22-02-2013, 03:24 PM
SEMINAR REPORT On CRUISE CONTROL DEVICES
CRUISE CONTROL.pdf (Size: 462.77 KB / Downloads: 118)
Abstract
The concept of assisting driver in the task of longitudinal vehicle control is
known as cruise control. Starting from the cruise control devices of the seventies and eighties,
now the technology has reached cooperative adaptive cruise control. This paper will address the
basic concept of adaptive cruise control and the requirement to realize its improved versions
including stop and go adaptive cruise control and cooperative adaptive cruise control. The
conventional cruise control was capable only to maintain a set speed by accelerating or
decelerating the vehicle. Adaptive cruise control devices are capable of assisting the driver to
keep a safe distance from the preceding vehicle by controlling the engine throttle and brake
according to the sensor data about the vehicle. Most of the systems use RADAR as the
sensor .a few use LIDAR also. Controller includes the digital signal processing modules and
microcontroller chips specially designed for actuating throttle and brake. The stop and go cruise
control is for the slow and congested traffic of the cities where the traffic may be frequently
stopped. Cooperative controllers are not yet released but postulations are already there. This
paper includes a brief theory of pulse Doppler radar and FM-CW LIDAR used as sensors and
the basic concept of the controller.
INTRODUCTION
Everyday the media brings us the horrible news on road accidents. Once a report said
that the damaged property and other costs may equal 3 % of the world’s gross domestic
product. The concept of assisting driver in longitudinal vehicle control to avoid collisions has
been a major focal point of research at many automobile companies and research
organizations. The idea of driver assistance was started with the ‘cruise control devices’ first
appeared in 1970’s in USA. When switched on, this device takes up the task of accelerating or
braking to maintain a constant speed. But it could not consider the other vehicles on the road.
An ‘Adaptive Cruise Control’ (ACC) system developed as the next generation assisted the
driver to keep a safe distance from the vehicle in front. Conventional cruise control was capable
only to maintain a set speed by accelerating or decelerating the vehicle. Adaptive cruise control
devices are capable of assisting the driver to keep a safe distance from the preceding vehicle by
controlling the engine throttle and brake according to the sensor data about the vehicle. This
system is now available only in some luxury cars like Mercedes S-class, Jaguar and Volvo
trucks the U.S. Department of transportation and Japan’s ACAHSR have started developing
‘Intelligent Vehicles’ that can communicate with each other with the help of a system called
‘ Co-operative Adaptive Cruise Control’ .this paper addresses the concept of Adaptive Cruise
and its improved version.
ADAPTIVE CRUISE CONTROL (ACC)
PRINCIPLE OF ACC
ACC works by detecting the distance and speed of the vehicles ahead by using either a
Lidar system or a Radar system .The time taken by the transmission and reception is the key of
the distance measurement while the shift in frequency of the reflected beam by Doppler Effect is
measured to know the speed. According to this, the brake and throttle controls are done to keep
the vehicle the vehicle in a safe position with respect to the other. These systems are
characterized by a moderately low level of brake and throttle authority.
Adaptive cruise control devices are capable of assisting the driver to keep a safe distance from
the preceding vehicle by controlling the engine throttle and brake according to the sensor data
about the vehicle. Most of the systems use RADAR as the sensor .a few use LIDAR also.
Controller includes the digital signal processing modules and microcontroller chips specially
designed for actuating throttle and brake. These are predominantly designed for highway
applications with rather homogenous traffic behavior. The second generation of ACC is the Stop
and Go Cruise Control (SACC) whose objective is to offer the customer longitudinal support on
cruise control at lower speeds down to zero velocity. The SACC can help a driver in situations
where all lanes are occupied by vehicles or where it is not possible to set a constant speed or in a
frequently stopped and congested traffic. There is a clear distinction between ACC and SACC
with respect to stationary targets. The ACC philosophy is that it will be operated in well
structured roads with an orderly traffic flow with speed of vehicles around 40km/hour. While
SACC system should be able to deal with stationary targets because within its area of operation
the system will encounter such objects very frequently.
