1. A Design & Implementation of Collision
Avoidance System (CAS) for Automobiles
using
EMBEDDED SYSTEMS

2. Abstract— The industry strategy for
automotive safety systems has been
evolving over the last 20 years. Initially,
individual passive devices and features
such as seatbelts, airbags, knee bolsters,
crush zones, etc. was developed for saving
lives and minimizing injuries when an
accident occurs. Later, preventive
measures such as improving visibility,
headlights, windshield wipers, tire traction,
etc. were deployed to reduce the probability
of getting into an accident. Now we are at
the stage of actively avoiding accidents as
well as providing maximum protection to
the vehicle occupants and even
pedestrians. Systems that are on the
threshold of being deployed or under
intense development include collision
avoidance systems.
In this dissertation, advanced ideas such as
pre-crash sensing, ultrasonic sensor is
used to sense the object in front of the
vehicle and gives the signal to the micro
controller unit. Based on the signal
received from the ultrasonic sensor, the
micro controller unit sends a signal to the
braking unit for applying the brake
automatically as per braking and throttle
control logic fed in to the micro controller
unit. To avoid the collision between the
vehicles during the period of running
conditions and automatically applying the
brake by means of actuators, Distance
measuring sensors & Electronic control
module.
INTRODUCTION
Despite all the advances made, the
overriding vision of zero-accident motoring
still remains a vision of unachieved. We
need to reduce further the number of
accident victims, and the use of new driver
assistance systems will enable us to make
significant progress in this field. Such
systems represent the second revolution in
active safety after Electronic Stability
Program (ESP).
Our new electronic assistance will be
systems that can “see” and therefore provide
active operating support for drivers. The

3. systems will also be able to see farther and
take in a wider spectrum than any human
ever could. The goal we have defined is to
make vehicles of tomorrow capable of
communicating with one another, and hence
able to issue warnings to drivers concerning
any imminent dangers. As a consequence for
the medium term, driver assistance and
communication systems will both be
featured as integrated vehicle modules to
reduce traffic accidents significantly. The
top model in our range, the phaeton, is
already available with the option of
Automatic Distance Control (ADC), which
is geared to maintain automatically a
minimum distance from the vehicle ahead
through system-initiated braking and
acceleration.
It is well known that driver errors are the
main cause for to increased severity, of most
accidents. An increasing amount of
automotive systems, such as brakes, steering
system and suspension, is controllable by
means of electronics and software. The
expanded use of electronics, micro
controllers, sensors, actuators, etc. in the
automotive industry will have a major
impact on the architecture of future safety
systems.
DESIGNING OF EMBEDDED SYSTEM
A typical embedded system has several
input, output, memory subsystem. The
memory subsystem stored the instruction
that controls the operation of the system.
These instruction comprise to program that
the system execute.
The instruction to be carried out is
written in any assembly language or C, C++
languages. Here designing includes
requirement analysis this involves a detailed
examination of the user needs, the problem
to be solved. Hardware may be custom
designed to follow any of the accepted
industrial standards.
Microprocessor & Microcontroller:
The terms processor refers to any three
types of devices known as microprocessors,
microcontrollers and digital signal
processors. The name microprocessor is
usually reserved for a chip that contains a
powerful CPU that has not been designed
with any particular computation in mind.
These chips are usually the foundation of
personal computers and high-end
workstations. The most common
microprocessors are members of Motorola’s
68k-found in older Macintosh computer –
and the ubiquitous 80 x 86 families.
A microcontroller is very much like a
microprocessor, except that it has been

4. designed specifically for use in embedded
systems. Microcontroller typically include a
CPU, memory and other peripherals in the
integrated circuit. Common examples are the
8051, Intel’s 80196 and Motorola’s 68HCxx
series. PIC 16F876, PIC 18C84.
HARDWARE & SOFTWARE INITIALISATION
The first stage of the initialization process
is the reset code. This is a small piece of
assembly that the processor executes
immediately after it is powered on or reset.
The sole purpose of this code is to transfer
control to the hardware initialization routine.
The first instruction of the reset code must
be placed in memory, usually called the
reset address that is specified in the
processor data book. The reset address for
the 80188EB is FFFF0h.
Most of the actual hardware initialization
takes place in the second stage. At this point,
we need to inform the processor about its
environment. This is also a good place to
initialize the interrupt controller and other
critical peripherals.
The hardware and software initialization process
The third initialization stage contains the
startup code. This is the assembly language
code. Of importance here is only that the
startup code calls main. From, that point
forward, all of your other software can be
written in C or C++.
PROBLEM DEFINITION
In this fast moving world, most of the
vehicles are equipped with manual braking
system, which is most important to stop the
vehicle. Also, now a day’s modern car are
equipped with Anti Lock Braking system,
powered with the electronic module. How
ever they are effective only when the driver
is alert with the road conditions and the
other vehicle, which moves along the same
road. Unless otherwise, the host vehicle may
face the collision or other difficulties, while
moving along the road. So, the system,
which can assist driver while braking, will
provide better active safety

