Seminar

On

CRUISE CONTROL SYSTEMS IN CARS

By:

S.GIRIDHARAN (1PI07ME087)

Guide:Dr. K.N. Seetharamu

Department of Mechanical EngineeringPES Institute of Technology

Jan 2011 – May 2011DEPARTMENT OF MECHANICAL

ENGINEERING

PES INSTITUTE OF TECHNOLOGY100 FEET RING ROAD, BANASHANKARI III

STAGEBANGALORE-560085

ABSTRACT

Cruise control is a new technological development which incorporates a

factor of comfort in driving. Safety is only a small benefit of this system. In

short, cruise control can be said to be a system which uses the principles of radar

to determine the distances between two consecutive moving vehicles in which

either one or both of them is incorporated with this system. The electromagnetic

rays from radar system are sensed by sensors in the vehicle which in turn rely

commands to the throttle and brakes of the vehicle to perform according to the

adjacent vehicle’s distance. So cruise control is a system which provides comfort

to drivers during long monotonous drives.

CONTENTS

1. INTRODUCTION 1

2. WHAT IS CRUISE CONTROL 3

3. HOW TO SET CRUISE CONTROL 4

4. ADAPTIVE CRUISE CONTROL 6

5. PARTS AND WORKING 9

5.1 MILLIMETER-WAVE RADAR 11

5.2 STEREO CAMERA 12

5.3 IMAGE PROCESSOR 12

5.4 FUSION PROCESSOR 12

5.5 HEADWAY CONTROL UNIT 13

6. FUTURE ASPECTS 15

7. DANGERS OF CRUISE CONTROL 17

8. CONCLUSION 18

9. REFERENCE 19

CHAPTER 1

INTRODUCTION

Every minute, on average, at least one person dies in a crash. If you read

this article from start to finish 30 or more deaths will have occurred across the

globe by the time you are done. Auto accidents will also injure at least 10 million

people this year, two or three million of them seriously. All told, the hospital

bills, damaged property and other costs will add up to 1 - 3 % of the world’s

gross domestic product according to the Paris based organization for economic

cooperation and development. And, of course, the losses that matter most is not

even captured by these statistics, because there is no way to put a dollar value on

them.

Engineers have been chipping away at this staggering numbers for a long

time. Many safety innovations in the areas of banking systems, air bags, seat

belts, body structures, steering and suspension have had a beneficial effect. Air

bags and seat belts save tens of thousands of people a year by preventing their

head from crashing into the windshield. Supercomputers now let designers create

car frames and bodies that protect the people inside by absorbing much of energy

of crash as possible. As a result, number of fatalities per million kilometers of

vehicle travel has decreased. But the ultimate solution and the only thing that will

save far more lives, limbs and money are to keep out cars from smashing into

each other in the first place.

That is exactly what engineers in the United States, Europe and Japan are

trying to do. They are applying advanced microprocessors, radars, high-speed

ICs and signal-processing chips and algorithms in R&D programs that mark an

about face in the automotive industry: from safety systems that kick in after an

accident occurs, attempting to minimize injury and damage, to ones that prevent

collisions altogether.

The first collision avoidance features are already on the road, as pricey

cruise control options on a small group of luxury cars. Over the next few years,

these systems will grow more capable and more widely available, until they

become standard equipment on luxury vehicles. Meanwhile, researchers will be

bringing the first cooperative systems to market. This will take active safety

technology to the next level, enabling vehicles to communicate and coordinate

responses to avoid collisions. Note that to avoid liability claims in the event of

cars equipped with cruise control systems, manufacturers of these systems and

the car companies that use them are careful not to refer them as safety devices.

Instead they are being marketed as driver aids, mere convenience made possible

by latest innovative technology.

CHAPTER 2

WHAT IS CRUISE CONTROL

Cruise control is a system, which automatically controls the speed of an

automobile. The driver sets the speed and the system will take over the throttle of

the car to maintain the speed. The system is thereby improving driver comfort in

steady traffic conditions. In congested traffic conditions where speeds vary

widely these systems are no longer effective.

Most cruise control systems don’t allow the use of cruise control below a

certain speed. The use of cruise control would be significantly increased if the

vehicle speed could automatically adapt to the traffic flow. This feature can be

handy for long drives along sparsely populated roads and usually results in better

fuel efficiency. It is also known in some places as “poor man’s radar detector”, as

by cruise control, a driver who otherwise tends to unconsciously increase speed

over the course of a highway journey may avoid a speeding ticket.

