Design, Modification and Manufacturing of a Stair Climbing Vehicle

MILITARY INSTITUTE OF SCIENCE AND TECHNOLOGY
ME-362: Instrumentation and Measurement Sessional
Design, Modification and Manufacturing
Of a Stair Climbing Vehicle
Submitted By: Group 08 (ME-12)
Raian Nur Islam (201418012)
Shariba Ahmed (201418017)
Iftekhar Anam (201418018)
Satya Brata Das (201418038)
Fatema-Tuz-Jahara(201418058)
Supervised By: Captain Md. Mahmudul Hasan, EME
Lecturer, Faculty of Mechanical Engineering.
MIST.

2 [STAIR CLIMBING VEHICLE] MIST
Title
Design and manufacturing of a “Stair Climbing Vehicle” modifying the
“Shrimp Rover Model” of EPFL
Abstract
To cope with the rough terrain encountered on any destined location, new locomotion
concepts for rovers and micro-rovers have to be developed and investigated. Scientific
exploration in hostile and rough surfaces like deserts, volcanoes, in the Antarctic or on
other planets where it’s dangerous for human locomotion, rover type stair climbing
vehicles can play the role of an efficient alternative. In this paper, the designing and
manufacturing of such kind of vehicle, which can climb stair or move along very rough
surface have been done considering two particular mechanisms. In the design of this
vehicle, the technical issues are also taken care of by assuring the stability of the
mechanisms applied and speed of the vehicle using gear motors while climbing stairs
and obstacles.
A ‘STAIR CLIMBING VEHICLE’ that is designed by following the mechanism of a
Shrimp Rover Model of EPFL ((Swiss Federal Institute of Technology Lausanne),
Switzerland) described in this paper. This stair climbing vehicle is able to climb stairs,
move on flat and rough surface. Here, we have detailed the designing and
manufacturing of such kind of vehicle. Along with building a well-functioning prototype,
experimental demonstration has been done with the final construction and the result
recorded is very promising.

CONTENTS
Page No.
i. Title & Abstract 02
ii. Introduction 04-05
iii. Model Description 05-06
iv. Parts of Model 06-11
 Front wheel 06
 Parallel bogies 06-07
 Rear wheel 07
 Base 07-09
 Wheels 10
 Motor 10-11
 Rivets 11
v. Assembly 12-14
 Structure Assembly 12-13
 Wheel Assembly 13-14
vi. Experimental Results 14-15
 Motion in stairs 14-15
 Motion in inclined planes 15
vii. Measurements 15
viii. Influence of The Friction Coefficient 16
ix. Power Distribution 16
x. Materials Used 16-17
xi. Comparisons 17-20
xii. Uses 21-22
xiii. Limitations 22
xiv. Future Recommendations 23
xv. Conclusion 23

Introduction
In the last two decades, over 300 concepts on stair climbing vehicles have been
generated and discussed. Most of the designs for Stair Climbing vehicle is based on
tri star wheel mechanism, caterpillars and legs rovers. To climb the stairs, the vehicle
needs to show strong off-road capabilities. Wheeled vehicles are the optimal solutions
for well structured environment like roads or habitations. But off-the road, their
efficiency is very much dependent on the typical size of obstacles encountered that
have to be overcome in a standard motion mode and they can typically overcome
obstacles which are half of their wheel size, also if the friction is high enough. But real
climbing abilities can be added to a wheeled rover using a special strategy.
Study of the classification of locomotion concepts makes the difference between active
and passive locomotion. Passive locomotion is based on passive suspensions, that
means no sensors or additional actuators to guarantee stable movement. On the
contrary, an active robot implies a close control loop to keep the stability of the system
during motion. It is clear that active locomotion extends the mobility of a robot but
increases the complexity and needs extended control resources. With the actual
speed of the controllers, it is yet imaginable to perform active locomotion and this is
one of our research axes. High complexity of active robots and the poor climbing
abilities of passive systems motivated us to develop and investigate new locomotion
concepts for passive and wheeled rovers.
‘The Shrimp Rover’ is highly suitable for these kind of missions because of its
unconventional wheel order, in-built passive adaptability and good ability to climb
obstacles. In this project, a ‘STAIR CLIMBING VEHICLE’ is designed following the
mechanism of a Shrimp Rover Model of EPFL (Swiss Federal Institute of Technology
Lausanne), Switzerland. This stair climbing vehicle is able to climb stairs, move on flat
and rough surface. The purpose of this report is to represent the mechanisms applied
and the entire job done to design & build the structure for the vehicle. From the starting
of the work, our goal was to conceive and build a unique vehicle based on the following
characteristics: a) Passive overcoming of steps of 2 times it’s wheel diameter b)
Wheeled rover showing good off-road abilities 3) Maximum gripping capacity and
stability during motion even in rough terrain. The project is successfully done by

