DESIGN AND FABRICATION OF SMART CHAIR
A PROJECT REPORT
Submitted by
NAME ENROLLMENT. NO
1. Patel Hardik 140980119064
2. Chaudhary Jimesh 140980119025
3. Joshi Maulik 140980119026
4. Chorasiya Dhaval 140980119018
In fulfillment for the award of the degree
Of
BACHELOR OF ENGINEERING
In
mechanical
HANSABA COLLEGE OF ENGINEERING & TECHNOLOGY SIDHPUR
Gujarat Technological University, Ahmedabad
MAY, 2018
HANSABA COLLEGE OF ENGINEERING & TECHNOLOGY SIDHPUR
EXTERNAL EXAMINOR APPROVAL
CERTIFICATE
Date:
This is to certify that the dissertation entitled ‘ DESIGN AND FABRICATION OF SMART CHAIR ‘ has been carried out by Patel Hardik (140980119064), Chaudhary Jimesh(140980119025), Joshi Maulik(140980119026), Chorasiya Dhaval(140980119018) under my guidance in fulfillment of the degree of Bachelor of Engineering in mechanical (8th Semester) of Gujarat Technological University, Ahmedabad during the academic year 2018-19.
Guide: Head of the department
PROF SUDHIR V CHAUDHARY PROF.KUMELNNAGORI
ACKNOWLEDGEMENT
I have taken efforts in this project. I would like to extend my sincere thanks to all of them. I am highly indebted to pro . Sudhir Chaudhary sir for their guidance and constant supervision as well as for providing necessary information regarding the project & also for their support in completing the 8th semester project design work. I would like to express my gratitude towards my group member of Group no 30 for their kind co-operation and encouragement which help me in completion of this project .My thanks and appreciations also go to my colleague in developing the project and people who have willingly helped me out with their abilities.
ABSTRACT
Through this topic we would try to Make a Remote Controlled Wheelchair ‘ for The Different Disabled people, Small Kids, People who are unable to walk etc’. ‘ Component that we used are Wheels, remote ,motor , wires, acrylic seat etc.
In these days there is lot of Chairs available in the markets. But we are going to Make a chair for disabled patients.
Even though many research studies have been reported in different fields to increase the independence of wheelchair users, the question of overcoming obstacles by a wheelchair always remains as topic of discussion for many researchers. In our project a motor operated stair climbing wheelchair concept which can overcome the architectural barriers to a considerable extent has been developed. This project involves the design of an ergonomically designed battery powered wheel chair for multipurpose use. Stair climbing functionality is embedded in the design through its structure and mechanism. All the design parameters of wheelchair were based on the standard design of the stairs in India. Major part of the project focuses on the proposed design concept and concludes by discussing upon the physical working model developed for the proposed design solution.
Keywords: Wheels, Gear motors acrylic seat, wires , motor operated, stair climbing etc
LIST OF FIGURES
Figure No Figure Description Page No
1 Lateral Stability 25
2 Longitudinal Stability 27
3 Centre stage Stairs 31
4 Calculation at centre stage 32
CONTENT
TITLE PAGE NO.