Blind inventor and mechanical engineer Ralph teetor invented cruise

control in 1945. His idea was born out of the frustration of riding in a car driven

by his lawyer, who kept speeding up and slowing down as he talked. The

Chrysler Corporation on the 1958 Chrysler imperial introduced first car with

cruise control systems.

CHAPTER 3

HOW TO SET CRUISE CONTROL

In modern designs, the cruise control may or may not need to be turned on

before use – in some designs it is always “on” but not always enabled. Most

designs have a separate “on” switch, as well as set, resume, accelerate and coast

functions. The system is operated with controls easily within the driver’s reach,

usually with two or more buttons on the steering wheel or on the windshield

wiper or turn signal stalk. The cruise switches of a latest Ford car are shown in

the figure below.

Fig 3.1

Driver should bring the car to speed manually and then use a button to set

cruise control to the current speed. Most systems do not allow the use of cruise

control below a certain speed to discourage use in city driving. The car will

maintain that speed by actuating the throttle. Most systems can be turned off both

explicitly or automatically, when the driver hits the brake or clutch. When the

cruise control is in effect, the throttle can still be used to accelerate the car,

although the car will then slow down until it reaches the previously set speed.

Fig 3.2

Now let us see the individual functions of each cruise switches in detail.

1. The on and off buttons really don’t do much. Some cruise controls don’t

have these buttons; instead, they turn off when the driver hits the brakes,

and turn on when the driver hits the set button.

2. The set/accelerate button tells the car to maintain the speed you are

currently driving. If you hit the set button at 45 km/hr, the car will maintain

your speed at 45 km/hr. holding down the set/accelerate button will make

the car accelerate. On most cars, tapping it once will make the car go 1

km/hr faster.

3. If recently disengaged the cruise control by hitting the brake or clutch

pedal, hitting the resume button will command the car to accelerate back

to the most recent speed setting.

4. Holding down the coast button will cause the car to decelerate, just as if

you took your foot completely off the gas. On most cars, tapping the coast

button once will cause the car to slow down by 1 km/hr.

5. The brake pedal and clutch pedal each have a switch that disengages the

cruise control as soon as the pedal is pressed. So you can disengage the

cruise control with a light tap on the brake or clutch.

CHAPTER 4

ADAPTIVE CRUISE CONTROL

There is a new type of cruise coming onto the market called adaptive

cruise control. Two companies, TRW and Delphi Automotive Systems are

developing a more advanced cruise control that can automatically adjust a car’s

speed to maintain a safe following distance.

Adaptive cruise control is similar to conventional cruise control in that it

maintains the vehicle’s pre-set speed. However, unlike conventional cruise

control, this new system can automatically adjust speed in order to maintain a

proper and safe distance between vehicles in the same lane.

These adaptive cruise control (ACC) systems, which add $1500 to $3000

to the cost of a car uses laser beams or forward looking radars to measure the

distance from the vehicle they are in to the car ahead and its speed relative to

theirs. If a car crosses into the lane ahead or if the lead vehicle slows down, say,

and the distance is now less than the preset minimum (typically a 1 or 2 second

interval of separation) or if another stationary object is detected, the system

applies brakes, slowing down the vehicle, until it is following at the desired

distance. If the leading car speeds up or moves out of the lane, the system opens

the throttle until the car has returned to the cruise control speed set by the driver.

In May 1998, Toyota became the first to introduce an ACC system on a

production vehicle when it unveiled a laser-based system for its progress

compact luxury sedan, which it sold in Japan. Then Nissan followed suit with a

radar-based system, in the company’s Cima 41LV-2, a luxury sedan also sold

only in Japan. In September 1999, Jaguar began offering an ACC for its XKR

coupes and convertibles sold in Germany and Britain. Delphi Delco Electronic

Systems supplies the radar sensing unit; TRW Automotive Electronics, the brake

control; and Siemens, the assembly that manipulates the throttle. Last fall,

Mercedes-Benz and Lexus joined the adaptive cruise control movement. Lexus

offers an ACC option for its top-of-the-line LS430; at the movement, it is the

only ACC system available in the United States. Mercedes’ system is an option

on its C-Class and S-Class models, which are available in Europe.

Fig 4.1

All of the ACC systems available today are built around sensors that

detect the vehicle ahead through the use of either radar or lidar (light detecting

and ranging, the laser based analog to radar). The choice of sensors presents

classic design tradeoffs. We will see the radar-based system in detail later. Lidar

is less expensive to produce and easier to package but performs poorly in rain

and snow. The light beams are narrower than water droplets and snowflakes,

pushing down the signal-to-noise ratio in bad weather. Another problem is that

accumulations of mud, dust or snow on the car can block lidar beams.

