalent to an overall, link
3‘s swing makes the body moving forward. In the last 180°of crank rotation, joint B leaves
sleeve, goes into rotating pair. Under the action of joint B, C and D and link 4, 3 lift off the
ground, no longer support the body, achieve the movement. This leg structure can convert
single rotary motion into leg walking exercise directly and has similar moving gesture with
quadruped mammals.
5.1.1 Gait Selection
Gait is the process that single leg put up and down according to a certain order and trajectory.
Gait choice should base on the leg structure. Suitable gait is the basis of the walking machine
to realize continuous stability walking motion. Currently, most of the six-legged walking
machine using tripod gait. Triangle gait refers to three pairs of legs are divided into two
groups, with alternating triangular support structure to move forward, number 1, 3, 5 legs for
a group, No. 2, 4, 6 legs for the other group, thereby formed two triangular brackets.
Tripod gait time plan for each leg; the gray portion represents contact with the ground. When
all the legs of one triangular bracket lift off the ground, the other triangular bracket’s legs
support the body and provide the driving force for forward movement. Two groups of legs
touch the ground alternately. The machine center of gravity projection is always falls in the
triangular bracket projection which has very good stability.

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5.2 Design of transmission system
There are many aspects should be considered in transmission system design, including leg
arrangement, motor position and transmission accuracy. It plays a vital role in body stability,
reliability and scalability.
This walking machine use rectangular body, both left and right sides of the machine arranged
three legs, respectively. Leg connects to body through a joint shaft. We use the symmetrical
arrangement to ensure the machine’s center of gravity coincides with the geometric center. In
order to ensure the six-legged gait coordination in walking, we use a single motor to drive 6
legs movement synchronously. System power pass through the chain, specific delivery path
are as follows: Motor output power pass through the sprocket 1, sprocket 2 to the shaft 2,
then drive shaft 2 and shaft 3, respectively. In order to ensure the same speed of shaft 1, 2 and
3, the transmission ratio both of sprocket 3 and sprocket 5, sprocket 4 and sprocket 6 choose
1 preferably, use the same specifications of the chain to achieve constant speed drive.
Fig.5.2.1. Six leg kinematic moving machine

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Fig.5.2.2- Simplified front view of the machine
The six legged moving machine shown in the figure.2 consists of flat aluminium bars, a chain
and sprocket arrangement, motor connected to give the required motion. This figure shows
the simplified diagram of the project drawn using AutoCAD.
5.3 Assessment of virtual prototype
Virtual prototype is built on prototype systems or subsystems of the computer models.
Compare to physical prototype, it have functional fidelity to a certain extent. In this study, we
use virtual prototypes to replace physical prototypes to test and evaluate the design
characteristics of the walking machine.

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5.4 Design and Drawing
Fig.5.4.1- Design of 12.5 mm Bush
Fig.5.4.2- Design of 58 mm Bush

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Fig.5.4.3- Design of 15 mm Bush
Fig.5.4.4- Design of 55 mm Bush

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Fig.5.4.5- Design of 51 mm Bush
Fig.5.4.6- Design of M6 Bar

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Fig.5.4.7- Design of 39 mm Bush
Fig.5.4.8- Design of Moving Link

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Fig.5.4.9- Design of Leg

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Fig.5.4.10- Design of 23 Teethed Sprocket
Fig5.4.11- Design of Fixed Link

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Fig.5.4.12- Design of assembled Six legged walking mechanism

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Chapter 6
Conclusion And Future Work
In this semester, a six legged walking mechanism is designed. Careful attention is paid to the
main design issues and constraints that influence the technical feasibility and performance of
these systems. A design procedure is outlined in order to systematically design a six-leg
walking machine. In particular, the proposed design procedure takes the mechanical structure
and leg configuration, the actuating and drive mechanisms, payload, motion conditions, and
walking gait, providing a useful tool for the systematic choice of main design characteristic.
Due to making this project we learnt that the mechanical walking concept of the six legged
animal like crab and spider. By using this mechanism, we have to make this project and
gather a concept on kinematic moving mechanism, 4 bar mechanism, and leg structure.
In next semester we make a mechanical structure by using these design and test the load
carrying capacity and its performance. The scope of our project is to make this machine walk
on any Surfaces with a stiff gait slow and carries a limited load. It could be used for
surveillance in sewer maintenance.

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REFERENCES
References of our project are listed below,
1. http://mechanicalprojects101.blogspot.in/2011/10/mechanical-projects_03.html By
Jagan, Praveen G, Prabhakar Narayanan, Pradyumn.
2. A project report on Inversion of 4 bar mechanism for kinematic motion by Dhaval
Patel, Government Polytechnic Chhotaudepur, mechanical department.
3. Fabrication of six legged kinematic moving mechanism by R.Arjunraj, A.Arunkumar,
R.Kalaiyarasan, B.Gokul, R.Elango, Department of Mechanical Engineering Nandha
Engineering College, Erode-638052, Tamilnadu, India.
4. https://en.wikipedia.org/wiki/Kinematics kinematic mechanism.
5. Design and Fabrication of Six leg kinematic moving machine. By Mahesh waran,
Kaviarasan, Muthu Kumar, Elavarasan.
6. Six leg kinematic moving machine- Mechanical engineering project from
http://www.hatchedeggs.com/blog/education/mechanical-engineering-project-six-leg-
kinematic-moving-machine
7. KinematicWalker from http://mechanicalprojects101.blogspot.in/2011/10/mechanical-
projects_03.html