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ABSTRACT
Automotive vehicles are increasingly being equipped with collision
avoidance and warning systems for predicting the potential collision with an
external object, such as another vehicle or a pedestrian. Upon detecting a
potential collision, such systems typically initiate an action to avoid the
collision and/or provide a warning to the vehicle operator. This system consist
of a distance-measuring system based on ultrasonic sound utilizing the PIC
16F877A microcontroller and transmits a burst of ultrasonic sound waves
towards the target and then receives the corresponding echo. An ultrasonic
sound sensor is used to detect the arrival of the echo to the system. The time
taken for the ultrasonic burst to travel the distance from the system to the
subject and back to the system is accurately measured by the microcontroller. It
also provides a warning signal to the driver if the distance between vehicle and
obstacle crosses a particular limit. It also monitors the speed of the vehicle and
if the speed limit is exceeded it is informed to the driver. The speed limit for
different class of vehicles is set by authorities at different. Different types of
vehicle speed limiters are in current use for regulating traffic especially across
roads near populated areas such as hospitals, malls and schools. This project
“DYNAMIC SPEED GOVERNOR” is a new method by which vehicle speed is
controlled externally rather than internally. The speed measurement and control
is accomplished via PIC16F877A microcontroller.
INTRODUCTION
Concerning about the work-related safety hazards, everyone probably
think about what goes on inside the workplace. But one of the greatest threats to
your safety is not in the work place but rather on the road. Someone is injured
every 18 seconds. Over 2 million of those injuries turn out to be disabling.
When we think about the serious accident, it could change your life and not for
the better. The increasing demand for flexibility as well as technological even
though there are several advanced technological innovations are available today
for vehicle safety, the growth in the number of accidents is continues regularly.
And most of these accidents are especially due to collision.
1.1 Rear End Collision
A rear-end collision is a traffic accident wherein a vehicle crashes into the
vehicle in front of it. Common factors that contribute to rear-end collisions
include by driver inattention or distraction, tailgating, panic stops, and reduced
traction due to weather or worn pavement. It may also be a rail accident wherein
a train runs into the rear of a preceding train.
Typical scenarios for rear-ends are a sudden deceleration by the first car
(for example, to avoid someone crossing the street) so that the car behind does
not have the time to brake and collides with the first. Alternatively the following
car may accelerate more rapidly than the leading (for example, leaving an
intersection) resulting in a collision.
As a rule of thumb, if the two vehicles have similar physical structure,
crashing into another car is equivalent to crashing into a rigid surface (like a
wall) at half of the closing speed. This means that rear-ending a stationary car
while travelling at 50 km/h (30 mph) is equivalent, in terms of deceleration, to
crashing into a wall at 25 km/h (15 mph).
The same is true for the vehicle crashed into. However, if one of the
vehicles is significantly more rigid (e.g. the rear of a truck) then the deceleration
is more typically reflected by the full closing speed for the less rigid vehicle.
Dynamic Speed Governor
The Dynamic Speed Governor is a system that can be implemented
effectively for an efficient and perfectly controlled traffic system. This system
can limit the speed of a moving vehicle over an area where the speed has to be
restricted and retained within a predetermined value. The Dynamic Speed
Governor consists of mainly two parts, the Transmitter section and the Receiver
section.
The transmitter section is mounted on the signal board, on which the
speed limit over that area is indicated. Receiver section is kept inside the
vehicle. The radio frequency signal from the transmitter is transmitted and the
receiver receives it. If the speed of the vehicle is greater than the speed limit
proposed for that particular area, which in turn is transmitted by the transmitter
section, the speed governor comes into action and restricts the driver from going
beyond that rated speed.
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If the system detects that the speed of the vehicle has gone beyond the
speed limit, a signal is generated from the dynamic speed governor circuit. This
signal in turn is used to drive the mechanical part of the vehicle, which closes
the fuel nozzle of the vehicle thereby restricting the vehicle from going beyond
that speed.
Dynamic speed governor is designed with the aim of dynamically
limiting the speed of the vehicle to a preset value, when the driver drives
through an area that has a preset speed limit, thereby encouraging safe driving
and preventing accidents.
1.3 Accident Avoidance System Using Dynamic Speed Governor
This report describes a distance-measuring system based on ultrasonic
sound utilizing the PIC 16F877A microcontroller. With the help of the distance
measured, the micro-controller will make the vehicle stop suddenly if the
vehicle is about to hit any obstacle or any other vehicle. With the help of this
technology accidents are avoided. The system transmits a burst of ultrasonic
sound waves towards the target and then receives the corresponding echo. An
ultrasonic sound sensor is used to detect the arrival of the echo to the system.