At present, only one automaker, Lexus, uses a laser-based ACC system, in

its LS430 luxury sedan. System engineers have acknowledged lidar’s

shortcomings and taken steps to make the system unavailable in situations where

the weather may limit its effectiveness. According to the LS430 owner’s manual,

the system will automatically shut itself off if the windshield wipers are turned to

a rapid setting, indicating heavy rain or snow; if something activates the anti-lock

braking system (which helps the driver maintain a steering control and reduces

stopping distances during emergency braking situations); or if the vehicle skid

control system detects the slipping of tires on turns that is common in wet

weather.

Fig 4.2

The Lexus LS430 laser sensor built into the front grille

CHAPTER 5

PARTS AND WORKING

We have already seen the working of a laser-based ACC system, its

limitations and all. Now let us take a look at how radar-based ACC system

works, in detail.

The main components of a typical radar-based ACC system are the

following.

1. Fusion sensor

2. Headway control unit

3. Throttle

4. Brake

5. Dashboard display

Fusion sensor is a combination of sensors and processors. The fusion

sensor consists of the following components.

1. Millimeter-wave radar

2. Stereo camera

3. Image processor

4. Fusion processor

.

Fig 5.1

Architecture of a radar-based ACC system

Let us take a close look at each of these components, their individual

roles, in detecting hazards in the roadway and responding in the correct manner

so as to avoid those detected hazards

5.1 MILLIMETER-WAVE RADAR

Fundamental to any cruise control system is a sensor that can reliably

detect obstacles in the traffic environment in a variety of conditions. Millimeter-

wave radar is a method used for detecting the position and velocity of a distant

object. This radar has a forward-looking range of up to 500 feet. The radar unit is

housed behind the radiator grille.

Every 60 milliseconds, the sensor sends out a trio of overlapping beams of

electromagnetic radiations of approximately 3 degrees each (roughly the width of

one traffic lane). The beam runs up to 500 feet ahead of the vehicle, and the

sensor receives signals that are reflected back from objects in the roadway.

Velocity and range is derived, by measuring the Doppler frequency shift and time

of flight of transmission. Range is calculated using the formula

C = 2*R/T

Where ‘C’ is the velocity of light

‘R’ is the range

‘T’ is the time of flight of transmission.

This information is then fed into a microprocessor (fusion processor)

inside the passenger compartment.

A major advantage of radar is that the performance is not affected by the

time of the day, and therefore no driver adaptation is required for nighttime

driving. The performance advantages of radar over other sensors are enhanced

during poor weather conditions. Systems that rely on visible light are known to

suffer significantly in the very conditions for which they are relied upon the

most. Experience of radar operations has shown that reliable results can be

obtained, even in inclement weather conditions. Radar-based systems can “see”

at least 150 meters ahead in fog or rain, heavy enough to cut the driver’s ability

to see down to 10 meters or less.

5.2 STEREO CAMERA

The camera’s function is the same, as that of the radar, detection of cars

and other objects in the roadway. Camera view reaches to a distance of 60 meters

ahead of the vehicle. The stereo camera is situated by the rear view mirror. The

camera view produces good lateral image, but it is unable to provide good

estimates of range. The lane markings on the road are also detected by processing

images from the camera. The image is then sent to the image processor.

5.3 IMAGE PROCESSOR

The image-processing unit acts as an intermediate between the stereo

camera and the fusion processor. It is also situated by the rear view mirror, along

with the stereo camera. What image-processing unit is doing is that, it processes

the images from the stereo camera and the data is then fed into the fusion

processor.

5.4 FUSION PROCESSOR

The function of fusion processor is termed as Data Fusion. Data fusion is a

collection of techniques for combining the measurements from more than one

sensor to provide a more unified result. This has several benefits.

The overall estimates of parameters can be more accurate than for

individual sensor estimate, as they reinforce each other.

Any parameter need not depend on one sensor alone. This has benefits of

Fault Tolerance by allowing redundancy to be introduced into the system.

For example, if the system had infrared and video based sensors, it could

survive the failure of either of these and continue to function although

accuracy and performance in certain conditions can be reduced.

