embedded system applications in automobiles report

EMBEDDED SYSTEM APPLICATIONS IN AUTOMOBILES TECHINICAL REPORT

ABSTRACT

There are several tasks in which real time OSs beat their desktop counterpart’s

hands-down. A common application of embedded systems in the real world is in

automobiles because these systems are cheap, efficient and problem free. Almost

every car that rolls off the production line these days makes use of embedded

technology in one form or the other. RTOSs are performed in this area due to their fast

response times and minimal system requirements.

Most of the embedded systems in automobiles are rugged in nature, as most of

these systems are made up of a single chip. Other factors aiding their use are the low

costs involved, ease of development, and the fact that embedded devices can be

networked to act as sub modules in a large system. No driver clashes or ‘system busy’

condition happen in these systems. Their compact profiles enable them to fit easily

under the cramped hood of a car.

Embedded systems can be used to implement features ranging from adjustment

of the suspension to suit road conditions and the octane content in the fuel to anti lock

braking systems (ABS) and security systems. Speaking of the things nearer home the

‘computer chip’ that control fuel injections in a Hyundai Santro or the one that controls

the activation of air bag in a Fiat in a weekend in nothing but an embedded system.

Right from brakes to automatic traction control to air bags and fuel/air mixture controls,

there may be up to 30-50 embedded systems within a present-day car.

TIRUMALA ENGINEERING COLLEGE


CHAPTER 1

INTRODUCTION



1.1 EMBEDDED SYSTEM:

An embedded system is any device controlled by instructions stored on a chip.

These devices are usually controlled by a micro processor that executes the instructions

stored on a read only memory (ROM) chip.

The software for the embedded system is called firmware. The firmware will be

written in assembly language for time or resource critical operations or using higher

level languages like C or embedded C. The software will be simulated using micro code

simulators for the target processor. Since they are supposed to perform only specific

tasks, these programs are stored in read only memories (ROMs).Moreover they may

need no or minimal inputs from the user, hence the user interface like monitor, mouse

and large keyboard etc, may be absent.

Embedded systems are also known as real time systems since they respond to

an input or event and produce the result within a guaranteed time period. This time

period can be few microseconds to days or months. The computer system must meet

various timing and other constraints that are imposed on it by the real-time behavior of

the external world to which it is interfaced. Hence comes the name real time. Another

Name for many of these systems is reactive systems, because their primary purpose is

to respond to or react to signals from their environment. A real time computer system

may be a component of a larger system in which it is embedded; reasonably such a

computer component is called an embedded system.

Applications and examples of real time systems are ubiquitous and proliferating,

appearing as part of our commercial, government, military, medical, educational, and

cultural infrastructures. Included are:

• Vehicle systems for automobiles, subways, aircraft, railways and ships.

• Traffic control for highways, airspace, railway tracks and shipping lanes.

• Process control for power plants, chemical plants and consumer products such as soft

drinks and beer.



• Medical systems for radiation therapy, patient monitoring and defibrillation

• Military uses such as firing weapons, tracking and command and control.

• Manufacturing systems with robots.

• Telephone, radio and satellite communications.

• Computer games.

• Multimedia systems that provide text, graphic, audio and video interfaces.

• Households systems for monitoring and controlling appliances.

• Building managers that controls such entities as heat, light, Doors and elevators.

1.2 CHARACTERISTICS OF EMBEDDED SYSTEMS:

Sophisticated functionality.

Often have to run sophisticated algorithms or multiple algorithms.

Often provide sophisticated user interfaces.

Real-time operation.

Must finish operations by deadlines.

Low manufacturing cost.

Low power.

Designed to tight deadlines by small teams.



CHAPTER 2

EMBEDDED SYSTEM IN AUTOMOBILE



EMBEDDED SYSTEM IN AUTOMOBILE

Automotive electronics are the electronics used in automobiles. This includes

body electronics, in car entertainment, computers, chassis electronics and telematics.

Automotive electronics first began with the need for better controls of the engine.

In fact, the first electronic parts in automobiles were used to control various engine

functions and were referred to as ECUs (Engine Control Units). However, as electronic

controls began to be used for other automotive applications, the acronym ECU took on

the more general meaning of “electronic control unit”. Today, specific ECUs are

generally referred to as modules [e.g. the engine control module (ECM) or the

Transmission Control Module (TCM)]. A modern car may have up to 100 electronic

control units and a commercial vehicle up to 40.

