FOUR WHEEL STEERING SYSTEM

Four wheel steering system 2017
Dept. Of Mechanical Engineering, BKEC Page 1
VISVESVARAYA TECHNOLOGICAL UNIVERSITY
BELAGAVI-590014
A PROJECT REPORT
ON
“FOUR WHEEL STEERING SYSTEM”
Submitted in the partial fulfillment of the requirement for the award of degree
BACHELOR OF ENGINEERING
IN
MECHANICAL ENGINEERING
Submitted by:
NAMES USN
KHADEER SAB (3BK13ME035)
MAHENDRA SHRESTHA (3BK13ME036)
MOSEEN CHAND (3BK13ME058)
SHAIK SUHEL AHMED (3BK13ME092)
Under the Guidance of
Asso. Prof. RAVI KIRANAGI
DEPARTMENT OF MECHANICAL ENGINEERING
BASAVAKALYAN ENGINEERING COLLEGE
BASAVAKALYAN-585327

BET’S
BASAVAKALYAN ENGINEERING COLLEGE
BASAVAKALYAN-585327
DEPARTMENT OF MECHANICAL ENGINEERING
CERTIFICATE
This is certify that the project entitled
“FOUR WHEEL STEERING SYSTEM”
Has been submitted by
NAMES USN
Students of 8th semester Bachelor of Engineering in MECHANICAL ENGINEERING under our
supervision and guidance, in partial fulfillment of the requirements for the award of
Bachelor of Engineering of Visvesvaraya Technological University, Belagavi during the
academic year 2016-2017.
PROF. RAVI KIRANAGI Prof. SANTOSH PATIL DR. S. B. KIVADE
Project guide Head of Department Principal
NAME OF THE EXAMINERS
1.
2.

ACKNOWLEDGEMENT
It is our proud privilege and duty to acknowledge the kind of help and guidance
received from several people in preparation of this report. It would not have
been possible to prepare this project in this form without their valuable help, co-
operation and guidance.
First and foremost, we wish to record our sincere gratitude to Management of
this College and to our beloved principal Dr. S.B. KIVADE, and H.O.D.
SANTOSH PATIL Basavakalyan Engineering College, Basavakalyan, for his
constant support and encouragement in preparation of this project and for
making available library and laboratory facilities needed to prepare this project.
We express our sincere gratitude to our guide, Asso. Prof. RAVI KIRANAGI
Department of Mechanical Engineering, Basavakalyan Engineering College,
Basavakalyan, for guiding us in investigations for this project and in carrying
out experimental work. Our numerous discussions with his were extremely
helpful. We hold his in esteem for guidance, encouragement, involvement and
inspiration received from him.
Our sincere thanks to Asso. Prof. RAVI KIRANGI and Prof. SHIVARAJ
BHALEKAR project co-ordinator for having supported the work related to this
project. Their contributions and technical support in preparing this project and
greatly acknowledged. So, our sincere thanks to all teaching and non teaching
faculty for supporting directly or indirectly to us.
Last but not least, we wish to thank our parents.
Place: Basavakalyan
Date:
Project Associates

1. INTRODUCTION
Steering is the term applied to the collection of components, linkages, etc.
which will allow a vessel (ship, boat) or vehicle (car, motorcycle and bicycles)
to follow the desired course. Four wheel steering, 4WS, also called rear-wheel
steering or all-wheel steering, provides a means to actively steer the rear wheels
during turning maneuvers. It should not be confused with four-wheel drive in
which all four wheels of vehicle are powered.
Four wheel steering is a method developed in automobile industry for
the effective turning of the vehicle, increase the maneuverability and reduce the
drivers steering effort. In city driving conditions, the vehicle with higher track
width and wheelbase face problems of turning as the space is confined the same
problem is faced in low speed cornering. The turning radius is reduced in the
four wheel steering of the vehicle which is effective in confined space, in this
project turning radius is reduced without changing the dimension of the
vehicles.
In situations like vehicle parking, low speed cornering and driving in
city conditions with heavy traffic in tight spaces, driving is very difficult due to
vehicle’s larger track width and wheelbase. When both the front and rear wheels
steer toward the same direction, they are said to be in-phase and this produces a
kind of sideways movement of the car at low speeds. When the front and rear
wheels are steered in opposite direction, this is called anti-phase, counter-phase
or opposite-phase and it produces a sharper, tighter turn.
Hence, there is a requirement of a mechanism which result in less
turning radius and it can be achieved by implementing four wheel steering.