researching of mechanisms, design, structure building, assembly and finally
demonstrating for several times. The result of this project is a first prototype
manufactured in our lab that shows the performance which satisfies our expectations.
The presentation of this prototype and its test results are the subject of this article.
This report is to demonstrate an example of stair climbing vehicle designed by group
8.
Model Description
The designed model is an innovative long-range rover architecture with 6 motorized
wheels. Using a rhombus configuration, the rover has a steering wheel in both, the
front and the rear, and two wheels arranged on a bogie on each side. The steering of
the rover is realized by synchronizing the steering of the front and rear wheel and the
speed difference of the bogie wheels. This allows for high precision maneuvers and
even turning on the spot with minimum slip. Although our bogies have a special
geometry, it is the same basic principle as used for a train suspension: a couple of two
wheels mounted on a support which can freely rotate around a central pivot. The rover
is designed to keep all its 6 motorized wheels in contact with the ground on a convex
ground up to a minimal radius of 30 cm and on a concave ground up to a minimal
radius of 35 cm. The total weight of the rover is 2.5 kg.

Fig-1: Shrimp Rover (schema form)
The use of parallel articulations for the front wheel and the bogies enables the
opportunity to set a virtual center of rotation at the level of the wheel axis while
maintaining a high ground clearance. This ensures maximum stability and climbing
abilities even for relatively low friction coefficients between the wheel and the ground.
PARTS OF THE MODEL:
1. Front wheel: The front wheel is connected
with a four bar mechanism. In a four bar
mechanism, the link on which input motion is
applied is known as driver. The output motion link
is follower and the middle link connecting these two
links is coupler link. The fourth links grounded. A
four bar mechanism has single degree of freedom.
Fig-2: Front bar(*Marked in blue*)
2. Parallel Bogies: It consists of a set of links, which form a couple of two
wheels, mounted on a support that can freely rotate around a central pivot. We used
Fig-3: Parallel Bogies (*MARKED IN BLUE*)

C-section links to build the frame of the bogies. The C-section allows for the frame to
be sufficiently light without compromising on its strength and rigidity. We used two
different cross-section sizes for the C-section links such that amongst the two, the
smaller one could be perfectly inserted inside the bigger one. The frame was so formed
that no adjacent links were of the same cross-section, thus, permitting us to create a
freely rotating revolute joint by merely using a rivet. It is advised to exercise caution
during the manufacture of the two bogies, because they need to be greatly identical.
Any mismatch between the twins will give rise to non-uniform travel of rover.
3. Rear wheel: The rear fork is a fixed link, at the end of which a wheel is
mounted. It too, has a steering system to rotate the wheel.
Fig-4: Rear Wheel (*MARKED IN BLUE*)
4. Base: A base is made to hold the total structure. It is a normal rectangular
shaped structure made by joining 4 parts perpendicularly one after another. Similar
two structures connected by connectors to make it a box shaped so that the front, rear
and side bars can be joined accurately and control the movements. The base is shown
in the fig below.