Automotive electronics or automotive embedded systems are distributed systems

and according to different domains in the automotive field they can be classified into:

1. Engine Electronics

2. Transmission Electronics

3. Chassis Electronics

4. Active Safety

5. Driver assistance

6. Passenger Comfort

7. Infotainment systems



Automotive Systems: Technology in today's vehicle:

FIG 2.1: EMBEDDED SYSTEMS INSIDE A MODERN CAR



CHAPTER 3ADAPTIVE CRUISE CONTROL (ACC)



3.1 ADAPTIVE CRUISE CONTROL (ACC)

Embedded systems can also make driverless vehicle control a reality. Major

automobile manufacturers are already engaged in work on these concepts. One such

technology is Adaptive Cruise Control (ACC).

FIG 3.1: ADAPTIVE CRUISE CONTROL

ACC allows cars to keep safe distances from other vehicles on busy highways.

The driver can set the speed of his car and the distance between his car and others.

When traffic slows down, ACC alters vehicle speed using moderate braking. This

ensures that a constant distance is maintained between cars. As soon as traffic

becomes less, ACC moves up to the desired cruise speed that has been set by the

driver. The driver can over ride the system any time he wants to be breaking.

Each car with ACC has a micro wave radar unit or laser transceiver fixed in front

of it to determine the distance and relative speed of any vehicle in the path. The ACC

computer (What else but an embedded system or a grouped system of embedded

system) constantly controls the throttle and brakes of the car. This helps to make sure

that the set cruise speed or adapted speed of traffic at that time is not exceeded.



3.2 ACC WORKING PRINCIPLE

As already mentioned each car with ACC have a micro wave radar unit fixed in

front of it to determine the distance and relative speed of any vehicle in its path. The

principle behind the working of this type of radar is- the Doppler Effect.

DOPPLER EFFECT

Doppler Effect is the change in frequency of the waves when there is a relative

motion between the transmitting and receiving units. The two figures below clearly show

the Doppler Effect.

High Pitch Sound

FIG 3.2: HIGHER PITCH SOUND

In this case the vehicle is speeding towards the stationary listener. The distance

between the listener and the car is decreasing. Then the listener will hear a higher pitch

sound from the car, which means the frequency of sound, is increased.

Lower Pitch Sound

FIG 3.3: LOWER PITCH SOUND



In this case the vehicle is moving away from the listener. The distance between

and the car is increasing. Then the listener will hear a lower pitch sound from the car,

which means the frequency of sound, is decreased. So that is the Doppler Effect in case

of sound waves.

Similarly the radar unit in ACC will be continuously transmitting radio waves.

They will be reflected and echo singles (reflected waves) will be having the same

frequency or different frequency depending on speed/position of the object due to which

the echo singles originate. If the echoes singles have the same frequency it is clear that

there is no relative motion between the transmitting and receiving ends. If the frequency

is increased it is clear that the distance between the two is decreasing and if the

frequency is decreased it means that the distance is increasing.

The figure below shows a car having ACC transmitting and receiving radio waves.

FIG 3.4: ACC TRANSMITTING AND RECEIVING RADIO WAVES

In the above case, the gun transmits the waves at a given frequency toward an

oncoming car. Reflecting waves return to the gun at a different frequency, depending on

how fast the car being tracked is moving. A device in the gun compares the

transmission frequency to the received frequency to determine the speed of the car.

Here, the high frequency or the reflected waves indicate the motorist in the left car is

speeding.



The embedded system is connected to the radar unit and its output will be sent to

breaking and accelerating unit as early mentioned the embedded system is a device

controlled by instructions stored in a chip. So we can design the chip or ACC having an

algorithm such that it will give output only when the input signals are less than the

corresponding safe distance value. So only when the between the car and the object in

front of it is less then the same distance value the embedded system will give output to

the breaking and the accelerating units. Thus the safe distance will be kept always.

That’s how the ACC works.

3.3 ACC TECHNICAL DETAILS

Adaptive cruise control typically uses radar in a frequency band that doesn’t

compete with police radar and doesn’t trigger radar detectors. For full-range ACC, some

automakers use two radars — one for close range out to about 100 feet and a second

that sees out to about 600 feet, or about 6-7 seconds at highway speeds. Partial ACC is

usually a single unit, while some full-range ACC implementations are now able to use

single radar as well.