2. PRINCIPLE
The steering mechanism consists of rack and pinion arrangements which are
used to turn the wheels in the front. And a bevel gear arrangement is made just
after the steering and power is transmitted through the transfer shaft to the gear
box assembly. Then power is transmitted to the rear wheels. Layout/Operation
of the system: Two subsystems: Rack and pinion for front and rear, identical
geometry and components. Steering column is fitted with 3 bevel gears meshes
and transmits power to front and rear rack and pinion. As steering wheel is
turned the entire rotation is transferred to front rack and pinion and only half of
the rotation is transferred to rear rack and pinion.
1. Ackermann steering mechanism
Ackermann steering mechanism is a geometric arrangement of linkages in
the steering of vehicle designed to solve the problem of wheels on the inside
and outside of a turn needing of different radii. The intention of Ackermann
geometry is to avoid the need for tyres to slip sideways when following the path
around a curve. The geometrical solution to this is for all wheels to have their
axles arranged as radii of circles with a common centre point. As the rear
wheels are fixed, this centre point must be on a line extended from the rear axle.
Intersecting the axes of the front wheels on this line as well requires that the
inside front wheel is turned, when steering, through a greater angle than the
outside wheel.
Fig2.1:Ackermann steering mechanism

2. Steering ratio
The steering ratio is the ratio of number of degrees of turn of the steering wheel
to the number of degrees the wheels turn. In cars, the ratio is between 12:1 and
20:1. For example, if one complete turn of the steering wheel, 360 degrees,
causes the wheels to turn 24 degrees, the ratio is then 360:24=15:1. A higher
steering ratio means that the steering wheel is turned more to get the wheels
turning, but it will be easier to turn the steering wheel. A lower steering ratio
means that the steering wheel is turned less to get the wheels turning, but it will
harder to turn the steering wheel. Larger and heavier vehicles will often have a
higher steering ratio.
3. Turning radius
The turning radius of a vehicle is the radius of the smallest circular turn (i.e. U-
turn) that the vehicle is capable of making. There is no hard and fast formula to
calculate the turning circle but an approximate value can be obtained using the
formula:
Turning circle radius = Track/2 + Wheel base/sin (Average steer angle)
Fig2.3: Turning radius view
4. Steering geometry
Steering geometry is the geometric arrangement of the parts of a steering system
and the value of the lengths and angles within it. Steering geometry changes due
to bumps in the road may cause the front wheels to steer in a different direction
together or independent of each other. Combined with the cars improved
steering geometry, a wide wheel and large footprint will notably improve
handling and grip.

3. BACKGROUND THEORY
The most effective type of steering, this type has all the four wheels of
the vehicle used for steering purpose. In a typical front wheel steering
system the rear wheels do not turn in the direction of the curve and thus
curb on the efficiency of the steering. Normally this system is not been
the preferred choice due to complexity of conventional mechanical four
wheel steering systems. However, a few cars like the Honda Prelude,
Nissan Skyline GT-R have been available with four wheel steering
systems, where the rear wheels turn by an angle to aid the front wheels in
steering. However, these systems had the rear wheels steered by only 2 or
3 degrees, as their main aim was to assist the front wheels rather than
steer by themselves. With advances in technology, modern four wheel
steering systems boast of fully electronic steer-by-wire systems, equal
steer angles for front and rear wheels, and sensors to monitor the vehicle
dynamics and adjust the steer angles in real time. Although such a
complex four wheel steering model has not been created for production
purposes, a number of experimental concepts with some of these
technologies have been built and tested successfully.
Usually in vehicles during turning, the tires are subject
to the forces of grip, momentum, and steering input when making a
movement other than straight ahead driving. These forces compete with
each other during steering manoeuvres. With a front-steered vehicle, the
rear end is always trying to catch up to the directional changes of the
front wheels. This causes the vehicle to sway. When turning, the driver is
putting into motion a complex series of forces. Each of these must be
balanced against the others. The tires are subjected to road grip and slip
angle. Grip holds the car’s wheels to the road, and momentum moves the
car straight ahead. Steering input causes the front wheels to turn. The car
momentarily resists the turning motion, causing a tire slip angle to form.
Once the vehicle begins to respond to the steering input, cornering forces
are generated. The vehicle sways as the rear wheels attempt to keep up
with the cornering forces already generated by the front tires. This is
referred to as rear-end lag because there is a time delay between steering
input and vehicle reaction. When the front wheels are turned back to a
straight-ahead position, the vehicle must again try to adjust by reversing
the same forces developed by the turn. As the steering is turned, the
vehicle body sways as the rear wheels again try to keep up with the
cornering forces generated by the front wheels.

