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

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

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

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

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

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.

Source: ContiTeves

Siemens EMB Prototype

Bayern-Mechatronik EMB for High Speed Train

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

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?

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

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.

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

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

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

Potential Electrical Demand (W)

Potential savings in Fuel Consumption (%) with 42 volts

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

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

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

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

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

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

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