Technolo gg for
`Electric and %=
`Hybrid Vehicles
`
`-~ ’r
`
`0000000000000000000000000000000000000
`
`0
`
`Inter Cooler
`
`[ Wastegate Control
`
`Intake ~
`Air
`
`Controller
`
`Intake
`Manifold
`
`m DC
`Dynamometer
`
`4-
`’
`
`[
`t
`!
`
`[
`[
`
`Compressor
`
`Power
`Turbine ........ !
`
`Turbine
`
`Register for
`Emergency
`Stop
`
`Voltage
`
`Exhaust
`
`Current
`
`\
`
`’~"’~ SP-1331 ooo
`
`0000
`
`INTERNATIONAL
`
`Page 1 of 151
`
`FORD 1110
`
`

`

`T y fo
`Electric and Hyb []
`
`SP-1331
`
`GLOBAL MOB|LJTY DATABASE
`All SAE papers, standards, and selected
`books are abstracted and indexed in the
`Global Mobility Database
`
`Published by:
`Society of Automotive Engineers, Inc,
`400 Commonwealth Drive
`Warrendale, PA 15096-0001
`USA
`Phone: (724) 776-4841
`Fax: (724) 776-5760
`February 1998
`
`Page 2 of 151
`
`FORD 1110
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`

`

`Permission to photocopy for internal or personal use of specific clients, is granted by SAE
`for libraries and other users registered with the Copyright Clearance Center (CCC), pro-
`vided that the base fee of $7.00 per article is paid directly to CCC, 222 Rosewood Drive,
`Danvers, MA 01923. Special requests should be addressed to the SAE Publications
`Group. 0-7680-0151 -X/9857.00.
`
`Any part of this publication authored solely by one or
`more U.S. Government employees in the course of their
`employment is considered to be in the public domain,
`and is not subject to this copyright.
`
`No part of this publication may be reproduced in any form, in an electronic retrieval sys-
`tem or otherwise, without the prior written permission of the publisher.
`
`ISBN 0-7680-0151 -X
`SAE/S P-98/1331
`Library of Congress Catalog Card Number: 97-81283
`Copyright © 1998 Society of Automotive Engineers, Inc.
`
`Positions and opinions advanced in this
`paper are those of the author(s) and not
`necessarily those of SAE. The author is
`solely responsible for the content of the
`paper. A process is available by which
`the discussions will be printed with the
`paper if is is published in SAE Transac-
`tions. For permission to publish this paper
`in full or in part, contact the SAE Publica-
`tions Group.
`
`Persons wishing to submit papers to be
`considered for presentation or publication
`through SAE should send the manuscript
`or a 300 word abstract to: Secretary,
`Engineering Meetings Board, SAE.
`
`Printed in USA
`
`Page 3 of 151
`
`FORD 1110
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`

`

`PREFACE
`
`This Special Publication, Technology for Electric and Hybrid Vehicles (SP-1331), is a
`collection of papers from the "Electric Vehicle Technology" and "Engines and Fuel
`Technology for Hybrid Vehicles" sessions of the 1998 SAE International Congress
`and Exposition.
`
`Hybrid vehicles are now a reality in Japan, and they could soon be coming to the
`United States. The heart of the Toyota Prius hybrid vehicle is its fuel-efficient engine
`and unique transmission, coupled with a limited-range battery. The hybrid vehicle’s
`advantage is its ability to run the engine at its "sweet spot" to minimize emissions of
`criteria pollutants or minimize energy consumption and CO2 production, depending
`on the control strategy. The key technical measure of success for a hybrid vehicle is
`a well designed engine--electrical-battery system that is matched to the load demand.
`
`The papers from the "Engines and Fuel Technology for Hybrid Vehicles" session
`focus on leading-edge engine design, engine management, and fuel strategies for low
`emission, high mileage hybrid cars and commercial vehicles.
`
`The papers from the "Electric Vehicle Technology" session focus on hybrid vehicle
`control technology, energy storage, and management for hybrid vehicles and
`simulation development.
`
`Bradford Bates
`Ford Research Laboratory
`
`Frank Stodolsksy
`Argonne National Laboratory
`
`Session Organizers
`
`Page 4 of 151
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`FORD 1110
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`