4. THE CONCEPTS
The Four Wheel Steering System consists of rack and pinion mechanism
assisted by bevel gears of which is connected to front pinion, steering rod in
which input is given by the driver and another will be connected to rear pinion.
Rear wheel system consists of two racks with two pinions. One of the racks will
be in front of the rear wheel axis and the other will be at the front axis. Also at
any point in the system, one of the rack & pinion assembly will be engaged with
the other being disengaged. At lower speeds, the pinion will be in contact with
rear rack so as to keep the wheels motion out of phase while for higher speeds
pinion will be in contact with front rack of rear steering system, giving in phase
motion to wheels. This position of the rear pinion on the rack is controlled by a
steering mechanism. The angle turned by rear wheels will not be as high as that
of front wheels because the function of rear steering system is to assist the
motion of front wheels and not provide its own direction. This change of angle
is obtained by changing gear ratio of rack and pinion.
Fig4.1: Conceptual model

5. LITERATURE REVIEW
New generation of active steering systems distinguishes a need of steering of
rear wheels for the reason of directional stability from a need of steering of rear
wheels for the reason of cornering at slow speed.
 Condition for True Rolling
While tackling a turn, the condition of perfect rolling motion will be satisfied if
all the four wheel axes when projected at one point called the instantaneous
centre, and when the following equation is satisfied:
Cot Ø – cot θ = c / b
Fig.5.1: True rolling condition

 Slow and High SpeedModes
At Slow Speeds rear wheels turn in direction oppositeto that of front wheels.
This mode is used for navigating through hilly areas and in congested city
where better cornering is required for U turn and tight streets with low turning
circle which can be reduced as shown in Fig 2.
Fig.5.2: Slow Speed

At High Speeds, turning the rear wheels through an angle opposite to front
wheels might lead to vehicle instability and is thus unsuitable. Hence the rear
wheels are turned in the same direction of front wheels in four-wheel steering
systems. This is shown in Fig 3.
Fig.5.3: High Speed
 In-Phase and Counter-Phase Steering
Fig.5.4:In-phase and counter
Phase steering
The 4WS systemperforms two distinct operations: in- phase steering, whereby
the rear wheels are turned in the same direction as the front wheels, and
counter phase steering, whereby the rear wheels are turned in the opposite
direction. The 4WS system is effective in the following situations:
 Lane Changes
 Gentle Curves
 Junctions
 Narrow Roads
 U-Turns
 Parallel Parking

Fig.5.5: Car in various
modes
 U-Turns
By minimizing the vehicle’s turning radius, counter-phase steering of the
rear wheels enables U-turns to be performed easily on narrow roads.
 High Speed Lane Changing
Another driving maneuver that frequently becomes cumbersome and even
dangerous is changing lanes at fairly high speeds. Although this is less steering
intensive, this does not require a lot concentration from the driver since he has
to judge the space and vehicles behind him. Here is how crab mode can simplify
this action.
 ParallelParking
Zero steer can significantly ease the parking process, due to its extremely
short turning footprint. This is exemplified by the parallel parking scenario,
which is common in foreign countries and is pretty relevant to our cities. Here, a
car has to park it between two other cars parked on the service lane. This
maneuver requires a three-way movement of the vehicle and consequently
heavy steering inputs. Moreover, to successfully park the vehicle without
incurring any damage, at least 1.75 times the length of the car must be available
for parking for a two-wheel steered car.

6. METHODOLOGY OF FOUR WHEEL STEERING
There are three types of production of four-wheel steering systems:
1. Mechanical 4WS system
2. Hydraulic 4WS system
3. Electro-hydraulic 4WS system
6.1 Mechanical 4WS system
In a straight-mechanical type of 4WS, two steering gears are used-one for the
front and the other for the rear wheels. A steel shaft connects the two steering
gearboxes and terminates at an eccentric shaft that is fitted with an offset pin.
This pin engages a second offset pin that fits into a planetary gear. The
planetary gear meshes with the matching teeth of an internal gear that is secured
in a fixed position to the gearbox housing. This means that the planetary gear
can rotate but the internal gear cannot. The eccentric pin of the planetary gear
fits into a hole in a slider for the steering gear. A 120-degree turn of the steering
wheel rotates the planetary gear to move the slider in the same direction that the
front wheels are headed. Proportionately, the rear wheels turn the steering wheel
about 1.5 to 10 degrees. Further rotation of the steering wheel, past the
120degree point, causes the rear wheels to start straightening out due to the
double-crank action (two eccentric pins) and rotation of the planetary gear.
Turning the steering wheel to a greater angle about 230 degrees, finds the rear
wheels in a neutral position regarding the front wheels. Further rotation of the
steering wheel results in the rear wheels going counter phase with regard to the
front wheels. About 5.3 degrees maximum counter phase rear steering is
possible. Mechanical 4WS is steering angle sensitive.
Fig.6.1: Mechanical 4WS
system

