K42 Volt Dry Brake-by Wire

(EMB) Systems

Brakenet Workshop:Complex Electronic Braking Systems

MIRA, September 12th 2002

Presented by

Michael Smith

KWhat is Dry Brake by Wire?

• EMB replaces hydraulic fluid as the brake actuating medium and uses electric motors at each wheel to operate the calipers

• EMB combines all the functions of ABS, TCS, EBC, ESP, BA, and parking brake

KWhat is Dry Brake by Wire?

• EMB replaces vacuum servo, master cylinder, hydraulic fluid, systems and components, parking brake controls and linkages

• No hoses and pipes, no hydraulic filling or bleeding at vehicle assembly plant

• No hydraulic fluid related environmental issues during vehicle use or end of life recycling

KWhat does EMB offer?

• Improved braking and stability control• Improved fuel consumption• Reduced maintenance• Overall weight reduction• Improved under-bonnet packaging• Simpler integration into other systems• Potentially lower costs

KWhat are the drawbacks?

• Requires 42v power supply– But does not justify it

• Complex system monitoring, fail safe and battery management systems

• Increased unsprung weight

KElectrical Demand

• Maximum peak demand is about 2kW for emergency application

• This is required for up to 0.2 secs after which 800 W maintains brake force

• 2kW is needed for each cycle of ABS• Typical braking power is about 100W

on motorway and 40W in town.

K

Source: ContiTeves

KSiemens EMB Prototype

K Bayern-Mechatronik EMB for High Speed Train

KWhy 42v for EMB?

• Maximum power demand is 2kW– At 14v this is 144 amp with unacceptable

wire diameter, weight and cost– At 42v it is reduced to 48 amp– 14v weight penalty is 10-15kg

• Need for EC brushless motors for performance, control and packaging

• High temperature, high density electronic components

KFail Safe Issues

• If alternator fails there must be enough battery stored power to operate the brakes– Requires battery management

system– Possibly additional dedicated

battery– Limp-home facility?

KFail Safe Issues

• Requires continuous system monitoring and fault detection– High reliability bus protocol ensuring

comprehensive fault tolerance– Deterministic time-triggered

communications for system fault tolerance

– Multiple micro controller units and digital signal processors

KIntegration into 42v net

• EMB needs full time 42v supply• Can be accommodated in 14/42v

dual voltage system• 42v systems will be first

introduced for energy saving and comfort and convenience systems

• EMB will be added later.

KEMB Prospects

• Needs 42v to operate, so depends on 42v availability.

• Will not be a driver for 42v but will use it to enhance braking and stability and other benefits

• Development needs are management and control systems

• Introduction likely 2006. European forecast, 1.8m vehicles in 2010

KOverall 42 volt Outlook

• To meet increasing demand for electrical power– Cannot be achieved at 14 volts

• To improve overall vehicle efficiency and meet demands for better fuel consumption and reduced emissions– Widespread efficiency gains with 42 volts

K Systems enabled by 42 volt power supply

Electric power steering (med and large cars)

Electric cabin heating

Electric powered air conditioning

Electromagnetic brakes

EMVIntegrated Starter Alternator--Stop/start operation--Acceleration boost--Regenerative braking

Windscreen de-icing

Electric oiland water pumps

Suspension control

Exhaust Aftertreatment

K Potential Electrical Demand (W)

Under Bonnet Interior BodyEPAS 1000 Heated screen 1000 EMB 250-2000

EMV 2000 Heated seats 600 Suspension 3000

Water pump 200-800

Int heating 3000 Heated Cat 3000

AC Comp 3000 ICEC 800 Wiper motor <300

EC fan 300-800 Body motors <300

Oil pump 500 Lighting 200

K Potential savings in Fuel Consumption (%) with 42 volts

0

2

4

6

8

10

12

14

16

%

ISA

EMV

EPAS

Stop/Start

Water pump

K 42v Vehicle Electrical System

14V

42V

DC

DC

Ctrl unit Ctrl unit Ctrl unit Ctrl unit

Alternator

Starter

Fuelpump

(100W)

Reardefroster(400W)

Windscreendefroster(500W)

Seatheating &

positioning(max.

2000W)

Windscreenwipers(90W)

Rearwiper(90W)

ABSpump

(600W)

Powersteering(300W)

Brake-by-wire

Electricalvalvetiming

Passengercomp.blower(500W)

Enginecoolant

fan(800W)

Lambdasensorheater(40W)

Waterpump

(300W)

Side-lights

(4 * 5W)

Dipped(low) head-

lights(2 * 55W)

Highbeam

(2 * 65W)

Rearfog

lights(2 * 21W)

Reversinglights

(2 * 21W)

Brakelights

(2 * 21W)

Indicators(blinkers)(4 * 21W)

Fuelinjector(s)

Interiorlight

(25W)

Glovebox light(10W)

Windscreenwashers(20W)

Windowlifters

(4 * 350W)

Doorlocks

(4 * 100W)

ISU Airbag ABS Radio/Cass

Instr. HVAC ECU

ValvesPyrotechn.gas gen.

To H.T.and spark plugs

Steeringwheel

heating(120W)

Source: Siemens

K European Outlook for 42v Car Production

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

2000 2002 2004 2006 2008 2010

Pro

duct

ion

(000

s)

• 2002-3: special niche applications

• 2004: 14/42v by variant

• 2006: introduction on new platforms

• 2007: first 42v only system

• 2010: All new vehicles

K Starter Alternators

Alter-nator

Starter

Gear

Engine

GearBox

Belt Drive

Fly Wheel Clutch

Current Separate Components

Engine

Fly wheel, Starter

Alternator

ECU

Clutch

Gearbox

ECU

StarterAlternator

Engine

Gearbox

Fly wheel Clutch

Combined Starter Alternators

Trans-mission

K Batteries and Power Storage• Initially, lead acid batteries will be used• Stop/Start puts heavy demand on battery

– 7,000 starts goes up to 350,000 per car life

• Lithium Ion, or Lithium Polymer look like preferred technology– Spec power, spec energy, discharge cycles,

packaging

• Ultracapacitors may be introduced to handle acceleration boost and regenerative braking

K Power Distribution

• Wiring harness weight savings frequently exaggerated

• 42v encourages multiplexing• Reduces connector problems• Requires more electronics in

switches and circuit protection• Issues still to be addressed for dual

voltage systems

K Motors• 42 volt motors would be more

expensive than simple 14v units– ie: those without speed or position control– very small motors eg: door locks, mirrors

• 42 volt motors would be cheaper and more efficient than– Brushless 14v motors– Motors with speed and position control

• There would be modest benefits in weight and packaging

K 42v: Implications for the Future

• Major Technical Challenges– Electronics, Power storage and

distribution

• Major Industry Implications– Motor manufacture, Hydraulic Systems,

Batteries, Lighting

• Implications for Future Trends– Hybrids, Fuel Cells, Transmissions