1. Presented by Michael Smith
42 Volt Dry Brake-by Wire (EMB) Systems Brakenet Workshop: Complex Electronic Braking Systems MIRA, September 12th 2002
Presented by
Michael Smith

2. What 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

3. What 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

4. What 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

5. What are the drawbacks? Requires 42v power supply
But does not justify it
Complex system monitoring, fail safe and battery management systems
Increased unsprung weight

6. Electrical 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.

7. Source:
ContiTeves

8. Siemens EMB Prototype

9. Bayern-Mechatronik EMB for High Speed Train

10. Why 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

11. Fail 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?

12. Fail 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

13. Integration 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.

14. EMB 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 European forecast, 1.8m vehicles in 2010

15. Overall 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

16. Systems enabled by 42 volt power supply
Electric cabin heating
Electric powered air conditioning
Integrated Starter Alternator
--Stop/start operation
--Acceleration boost
--Regenerative braking
EMV
Electric power steering (med and large cars)
Windscreen de-icing
Electric oil
and water pumps
Exhaust Aftertreatment
Electromagnetic brakes
Suspension control

17. Potential Electrical Demand (W)

18. Potential savings in Fuel Consumption (%) with 42 volts

19. 42v Vehicle Electrical System
Alternator
42V
Ctrl unit
Ctrl unit
Ctrl unit
Ctrl unit
Starter
Fuel
Windscreen
Rear
Steering
Seat
Rear
Windscreen
ABS
Power
Brake-
Electrical
Passenger
Engine
Lambda
pump
defroster
defroster
wheel
heating &
wiper
wipers
pump
steering
by-
valve
coolant
sensor
Water
(100W)
(500W)
(400W)
heating
positioning
(90W)
(90W)
(600W)
(300W)
wire
timing
comp.
blower
fan
heater
pump
(120W)
(max.
2000W)
(500W)
(800W)
(40W)
(300W) DC
To H.T. DC
Pyrotechn.
and spark plugs
gas gen.
Valves
ISU
Airbag
ABS
Radio/
Cass
Instr.
HVAC
ECU
Typical architecture for a 14-42v electrical system which will initially be used on cars with 42v components
This example has both 12-36v batteries and dual circuits. All power is generated at 42v. For 14v applications a DC/DC converter is used to provide 14v power to change the 12v battery and operate 14v components
Eventually the 14v distribution will disappear as all but a few applications move to 42v and the remaining 14v components will have integrated voltage conversion.
14V
Side-
Dipped
Rear
(low) head-
High
fog
Reversing
Brake
Indicators
Interior
Glove
Windscreen
Window
Door
Fuel
lights
lights
beam
lights
lights
(blinkers)
light
box light
washers
lifters
locks
injector(s)
(4 * 5W)
(2 * 55W)
(2 * 65W)
lights
(2 * 21W)
(2 * 21W)
(2 * 21W)
(4 * 21W)
(25W)
(10W)
(20W)
(4 * 350W)
(4 * 100W)
Source: Siemens

20. European Outlook for 42v Car Production
2002-3: special niche applications
2004: 14/42v by variant
2006: introduction on new platforms
2007: first 42v only system
2010: All new vehicles

21. Current Separate Components Combined Starter Alternators
Gear
Engine
Box
Belt Drive
Fly Wheel
Clutch
Current Separate Components
Fly wheel,
Alternator
ECU
box
Fly wheel
Combined Starter Alternators
Trans-
mission

22. 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

23. 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

24. 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

25. 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