Embedded Systems in Automotive

o Recently Drive-by-wire

(DBW)technology appear on

Automotive industry.

o Replaces the traditional

mechanical systems with

electronic systems.

o ECU is used in the automotive

domain.

o Electronic Control Unit(ECU)consists of:

• Microcontroller(s).

• Sensors.

• Power switches.

• Drivers.

• Voltage regulator(s).

o Connect the sensors and actuators

directly to central ECU.

o Its disadvantage:

1-Very high number of connectors.

2-High length network cable.

Point to Point Network

Single Bus Network

o Automotive applications ECUs

communicate through automotive bus

protocols:

• CAN.

• LIN.

• Felx Rays.

“It would be easy to say the modern car is a computer on wheels, but it’s more like 30 or more computers on wheels. “

Bruce Emaus, The chairman of SAE International embedded

software standards committee.

SAE: Society of Automotive Engineers

CAN

CAN

Power Train

Light

Sub-Bus

ITS

Window Lift

InteriorLight

Lock

Mirror

Lock

Mirror

Lock

Lock

Seat

Htng

Seat

Htng

Instruments

Central

Body Ctrl

Climate

Universal Motor

Universal Panel

Light

Roof

1 backbone, 13 nodes8 subnets, 1-8 local nodes52 nodes total

St-Wheel Panel

x6

Htng

Htng

Seat

Wiper

Trunk

WHtg

Universal Light

LEXUS LS-460

o Released in Sep., 2006.

o More than 100 ECUs when all

optional equipment are installed.

o About 7,000,000 lines of code.

o One modern car is packed with up to 100 million lines of

computer code, more than the F-22 Raptor Jet fighter.

o More luxurious cars can contain up to 100 Electronic Control

Unit (ECU).

•Door/window/seat: Mirror,Central ECU,

Mirror, Switch, Window

Lift,

Seat Control Switch,

Door Lock, etc.

Roof: (high amount of wiring)

Rain Sensor, Light Sensor,

Light Control, Sun Roof

… (Rain Sensor needs to be

interrogated every 10-20ms)

Seat: many Seat Position Motors, Occupancy Sensor, Control Panel

Steering Wheel: (very many controls are going to be

positioned on the steering wheel)

Cruise Control, Wiper,

Turning Light, …

Optional: Climate Control,

Radio, Telephone, etc.

Climate: many Small Motors

Control Panel

Features of Automotive Embedded Systems

o ECUs are used for :

• energy saving & low emission • safety (active & passive) • comfortableness, convenience, entertainment • cost & weight reduction

o ECUs are connected with several in-vehicle networks.

o High reliability and safety requirements

o Strict real-time property required

o Severe environmental conditions (temperature, EMC)

o Severe production cost restriction

o The speed of the car and the

rotational speed of the wheel are

monitored, and a skid is detected.

o When a skid is detected, hydraulic

pressure to the brake is reduced to

stop the skid.

Applications of Automotive Embedded Systems

Anti-lock Breaking System(ABS)

o Safety Requirement Design:

• Continuous reduction of hydraulic

pressure causes non-braking.

• If some fault is detected, ABS stops

functioning.

• Then ,the brake works though a

skid cannot be avoided.


Anti-lock Breaking System(ABS)

Traction Control System(TCS)

o Prevent loss of traction of driven

road wheels.

o Enhances driver control as throttle

input applied is mismatched to road

surface conditions (due to varying

factors) being unable to manage

applied torque.


o Consider the secondary function of

APS.

o Helps limit tire slip in acceleration

on slippery surfaces.


Traction Control System(TCS)

o Improves the safety of a vehicle's

stability by detecting and reducing

loss of traction (skidding).

o When ESC detects loss of steering

control, it automatically applies the

brakes to help "steer" the vehicle

where the driver intends to go.

o


Electronic Stability Control(ESP)


Electronic Stability Control(ESP)

o Braking is automatically applied to

wheels individually.

o Some ESC systems also reduce engine

power until control is regained.

o ESC does not improve a vehicle's

cornering performance; instead, it

helps to minimize the loss of control.

Airbag

o Airbag control system:

• Monitors various sensors including

accelerometers and detects a collision.

• If a collision is detected, the ignition

of a gas generator propellant is

triggered to inflate a bag.

o Real-Time Constraint:

• The trigger must be within 10-20msec.

after the collision.


Pre-crash Safety System (PCS)

o When an obstacle is detected with stereo camera and wave radar • the system retracts the seatbelts, warns the driver, and applies the brake.

o Driver's condition (eg. face direction) is monitored.