`

`TABLE OF CONTENTS
`
`980890
`
`980891
`
`981122
`
`981124
`
`981125
`
`981126
`
`981127
`
`981128
`
`An Algorithm of Optimum Torque Control for Hybrid Vehicle ................ 1
`Yoshishige Ohyama
`Hitachi Car Engineering Co., Ltd.
`
`Energy Regeneration of Heavy Duty Diesel Powered
`Vehicles ............................................................................................... 11
`Matsuo Odaka and Noriyuki Koike
`Ministry of Transport, Japan
`Yoshito Hijikata and Toshihide Miyajima
`Hino Motors, Ltd.
`
`Development of the Hybrid/Battery ECU for the Toyota
`Hybrid System ...................................................................................... 19
`Akira Nagasaka, Mitsuhiro Nada, Hidetsugu Hamada, Shu Hiramatsu,
`and Yoshiaki Kikuchi
`Toyota Motor Corporation
`Hidetoshi Kato
`Denso Corporation
`
`Hybrid Power Unit Development for FIAT MULTIPLA Vehicle ................ 29
`Caraceni and G. Cipolla
`ELASIS ScPA - Motori
`R. Barbiero
`FIAT AUTO -VAMIA
`
`The Development of a Simulation Software Tool for Evaluating
`Advanced Powertrain Solutions and New Technology Vehicles ............ 37
`Jaimie Swann and Andy Green
`Motor Industry Research Association (MIRA)
`
`Styling for a Small Electric City Car ...................................................... 43
`T. G. Chondros, S. D. Panteliou, S. Pipano, and D. Vergos,
`P. A. Dimarogonas and D. V. Spanos
`University of Patras, Greece
`A.D. Dimarogonas
`Washington University in St. Louis, Mo.
`
`Patents and Alternatively Powered Vehicles ......................................... 53
`Rob Adams
`Derwent Information
`
`An Electric Vehicle with Racing Speeds ............................................... 59
`Edward Hell, Colin Jordan, Karim J. Nasr and Keith M. Plagens,
`Massoud Tavakoli, Mark Thompson and Jeffrey T. Wolak
`GMI Engineering & Management Institute
`
`Page 5 of 151
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`

`

`981129
`
`981130
`
`981132
`
`981133
`
`981135
`
`981187
`
`981123
`
`Battery State Control Techniques for Charge Sustaining
`Applications ........................................................................................ 65
`Herman L.N. Wiegman
`University of Wisconsin - Madison
`A. J. A. Vandenput
`Technical University of Eindhoven
`
`Load Leveling Device Selection for Hybrid Electric Vehicles .............. 77
`Paul B. Koeneman and Daniel A. McAdams
`The University of Texas at Austin
`
`Simulation of Hybrid Electric Vehicles with Emphasis
`on Fuel Economy Estimation ............................................................. 85
`Erbis L. Biscarri and M. A. Tamor
`Ford Motor Company
`Syed Murtuza
`University of Michigan
`
`Validation of ADVISOR as a Simulation Tool for a Series Hybrid
`Electric Vehicle .................................................................................... 95
`Randall D. Senger, Matthew A. Merkle and and Douglas J. Nelson
`Virginia Polytechnic Institute and State University
`
`The Electric Automobile .................................................................... 1 17
`E. Larrod~, L. Castej6n, and A. Miravete and J. Cuartero
`University of Zaragoza
`
`The Capstone MicroTurbineTM as a Hybrid Vehicle
`Energy Source ................................................................................... 127
`Howard Longee
`Capstone Turbine Corporation
`
`The Mercedes-Benz C-Class Series Hybrid ........................................ 133
`Joerg O. Abthoff, Peter Antony, and Michael KrAmer and Jakob Seller
`Daimler-Benz AG
`
`Page 6 of 151
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`

