Transcript 42 Volts: A Milestone in Passenger car Development Automotex

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42 Volt Dry Brake-by Wire
(EMB) Systems
Brakenet Workshop:
Complex Electronic Braking Systems
MIRA, September 12th 2002
Presented by
Michael Smith
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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
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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
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What does EMB offer?
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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
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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
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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.
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Source:
ContiTeves
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Siemens EMB Prototype
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Bayern-Mechatronik EMB for
High Speed Train
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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
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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?
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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
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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.
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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 2006. European
forecast, 1.8m vehicles in 2010
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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
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Systems enabled by 42 volt power
supply
Integrated Starter Alternator
--Stop/start operation
--Acceleration boost
--Regenerative braking
EMV
Electric cabin
heating
Electric powered
air conditioning
Windscreen de-icing
Electric power
steering (med
and large cars)
Electric oil
and water pumps
Exhaust Aftertreatment
Suspension control
Electromagnetic
brakes
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Potential Electrical Demand
(W)
Under Bonnet
Interior
Body
EPAS
1000 Heated screen 1000 EMB
EMV
2000 Heated seats
Water pump 200- Int heating
800
AC Comp 3000 ICEC
EC fan
Oil pump
300-800
500
250-2000
600 Suspension
3000
3000 Heated Cat
3000
800
Wiper motor <300
Body motors <300
Lighting
200
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Potential savings in Fuel
Consumption (%) with 42 volts
16
ISA
14
EMV
12
EPAS
10
Stop/Start
% 8
6
4
2
0
Water pump
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42v Vehicle Electrical
System
Alternator
42V
Ctrl unit
Ctrl unit
Ctrl unit
Ctrl unit
Power
steering
(300W)
Brakebywire
Electrical
valve
timing
Starter
Seat
Steering
Fuel Windscreen Rear
Rear Windscreen ABS
heating & wiper
wheel
pump
defroster defroster
wipers
pump
(100W)
(500W)
(400W) heating positioning (90W)
(90W) (600W)
(max.
(120W)
2000W)
DC
Pyrotechn.
gas gen.
DC
ISU
Airbag
Passenger Engine Lambda
coolant sensor Water
comp.
fan
heater pump
blower
(800W) (40W) (300W)
(500W)
To H.T.
and spark plugs
Valves
Radio/
Cass
ABS
Instr.
HVAC
ECU
14V
Sidelights
(4 * 5W)
Source: Siemens
Dipped
High
(low) headbeam
lights
(2 * 65W)
(2 * 55W)
Rear
fog
lights
(2 * 21W)
Reversing
lights
(2 * 21W)
Brake
lights
(2 * 21W)
Indicators
(blinkers)
(4 * 21W)
Interior
light
(25W)
Window
Door
Glove Windscreen
lifters
locks
box light
washers
(4
*
350W)
(4
*
100W)
(10W)
(20W)
Fuel
injector(s)
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European Outlook for
42v Car Production
Production (000s)
4,500
4,000
3,500
3,000
2,500
2,000
1,500
1,000
500
0
2000 2002 2004 2006 2008 2010
• 2002-3: special
niche applications
• 2004: 14/42v by
variant
• 2006: introduction
on new platforms
• 2007: first 42v only
system
• 2010: All new
vehicles
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Starter Alternators
Current Separate
Components
Combined Starter Alternators
Fly wheel,
Starter
Alternator
Clutch
Gear
box
Engine
Fly Wheel
ECU
Clutch
Gear
Box
Engine
Gear
Belt Drive
Fly wheel
Clutch
Starter
Alternator
Engine
Transmission
Starter
Alternator
ECU
Gear
box
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• 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
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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
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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
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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