Car Navigation System

o The current position of the car obtained from GPS,

gyroscope, and others is displayed with the map.


Classification of Automotive Embedded Systems

o Powertrain and Control

▶ Engine, automatic transmission, hybrid control, ...

▶ Steering, brake, suspension, ...

o Body Electronics

▶ Instrument panel, key, door, window, lighting, …

▶ Air bag, seat belt, ...

o Multimedia Applications

▶ Car audio, car navigation, traffic information, ...

▶ Electronic toll collection (ETC), backguide monitor, ...

o Integrated Systems/Services

▶ Electronic stability control, pre-crash safety, … ▶ Parking assistance, lane keeping assistance, ...

o Stage 1: ECU is applied to various component independently network is not used.

o Stage 2: ECU exchanges data for improving the quality

o Stage 3: • Each system still operates autonomously. • some services are provided with multiple ECUs connected via

networks. • Mechanical backup system still exists even if an electronic system fails.

Evolution Steps of Automotive Control Systems

Evolution of automotive control systems and networks is well understood with the following 4 stages.

(Current) integrated systems/services

o Stage 4: • Networks with outside of the car (communication with another car and

the road) are intensively used. • Mechanical systems (incl. backups) are replaced with ECUs and

networks. • A failure of electronic systems is life-critical.

Evolution Steps of Automotive Control Systems

(Future) (true) by-wire systems

Problems of Automotive Embedded Systems

o Complicated system design

• Increasing development cost and time

• How to achieve high reliability and safety?

o Large-scale and complicated software

• How to effectively reuse existing software?

o Too large number of ECUs

• Increasing cost

• Insufficient space (in a car) for ECUs

o Complicated network architecture

• Increasing design complexity

Platform-base Development

Conventional Component-base Development o Each ECU (component) is developed independently.

o Automotive component supplier develops both of the hardware and

software of ECU.

o Car (system) is designed by integrating the ECUs developed by different

suppliers.

Platform-base Development o Platform should be developed at first.

o Platform = Hardware + Software + Network

o Application software should be developed on the Platform .

Automotive Architecture

AUTOSAR (Automotive Open System Architecture)

o global partnership of carmakers, car component ,electronics,

semiconductor, software industries

o founded in 2003.

o defines a methodology that supports a distributed, function-

driven development process.

o standardizes the software-architecture for ECU.

o Core partners: ▶ BMW ▶ Daimler ▶ PSA Peugeot Citroen ▶ Bosch ▶ Ford ▶ Toyota Motor ▶ Continental ▶ GM ▶ Volkswagen

Automotive Architecture

JASPAR (Japan Automotive Software Platform Architecture)

o Car makers and other companies develop network technology,

middleware, software platform for automotive control systems.

o founded in 2004.

o Board Members ▶ Toyota Motor ▶ Honda ▶ DENSO ▶ Nissan ▶ Toyota Tsusho Electronics

o Members about 100 carmakers, car component suppliers, semiconductor companies, and software companies

o Major Activities and Results ▶ Standardization related to FlexRay (wiring rule, ...) ▶ Development of software platform based on AUTOSAR Standard. ▶ Development of design guidelines for ISO 26262.

Automotive Network protocol

Sp

eed

[b

it/s

]

Byteflight optical bus

LIN master-slave

single wire bus no quartz

CAN-B event triggered fault tolerant dual wire

CAN-C event triggered

dual wire

Flex Ray

25.6M

20K

10M

1M

125K

incremental cost per node [$]

D2B, MOST token ring

optical bus

1 2 4.5 10

Automotive Network dominos

o Class A:

• low cost and data rate lower than 10 kbps

• Example: LIN

• used for body domain light functions.

o Class B:

• data rate (10‐125 kbps)

• Example : low‐rate CAN

• used for data exchange between ECUs to reduce the number of sensors

by sharing information.

Automotive Network dominos

o Class C:

• data rate (125kbps‐1Mbps)

• Example : high‐speed CAN

• used for power train and chassis domain functions (ABS & EPS)

o Class D:

• data rate (over 1Mbps)

• Example : MOST (media‐oriented system transport)

• multimedia data and safety critical applications .

Automotive Network Triggered

Event Triggered:

o Messages are transmitted due to occurrence of significant events

o Example :a door has been closed.

o No detection of node failure, no grantee for certain constrains.

Time Triggered:

o Frames are transmitted at predetermined points in time .

o Example: TDMA.

o Behavior is fully predictable, detection of failure. but, inefficient

utilization, not extendable.

Embedded Systems in Automotive

Engineering

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