Fig-5: Rear Wheel (*MARKED IN BLUE*)
The front bar is a ‘Four Bar Mechanism’ is used. In four bar mechanism shown in the
picture link 1 is fixed in both ends where other ends are free. Here the front bar is
connected in two fixed points with the base. Those are the two fixed points of the four
bar mechanism (Marked in blue in the figure below).
Fig-6: Front bar connected with base Fig-7: Four bar mechanism

Fig-8: working mechanism of front bar
The side bars is connected with the base in such a way that it can move centering the
joints smoothly. Rivets being used for giving this kind of motion.
Fig-9: parallel Bars connected with Base (*MARKED IN BLUE*)

6. Wheels: Six wheels used of diameter 63mm/6.3cm with 6 motors. One each
for front & rear part and two each in two parallel side bar. The wheels have rubber tire
FIG: Wheels and circular thread on the tire gives the wheels a better grip so that it.
doesn’t slip on the plane. As better grip is very much important for this vehicle we have
chosen these wheels.
Fig-10: Wheels
7. Motor: Powerful motors used with wheels to create the force to climb heights.
Metal gear motors of 12V is used. In this vehicle motor of two different rpm is used.
For front and rear wheel the motor is of 350rpm.For parallel bars is of 450rpm.
Fig-11: Gear Motors 450 & 350 rpm

Fig-12: Gears inside motors
8. Rivets: Rivets are used to join selected links of the structure so that those can
slide. Two different types of rivets used here, i) Solid rivets and ii) Blind rivets. Blind
rivets are used for fixed joints. But solid joints are used to join movable joints like the
front bar and the parallel bogies.
Fig-13: Rivets ( Solid , Blind)

ASSEMBLY:
Fig-14 : Assembled model (Designed in Solidworks 2015)
Structure Assembly: TO begin the main assembly at first the base is made.
The front bars, rear links and the side bogies were joined as designed. Then these
parts were connected with the base in the right position.
Fig-15: Structure

Fig-15: Structure assembled
Wheel Assembly: As the Wheels are parallel to the bars the motors are
perpendicular to the bars. For that, keeping the motor joined with the bars a motor
holder is made. Pictures of motor mounted with the structure is given.
Fig-16: Front &Rear Wheel Fig-17: Parallel bogies

Fig-17: Motor, Shaft holder, Wheel, Fig-18: Wheel connected with motor
Connecting screws
Experimental Results:
 Motion in stairs: One of the requirements of this rover was the overcoming
of a step which height had to be at least 1.5 times the wheel diameter. The fig
below shows the main sequences of the rover climbing a step.
Fig-18: Motion in stairs

First, the front fork gets on the step, the wheel contacts with the steps, gives a
backward force in the links. Then the energy accumulated in the upper links.
The front wheel goes up and helps the first wheel of the bogie to climb. When
the second bogie wheel is in contact with the wall, the bogie turns around the
step. At this time the center of gravity reached almost its final height. Finally,
the last wheel can easily get on the step.
 Motion in inclined plane: The vehicle can easily run on inclined plane of
60˚.For higher friction coefficient between the surface and the wheels because
of the rubber tire, the grip is strong. Therefore, the vehicle easily climbs some
larger than 60˚ inclined surface.
Measurement of Specifications:
a. Length of the vehicle: 18 inches
b. Width: 7.87 inches
c. Maximum average speed: 54.2 in/sec (137.668n cm/sec)
d. Weight: 2.5 Kg
e. Height: 22.9 cm
f. Inclination angle of step: 0˚
g. Maximum riding capacity: 3.5 inches
h. Maximum climbing Ramp angle: 60˚
Measurement of speed:
Over flat surface:
Test 1 = 54.55 in/sec
So the maximum average speed = 54.2 in/sec
Speed per stair:
So the maximum average speed = 8.09 in/sec

Influence of the Friction Coefficient: A rolling wheel requires a certain
amount of friction so that the point of contact of the wheel with the surface will not slip.
The amount of traction which can be obtained for an auto tire is determined by the
coefficient of static friction between the tire and the road. In This vehicle frictions has
a very important role to play. Here we need wheels with better grip that has a good
friction coefficient with the stairs made of cardboard for testing. Wheels of good rubber
tire is used which as a friction coefficient of around 0.7 with cardboard. For that the
wheels will get a better grip on the plane, have full contact with the surface and for the
torque of motor the vehicle will climb up the stairs. Here plastic wheels are not used
because of the friction coefficient goes down to around 0.3, for that the rover will not
able to climb stairs.
Power Distribution:
The vehicle is powered by 11.1V, 3000mAh dc supply directly to run the vehicle. And
a switch is added to power the vehicle. The speed is not controlled. The whole circuit
is kept tightly on the base so it cannot move while the vehicle is in motion.
Fig-19: Li-po battery( 12V, 3000mAh)
Materials Used: Mainly for this kind structure the material very important.
Because the links here cannot be much heavy that they cannot lift up. So at the time
of choosing material for this structure the weight is mainly considered. The material