ACKNOLEDGEMENT I
ABSTACT II
LIST OF FIGURES III
LIST OF TABLES IV
CHAPTER: 1 INTRODUCTION
1.1 DEFINATION 8
1.2 NEED AND MOTIVATION FOR 9
THE SECTION OF THE PROJECT
CHAPTER:2 AIM AND OBJECTIVES
2.1 AIM 11
2.2 OBJECTIVES 11
CHAPTER: 3 LITERATURE REVIEW
3.1TYPES OF WHEEL CHAIR 12
3.2 VARIOUS TECHNIQUE USED IN WHEELCHAIR CONTROL 14
3.3 DRAW BACKS OF PRESENTLY AVAILABLE WHEELCHAIRS 15
CHAPTER: 4 MATHODOLOGY
4.1 DESIGN REQUIREMENT & 22
SPECIFICATION
4.2 Related Concepts
4.1.1 TRACTION AND SLIP 22
4.1.2 LATERAL STABILITY 24
4.1.3 LONGITUDINAL STABILITY 27
4.1.4 STATIC STABILITY FACTOR
4.3 Calculations
4.3.1 DIAMETER OF WHEEL 29
4.3.2 CALCULATION OF WHEEL BASE 31
4.3.3 LENGTH OF LINKS 32
4.3.4 HEIGHT CALCULATION 34
4.3.5 TRACK WIDTH 35
CHAPTER: 5 CONCLUSIONS
5.1 CONCLUSION 36
5.2 BUDGET AND TABLE OF REQUIREMENTS 36
CHAPTER: 6 FUTURE SCOPE 38
CHAPTER: 7 REFERANCE 39
1 Introduction
1.1 Defination
A stair climbing mechanism is a semi-automated vehicle, which has the capability to climb the stairs easily. Stair climbing is one of the most attractive performances of mobile robot. Stair climbing mechanism is utilized mainly for two purposes, one is for making stair climbing wheel chair and other is for the shifting of heavy objects. It is more helpful for the physical handicapped persons and the persons who are unable to climb the stairs. So the freedom of mobility for a handicapped person increases. And heavy objects can be shifted from ground floor to top floor through the stairs
There is an increasing need for mobile robots which can operate in unstructured environments with highly uneven terrain. These robots are mainly used for tasks which humans cannot do and which are not safe. To achieve these tasks, any mobile robot needs to have a suitable mobile system according to each situation. Among these mobile systems, it’s the rocker-bogie suspension system that was first used for the Mars Rover Sojourner and it’s currently NASA’s favored design for rover wheel suspension. The rocker-bogie suspension is a mechanism that enables a six-wheeled vehicle to passively keep all six wheels in contact with a surface even when driving on severely uneven terrain. There are two key advantages to this feature. The first advantage is that the wheels' pressure on the ground will be equilibrated. This is extremely important in soft terrain where excessive ground pressure can result in the vehicle sinking into the driving surface. The second advantage is that while climbing over hard, uneven terrain, all six wheels will nominally remain in contact with the surface and under load, helping to propel the vehicle over the terrain. Exploration rovers take advantage of this configuration by integrating each wheel with a drive actuator, maximizing the vehicle's motive force capability. One of the major shortcomings of current rocker-bogie rovers is that they are slow. To be able to overcome significantly rough terrain (i.e., obstacles more than a few percent of wheel radius) without significant risk of flipping the vehicle or damaging the suspension, these robots move slowly and climb over the obstacles by having wheels lift each piece of the suspension over the obstacle one portion at a time. While performance on rough terrain obstacles is important, it should be also considered situations where the surface is flat or it has almost imperceptible obstacles, where the rover should increase its speed to arrive faster from point A to point B.
1.2 Need and Motivation for the selection of the project
Rocker-bogie suspension system in Smart Wheel Chair that was first used for the Mars Rover Sojourner and it’s currently NASA’s favored design for rover wheel suspension. This is a very less explored field of study and could be developed into exploration purpose instrument. The need to develop specialized high-fidelity systems capable of operating in harsh earth environments typically leads to longer development timelines and greater expenditures. While specific applications will always require unique designs, there are many commonalities in planetary rovers. Issues such as mobility, navigation, and vision, may differ slightly between missions but are largely the same in most scenarios. Given these fundamental characteristics of many planetary rovers we believe that a modular and ruggedized system meeting these basic requirements would aid in the process of developing space-ready technology. There are currently many mobile research platforms available, yet few are designed to operate in the harsh earth environments that are often used for planetary surface rover testing. By creating a rover that is suitable for these types of environments, our goal is to facilitate the development of rovers and their related technologies, in addition to lowering development costs. We also hope that the platform developed can be tested and improved upon, to potentially serve as a model for a rover that could go to the moon or Mars in the future.
Our mission is to design, develop, and test a rover to serve as a research platform, suitable for testing planetary surface exploration technologies in harsh earth environments. The design will focus on incorporating features that are believed to be essential for most planetary exploration missions.The Rocker bogie Suspension system can be sent for reconnaissance purpose,which is exploring the surrounding to give a visualisation to a person or operator sitting somewhere for carrying the operation, by the help of a video camera. Hence, due to this feature of the rocker bogie suspension system this can be used in military for visualising the scenario at a region where a bomb is planted. Not only this, the rocker bogie suspension system can be developed into a wheel chair too to take the patients from one place to another climbing the stairs on its own. It can also be used for material delivery purposes. As explained this is a wide field of study and very less
2 AIM AND OBJECTIVES
2.1 AIM
The Main Aim of this project is to design a battery operated wheelchair , the speed and direction can be controlled by a touch screen .The wheelchair moves by means of Dc motor . Our motive is to provide them independent mobility for that they need a wheelchair which can be easily move . It should be not expansive and also it should be based on clean source of charging .Our another motive is to make a chair which can used by a store keeper ,In Medical stores, In Hospitals For different disabled peoples .It give them a respect from others and provide a batter and comfortable life.