The time taken for the ultrasonic burst to travel the distance from the system to
the subject and back to the system is accurately measured by the
microcontroller.
Different types of vehicle speed limiters are in current use for regulating
traffic especially across roads near populated areas such as hospitals, malls and
schools. This project “DYNAMIC SPEED GOVERNOR” is a new method by
which vehicle speed is controlled externally rather than internally. The speed
measurement and control is accomplished via two PIC16F877As with a RF
transmitter and a receiver.
The speed limiting system presented in this project combines several
pioneering techniques that integrate wireless technologies in order to implement
a reliable speed control system. The power of the proposed system lies in its
flexibility and capability of development with little hardware changes such as
changing the speed limits and speed control methods using the software of the
base station in negligible amount of time.
Speed Governor regulates the top speed and/or maximum rpm of a
vehicle, whether it is electronically or mechanical. The governor protect the
drivers from operating at unsafe speed, or to protect the car from being driving
beyond its physical or mechanical threshold. Systems designed to avoid
collisions or reduce accident damage using brake control and external sensing
technology such as radar sensors to predict collisions with the vehicle ahead
have been proposed in the first phase of the ASV project.
The present system concept was defined to assist the driver with accident
avoidance. The type of accident target was defined rear-end collisions. This
report describes the creation of a system aimed to achieve practical application.
The automotive vehicles are maximized by warning systems and collision
avoidance for potential collision with an object like pedestrian or vehicle. Based
on potential collision, these systems typically start to ignore collision and/or
offer an advice to an operator of the vehicle.
LITERATURE REVIEW
The new speed limiting system presented in this project combines several
pioneering techniques that integrate wireless technologies in order to implement
a reliable speed control system. This proposed system can be easily
implemented near different populated areas. The power of the proposed system
lies in its flexibility and capability of development with little hardware changes
such as changing the speed limits and speed control methods using the software
of the base station in negligible amount of time.
The proposed system is based on microcontroller technology for
collecting data related to speed and transmitting it through a transceiver to a
base station that analyzes the transmitted data and takes appropriate decisions
related to speed limit and control requirements.
Speed Governor regulates the top speed and/or maximum rpm of a
vehicle, whether it is electronically or mechanical. The governor is emplaced by
the manufacturer to meet laws of the nation is which the vehicle will be sold,
protect the drivers from operating at unsafe speed, or to protect the car from
being driving beyond its physical or mechanical threshold.
2.1 Evolution of Accident Avoidance System
The first demonstration of forward collision avoidance was performed in
1995 by a team of scientists and engineers at Hughes Research Laboratories in
Malibu, California. The system was radar based technology that was readily
available at Hughes Electronics, but virtually no place else in the world. A small
custom fabricated radar-head was developed specifically for this automotive
application at 77 GHz. The forward radar-head, plus the signal processing unit
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and visual-audio-tactile feedbacks were first integrated into a Lexus SC400, and
shortly thereafter into a Cadillac STS.
An SUV-style concept vehicle known as SSC (Safety Security &
Communications), that contained many other of Delco's most advanced
technologies, also received the "Forewarn" collision avoidance system and was
shown to the public for the first time at the North American International Auto
Show at Cobo Hall in Detroit in 1996. This was a fully functional vehicle, and
demonstrations were concurrently being provided by a duplicate vehicle.
While primarily a warning system, with various feedbacks, the system did
have minor control of the brakes which were pulsed to begin a braking action in
the event of a potential collision, making it also the beginning of avoidance
systems. These SSC vehicles were sent around the world, including Europe and
Asia, to share this very important life-saving technology with all the major
automotive manufacturers in an effort to quick-start their individual
development efforts. It took almost 20 years for this important technology to
reach the consumer marketplace.
In 2011, a question was submitted to the European Commission regarding
stimulation of these "collision mitigation by braking" systems. The mandatory
fitting of Advanced Emergency Braking System in commercial vehicles will be
implemented on 1 November 2013 for new vehicle types and on 1 November
2015 for all new vehicles in the European Union. This could, according to the
impact assessment, ultimately prevent around 5,000 fatalities and 50,000 serious
injuries per year across the EU.
Crash imminent braking (CIB) systems have been equipped in high Ͳend
passenger vehicles by many auto manufactures. Due to the complex nature of the CIB technology, the features and performance of various CIB systems differ
significantly. As to date, there are no standards to evaluate and compare the
comprehensive performance of different CIB systems. The percentage kinetic
energy reduction is a measure used in the performance evaluation.
