Implementing supervisory control strategies for Mercedes-Benz ...

Implementing supervisory control strategies for Mercedes-Benz hybrid vehicles Dr. Michael Back, Mercedes-Benz Cars Development

Why alternative powertrains?

Legislation §§

Emission regulations

§

§§

Consumption regulations

Competition Increasing activities of all OEMs

Incentives/tax advantages Limited driving permissions (e.g. London)

Positioning of hybrids as a suitable transit technology towards fully electrical drives (fuel-cell, battery, ..) Alternative powertrains as a competitive measure.

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Conventional powertrains

Energy ressources Oil shortage Political situation in middle east

Gasoline

Diesel

Society Increasing sense for environmental issues Global warming lobbying Michael Back: Implementing supervisory control strategies for Mercedes-Benz hybrid vehicles

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General types of hybrid powertrains

Parallel-Hybrid Combustion engine and electric motor are directly coupled to the drivetrain. Both aggregats can operate independently.

Split-Hybrid The combustion engine‘s power can be transfered to the drivetrain and/or the generator.

Serial Hybrid The combustion engine‘s power is converted completely into electric energy.

IC engine with clutch and transmission

IC engine with generator

Electric motor

Michael Back: Implementing supervisory control strategies for Mercedes-Benz hybrid vehicles

fuel tank

traction battery

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Outline

Configuration of the Mercedes-Benz S400 Hybrid System Hybrid Components and Package Goals and Requirements for a Supervisory Control Strategy Operation Strategy ¾ Electric Energy Management ¾ Regenerative Braking ¾ Boost ¾ Electric Load Shift ¾ Start-Stop Summary


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Configuration of the Mercedes-Benz S400 Hybrid System


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Configuration of the Mercedes-Benz S400 Hybrid System


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Hybrid Components: Lithium Ion Battery

mounting engine mountingplace place: : enginecompartment compartment performance data : 118 performance data : 118VV(nominal (nominalvoltage), voltage),6.5 6.5Ah Ah (capacity), 0.82 kWh (energy) (capacity), 0.82 kWh (energy)

weight approx. weight: : approx.25 25kg kg Embedded in A/C cooling circuit Embedded in A/C cooling circuit


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Hybrid Components: Electric Motor (PESM)

mounting mountingplace: place:

between betweenengine engineand and transmission on the transmission on the crank-shaft crank-shaft

performance performancedata data: :

118 118V,V,15 15kW kW approx. approx.24 24kg kg

weight: weight:

Permanent Permanentmagnetic magneticsynchronous synchronousmotor motor Aussenläufer Aussenläufer no noextra extracooling coolingsystem system


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Hybrid Components: Power Electronics

mounting mountingplace: place:

engine enginecompartment, compartment, conventional conventionalstarter starter


max. max.motor motorcurrent: current:150 150AA Power Powerinverter inverterfor foroperating operatingaathree-phase three-phasemachine machinewithin within the thehigh highvoltage voltageDC DCnetwork network Cooling Coolingvia viaaaseparate separatecooling coolingcircuit circuit


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Hybrid Components: DC/DC converter

mounting mountingplace place: :

Haltepunkte HaltepunkteStandheizung Standheizung (right front wheel) (right front wheel)


HV HV->->12 12V:V:1,5 1,5kW kW 12V 12V->->HV: HV: 0,5 0,5kW kW

bidirectional

supporting supporting12V-battery 12V-batteryduring duringautomatic automaticstop stop

(energy (energyflow flowHV-battery HV-battery=> =>12V-battery) 12V-battery) Jump-start Jump-startvia via12V-charger 12V-chargeror orsecond secondverhicle verhicle (energy flow 12V-battery => HV-battery) (energy flow 12V-battery => HV-battery) Supporting SupportingHV-battery HV-batteryduring duringboost boostor orengine engine

start start (energy (energyflow flow12V-battery 12V-battery=> =>HV-battery) HV-battery)

Cooled Cooledby byseperate seperatecooling coolingcircuit circuit


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Optimized Combustion Engine: The V6 gasoline atkinson cycle engine

Atkinson Atkinsonprinciple: principle:expansion expansionphase phase

isislonger longerthan thanthe thecompression compression phase phaseby bykeeping keepingintake intakevalves valves longer longeropen open

improved improvedthermal thermalefficiency efficiency=> =>

reduction reductionofofthe thespecific specificfuel fuel consumption. consumption.