had to be of some kind which is light weight, strong, hard enough, corrosion resistant
and suitable for machining.
For that steel and aluminum, between these two aluminum was taken as the material
because it’s light weight. The main links of the structure is made of Aluminum. For that
the body is very light and strong. As we get heavy motor to run the vehicle the body
had to be light weight.
Beside aluminum we have also used 2 bars of mild steel to hold the motors in the front
and rear wheel. Though it doesn’t satisfy the fact of light weight but aluminum bars
can break if bent. That’s why angles of certain measurement of mild steel is used on
that purpose.
Fig-20: Aluminum plates and 2cm wide pieces used for structure
Previous models:
There are some models of stair climbing vehicle using the same or different
mechanism in the past. Some has been made in our university and some in others.
Some of the previous models is shown in figures.

Courtesy: Prof. Dr. Engr.
Alamgir Hossain , Team 7 ME-
08.Disign modification of a stair
climbing vehicle.
Alamgir Hossain,
Nafis Ahmed Chowdhury,
Rubaiat Islam Linda,
Shamimuzzaman Akhtar;
“Design and Manufacturing
of Stair Climbing Vehicle”
Proceedings of the
IEOM, International
Conference on
Industrial Engineering and
Operations Management
(IEOM),Dhaka, Bangladesh
Alamgir Hossain, Mustafa
Shafee Saleheen Towfique,
Tauhidul Hossain;
“Design Modification and
Manufacturing of an
Intelligent
Stair Climbing vehicle with
self-controlled
system”

Fig-21: Aerial View of the previous models (From Left to right)
Fig-22: Front view of the previous models (from left to right)
Fig-23: Side view of the Previous Models (From left to right)

Comparison with the Previous Models:
Serial Characteristics
Previous
Model 1
Previous
Model 2
Previous
model 3
Number
Modified
model
1 Weight 30 kg 22 kg 4.5 Kg 2.5kg
2 No of wheels 04 04 04 06
3 Maximum Speed 0.295 in/sec 1.18 in/sec 4.376 in/sec 54.2 in/sec
4 Wheel Frame Depends on Depends on Independent
sensor sensor independent
5
Number of
motors 2 AC motor 1 AC motor 3 DC Gear Motor
6DC gear
motors
6 Clutch system Not available Available Not Available Not available
7 Chain System Complicated Simple Not available Not available
8 Sensor Not Available Available Not Available No sensors
9 Wheel Frame Mild Steel Aluminum Wood Aluminum
made of
10 Gears Mesh Not Available Not Available Available
between Motor Not available
and Shaft
11 Front and Rear Not Available Not Available Available Available
Wheel
12 DC motor Used Not Available Not Available Available Available
13 Forward and Not Available Not Available Available Available
Reverse
movement from
same position