2.2 OBJECTIVE
We will be focusing on eliminating the shortcomings of the rover. one of the major shortcomings of current wheel chair is not capable of climbing stair. In order to be able to overcome significantly rough terrain without significant risk of flipping the vehicle or damaging the suspension, these robots move slowly and climb over the obstacles by having wheels lift each piece of the suspension over the obstacle one portion at a time. While performance on rough terrain obstacles is important, it should be also considered situations where the surface is flat or it has almost imperceptible obstacles
3 LITERATURE REVIEW
3.1 Types of wheel chair
A handicapped person with locomotive disabilities needs a wheelchair to perform functions that require him or her to move around. He can do so manually by pushing the wheelchair with his hands. However, many individuals have weak upper limbs or find the manual mode of operating too tiring. Hence, it is desirable to provide them with a motorized smart wheelchair that can be controlled by bio-signal & non bio-signal approach. Since the motorized wheelchair can move at a fair speed with minimum efforts. There are different types of wheelchairs available now days which are discussed below.
A. Manual Wheelchairs
These are the type of devices that help a person to move him without any assistance of battery. There are three types of manual wheelchairs namely self-propelled, attendant propelled, and wheelbase. A single-arm drive enables the user to turn either left or right while the two-armed drive enables user to move forward or backward on a straight line. Another type of wheelchair commonly used is a lever-drive wheelchair. This type of chair enables the user to move forward by pumping the lever back and forth [1].
B. Electric Wheelchairs
A power chair can be used by someone who hasn’t got the dexterity or mobility, perhaps, to drive a mobility scooter due to arm, hand, shoulder or more general disabling conditions, and do not have the leg strength to propel a manual chair with their feet. Powered wheelchair can offer various powered functions such as tilt, recline, leg elevation, seat elevation, and others useful or necessary to health function [1].
C. Standing Wheelchairs
‘Redman power chair’, it is the world’s highest quality standing wheelchair. People with spinal cord injury can reap the health benefits of standing wheelchair. Physical benefits of standing wheelchairs are
Decrease urinary tract infection problem
Improver blood circulation around the body
Standing exercise greatly improve bowl function
Wheelchair helps distribute your weight and improve healing bed sores
Decrease the amount of muscle stiffness
Increase bone density
D. Pediatric Wheelchair
These types of wheelchair provide a key-enabling technology to young children who would be unable to navigate independently in their environment. Standard powered wheelchairs are still heavily dependent on the cognitive capabilities of users. Unfortunately, this excludes disabled users who lack the required problem-solving and spatial skills, particularly young children. For these children to be denied powered mobility is a crucial set-back; exploration is important for their cognitive, emotional and psychosocial development [3].
E. STAIR CLIMBING WHEEL CHAIR
The stair-climbing wheelchair exists at present can be grouped into 3 categories: – continuous stair climbing wheelchair, intermittent-stair climbing wheelchair and auxiliary stair climbing wheelchair. Continuous stair climbing wheelchair has only one set of supporting device, the wheelchair relies on this supporting device for continuous motions. In Intermittent stair climbing wheelchair the process of climbing stairs of is similar to the people climbing up and down stairs, it is also called walking stair climbing wheelchair. Intermittent stair climbing wheelchair is one of the supporting devices that elevate the wheelchair and other set of support system. In auxiliary stair climbing wheelchair, the attachments rely on another device installed on the wheelchair and it needs assistance to help realize the function of climbing stairs. Stair lift requires wide stair way which is very expensive [4].
3.2 Various Technique use in wheelchair control
There is a vast development in the field of wheelchairs. Out of all the methodologies, HCI (Human Computer Interface) and HMI (Human Machine Interface) are the latest and most effective techniques. In user interface systems both bio-signals and non bio-signals are used as a medium of control. Bio-signal based devices mainly use bio-signals like EEG, EOG or EMG as control signals. The bio-signal based approach is used for completely paralyzed patients who can only use their bio-signals as the only resource to control [5].