6.2 Hydraulic 4WS system
In the hydraulic four-wheel-steering system, the rear wheel turns only in the
same direction as the front wheels. This system limits rear wheel movement to
5.5 degrees in either the left or right direction. A two-way hydraulic cylinder
mounted on the rear stub frame turn the wheels. Fluid for this cylinder is
supplied by a rear steering pump that is driven by the differential. The pump
only operates when the front wheels are turning. When the steering wheel is
turned, the front steering pump sends fluid under pressure to the rotary valve in
the front rack and pinion unit. This forces fluid into the front power cylinder,
and the front wheels turn in the direction steered. The fluid pressure varies with
the turning of the steering wheel. The faster and farther the steering wheel is
turned, the greater the fluid pressure. The fluid is also fed under the same
pressure to the control valve where it opens a spool valve in the control valve
housing. As the spool valve moves, it allows fluid from the rear steering pump
to move through and operate the rear power cylinder. The higher the pressure on
the spool, the farther it moves. The farther it moves, the more fluid it allows
through to move the rear wheels.
Fig.6.2: Hydraulic 4WS system

6.3 Electro- hydraulic 4WS system
In this system, a speed sensor and steering wheel angle sensor feed information
to the electronic control unit (ECU). By processing the information received,
the ECU commands the hydraulic system to steer the rear wheels. At low speed,
the rear wheels of this system are not considered a dynamic factor in the
steering process. At moderate speeds, the rear wheels are steered momentarily
counter 45 phase, through neutral, then in phase with the front wheels. At high
speeds, the rear wheel turns only in phase with the front wheels. The ECU must
know not only road speed, but also how much and quickly the steering wheel is
turned. These three factors - road speed, amount of steering wheel turn, and the
quickness of the steering wheel turn - are interpreted by the ECU to maintain
continuous and desired steer angle of the rear wheels. The yoke is a major
mechanical component of this electro-hydraulic design. The position of the
control yoke varies with vehicle road speed. The stepper motor moves the
control yoke. A swing arm is attached to the control yoke. The position of the
yoke determines the arc of the swing rod. The arc of the swing arm is
transmitted through a control arm that passes through a large bevel gear.
Stepper motor action eventually causes a push-or-pull movement of its output
shaft to steer the rear wheels up to a maximum of 5 degrees in either direction.
The electronically controlled, 4WS system regulates the angle and direction of
the rear wheels in response to speed and driver's steering. This speed-sensing
system optimizes the vehicle's dynamic characteristics, thereby producing
enhanced stability.
Fig.6.3: Electro hydraulic 4WS

7. IMPORTANT MATERIALS REQUIRED
7.1 Bevel gear:
Bevel gears are gears where the axes of the two shafts intersect and the tooth-
bearing faces of the gears themselves are conically shaped. Bevel gears are most
often mounted on shafts that are 90 degrees apart, but can be designed to work
at other angles as well. The pitch surface of bevel gears is a cone.
Fig.7.1: Bevel gear
7.2 Ball bearing:
A bearing is a machine element that constrains relative motion to only the
desired motion, and reduces friction between moving parts. The design of the
bearing may, for example, provide for free linear movement of the moving part
or for free rotation around a fixed axis; or, it may prevent a motion by
controlling the vectors of normal forces that bear on the moving parts. Most
bearings facilitate the desired motion by minimizing friction
Fig.7.2: Ball bearing

7.3 Tire:
A tire (British tyre) is a ring of material that covers the rim of a wheel. Most
road vehicles and many other vehicles use rubber tires. Tires help vehicles to
move smoothly. Tires need to be changed after their treads wear away. Driving
with worn tires is very dangerous. It can cause the tire to explode and the driver
to lose control. Tires are made of different types of rubber. Tires made of harder
rubber are made for long lasting performance, like long-distance truck carriers.
They come in different sizes and have different tread patterns. There are many
different sizes of tires. On car and truck tires, they are marked with 3 numbers
and might look like: 225/60R16.
Example
Tire size: 225/60R16
Tire width = 225mm
Sidewall height = 135mm (225 * .60 = 135)
Wheel diameter = 16 inches
Fig.7.3: Tire
7.4 Wheelhub or Spindle:
fig7.4: Wheel hub

7.5 Nuts and bolts:
A nut is a type of fastener with a threaded hole. Nuts are almost always used in
conjunction with a mating bolt to fasten multiple parts together. The two
partners are kept together by a combination of their threads' friction (with slight
elastic deformation), a slight stretching of the bolt, and compressionof the parts
to be held together. A bolt is a form of threaded fastener with an external male
thread.
Fig.7.5: nuts and bolts
7.6 Drive shaft:
A drive shaft, driveshaft, driving shaft, propeller shaft is a mechanical
component for transmitting torque and rotation, usually used to connect other
components of a drive train that cannot be connected directly because of
distance or the need to allow for relative movement between them. As torque
carriers, drive shafts are subject to torsion and shear stress, equivalent to the
difference between the input torque and the load. They must therefore be strong
enough to bear the stress, whilst avoiding too much additional weight as that
would in turn increase their inertia.
Fig.7.6: Drive shaft