Integrated Collision Avoidance and Vehicle Path Control: In an
emergency situation, in vehicle warning systems intervene and aim to make the
driver to take a suitable action. If the risk of an accident persists, then an
autonomous collision avoidance manoeuvre can prevent it. Path and speed
controls are developed in order to enable such a manoeuvre by using steering
and braking actuators respectively.
Collision mitigation systems are the next step towards active safety.
Whereas collision avoidance requires expensive environmental perception,
collision mitigation can be realized at reasonable costs. The goal is to develop
solutions for collision mitigation that are able to improve the market potential
towards low segments
EXISTING METHOD
3.1 Collision Avoidance System
A collision avoidance system is an automobile safety system designed to
reduce the severity of a collision. Also known as pre-crash system, forward
collision warning system or collision mitigating system, it uses radar and
sometimes laser and camera to detect an imminent crash. Once the detection is
done, these systems either provide a warning to the driver when there is an
imminent collision or take action autonomously without any driver input (by
braking or steering or both).
Collision avoidance by braking is appropriate at low vehicle speeds (e.g.
below 50 km/h), while collision avoidance by steering is appropriate at higher
vehicle speeds. Cars with collision avoidance may also be equipped
with adaptive cruise control, and use the same forward-looking sensors.
The first demonstration of forward collision avoidance was performed in
1995 by a team of scientists and engineers at Hughes Research Laboratories in
Malibu, California. The project was funded by Delco Electronics, and was led
by HRL physicist Ross D. Olney.
The technology was labeled for marketing purposes as "Forewarn". The
system was radar based - a technology that was readily available at Hughes
Electronics, but virtually no place else in the world. A small custom fabricated
radar-head was developed specifically for this automotive application at
77 GHz.
While primarily a warning system, with various feedbacks, the system did
have minor control of the brakes which were pulsed to begin a braking action in
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the event of a potential collision, making it also the beginning of avoidance
systems.
Adjustable Speed Limiter Device
Adjustable Speed Limiter Device allows the driver to set a speed limit
that cannot be exceeded by standard gas pedal operation. The driver can
override the limit, however, by pressing the accelerator pedal beyond normal
usage limits (>90 percent pedal travel).
Adaptive Cruise Control
Adaptive Cruise Control helps drivers maintain a preset distance from the
vehicle they are following, using a radar module mounted at the front of the
vehicle that measures the gap and closing speed to the vehicle ahead. The
system automatically adjusts the speed of the car to help maintain a preset
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distance from the vehicle in front. If the radar sensor becomes blocked by snow,
ice or mud, the driver receives a notice of reduced or suspended functionality.
ACC is available on select Ford and Lincoln vehicles in North America. In
Europe and China, ACC is available with another technology called Distance
Alert. Distance Alert helps the driver to keep a proper distance from the vehicle
ahead by providing a visual warning if the driver-selected following distance is
exceeded.
Forward Collision Warning with Brake Support
Forward Collision Warning with Brake Support technology uses the same
radar module as Adaptive Cruise Control to detect range and speed. Forward
Collision Warning with Brake Support activates a visual and audible warning
when the system detects a high risk of collision with the vehicle in front. In
addition, the brake system is pretension and the “servo boost” assistance system
is modulated to provide faster brake performance (e.g., as soon as the driver lifts
the gas pedal), if required by the driver. As with ACC, if the sensor becomes
blocked, the driver receives a notice of reduced or suspended functionality. This
technology is available on certain Ford and Lincoln vehicles in North America
and Europe.
3.2 Collision Warning Systems
A CWS assists a driver in preventing or mitigating a rear-end collision by
presenting auditory, visual, and/or haptic warnings.7 The current humanmachine
interfaces the manner in which a CWS alerts a driver are consistent
with the key findings of the research on CWS development. This research has
examined the extent to which various warning alerts aid drivers in a variety of
potentially dangerous situations, including frontal collision, blind spot
detection, and lane departure. Researchers consistently reported faster response
times to sudden events when drivers were alerted by multi-modal signals, such
as an auditory/visual or auditory/haptic, rather than a single sensory cue.
The findings of the research into the efficacy of different warning cues to
alert a driver to a potential collision, although conducted with passenger
vehicles, also apply to commercial vehicles. While the timing of the warnings
presented to a heavy truck driver may differ from the timing posed to a driver in
a passenger vehicle, the basic findings of the benefits of multi-modal cues
remain.