A.EEG based
The Electroencephalography (EEG) records electrical brain signals from the scalp, where the brain signal originates from post-synaptic potentials, aggregates at the cortex, and transfers through the skull to the scalp. BCI is a device that extracts EEG data from brain and converts it into device control commands using signal processing techniques. EEG techniques are non-invasive and low cost. However, it brings great challenges to signal processing and pattern recognition, since it has relatively poor signal-to-noise ratio and limited topographical resolution and frequency range [6, 7, and 8].
B. EMG based
EMG measures electrical currents that are generated in muscles during its contraction. A muscle fiber contracts when it receives an action potential. The EMG observed is the sum of all the action potentials that occur around the electrode site. In almost all cases, muscle contraction causes an increase in the overall amplitude of the EMG. EMG signals can be used for a variety of applications including clinical applications, HCI and interactive computer gaming. They are easy to acquire and of relatively high magnitude than other bio-signals. On the other hand, EMG signals are easily susceptible to noise. EMG signals contain complicated types of noise that are caused by inherent equipment noise, electromagnetic radiation, motion artifacts, and the interaction of different tissues. Hence preprocessing is necessary to filter unwanted noise in EMG. The EMG signals also have different signatures depending on age, muscle development, motor unit paths, skin fat layer, and gesture styles. The external appearances of two individuals’ gestures might look identical, but the characteristic EMG signals are different [9].
C. EOG based
EOG based technique are very useful for persons who born with any congenital brain disorder or for those who are suffer from severe brain trauma. EOG signals records the potential difference between the retina and cornea of the eye. When the eyes are rolled upward or downward, positive or negative pulses are generated. As the rolling angle increases, amplitude of pulse also increases and the width of the pulse is in directly proportional to the eyeball rolling process [10, 11].
C. Non Bio-signal based
Non bio-signal based devices provide 100% accuracy and require less training for patients. In general, non biosignal based techniques which make use of joystick control, sip-n-puff control, tongue control, Touch screen controlled, Voice actuated, head movement tracking etc [5].
D. Sip-n-Puff Technology
In this method using air presser to generates control signals by sipping (inhaling) or puffing (exhaling) in a tube. This technology generates four control signals for motorized wheelchair which are initial hard puffs, hard sip, initial hard sip, and hard puff. It is mostly used for quadriplegics having injury in their spinal cord or people with ALS. But this is not good for individual with week breathing.
E. Head Orientation Tracking Technique
Here in this method, head movements are transformed into cursor movements on the screen. Cursor movements are proportional to head movements. Head movements are calculated by different methods like accelerometer placed in a patient’s cap or by capturing video of head movements. But the problem with this technique is that differentially able people of certain categories such as cerebral palsy patients cannot even move their head comfortably. Another problem of this technique is that forehead continuously needs to face the camera [12, 13].
F. Chin Control Technique
In this technique chin is put in cup shape joystick and is usually controlled by neck movements (flexion, extension, and rotation). The major problem that arises in this mode of control is the need for constant pressure in chin cup [14].
G. Eye Tracking Technique
In this technique wheelchair is controlled by an optical type eye tracking system (screen based system). Camera is used to continuously track the features of eye. There after a calibration algorithm is used to find the direction of eye gaze in real time. Than according to gazed position, screen movement control signals are calculated to control the wheelchair [15, 16 and 17].
H. Tongue Controlled
This technology is based on Faraday’s law. Permanent magnet is used here and is attached to tongue. As the tongue move in air core induction coil, the inductance is changed. A Hall Effect sensor is placed in the stud of tongue. Hall Effect sensor is a transducer that varies its output in response to change in magnetic field. The movement of tongue is traced by of Hall Effect sensor. Thereafter, the Output signals are collected that provide continuous real time analog output [18].
I. Image Processing Algorithm
Here, webcam is used for capturing image input from the finger of user. After that we use an image processing algorithm (image blurring, RGB to HSV conversion, HSV thresholding) that helps in finger detection. According to direction of finger, wheelchair moves in left-right or in front back direction [19].
J. Brain Actuated Wheelchair using Brain Wave Sensor
There is billions of interconnected neuron in human brain. The way, neurons are connected to each other depicts the various thought processes and emotional states. This pattern of neurons connection keeps on changing according to the human thought
process different electrical signals. For sensing these electrical signals, brain wave sensor is used that convert the data into packets- which are transmitted through bluetooth medium. Level analyzer unit (LAU) is used to receive raw data. The extraction and processing of the signal is done using Matlab platform. The control commands are transmitted to the robotic module to process. With this entire system, any robot can be moved according to the human thoughts and it can be turned by blink muscle contraction. By using this brainwave concept executed in wheelchair the handicap can easily controls wheel chair [20].