7.7 Steering:
Steering is the collection of components, linkages, etc. which allows any vehicle
(car, motorcycle, bicycle) to follow the desired course. The primary purpose of
the steering system is to allow the driver to guide the vehicle. Four-wheel
steering is a system employed by some vehicles to improve steering response,
increase vehicle stability while maneuvering at high speed, or to decrease
turning radius at low speed.
fig.7.7: Steering
7.8 Chain:
A chain is typically made of metal. A chain may consist of two or more links.
Those designed for transferring power in machines have links designed to mesh
with the teeth of the sprockets of the machine, and are flexible in only one
dimension. They are known as roller chains, though there are also non-roller
chains such as block chain.
Fig.7.8: chains

8. PHASES OF QUADRA STEERING SYSTEM
In this type of steering system, we can steer a front wheel, as well as the rear
wheel of the vehicles simultaneously. This steering mainly includes two types
of steering:
Front wheels and rear wheels are steered in the same direction and are parallel
to each other. This type of system is very useful during lane changing. Front
wheels are steered in the direction opposite to that of the rear wheel. This
steering system reduces the space required by the vehicle during turning as
compared to that of the two wheel steering system. The present “Four Wheel
Steering” works mechanically with help of linkages. The system utilizes a
manual manipulator to control and direct the articulation (left and right turning)
of rear wheels. The system operates in three phases: Negative, Neutral and
Positive.
At lower speeds, rear wheel turns in opposite direction from the front
wheel. This is negative phase. At moderate speed, the rear wheel remains
straight or neutral.
At higher speed, the rear wheel are in the positive phase turning in the
same direction as the front wheels.
8.1 Negative Phase
In this drive the axles both the front and the rear move in opposite direction
relative to each other. This drive is mainly used during parking of the vehicle.
As both the axle move in different directions the radius of curvature while
turning reduces. This means the vehicle will require less space for parking and
this will be helpful in places where traffic and parking is a major problem.
Fig8.1: Negative phase

8.2 Neutral Phase
In this drive only the front axle moves either in clockwise or anticlockwise
direction and the rear wheel being unmoved. This is the drive that we see in day
to day life in all the four wheelers. It is generally used at moderate speed.
Fig.8.2 neutral phase
8.3 Positive Phase
As the name suggest, in this drive both the axle viz. front and rear move in same
direction relative to the each other. This motion of both the front and the rear
axle helps Quadra steering system enabled vehicle to change the lane during
highway driving. It is generally applied at higher speed.
Fig.8.3: positive phase

9. TYPES OF STEER
Balancing of vehicle is very important and it can be achieved in different ways
i.e. under-steer, over-steer and neutral-steer.
9.1 Under-Steer
Under steer is so called because when the slip angle of front wheels is greater
than slip angle of rear wheels. The diagram for the under steer is given below,
from the diagram the explanation is made out clear very well.
Fig.9.1: Under steer
9.2 Over-Steer
Over steer is defined when the slip angle of front wheels lesser than the slip
angle of rear wheels.
Fig.9.2: Over steer
9.3 Neutral-steerorCounter-steering
Counter-steering can defined as when the slip angle of front wheels is equal to
slip angle of rear wheels.
Fig.9.3: Neutral steer

10. OPERATIONS
10.1 Welding:
Welding is a fabrication or sculptural process that joins materials, usually
metals or thermoplastics, by causing fusion, which is distinct from lower
temperature metal-joining techniques such as brazing and soldering, which do
not melt the base metal. In addition to melting the base metal, a filler material is
typically added to the joint to form a pool of molten material (the weld pool)
that cools to form a joint that is usually stronger than the base material. Pressure
may also be used in conjunction with heat, or by itself, to produce a weld. We
used GMAW for welding operation purpose. Gas Metal Arc Welding (GMAW)
– commonly termed MIG (metal, inert gas), uses a wire feeding gun that feeds
wire at an adjustable speed and flows an argon-based shielding gas or a mix of
argon and carbon dioxide (CO2) over the weld puddle to protect it from
atmospheric contamination.
Fig.10.1: Operations of Welding

10.2 Cutting:
Cutting is the separation of a physical object, into two or more portions, through
the application of an acutely directed force. Cutting is a compressive and
shearing phenomenon, and occurs only when the total stress generated by the
cutting implement exceeds the ultimate strength of the material of the object
being cut. Cutting has been at the core of manufacturing throughout history. For
metals many methods are used and can be grouped by the physical phenomenon
used.
Fig10.2: Operations of Cutting

10.3 Grinding:
A grinding machine, often shortened to grinder, is any of various power tools or
machine tools used for grinding, which is a type of machining using an abrasive
wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a
small chip from the work piece via shear deformation. Grinding is used to finish
work piece that must show high surface quality (e.g., low surface roughness)
and high accuracy of shape and dimension. As the accuracy in dimensions in
grinding is of the order of 0.000025 mm, in most applications it tends to be a
finishing operation and removes comparatively little metal, about 0.25 to
0.50 mm depth. However, there are some roughing applications in which
grinding removes high volumes of metal quite rapidly. Thus, grinding is a
diverse field.
Fig10.3: Operation of Grinding