Reduced Reducedtorque torqueoutput outputatatlow low

engine enginespeed speedisiscompensated compensatedby bythe the electric motor (down-sizing) electric motor (down-sizing)

new newcylinder cylinderhead, head,different differentpistons pistons

and andmodified modifiedcamshaft camshaftwith with different camshaft control different camshaft controlincreases increases the output by 5 kW/7 hp to the output by 5 kW/7 hp to205 205 kW/279 kW/279hp hp


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7-Gtronic Transmission

Using Usingaamodified modifiedstandard standardautomatic automatictransmission transmission Differences Differencesto toseries-production series-productiontransmission: transmission:torque torqueconverter, converter,

Software Softwaretransmission transmissioncontrol controland andauxiliariy auxiliariyoil oilpump. pump. Reasons Reasonsfor forthe theneed needofofan anauciliary auciliaryoil oilpump.: pump.:

Prinmary Prinmaryoil oilpumnp pumnpduring duringautomatic automaticstop stopinactive inactive Avoiding Avoidingshifting shiftingdelays delaysafter afterengine enginestart start


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Regenerative Braking System (RBS)

first firstsection sectionofofthe thepedal pedaltravel travelisis

laid laidout outas asaashift-by-wire shift-by-wiresystem system with pedal force simulator with pedal force simulator

After Afterpedal pedalleeway leewayfully fully

mechanical mechanicalbraking brakingsystem systemwith with underpressure booster and underpressure booster and mechanical mechanicalback-up back-up

Electric Electricvacuum vacuumpump pumpto toprovide provide

underpressure underpressureduring duringauto autostop stop


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Electric Steering


between betweenright rightwheel wheelhouse house and andfront frontlight lightunit unit

performance performancedata: data: wight: wight:

12 12V,V,max. max.100 100WW approx. approx.88kg kg

Full Fullservo-steering servo-steeringininautomatic automaticstop stop Reduction Reductionofofconsumption consumptionby by0,2 0,2l/100km l/100km Replacing Replacingbelt beltdriven drivensteering steeringpump pumpby byelectric electric

pump pumpwith withintegrated integratedpower powerelectronics electronics


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Electric A/C compressor


replacing replacingconventional conventionalA/C A/C compressor compressor

Performance Performancedata: data:

120V, 120V,4,5 4,5kW kW approx. approx.99kg kg

weight: weight:

To Toguarantee guaranteeA/C A/Ccomfort comfortduring duringautomatic automaticstop stop adjustment adjustmentofofbelt beltdrive drivenecessary necessary


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Essential customer demands from a OEM‘s point of view

Fuel Efficiency and emissions •

Increasing fuel efficiency = increasing cruising range

•

Stop-start function

•

Regeneration (charging the battery by using kinetic energy)

•

Zero emission at standstill

Driving Comfort: •

Shifting comfort during acceleration and regeneration

•

Source of energy for auxiliaries (power steering, AC compressor)

Driving dynamics •

Increased driving dynamics and agility

•

Powerful, continously driving torque

•

Boost-function (short term extended torque, e.g. during overtaking manoeuvres )


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Operation strategy of a parellel hybrid

Technical Data • PICE = 205 kW • PEM = 15 kW • mHybrid = 75kg • mFzg = 1955 kg • UBat = 120V

Goal: Maximize average efficiency


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Pedal plausibility check comb. engine

Min/Maxtorque ICE

conventional torque-based functions driver request

driver requested torque

ACC

max trq

Torque coordination

RBS


ESP

coord. torque request

comfort functions

engine torque request

Trans. max speed limit

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conventional torque-based functions