K. Accelerometer Based
In accelerometer based wheelchair, we have an acceleration sensor that is also known as tilt sensor. When we tilt the object, the values registered by sensor are changed and these values are given to microcontroller. Depending on the direction of the tilt, microcontroller controls the wheelchair directions as LEFT, RIGHT, FRONT and BACK [21].
L. Based on Deictic Approach
The deictic approach uses the vision of the environment as a control interface. This vision must be as close as possible to the perception of the user so that the interface is intuitive and therefore easy to use. To move, the user specifies the location within the environment he wants to go to by pointing at it on the interface. Then the wheelchair will move automatically to that position. As the command is given from time to time, it does not require much effort from the user [22].
M.Touch screen controlled
The mode of input control to the wheelchair is touch screen. When user wants to change the direction, the touch screen sensor is modeled by pressing finger against the various quadrants on the touch screen, which has different values for different direction [23].
N. Voice actuated
In this technique user speak in microphone and the voice recognition system compares the voice command with pre-stored memory and generates a control signal to control the movements of wheels [24, 25 and 26].
3.3 Draw Backs of Presently available Wheelchair
Most significant technical issue in the currently available wheelchairs is cost versus accuracy. Unavailability of wheelchairs for particular disabilitiy is also a considerable issue. Also, the present systems are unable to monitor the surrounding conditions and the health condition of the patient. There is also no wheelchair available till date for the bed lying patient. No wheelchair available for mentally challenged people also. Above all the other important aspect to consider is the physical barrier that place additional requirement on strength and durability of wheelchairs.The initiation of rocker bogie suspension system can be traced to the development of planetary rover which are mobile robots, especially designed to move on a planet surface. Early rovers were tele-operated like the Lunokhod I while recent ones are fully autonomous, such as FIDO, Discovery and recently developed Curiosity mars exploration rover. The rovers needed to be very robust and reliable, as it has to withstand dust, strong winds, corrosion and large temperature changes under mysterious conditions. Maximum rovers remain powered by batteries which are recharged by solar panels during the day installed over there surface.
The locomotion system of rovers remains crucial to enable it to reach objective sites, conduct research, and collect data and to position itself according to the demand. There are three main types of rover locomotion developed so far i.e. wheeled, legged and caterpillar locomotion. The main difference between the miscellaneous designs of planetary robots lies in the type of locomotion system. Even after developing many legged and hybrid robots, most researchers still focus on wheeled locomotion for rovers because of its locomotive ease and advantages and among wheeled locomotion design, the rocker bogie suspension system based design remain most favoured. The ancient FIDO rover and the Sojourner contain 6 independently steered and driven wheels suspended from a rocker-bogie mechanism for maximum suspension and ground clearance. Rocky Seven Rover has a similar suspension system just differ in front wheels. The Nanorover&Nomad Rovers have four steered wheels suspended from two bogies & CRAB Rover utilizes two parallel bogie mechanisms on each side to overcome obstacles and large holes. As far as the initial research is concerned, the software optimization seeks for an optimum in the constrained solution space given an initial solution and Dr. Li et al. derive a mathematical model to generalize rover suspension parameters which define the geometry of the rocker-bogie system. The objective behind evolution of rocker bogie suspension system is to develop a system which minimizes the energy consumption, the vertical displacement of the rover’s centre of mass and its pitch angle. In this research, our endeavour is to transfer these major advantages embedded with the rocker bogie system into conventional vehicles in order to remove discomfort and complexities present in conventional suspension system in general and suspension system of heavy vehicles in particular.