FIG 3.5: TECHNOLOGY BEHIND ACC

Radar-based systems employ a variety of sensing and processing methods to

determine the position and speed of the vehicle ahead. A fairly simple scheme (like the

one used by Mercedes) switches rapidly among three beams by changing feed points

along the antenna, creating a scanning effect inexpensively and with no moving parts.

The beams are wide enough to ensure that each overlaps those adjacent, providing a

combined 12-degree field of view. An advantage is that the wider beams permit the use

of a smaller antenna.



More advanced and costlier sensing schemes rely on an antenna that is

mechanically scanned and that emits a narrow beam. These systems scan between 64

and 128 points in the radar's field of view, also typically 12 degrees, so that resolution is

much higher than for a three-beam system. The beams are much narrower than in the

three-beam models, however, so the antenna has to be larger. And the multiplicity of

beams requires much more processing power to handle the streams of data that pour

out as the radar scans across the multiple points of focus to determine the leading car's

position and speed.

Regardless of the scanning mechanism, the radars typically operate in the

millimeter-wave region at 76-77 GHz. The automakers refused to alter the shape or

construction of their vehicles to accommodate ACC, so designers had to build systems

small enough to be mounted inside a car's front grille. That stringent size requirement in

turn demanded a compact antenna, which in turn forced the use of the high frequencies,

antenna size being inversely related to frequency. At 76-77 GHz, frequencies are high

enough to work with small antennas, yet not so high that the components are exotic and

stupendously expensive. Typical automotive radar, produced by Delphi Delco

Electronics Systems, of Kokomo, Ind., is roughly the size of two stacked paperback

books--just 14 by 7 by 10 cm.

The radar and the cameras work together to track the car ahead and distinguish

it from extraneous nonmoving objects more rapidly than would be possible with either

alone, according to Keiji Fujimura, a senior manager at Fujitsu Ten. While the radar

homes in on the lead car's rear bumper, the stereo camera is constantly measuring the

widths of all the items in its wide field of view [see illustration, above ]. To calculate

them, it uses an algorithm based on the detection of vertical edges and the distance.

Bridges, trees, and other stationary objects that are much wider or narrower than a car

are quickly rejected as reasons for the system to apply the brakes.



CHAPTER 4ANTILOCK BRAKING SYSTEM (ABS)



4.1 DESCRIPTION OF ANTILOCK BRAKING SYSTEM (ABS):

Anti-lock braking system (ABS) is an automobile safety system that allows the

wheels on a motor vehicle to maintain tractive contact with the road surface according

to driver inputs while braking, preventing the wheels from locking up (ceasing rotation)

and avoiding uncontrolled skidding. It is an automated system that uses the principles of

threshold braking and cadence braking which were practiced by skillful drivers with

previous generation braking systems. It does this at a much faster rate and with better

control than a driver could manage.

ABS generally offers improved vehicle control and decreases stopping distances

on dry and slippery surfaces for many drivers; however, on loose surfaces like gravel or

snow-covered pavement, ABS can significantly increase braking distance, although still

improving vehicle control.

Since initial widespread use in production cars, anti-lock braking systems have

evolved considerably. Recent versions not only prevent wheel lock under braking, but

also electronically control the front-to-rear brake bias. This function, depending on its

specific capabilities and implementation, is known as electronic brake force distribution

(EBD), traction control system, emergency brake assist, or electronic stability control

(ESC).

FIG 4.1: ANTILOCK BRAKING SYSTEM



4.2 ABS OPERATION:

FIG 4.2: ABS OPERATION

The anti-lock brake controller is also known as the CAB (Controller Antilock

Brake. Typically ABS includes a central electronic control unit (ECU), four wheel speed

sensors, and at least two hydraulic valves within the brake hydraulics. The ECU

constantly monitors the rotational speed of each wheel; if it detects a wheel rotating

significantly slower than the others, a condition indicative of impending wheel lock, it

actuates the valves to reduce hydraulic pressure to the brake at the affected wheel, thus

reducing the braking force on that wheel; the wheel then turns faster. Conversely, if the

ECU detects a wheel turning significantly faster than the others, brake hydraulic

pressure to the wheel is increased so the braking force is reapplied, slowing down the

wheel. This process is repeated continuously and can be detected by the driver via

brake pedal pulsation. Some anti-lock systems can apply or release braking pressure

15 times per second.[17] Because of this, the wheels of cars equipped with ABS are

practically impossible to lock even during panic braking in extreme conditions.