3.3 Dynamic Brake Support
Various versions of a DBS system exist, but they all share a common
purpose: to assist when a driver brakes in response to a sudden emergency
situation.8 A DBS system uses information from forward-looking
sensors/cameras to ascertain driving situations and potential conflicts. One
function includes pre-charging brakes in anticipation of the driver’s braking
response. As part of this function, the system builds up preventive brake
pressure by placing the braking pads on the brake disks and putting the
hydraulic brake assist into an alert state. When a driver actually brakes, the
fastest braking response time is achieved. The pre-charging of the brake system,
which can save about 30 milliseconds in passenger vehicles, may result in a
reduction of impact velocity but is unlikely to actually prevent a collision.
Some DBS systems can aid a driver by delivering a predetermined
braking force when a driver initiates a sudden braking response to avoid an
imminent collision. This braking assistance is particularly useful because most
drivers do not apply sufficient pressure when braking in emergency situations
(Page and others 2005). A DBS system can also measure the speed at which the
brake pedal is applied, as well as the braking force, differentiating braking in
response to a sudden emergency event from controlled deceleration. When a
certain threshold is reached, the system can apply full braking pressure,
assisting the driver in achieving the shortest stopping distance.
Most passenger vehicle manufacturers in the United States that offer
forward CAS offer some version of a DBS system in their vehicles. The
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functionalities of a DBS system, described above, are more limited in trucktractors
and motor coaches. Due to the current design of brakes on such
vehicles—in particular, air brake systems—pre-charging of brakes is not
feasible.
3.4Autonomous Emergency Braking
AEB refers to a component of forward CAS that autonomously applies
brakes in order to prevent or mitigate a collision. AEB is typically activated
after a warning system alerts a driver about a potential rear-end collision and the
driver fails to respond. The AEB may apply either partial or full braking force,
or cascaded braking, which is the application of partial braking followed by full
braking force.
AEB systems designed to work at high speeds require different types of
sensors, such as mid- or long-range sensors, while those designed for lower
speeds use short-range sensors. Some of the current AEB systems are designed
to prevent collisions (up to certain speeds), while others may be capable only of
collision mitigation.
An ultrasonic sound sensor is used to detect the arrival of the echo to the
system. It consist of a distance-measuring system based on ultrasonic sound
utilizing the microcontroller and transmits a burst of ultrasonic sound waves
towards the target and then receives the corresponding echo. The time taken for
the ultrasonic burst to travel the distance from the system to the subject and
back to the system is accurately measured by the microcontroller. It also
provides a warning signal to the driver if the distance between vehicle and
obstacle crosses a particular limit. It also monitors the speed of the vehicle and
if the speed limit is exceeded it is informed to the driver. The speed limit for
different class of vehicles is set by authorities at different.
MICRO
CONTROLLER
16F877A
MOTOR WHEELS
BUFFER
ALARM CIRCUIT
SPEED
REGULATOR CKT
ULTRASONIC RX
ULTRASONIC TX
KEY BOARD
OBJECT
LCD
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4.1.1 Ultrasonic Sensor
Ultrasonic sensor offers very short to long-range detection and ranging, in
an incredibly small package with ultra low power consumption. It is used to
detect the object. Ultrasonic ranging module HC - SR04 provides 2cm - 40cm
the ranging accuracy can reach to 3mm.The modules includes ultrasonic
transmitter, receiver and control circuit. The Ultrasonic sensor line is the most
cost-effective solution for applications where precision range-finding, lowvoltage
operation, space saving, and low-cost are needed. This output is fed to
the microcontroller. Ultrasonic sensors are commonly used for a wide variety of
noncontact presence, proximity, or distance measuring applications. These
devices typically transmit ultrasonic sound toward a target, which reflects the
sound back to the sensor. The system then measures the time for the echo to
return to the sensor and computes the distance to the target using the speed of
sound in the medium.
Ultrasonic Ranging System
The development of applications using ultrasonic sensors requires
good understanding of its operating principles and its interaction with the
environment. They rely on the principle of time of flight or propagation of
sound waves in air. The system either measures the echo reflection of the sound
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from the object (in case where the transmitter and the receiver is on the same
device) or the time of flight of the sound wave from the transmitter to the
receiver (in case either the transmitter or the receiver is mounted on the object).
4.1.3 Ultrasonic Transmitter
The transmitter consists of an electronic circuitry and an
electromechanical transducer. The electronic circuitry generates the required
frequency electrical signal and the electromechanical transducer converts that
electrical signal into the physical form and activates the open medium surface.
This oscillating physical surface creates the ultrasonic waves. The oscillating
surface creates a pressure variation and ultimately a pressure wave with a
frequency equal to that of the surface oscillation. The figure below shows the
generation of ultrasonic waves.