4 MATHODOLOGY
4.1 Design Requirement & Specifications
Our main goal is to design, develop, and test a rover to serve as a mobility platform, suitable for testing planetary surface exploration technologies in harsh earth environments. The design will focus on incorporating features that are believed to be essential for most planetary exploration missions based on research of past and current rovers. Given what we have learned about existing rovers and the types of missions they aim to accomplish, our design goals for our rover have been made into these categories:
Mobility and navigation
Size and weight restrictions
While our rover will not be travelling to space, it is our goal to make a robust and ruggedized platform that will be suitable for testing in harsh earth environments, on terrain similar to that of our moon and Mars. Given sufficient mobility in planetary environments, the rover must also be able to accommodate payloads,if possible. Transporting sensitive scientific instruments across rough terrain is the main goal for nearly all exploration rovers, and thus one of our central requirements. Additionally, to be useful for other users both in academia or industry, the rover needs to easily integrate new hardware and software as part of its payloads. By providing a robust mobility platform that can accommodate a wide range of payloads, the rover should prove useful to anyone interested in testing rover related technologies or conducting research in the field of space exploration. Lastly, the rover will aim to recognize the size and weight constraints that all space bound vehicles face. While there are many resource constraints that prohibit us from designing a space-ready rover, the design will attempt to accommodate space considerations when possible. In formulating the design specifications relating to mobility we wanted to ensure that the rover could traverse a wide variety of harsh Earth environments. Such terrain includes deserts, rock fields, gravel pits, sand dunes, and mountainous areas in many different climates.
In examining these terrains we will make design criterias relating to the size of obstacles, inclines, and speeds that the rover must achieve, in order to ensure that it could maneuver in many different environments. in most scenarios the ability to go over larger obstacles always increases mobility potential. For our rover we set the goal of being able to traverse obstacles, both positive and negative to the ground plane.
4.2 Related Concepts
4.2.1 Traction and Slip
The rover must maintain good wheel traction in challenging rough terrains. If traction is too high, the vehicle consumes a lot of power in order to overcome the force and move. If traction is too low, the rover is not able to climb over obstacles or inclined surfaces. Slip occurs when the traction force at a wheel-terrain contact point is larger than the product of the normal force at the same wheel and the friction coefficient. Hence, no slip occurs if the condition
Ti ‘ ”Ni
is satisfied. In reality it is very challenging to determine the precise friction coefficient ” for the interaction of two surfaces.
4.2.2 Lateral Stability
The rover is said to be stable when it is in a quasi-static state in which it does not tilt over. The simplest approach to find the static stability is using the geometric model, which is commonly referred to as stability margin. As the asymmetric suspension system of the passively articulated rover has a great influence on the vehicle’s effective stability, a more advanced approach is using a static model.
The lateral stability of the rover ensures that the rover does not tip sideways. As the rover has two symmetric sides, the geometric model is used to find the lateral stability of the vehicle. Lateral stability is computed by finding the minimum allowed angle on the slope before the rover tips over. Lateral stability is ensured if this angle is smaller
than the maximum angle of incline ” on the slope at the wheel-terrain contact points. The angles ”l and ”r are obtained geometrically. The overall stability angle ”stab can be computed by
”stab = min(”r,”l)
Lateral stability of the rover is ensured if the overall stability angle
”stab ‘ ”
.:. min(”r,”l) ‘ ”
Fig 4 Lateral Stability
Let N1 be the reaction on the right wheel and N2 be the reaction on the left wheel.
Let ” be the slope of the inclination, ”r&”l be the angle that the point of contact makes with the Centre of Gravity on the left and right wheels respectively.Zbe the height of the centre of gravity. And yl and yr be the perpendicular between the point of contact and the Centre of Gravity.
In this condition to ensure the stability the rover should not tip off the inclined. And hence the normal reaction on any of the wheel should not be 0. Taking moment at the left wheel.
Mg z sin ” + Mg ylcos ” = N1 (yl+yr)
Dividing the equation by z
Mg sin ” + Mg yl/z cos ” = N1 (yl+yr)/z
From the figure above the yl/z = tan ”l and yr/z =tan ”r
Mg sin ” + Mg tan ”lcos ” = N1 (tan ”l + tan ”r)
Let ”l”r and ” be very small then
Mg ” + Mg ”l = N1 (”l + ”r)
Mg( ” + ”l ) = N1 (”l +”r)
Mg > N1
( ” + ”l ) < (”l +”r)
” <”r
Hence to ensure stability this condition should be fulfilled.
4.2.3 Longitudinal Stability
The computation of the longitudinal stability of the rover makes use of a statical model as it is not symmetric in longitudinal direction. Using a statical model, the mechanical properties of the suspension system are taken into account. According to , longitudinal stability of the vehicle is given when all wheels have ground contact and the condition Ni > 0 is satisfied, where Ni is the normal force at wheel i. It should be noted that even though this condition is compulsory for the statical model to work, a physical rover does not necessarily tip if a wheel looses contact to the ground. However, it is less steerable.