Uses:
 Rover: Planetary exploration rovers need to show strong off-road capabilities due
to the unstructured environment met during their mission. Wheeled rovers are the
optimal solutions for well structured environment like roads or habitations. But off-
the road, their efficiency is very dependent on the typical size of encountered
obstacles that have to be overcome in a standard motion mode. As this model can
easily ran through a rough surface, climb obstacles it can be used as a rover. This
is the case for Sojourner [STO96], its son Rocky 7 [VOL97] or Micro5[KUB99],
which can typically overcome obstacles of their wheel size, if friction is high
enough. Adding real climbing abilities to a wheeled rover requires the use of a
special strategy and often implies dedicated actuators like for the Marsokhod
[KEM92] and Hybtor [LEP98] or complex control procedure like for the SpaceCat
[LAU98] or for the Nanorover [TUN99]
 Remote controlled transportation: In the era of science we use
various remote control robots for short and long distance transportation. Normally
these bots can move in plane surface. Its tough to climb and lower down the stairs
by sensing. But this model provides a light weight design with simple mechanism
that can climb stairs at normal speed using only the mechanism.
 Terrain Robot: All-terrain robots are supposed to handle a wider variety of
terrain than ordinary robots. Whatever the terrain surface is (tough terrain, steep
slopes, sand, etc.) the bot has to run.
Our model can also be used as a terrain robot if some modification is done. To
make it a terrain robot a few thing just needs to be modified. Such as, the model
needs to be a little heavier as well as stronger and the wheels for that have to be
of larger diameter with a good thread on that. The structure might be a size
bigger also.
 Military Operations: This technology has applications as military robots or
security robots in urban environments where stair climbing and agile operation is

an essential part of the mission. The robot is not only a stair climbing robot but
operates in terrain where wheeled robots would operate.
 Others: Including these main uses this model can be used also for;
 Rescuer
 Racing bot
 Surfing dangerous or inaccessible areas
Limitations:
Even though the designed structure has a lot of advantage, it has certain limitations
as well.
 The vehicle has one directional movement, it cannot move left or right.
 The vehicle cannot climb beyond the specified height.
 The vehicle do not have any speed control. The motors are powered directly from
the battery and a switch is used as a remote. So when the vehicle is turned on it
starts to run at its full speed. But to climb down the speed must be low.
 The machining was done in normal workshop, so there are machining errors. And
very small margin of errors occurs big problems in movement. Like, the two parallel
bogies are not exactly same. It creates some unwanted directional errors while
climbing stairs.
 All the rivet joints do not give exactly same performance which creates some
unwanted vibrations at different portions.
 The vehicle do not move in a perfectly straight line. There is some machining error
in the front bar mechanism. For that that the front wheel makes a small angle with
the body which takes the vehicle out of the line from which it should be moving.
 The motors are not giving enough torque. High torque and bigger wheel diameter
help to climb higher height.
 The movable joints of the side bogies are not perfectly smooth. Frictional loss in
those joints makes the job hard for the vehicle, specially at the joint of bogie with
the base.

Future Recommendations:
This stair climbing vehicle designed has some limitations and errors. Those can be
developed in the future operations. In future updates of the model some of the
limitations must be fixed and some facts should be taken care of. Such as:
 Motors of high torque have to be used for better efficiency.
 Structure design has to be perfect so that it can climb the average height of
stairs.(14-16 cm)
 The machining should be done precisely. The holes have to be accurate and
the joints should be fastened as it needed to be.
 The alignment of the front wheel has to be made carefully so that the vehicle
moves perfectly in a straight line.
 Battery of higher power should be used to power the motors. That will help to
climb and also increase the average running speed of the vehicle.
 A coding system to run the vehicle remotely. Controlling the power input in the
motor using PWM speed can be controlled. It will add extra cost but it is an
important upgrade to be done for the vehicle.
 Servo motors to be used to move the vehicle also left and right.
 Sensor would be use to avoid the heights it cannot climb and go other
directions.
Conclusion
In this paper we have described the details of a well-functioning prototype of a STAIR
CLIMBING VEHICLE that has been designed and manufactured by following
theoretical analysis. The purpose of this paper was to document how the entire
structure of this project is designed and built to investigate for a further developed
example of autonomous rover vehicles. This rover is the perfect candidate for long
range planetary missions as well as for operations in environment that are both
structured and unstructured like for space construction robotics. Terrestrial
applications are also numerous: indoor and outdoor surveillance, ventilating shaft
cleaning, mining and construction machines, agriculture, post-earthquake assistance
or even mine clearance if good sensors appear.

Design, Modification and Manufacturing of a Stair Climbing Vehicle

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Design, Modification and Manufacturing of a Stair Climbing Vehicle

Similar to Design, Modification and Manufacturing of a Stair Climbing Vehicle (20)

Recently uploaded

Recently uploaded (20)

Design, Modification and Manufacturing of a Stair Climbing Vehicle