10.4 Drilling:
Drilling is a cutting process that uses a drill bit to cut a hole of circular cross-
section in solid materials. The drill bit is usually a rotary cutting tool, often
multipoint. The bit is pressed against the work piece and rotated at rates from
hundreds to thousands of revolutions per minute. This forces the cutting edge
against the work piece, cutting off chips (swarf) from the hole as it is drilled. In
rock drilling, the hole is usually not made through a circular cutting motion,
though the bit is usually rotated. Instead, the hole is usually made by
hammering a drill bit into the hole with quickly repeated short movements. The
hammering action can be performed from outside of the hole (top-hammer drill)
or within the hole (down-the-hole drill, DTH). Drills used for horizontal drilling
are called drifter drills.
Fig.10.4: Operation of Drilling

11. DESIGN OF FRAME
For building of prototype model, the designed model is considered along with
that a frame is built to support the steering, suspension and seat.
The frame is designed considering the wheelbase and track width of Maruti
Suzuki 800 and also it has to supportfor the suspension part as the suspension is
welded to the frame, seat is also welded to the frame, the support structure for
steering column and rack body is welded to the frame. The frame also takes the
road load and load of the driver, so considering all the factors the frame is
designed and developed.
35 cm
65cm
140cm
Fig.11.1: Design of Frame

12. CALCULATIONS
Calculation for steering angle for the turning radius of 4.4m.
From the benchmark vehicle we know that turning radius is 4.4 m.
We know that
R2 = A2
2 + R1
2…………………………….. (1)
Where R = Turning radius of the vehicle.
A2 = Distance of CG from rear axle.
R1 = Distance between instantaneous centre and the axis of the vehicle.
To find A2
Wf = (W * A2) / L………………………… (2)
Where Wf = Load on front axle.
W = Total weight of car.
L = Wheelbase.
So from equation 2 and 1
A2 = 1305 mm.
R1 = 4202 mm.
To find steering angles;
From test we found that the inner angle of front tire is,
Δif = 25.60.
tan Δif = C1 / (R1 – Wf / 2)………………. (3)
C1 + C2 = L…………………………….. (4)
Where C1 = Distance of instantaneous centre from front axle axis.
C2 = Distance of instantaneous centre from rear axle axis.
wf = Front trackwidth.
From equation 3 and 4
C1 = 1722.19 mm.
C2 = 452.80 mm.
To find δof = outer angle of front tire.
tan δof = C1 / (R1 + wf / 2)…….………. (5)
δof = 19.700
To find δir = inner angle of rear tire.
tan δir = C2 / (R1 – wr / 2)……….……. (6)
δir = 7.1640
To find δor = outer angle of rear tire.
tan δor = C2 / (R1 + wr / 2)……………. (7)
δor = 5.3860

Fig.12.1: Steering angles position of instantaneous centre for turning radius 4.4m.
Now considering the same steering angles for front and rear tires, we reduce in
the turning radius of the vehicle but keeping the wheelbase and track width
same as the benchmark vehicle.
Calculation for turning radius for same steering angles.
To find turning radius, R
R2 = A22 + L2 cot2δ…………………… (8)
Where δ = Total steering angle of the vehicle.
To find δ
cotδ = (cotδi + cotδo) / 2…………….. (9)
Where δi = total inner angle of the vehicle.
δo = total outer angle of the vehicle.
cotδ = 1.032.
From equation 8
R = 2596 mm.
Further calculation for C1 and C2 from equation 3 and 4
considering turning radius as 2596 mm.
C1 = 780.82 mm.
C2 = 1394.17 mm.

13. ANALYSIS OF COMPONENTS
Analysis is process of analyzing the components by applying external factors
such as loads, temperature, pressure etc. and obtaining the values such as
stresses (bending, tangential and normal), deformations etc. in order to
determine the safety of the components when implemented in practical use. It
gives optimum result of the safety of components and very easy to understand
various factors applicable in the process. These Analyses gives optimum result
of safety of components and minimize the chances of failure. There are various
packages in market to carry out these simulations on computer such as ANSYS,
HYPERWORKS, and FLOTRAN etc. In this project, we have used ANSYS
14.0 as the software to analyze the safety of our components under various
loading conditions. Two major analyses carried out in this project are:
1) Deformation analysis
2) Stress analysis
Various components analyzed in this project are:
1) Bevel gear (top surface)
2) Bevel gear (side)
3) Roller bearing
4) Telescopic shaft
5) Rack and pinion system
6) Spindle
7) Bevel gear casing
8) Double rack /pinion casing
Process for performing the analysis:
1) Making or importing the geometry to software interface (GUI).
2) Defining the field.
3) Applying the material properties.
4) Meshing the components with appropriate element size.
5) Applying the actions such as load, pressure etc. on the body.
6) Applying the boundary conditions such as fixed supports (constraints).
7) Solving using the solver.
8) Obtaining required reactions such as stresses deformations etc.