The ECU is programmed to disregard differences in wheel rotational speed

below a critical threshold, because when the car is turning, the two wheels towards the

center of the curve turn slower than the outer two. For this same reason, a differential is

used in virtually all road going vehicles.

If a fault develops in any part of the ABS, a warning light will usually be

illuminated on the vehicle instrument panel, and the ABS will be disabled until the fault

is rectified.

Modern ABS applies individual brake pressure to all four wheels through a

control system of hub-mounted sensors and a dedicated micro-controller. ABS is

offered or comes standard on most road vehicles produced today and is the foundation

for electronic stability control systems, which are rapidly increasing in popularity due to

the vast reduction in price of vehicle electronics over the years.

Modern electronic stability control systems are an evolution of the ABS concept.

Here, a minimum of two additional sensors are added to help the system work: these

are a steering wheel angle sensor, and a gyroscopic sensor. The theory of operation is

simple: when the gyroscopic sensor detects that the direction taken by the car does not

coincide with what the steering wheel sensor reports, the ESC software will brake the

necessary individual wheel(s) (up to three with the most sophisticated systems), so that

the vehicle goes the way the driver intends. The steering wheel sensor also helps in the

operation of Cornering Brake Control (CBC), since this will tell the ABS that wheels on

the inside of the curve should brake more than wheels on the outside, and by how

much.

ABS equipment may also be used to implement a traction control system (TCS)

on acceleration of the vehicle. If, when accelerating, the tire loses traction, the ABS

controller can detect the situation and take suitable action so that traction is regained.

More sophisticated versions of this can also control throttle levels and brakes

simultaneously.

Upon the introduction of the Subaru Legacy in 1989, Subaru networked the four

channel anti-lock brake function with the all wheel drive system so that if the car



detected any wheel beginning to lock up, the variable assists the all wheel drive system

installed on vehicles with the automatic transmission would engage to ensure all wheels

were actively gripping while the anti-lock system was attempting to stop the car.



CHAPTER 5

DYNAMIC TRACTION CONTROL



DYNAMIC TRACTION CONTROL

Dynamic Traction Control (DTC) allows more wheel slip and thus a more

dynamic driving style with higher wheel traction and DSC controlling stability. A small

amount of spin on the drive wheels improves traction when pulling off from a standstill in

snow or on loose terrain.

Dynamic Traction Control (DTC) is a sub-function of the Dynamic Stability

Control (DSC) system that can be turned on and off. DTC has two major roles: to

regulate traction and to enable sports-style driving while providing active stability

control.

When the drive wheels start losing traction the DSC automatically begins stabilization

measures. The Dynamic Stability Control system curbs the engine output and stops slip

on the wheels. In exceptional situations, however, a small amount of wheel slip can be

an advantage.

When driving in deep snow, slush or on loose terrain a small amount of wheel

spin improves traction. For these occasions, as well as those when the drivers want a

sportier driving style, the DTC can be activated by pressing a button and this allows

more slip and reduces the DSC’s curbing of the engine. The result: better traction and

more thrust.

The DTC also makes driving on snow and ice-free roads more dynamic. When

activated, the DTC allows sporty drivers more room to maneuver around curves than

the Dynamic Stability Control and even permits controlled drifts. The driver retains

complete control over the vehicle in every situation and the Dynamic Stability Control’s

stabilizing measures remain active even when the DTC is activated.



Fig 5.1: With and Without Dynamic Traction Control System



CHAPTER 6

DRIVE BY WIRE TECHNOLOGY



6.1 DRIVE BY WIRE TECHNOLOGY

Traditional hydraulic brakes make use of a master cylinder and several slave

cylinders. When the driver pushes down on the brake pedal, it physically applies

pressure to the master cylinder. In most cases, that pressure is amplified by a vacuum

or hydraulic brake booster. The pressure is then transmitted via brake lines to the brake

calipers or wheel cylinders.

Anti-lock brake systems were early precursors of modern brake-by-wire

technologies. Most vehicles that are equipped with ABS still use hydraulic brakes, but

the brakes can also be pulsed without any input from the driver. That is accomplished

by an electronic actuator. Electronic, traction control, and automatic braking systems

are also related to brake-by-wire technology.

In vehicles that use true brake-by-wire systems, there are no mechanical

connections between the brake pedals and the brakes. When the driver pushes down

on the brake pedal in one of these systems, it activates an electronic switch. An

appropriate level of braking force is then applied by an electromechanical actuator.