Pedal plausibility check comb. engine

Min/Maxtorque ICE

driver request

ACC

driver requested torque

recuperation torque request and boost max torque

torque prediction (power elctr.)

dynamic and static torque limits

ESP

max trq

Torque coordination

RBS

coord. torque request

comfort functions

Trans. max speed limit

powertrain torque request

Min/Max- voltage and current

battery power prediction

SOC

battery stateof-charge estimation

Elektr. Messgrößen

battery hybrid electric management functions system

control strategy:

SOC charge mode (trq limits) boost recuperation electric load shift anti-stall start-stop Auxiliaries-control (el. A/C, DC/DC, …)


+ electric motor ICE torque torque request

request

hybrid torquebased functions

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Electric Energy Management System: Power Prediciton and Safety Functions

LV -Bat .

Limiting control system

LV power Bordnetz supply LIN Gen. MSG ECU AGK Control Sup.

DC

VM ICE

DC

EMM

ISG

Getriebe transmission

MK Trq

LE PE HV -Bat .

HV Bordnetz power supply

energy

power prediction prevents from hitting the boundaries HV BMS

Trq Pr ed =

safety disconnection using conductor switch Michael Back: Implementing supervisory control strategies for Mercedes-Benz hybrid vehicles

TrqPred: IPred: UPred:

information

U Pr ed ⋅ I Pr ed ω ⋅η (U Pr ed , ω ) predicted max EM torque predicted max EM current predicted EM voltage at predicted EM current 20

Regenerative Braking System (RBS)

electric motor torque request

Regen torque request

actual torque

RBS

available regen torque

engine control unit

electric motor controller Actual torque

gear Available regen torque

CAN

CAN CAN transmission controller


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Boost

Torque

increasing maximum powertrain torque in full-load

Optimised torque characteristics at low engine speed

powertrain torque request

ICE torque

-

boost torque

time acc. pedal position

time


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Start-Stopp, boost, regeneration and electric load shift Start-Stopp

Automatic stop of the ICE when all stop preconditions are true (engine temperature, SOC, no component failures, lock-up clutch open, no diagnostics engine run-request,…)

Engine stop at 20 km/h or slower

automatic start when releasing brake pedal, pressing acc. pedal, switching gear, hitting lower threshold of SOC

Anti-Stall

Electric Load Shift

Discharging Battery when SOC is above set-point

Best ICE efficiency vs. keeping enough regencapacity as a function of SOC

Electric Load Shift Diagnostics

Supporting Idle Speed Control when engine speed is dropping very fast

Onboard Diagnostic Service needs ICE operation within a specific torque interval

If engine is going to stall, electric motor keeps the engine running

Electric motor contributes to driving power or generates extra load to keep ICE in torque range

Extended deceleration fuel shut-off with delayed begin of fuel injection to increase fuel-efficiency


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Boost, regeneration and electric load shift

Ucell [V]

•discharging at high SOC

4,1

•load shift requested by diagnostics

•recuperation

Udesired

•boost 3,3

•charge mode

OCV

• boost set-point

•load shift requested by diagnostics

charging above set-point only by: •Recuperation •load shift requested by diagnostics

2,5

SOC [%] 10 Michael Back: Implementing supervisory control strategies for Mercedes-Benz hybrid vehicles

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Summary

• no restrictions of space and driving comfort due to hybridization • optimized combustion engine (atkinson cycle) in combination with electric boost to increase fuel efficiency at constant speed/load • start-stopp and regenerative braking system to increase fuel efficiency in urban driving situations • electric load shift to avoid poor efficient operating conditions • electrical powered auxiliaries in combination with bi-directional DC/DC-converter to decrease energy losses • lithium ion battery with high efficiency and high energy density contributing in a hybrid surplus weight of only 75 kg => CO2-champion in luxury class with only 7.9 l per 100 km fuel consumption (190 g CO2/km) in the new european driving cycle (compared to 10.1 l of the basis S350 vehicle) Michael Back: Implementing supervisory control strategies for Mercedes-Benz hybrid vehicles

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