5. PROJECT OVERVIEW
This project aims in developing and
demonstrating a collision avoidance system
that improves safety. The implementation of
collision avoidance system (CAS) in vehicle
improves highway traffic safety
significantly. These electronic systems scan
the direct environment of the vehicle,
predicting the danger. A wide range of
possible CAS was researched and
developed, varying from systems which
support the driver on one specific driving
task (e.g., proper distance keeping, blind
spot obstacle warning and lane keeping) up
to more advanced systems where the
driver’s throttling, and braking tasks are
totally controlled in case of predetermined
collision. The technological feasibility of
most CASs was demonstrated within several
experiments and pilots as well as their
potential in improving road traffic safety.
Consequently, the focus in this field is now
gradually moving from technology
development towards implementing these
systems in real time transportation. The
implementation is based on the results of
various studies about the impact of CASs on
traffic performance. It was found that large-
scale implementation of collision avoidance
systems, supporting the driver in case of
crash danger with oncoming vehicles or
obstacles will reduce road fatalities. The
implementation of ultrasonic Braking
System prevents collision by keeping the
distance between vehicles or applies the
brake in case.
The development of this system is
strongly technology driven. The prototype is
experimented under strictly controlled
conditions. So far, traffic safety performance
improvements depend strongly on the
systems’ specific operating characteristics
and on the actual traffic conditions such as
flow density, speed, the mix between
manual and instrumented vehicles. Vehicles
equipped with this system become safer and
have more comfortable car usage. These
effects will counteract with traffic
conditions. Therefore, a lot of questions
remain unanswered with the implementation
of CASs in traffic conditions.
This unanswered condition is studied in
this project, by identifying and assessing the

6. current knowledge on collision avoidance
systems (CAS) with respect to different
conditions as presented in the project. The
study spreads over three safety levels the
functional safety level, the driver safety
level and the traffic safety level. Information
of the safety impacts on all three levels is
necessary in order to evaluate the safety of
collision avoidance systems in a real world
situation.
Figure 1 shows the block diagram
Ultrasonic technology to detect objects as
they come within range of sensor. Also the
other vehicle operating parameters like
speed of the vehicle, throttle position and the
brake pedal position.
According to the inputs, the control
algorithm that fed into the
microcontroller processes the inputs and
actuates the actuators. The actuators used
here for our prototype is going to be
stepper motor with which we can imply
step rotation in both direction. The
control algorithm that fed into the micro
controller has been given below. This
control algorithm has been fed to the
controller as programming.
Figure 1: Block Schematic diagram of
Ultrasonic Sensor
CONCEPTUAL DESIGN OF COLLISION
AVOIDANCE SYSTEM
FUNDAMENTALLY, CAS IS STRIVING TO PROVIDE
ACTIVE COLLISION AVOIDANCE SAFETY FOR THE
HOST VEHICLE. THE SYSTEM BASICALLY CONSIST AN
OBSTACLE SENSING DEVICE, CONTROL MODULE AS
WELL AS THE ACTUATOR FOR ENABLING desired
output. As far as CAS is concerned, it
follows the following procedure for
developing an active safety system.
CAS deals with two basic object detection
modes. First one is deceleration range and
another one is braking range. The system,
which is provided with obstacle sensing
device, gets the obstacle warning ahead of
the host vehicle, and also the distance that
object has been detected. After the data
received by the control module from sensing
device, it decides whether the object is in
deceleration range or in braking range