13.1 Bevel Gear Analysis
Fig.13.1.1: Bevel gear on top deformation
Fig.13.1.2: Bevel gear on top normal stress
Material Type: Grey Cast Iron
Ultimate Tensile Strength = 297 MPa
Maximum Stress Obtained = 4.855 MPa
Factor of Safety = 297/4.855 = 61.174
Design Completely Safe
Maximum Deflection = 6.2 * 10-4mm

Fig.13.1.3: Bevel gear side deformation
Fig.13.1.4: Bevel gear normal stress (Bending)
Material Type: Grey Cast Iron
Factor of Safety = 297/2.2009 = 134.94

13.2 Ball Bearing Analysis
Fig.13.2.1: Ball bearing deformation
Fig.13.2.2: Ball bearing normal stress
Material: Mild Steel (AISI 1020)
Ultimate Tensile Strength = 394MPa
Factorof safety = 394/0.75 = 525.33

13.3 Telescopic Shaft Analysis
Fig.13.3.1 Deformation of telescopic shaft
Fig.13.3.2: Normal stress in telescopic shaft
Factor of safety = 394/3.82 = 103.41

13.4 Pinion Analysis
Fig.13.4.1: pinion deformation
Fig.13.4.2: Pinion stress
Material: Grey Cast Iron
Factor of safety = 297/7.25 = 40.96

13.5 Rack analysis
Fig.13.5.1: Rack deformation
Fig.13.5.2: Rack normal stress
Material: Grey Cast Iron
Factor of safety = 297/108.15 = 2.746
Design is Safe
Maximum Deflection = 1.0902mm

13.6 Spindle analysis
Fig.13.6.1: Spindle deformation
Fig.13.6.2 spindle normal stress
Factor of safety = 394/89.5 = 4.4
Design is Safe
Maximum Deflection = 0.027mm

14. COST AND DESIGN ANALYSIS
Components Dimensions ( cm ) Quantity Cost
Rs.
Frame Length: 52*120 1 1200
Sprocket Pitch:0.5
Outer diameter:7.5
Inner diameter:2.2
Width:0.125
No. Of teeth:18
4 200
Chain Length: 45 6 400
Bearing Outer diameter:2.0
Inner diameter:4.1
10 2500
Outer diameter:2.5
Inner diameter:5.3
1 180
Spindle hub Diameter:2.0 4 2400
Steering Diameter: 1 600
Knuckle arms Length: 40 1 500
Nuts Length:11
Diameter:1.1
16 160
Length:10.5
Diameter:1.1
8 80
Bolts Outer diameter:2.0
Inner diameter:1.1
16 80
Outer diameter:2.0
Inner diameter: 1.1
8 40
Bevel gears Outer diameter:9
Inner diameter:3.2
No. Of teeth:10
Module:0.6
Face width:5
2 400
Wheel Outer diameter: 48
Inner diameter: 40
4 2800
Rack Length: 45
Face width:0.5
6 300
Pedals 4 600
Drive shaft Length:25
Diameter:2.2
2 3000
Rear shaft Outer diameter:3.2
Inner diameter:2.6
Face width:96
1 400
Sheet metal 450
Paint 1 500
Drill bit Diameter: 10 mm 2 400
Lubrication 150
Total material cost 17340/-
Transportation cost - 1500
Total cost ᷈18900/-

15. COMPARISON
 Car more efficient and stable on cornering.
 Improved steering responsiveness and precision
 High speed straight line stability
 Notable improvement in rapid, easier, safer lane changing maneuvers.
 Smaller turning radius and tight spacemaneuverability at low speed
 Relative wheel angles and their control.
 Risk of hitting an obstacle is greatly reduced
Fig.15.1: comparison between 4WS and 2WS

16. ADVANTAGES
1. Superior cornering stability: The vehicle cornering behaviour becomes
more stable and controllable at high speed as well as on wet slippering
road surfaces.
2. Improved steering response andprecision: The vehicle responseto
steering input becomes quicker and more precise throughout the vehicle
enter speed range.
3. High speedstraight line stability: The vehicle’s straight –line stability
at high speed is improved. Negative effects of road irregularities and
crosswinds on the vehicles stability are minimized.
4. Improved rapid lane-changing maneuvers: This is stability in lane
changing at high speed is improved. In high speed type operation become
easier. The vehicle is less likely to go into a spin even in situations in
which the driver must make a sudden and relatively large change of
direction.
5. Smaller turning radius: By steering the rear wheels in the duration
oppositethe front wheels at low speed, the vehicle’s turning circle is
greatly reduced. Therefore, vehicle maneuvering on narrow roads and
during parking become easier.
6. Controlling: Computer-controlled Quadra steer can be switched on and
off and has an effective trailer towing mode.