The fusion processor receives information from the two sensors,

millimeter-wave radar and stereo camera. The data contains information like lane

path, vehicle speed, range etc relative to host vehicle. The video produces good

lateral image, but it is not able to provide good estimate of range. The radar

conversely produces good estimates of range and hence good relative velocity

estimates, but has poor lateral positional accuracy. Thus by fusing data from

these two sensors the object position can be localized to a better accuracy by

considering the intersection of the two areas of positional uncertainty generated

by each sensor.

Another possible benefit of data fusion is that of object identification, by

combining the expected responses of an object in the sensors. For example, the

image processing may confuse a stationary pedestrian and a traffic sign,

especially at longer ranges, as they both are tall, thin objects. However fusing

data would allow an unambiguous decision to be reached immediately as the two

objects have radically different radar responses.

5.5 HEADWAY CONTROL UNIT

Having detected a hazard the system must respond in the most appropriate

manner so as to avoid the hazard. Evidence suggests that a small reduction in

driver reaction time will dramatically reduce the number of accidents. This can

be achieved by intervening with the controls of the vehicle. Headway control unit

takes up this job. Headway control unit has control on the brakes and throttle.

Headway control unit makes necessary adjustments to the brakes and throttle that

would allow maintaining a constant and safer distance behind the vehicle in

front. In addition to all these, if a suddenly stopped vehicle or a large object in

the roadway or even a bend in the road is detected, a red triangle flashes on the

dashboard, warning the driver. Then the driver must stop the vehicle by applying

brakes manually in the first two cases and steer the vehicle in the third case.

Fig 5.2

CHAPTER 6

FUTURE ASPECTS

Though conventional cruise control is still an expensive novelty, the next

generation, called co-operative adaptive cruise control, or CACC, is already

being tested in California and elsewhere. While ACC can only respond to a

difference between its own speed and the speed of the car ahead, cooperative

systems will two or more cars to communicate and work together to avoid a

collision. Ultimately, experiments say, the technology may let cars follow each

other at intervals as short as half a second. At 100 km/hr, that would amount to a

distance between cars of less than 14 meters (roughly two car lengths).

Fig 6.1

Meanwhile at Fujitsu Ten Ltd, Japan, engineers are working towards

another vision of the future of adaptive cruise control-one targeted squarely at the

realities of driving on often-congested urban and suburban highways. Fujitsu Ten

has demonstrated a prototype system for so called stop-and-go adaptive cruise

control. Ordinary ACC systems maintain a safe distance between cars at speeds

above 40 km/hr, whereas Fujitsu Ten’s system will work primarily at lower

speeds in heavy traffic. If the car in front stops, it will bring a vehicle to a

complete stop. Afterward, it will not re-engage the throttle-that’s up to the driver-

but as soon as the throttle is engaged, it will accelerate and decelerate along with

the leading car over any range of speeds between zero and the cruising speed set

by the driver.

Within a decade or so, the drivers of the most advanced cars will only

have to steer. Eventually, people might not be even entrusted with that task, at

least on limited access highways.

CHAPTER 7

DANGERS OF CRUISE CONTROL

The only danger with cruise control is the use of cruise control in wet and

slippery roads. You should turn off cruise control while driving through such

conditions. It is very dangerous to use cruise control in any slippery conditions

like rain, snow, or ice as it takes the complete control of the vehicle out of your

hands. That is because most cruise control systems are designed for normal dry

conditions and can’t sense whether the wheels are spinning uselessly. If your car

begins to careen out of control, cruise control will continue to accelerate as it

tries to maintain a constant speed. It would put your car into a sideway spin cause

the vehicle to flip over.

Fig 7.1

CHAPTER 8

CONCLUSION

This seminar has described about the cruise control systems that are

commonly seen in luxury cars now a day. Fully autonomous car is probably not

viable in the foreseen future. The Intelligent Vehicle Initiative in the United

States and Ertico program in Europe are among dozens of groups working on

technologies that may ultimately lead to vehicles that are wrapped in a cocoon of

sensors, with a 360 view of their environment. Then nearby vehicles would be in

constant communication with each other and act co-operatively, enabling groups

of cars to race along like train cars, almost bumper to bumper, at speeds above

100 km/hr.

It will probably take decades, but car accidents may eventually become

almost as rare as plane crashes are now. The automobile, which transformed the

developed world by offering mobility and autonomy, will finally stop exacting

such an enormous cost in human lives.

REFERENCE

1. www.howstuffworks.com

2. www.cars.com/features/adaptivecruisecontrol

3. www.autorepair.com

4. www.narticle.com

5. www.ukcar.com