Figure 5 Longitudinal Stability
4.2.4 Static Stability Factor
The Static Stability Factor (SSF) of a vehicle is one half the track width, TW, divided by h, the height of the center of gravity above the road. The inertial force which causes a vehicle to sway on its suspension (and roll over in extreme cases) in response to cornering, rapid steering reversals or striking a tripping mechanism, when sliding laterally may be thought of as a force acting at the CoG to pull the vehicle body laterally. A reduction in CoG height increases the lateral inertial force necessary to cause rollover by reducing its leverage, and the advantage is represented by an increase in the computed value of SSF. A wider track width also increases the lateral force necessary to cause rollover by increasing the leverage of the vehicle's weight in resisting rollover, and that advantage also increases the computed value of SSF. The factor of two in the computation "TW over 2h" makes SSF equal to the lateral acceleration in g's (g-force) at which rollover begins in the most simplified rollover analysis of a vehicle represented by a rigid body without suspension movement or tire deflections
4.3 CALCULATION
4.3.1 Diameter of Wheel
”DN
= 60
Assumed speed be 10 cm/s i.e. 100mm/s
Therefore,
”DN
100 = 60
DN=1909.86
D N
10 190.99
20 95.49
30 63.66
40 47.75
50 38.2
60 31.83
70 27.28
80 23.87
90 21.22
100 19.1
Table 2 Calculation of Diameter and RPM
So the selected D-N combination is-
D = 70 mm
N = 27.28 rpm
4.3.2 Calculation of Wheel Base
Fig 6 Centre Stage Stairs
= tan’1yx
= tan’1160400
Therefore, ” = 21.80”
Now, width of the stairs is 400 mm. So the maximum length of the rover can be 400mm.
To deduce the wheel base,
Total length ‘ (radius of front wheel + radius of rear wheel)
=400-(35+35)
=330 mm
4.3.3 Length of Links
Figure 7 Calculations at Centre Stage Stairs
Total Wheel base = 330 mm
Let us assume, ”=45”
In Triangle BNC, angle BNC = 90”
Angle NBC = Angle NCB = 45”
Therefore, NC = NB
NC2 + NB2 = BC2 ‘ (Pythagporas Theorem)
BC2 = 2(NC)2 ‘ (1)
=2(165)2
=54450
Therefore, BC = 233.33mm
Rounding off to 230mm
Substituting to eqn (1) we get,
2302 = 2(NC) 2
NC = 162.63
Also, AN = NC = 162.63
In triangle AMN, angle AMN = 90
AM2 + MN2 = AN2 ‘ (Pythagoras Theorem)
2AM2 = AN2
2AM2 = 162.63 2
AM = 114.99
=115 mm
Now, due to symmetry,
AM = MN = 115 mm
BM = AB ‘ AM
=230 ‘ 115
=115 mm
Therefore, BM = 115
4.3.4 Height Calculation:
Height2 = BC2 ‘ NC2
(2302 ‘ 162.632)1/2 = 162.639 mm
Net Height = 162.639 + 35 ‘ (net ht = ht + radius)
= 197.639 mm
4.3.5 Track Width
= 2′
1.3 = 2 ” 197.639
Tw = 513.86
5 CONCLUSIONS
5.1 Conclusion
This project will try reaching nearly all of our design requirements, and in many respects exceeding original design goals. Furthermore all components, mechanical and electrical, will be thoroughly tested as a completed system in real-world field testing conditions to validate their success. Overall, preliminary estimates for the general scope, budget, and timeline, for the project will be closely followed; with the exception if the project goes moderately over budget.
5.2 Budget and Table of Requirements
S. No Item Qty Material Budget Net
1 Link 4 Acrylic 90 360
2 Shaft 1 Acrylic 50 50
3 Wheel 6 Plastic 90 540
4 Motor 6 Alloy 220 1320
Total 2270
Table Hardware to be Purchased
Electrical
Purchase
S. No Item Qty Budget Net
1 Power Supply 1 450 450
2 Box 1 30 30
3 Switches 2 30 60
4 Wires and Cables 150 150
Total 1380
Table ElectricalEquipments to be Purchased With the total of Electrical and Hardware Purchases the rover will cost around Rs. 3650 or a little more.
6 FUTURE SCOPE
The frame weight can be reduced by using high strength lightweight materials such as composites, carbon fibre.
The wheelchair can be automated by using electronics so that it will automatically sense and climb the stairs.
7 REFERANCE
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