Electronic Throttle Control

The most common type of throttle control uses a cable that is directly connected

to both the gas pedal and the throttle. When the gas pedal is pressed down, the cable

pulls the throttle open. In vehicles that use electronic throttle control (ETC), there is no

physical connection between the gas pedal and the throttle. Like brake-by-wire systems,

the gas pedal sends a signal that causes an electromechanical actuator to open the

throttle.


http://cartech.about.com/od/Safety/a/What-Is-An-Automatic-Braking-System.htm

http://cartech.about.com/od/Safety/a/Traction-Control-Abs-Evolved.htm

http://cartech.about.com/od/Safety/a/Anti-Lock-Brakes.htm


FIG 6.1: Drive by Throttle

Steer-By-Wire

Most vehicles use a rack and pinion unit or worm and sector steering gear that is

physically connected to the steering wheel. When the steering wheel is rotated, the rack

and pinion unit or steering box also turns. A rack and pinion unit can then apply torque

to the ball joints via tie rods, and a steering box will typically move the steering linkage

via pitman arm. In vehicles that are equipped with steer-by-wire technology, there is no

physical connection between the steering wheel and the tires. In fact, steer-by-wire

systems don’t technically need to use steering wheels at all. When a steering wheel is

used, some type of steering feel emulator is typically used to provide the driver with

feedback.


http://autorepair.about.com/cs/generalinfo/l/bldef_702.htm


Fig 6.2: Steer by Wire

6.2 What Vehicles Already Have Drive-By-Wire Technology?

There are no fully drive-by-wire production vehicles, but a number of

manufacturers have built concept vehicles that fit the description. General Motors

demonstrated a drive-by-wire system in 2003 with its Hy-Wire concept, and Mazda’s

Ryuga concept also used the technology in 2007. Drive-by-wire can be found in

equipment like tractors and forklifts, but even cars and trucks that feature electronic

power steering still have physical steering linkage.

Electronic throttle control is far more prevalent, and a variety of makes and

models make use of the technology. Brake-by-wire can also be found in production

models, and two examples of the technology are Toyota’s Electronic Controlled Brake

and Mercedes Benz’s Sensotronic.



6.3 The Future of Drive-By-Wire

Fig 6.3: Future Drive By Wire

Safety concerns have slowed the adoption of drive-by-wire technologies.

Mechanical systems can and do fail, but regulatory authorities still see them as being

more reliable than electronic systems. Drive-by-wire systems are also more expensive

than mechanical controls due to the fact that they are significantly more complex.

However, the future of drive-by-wire technology could lead to a number of

interesting developments. The removal of mechanical controls could allow automakers

to design vehicles that are radically different from the cars and trucks that are on the

road today. Concept cars like the Hy-Wire have even allowed the seating configuration

to be moved around, since there are no mechanical controls that dictate the position of

the driver.

Drive-by-wire technology could also be integrated with driverless car technology,

which would allow vehicles to be operated remotely or by a computer. Current driverless

car projects use electromechanical actuators to control steering, braking, and

acceleration, which could be simplified by connecting directly to drive-by-wire

technology.



CHAPTER 7CONCLUSION



CONCLUSION

There is lot of scope for the development of newer technologies in the

automotive electronics domain. Electronic Control Units (ECU) can be designed to

provide optimum driving conditions which increase the efficiency.

Areas such as firmware, dedicated intelligence chips and ECUs are in demand in

the Automotive Electronics Industry. The recent trends in the automobile industry

highlight the scope for electronics in the industry. On an average any automobile has 50

ECUs. 13% of manufacturing cost is for the software developed. 35% of the cost of the

car comes from the electronics involved in it. Also 80% of the automotive innovation in

the recent years has been from Automobile electronics.



REFERENCES

1. www.spectrum.ieee.org

2. www.extremetech.com

3. www.auto.howstuffworks.com

4. www.wiki.fot-net.eu

5. www.wikipedia.com

6. Report of 5th Meeting of the U.S. Software System Safety Working Group April

12th-14th 2005 @ Anaheim, California USA


http://www.wikipedia.com/

http://www.wiki.fot-net.eu/

http://www.auto.howstuffworks.com/

http://www.extremetech.com/

http://www.spectrum.ieee.org/

embedded system applications in automobiles report

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