17. DISADVANTAGES
1. The 4ws, due to construction of many new components, the system
becomes more expensive.
2. The system includes as many components (especially electronically)
there is always a chance to get any of the part inactive, thus the system
become in operative.
3. The system is not stable at high speed gets overpowered and topple in
some cases.
4. Pump and sensors should be checked regularly to avoid its failure.

18. FUTURE SCOPE
An innovative feature of this steering linkage design is its ability to drive all
four Wheels using a single steering actuator. Having studied how 4WS has an
effect on the vehicles stability and driver maneuverability, we now look at what
the future will present us with. It’s successful implementation will allow for the
development of a four-wheel, steered power base with maximum
maneuverability, uncompromised static stability, front- and rear-wheel tracking,
and optimum obstacle climbing capability. The advanced system of “Four
wheel steering” will work electronically with the help or microprocessors. The
system will utilize an onboard computer to control and direct the turning left
and right of the rear wheels.

19. APPLICATION
1. Gentle curve: on gentle curves, in phase steering of the rear wheels
improves the vehicle stability.
2. Parking: during a parking a vehicles driver typically turns the steering
wheels through a large angle to achieve a small turning radius. By
counter phase steering of the rear wheels, 4ws system realizes a smaller
radius then is possible with 2ws. As a result vehicle is turned in small
radius at parking.
3. Junctions: on a cross roads or other junction where roads intersect at 90
degree or tighter angles, counter phase steering of the rear wheels causes
the front and rear wheels to follow more-or-less path. As a result the
vehicle can be turned easily at a function.
4. Slippery road surfaces: during steering operation on snow, icy, muddy
and other low friction surfaces, steering of the rear wheels suppress
sideways drift of the vehicles rear end. As a result the vehicles direction
is easier to control.
5. U-turns: by minimizing the vehicles turning radius, counter phase
steering of the rear wheels enables U-turns to be performed easily on
narrow roads.

20. CONCLUSION
This paper focused on a steering mechanism which offers feasible solutions to a
number of current maneuvering limitations. Different mechanisms were adopted
by trial and error method in order to facilitate the engagement of the wheels in
the required direction, and the most convenient method was adopted. Thus the
four-wheel steering system is a relatively new technology that imposes
cornering capability, steering response, straight-line stability, lane changing and
low-speed maneuverability in cars, trucks and trailers. The aim of 4WS system
is a better stability during overtaking manoeuvres, reduction of vehicle
oscillation around its vertical axis, reduced sensibility to lateral wind, neutral
behaviour during cornering, improvement of active safety. Even though it is
advantageous over the conventional two-wheel steering system, 4WS is
complex and expensive. Currently the cost of a vehicle with four wheel steering
is more than that for a vehicle with the conventional two wheel steering. Four
wheel steering is growing in popularity and it is likely to have with all vehicles.
As the systems takes over market the cost of four wheel steering will fall down.

21. CLICKS OF PROJECT

22. REFERENCES
1. K. Lohith, Dr. S.R. Shankapal, M.H. Monish Gowda, “DEVELOPMENT
OF FOUR WHEEL STEERING SYSTEM FOR A CAR”.
2. DILIP S. CHOUDHARY, “FOUR WHEEL STEERING SYSTEM”.
International Journal of Mechanical Engineering and Robotic Research”.
Volume: 3 Issue: 4, ISSN 2278-0149
3. K.Lohith, Dr. S.R. shankapal, M.H. Monish Gowda, “ Development of
Four Wheel Steering system for a Car” vol. 12, pg. 90-97, Issue 1, April
2013.
4. V. B. Bhandari “ Design of Machine Elements” McGraw Hill Education
India Pvt. Ltd., vol. 3, 11th Edition, 2013.
5. Abhinav Tikley, Mayur Khangan, “FOUR WHEEL STEERING- A
REVIEW”. International Journal of Research In Science And
Engineering. volume: 1 Issue: 3 e-ISSN: 2394-8299, p-ISSN: 2394-8280
6. Arun Singh, Abhishek Kumar, Rajiv Chaudhary, R.C Singh. “Study of
Four Wheel Steering System to Reduce Turning Radius and Increase
Stability”. International Conference of Advance Research And Innovation
ISBN 978-93-5156-328-0
7. Saket Bhishikar, Vatsal Gudhka, Neel Dalal, Paarth Mehta. “Design and
Simulation of 4 Wheel Steering system”. International Journal of
Engineering and Innovative Technology (IJEIT) Volume 3, Issue 12,
June 2014 ISSN: 2277-3754
8. Kripal singh volume 1 and 2 Automobile Engineering

FOUR WHEEL STEERING SYSTEM

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