RADAR (Radio Detection and Ranging):
RADAR is an electromagnetic system for the detection and location of reflecting objects like air
crafts, ships, space crafts or vehicles. It is operated by radiating energy into space and detecting
the echo signal reflected from an object (target) the reflected energy is not only indicative of the
presence but on comparison with the transmitted signal, other information of the target can be
obtained. The currently used ‘Pulse Doppler RADAR’ uses the principle of ‘Doppler effect’ in
determining the velocity of the target.
PULSE DOPPLER RADAR:
The block diagram of pulse Doppler radar is as shown in figure.2.The continuous wave
oscillator produces the signal to be transmitted and it is pulse modulated and power amplified.
The ‘duplexer’ is a switching device which is fast-acting to switch the single antenna from
transmitter to receiver and back. The duplexer is a gas-discharge device called TR-switch. The
high power pulse from transmitter causes the device to breakdown and to protect the receiver.
On reception, duplexer directs the echo signal to the receiver. The detector demodulates the
received signal and the Doppler filter removes the noise and outputs the frequency shift ‘fd’.
RADAR ANTENNA SCHEMES:
Radar systems employ a variety of sensing and processing methods to determine the position
and speed of vehicles ahead. Two such important schemes are:
1. mechanically steered antenna
2. electronically steered antenna
1. Mechanically steered antenna:
A parabolic reflector is used as mechanically steered antenna. The parabolic surface is
illuminated by the source of energy placed at the focus of the parabola. Rotating about its
axis, a circular parabola is formed. A symmetrical beam can be thus obtained. The rays
originating from focus are reflected parallel to the axis of parabola. [Fig (3.2.3).]
Electronically steered phased array radar antenna
A phased array is a directive antenna made up of a number of individual antennas, or radiating
elements. The radiation pattern is determined by the amplitude and phase of current at each of
its elements. It has the advantage of being able to have its beam electronically steered in angles
by changing phase of current at each element. The beam of a large fixed phased array antenna is
therefore can be rapidly steered from one direction to another without mechanical positioning
Consider the following figure with ‘N elements placed (equally separated) with a distance‘d’
apart. Suppose they have uniform response to signals from all directions. Element ‘1’ is taken as
reference with zero phase.
FUSION SENSOR
The new sensor system introduced by Fujitsu Ten Ltd. and Honda through their PATH program
includes millimeter wave radar linked to a 640x480 pixel stereo camera with a 40 degree
viewing angle. These two parts work together to track the car from the non-moving objects.
While RADAR target is the car’s rear bumper, the stereo camera is constantly captures all
objects in its field of view.
COOPERATIVE ADAPTIVE CRUISE CONTROL [CACC]
Though conventional ACC and SACC are still expensive novelties, the next generation
called Cooperative ACC is already being tested. While ACC can respond to the difference
between its own behavior and that of the preceding vehicle, the CACC system allows the
vehicles to communicate and to work together to avoid collision.
Partners of Advanced Transit Highways (PATH) –a program of California Department of
Transportation and University of California with companies like Honda conducted an
experiment in which three test vehicles used a communication protocol in which the lead car
can broadcast information about its speed, acceleration ,breaking capacity to the rest of the
groups in every 20ms.
CONCLUSION
The accidents caused by automobiles are injuring lakhs of people every year. The safety
measures starting from air bags and seat belts have now reached to ACC, SACC and CACC
systems. The researchers of Intelligent Vehicles Initiative in USA and the Ertico program of
Europe are working on technologies that may ultimately lead to vehicles that are wrapped in a
cocoon of sensors with a 360 –degree view of their surroundings. It will probably take decades,
but car accidents may eventually become as rare as plane accidents are now, even though the
road laws will have to be changed, upto an extent since the non-human part of the vehicle
controlling will become predominant.