7. according to the data fed already in to the
control module as per control algorithm.
Simply, as the object found with in the
deceleration range controller actuates only
the throttle actuator for deceleration.
Otherwise if the object found closer than
deceleration range i.e., braking range
controller actuates both throttle and brake
for deceleration as well as applying brake
respectively. If the obstacle found in the
range of deceleration there will be no need
to apply the brake. That is the vehicle has
enough distance to decelerate and to have a
control over steering. Hence the driver can
ultimately steer the vehicle from obstacle. If
the object is found within the braking range
CAS will not have enough distance to
decelerate and take steer. So that ultimately
it goes for brake for avoiding smash.
Also, the systems deceleration range and
braking ranges were decided according to
the vehicle’s individual dynamics as well as
its deceleration ability and Braking
performance. i.e., stopping distance.
The below shown figure 2 is the proposed
model for Collision Avoidance Systems for
vehicles. As per the circuit the signal goes to
the input conditioning that may be Analogue
to digital converter from various input
sensors as shown in circuit diagram. The
micro controller processes the input
according to the algorithm, which was fed
in to the micro controller. The output of the
micro controller is modified to the output
conditioning i.e., Digital to Analog
converter. The appropriate pulses control
the actuator unit, which is gaining operation
signals from micro controller output.
As per the design an ultrasonic distance
measurement sensor has been proposed as
obstacle detecting sensor. The inductive
sensor, which gives the pulses to the micro-
controller, is the source for vehicle speed
measurement. And the Rotary
potentiometers are used here as the pedal
position sensor for both Accelerator as well
as Brake. The micro controller used here is
89C51. And the actuator proposed here is
stepper motor for both throttle and brake
control. Stepper motor can be rotate as steps
so that we can achieve similar to the normal
operation of the throttle and brake pedals.
REACTION TIMES AND STOPPING
DISTANCES
In our studies we investigated the effects
of luminance, contrast and spatial frequency
on reaction time. Of particular interest were
the combinations of parameters, which

8. simulate urban night driving conditions that
are low luminance, low contrast and low
spatial frequencies. As expected, we found
that visual reaction time increases with
reducing target visibility. Reaction time
varied from 200 msec in optimal conditions,
usually encountered during daytime driving
(i.e. high contrast, photonic luminance), to
about 600 msec in non-optimal conditions
experienced during night driving (i.e. low
luminance, low contrast)
It is of interest to note how the RT data
might translate into critical (safe) stopping
distances. The Highway Code
recommendation s for “the shortest
stopping distances” for various vehicles
speed break these down to "thinking" and
"braking" distances. The "thinking distance"
is a component, which includes the visual
reaction time, the pedal response and the
mechanical action of the brakes. The
"braking distance" is the time taken to
decelerate to zero Kmph. For example, the
overall stopping distance for 50 kmph speed
is composed of a 9 m thinking distance and
a 14 m braking distance. Given a visual
reaction time of 200 msec for the calculation
of the "thinking distances" under optimal
daytime conditions (as suggested by the
Highway Code), it is possible to estimate the
corresponding "thinking distances" for the
non-optimal nighttime conditions.
Table illustrates the increase in thinking
and overall stopping distances for different
speeds, which would occur if the target were
of low contrast and luminance. Effectively,
we have calculated an increase in RT from
200 to 600 msec. This modest increase in
thinking time results in significant increases
in stopping distances despite the
conservative characteristics of our model.
For example, for a speed of 80 kmph the
increase in stopping distance is about 8.9
metres.
Table 1 Illustrating Thinking and Stopping
Table 1: "Thinking" and "stopping"
distances (in metres) under optimal photopic
conditions and non-optimal night-time
conditions for different vehicle speeds. The
additional distance is the calculated increase
in overall stopping distance under night-time
conditions. Note that 4 m is the length of an
average vehicle.
Factors, which affect the stopping distance
of the vehicle are, the mass of the car will
affect the stopping distance of the car due to
the effects offriction that will increase as the
mass of the car increases. Therefore the
stopping distance of the car will shorten as
the mass increases.

9. • Speed of the car affects the
stopping distance because it has
more energy to carry it further and
to overcome frictional force
therefore greater speed should
mean greater stopping distance.
• Aerodynamics will effect the
stopping distance because the more
aerodynamic the object in this case,
the car has less drag or air
resistance will be produced
therefore a greater stopping
distance will be achieved.
• The surface on which the car is to
stop on will affect the stopping
distance. Because, for example if
the road surface is textured, it will
require more energy from the car to
overcome friction from the rough
surface therefore this car will not
travel as far as on a non-textured or
smooth surface.
• Also all other frictional forces will
affect the car like the surface area
of the tyres on the car, the friction
between the axle and the chassis.
Also the amount of friction will
increases with temperature of the
surface and the tyres.
• Gravity, although I will be unable
to vary this in my experiment, it
would affect the friction between
the car and the road therefore
would increase the stopping
distance of the car if you could
decrease the gravitational pull on
the car.
VIII.Conclusion
Collision avoidance systems are especially
useful in bad weather conditions.
The sensors in the car would be capable of
detecting the poor conditions and would
inform the driver on how to drive in them.
For example, because fog affects visibility,
the sensors would recognize this and alert
the driver of any dangers that lie ahead, like
a windy turn or another car, giving the
driver enough time to slow down, allowing
him to escape from what could have been a
bad accident.
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