`An Algorithm of Optimum Torque Control for Hybrid Vehicle
`
`980890
`
`Yoshishige Ohyama
`Hitachi Car Engineering Co., Ltd.
`
`Copyright © 1998 Society of Automotive Engineers, Inc.
`
`Abstract
`
`An algorithm for a fuel efficient hybrid drivetrain
`control system that can attain fewer exhaust
`emissions and higher fuel economy was investigated.
`The system integrates a lean burn engine with high
`supercharging, an exhaust gas recycle system, an
`electric machine for power assist, and an
`electronically controlled gear transmission. Smooth
`switching of the power source, the air-fuel ratio,
`pressure ratio, exhaust gas ratio as a function of the
`target torque were analyzed. The estimation of air
`mass in cylinder by using an air flow meter was
`investegated to control the air-fuel ratio precisely
`during transients.
`
`1.INTRODUCTION
`
`Consumers are inceasing their demands for
`vehicles that are more fuel efficient, environmentally
`friendly, and affordable. Some form of electric and
`hybrid vehicle is increasingly being viewed as one
`answer to user demands. Thus, introduction of a
`future car system integrating an internal combustion
`engine and an electric machine seems inevitable [1].
`While electric vehicles and hybrid-electric vehicles
`are still dominant [2-4], conventional hybrid systems,
`with their complicated energy management and
`storage systems, may not be the final answer to the
`ultimate high-mileage, low-emissions passenger
`vehicle. Many of today’s hybrid and electric designs
`are simply too complex, heavy and costly to be
`considered a viable supercar-type vehicle.
`Minimal hybridization will present the best solution
`to the low-emitting, high-economy passenger vehicle
`
`of the future [1]. The internal combustion engine will
`continue to dominate the world passenger-vehicle
`market for at least the next 25 years [5]. The engine
`will require better efficiency and lowered emissions
`output which means that fuels will similarly require
`refinement, so that the engines can eventually be
`refined to the point that they produce almost no
`harmful emissions. Internal combustion engines using
`synthetic fuel made of natural gas, similar to light
`quality gasoline, seem to be the most promising
`advancement in the near future [5].
`To reduce the system’s cost and increase its
`efficiency, the engine is driven at the lowest possible
`speed at the maximum gear ratio of the transmission
`at low vehicle speed. Thus, the capacity of the electric
`machine and battery can be kept small. Systems that
`combine an integrated interactive hybrid drivetrain
`control system, such as to give lean burn, with an
`electronically controlled transmission, and electric
`machine control systems mentioned above, have
`been partially examined [1]. The optimum
`combination of two power sources-a hybrid drivetrain
`with an internal combustion engine and a small
`electric machine-would make it possible to get
`significant reductions in fuel consumption and
`exhaust emissions. The control system without the
`electric machine has been already investigated [6], as
`well as the control system with the electric machine
`and a continuously variable transmission [7]. A control
`system with the electric machine and simple gear
`transmission was presented [8]. A concept for an
`advanced hybrid control system was investegated
`that combined a high supercharging engine and a
`small electric machine [9]. In this paper, an algorithm
`for an advanced hybrid drivetrain control system
`
`Page 7 of 151
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`

`

`that combines the engine drivetrain control system
`and electric machine systems is investegated.
`
`2. SYSTEM CONCEPT
`
`2.1 Outline
`Idealized, the concept would include an engine
`and electric machine drivetrain, such as in Figure 1
`and Table 1. The electric machine is usually
`functioned as an electric motor. On one hand this
`provides fuel saving and lower exhaust emissions
`while using the engine system such as direct injection
`stratified charge sytem [10], or rapid combustion
`system with high dispersed fuel-air mixture [11] and
`high supercharging, on the other hand, it allows for
`short-distance driving and low load driving with the
`electric machine such as electrically exited
`synchronous drive with power inverter. The engine
`brake, wheel brake, and regeneration by the electric
`machine are controlled optimally during deceleration
`and downhill travel. A transmission with electronically
`controlled synchromesh gear sets is used for this
`purpose.
`
`Wheel
`(~--)
`
`C--)
`
`Engine ]---I I~--
`Drivetrain
`
`Electric ~_~ ~__
`machine
`
`Fig. 1 Hybrid drivetrain
`
`Table 1 Hybrid drivetrain
`
`(1) Engine
`(a) Rapid combustion with high dispersed mixture
`(b) High supercharging
`--> lower nitrogen oxides emissions
`
`(2) Electric machine
`Electrically exited synchronous drive
`with power inverter
`--> short distance and low load driving
`
`(3) Transmission
`Electronically controlled synchromesh gear set
`--> lower power loss
`
`2.2 Basic control technique
`The aim of the control system is to obtain a
`smooth drivetrain force change relative to the torque
`set point, which is given by the accelerator position,
`over a wide range of vehicle speeds and loads. The
`system should be able to cope with large changes in
`engine load and drivetrain switches from the electric
`machine to the engine and from the engine to the
`electric machine without increasing nitrogen oxides
`emissions, and without degrading driveability.
`
`T: Target torque
`
`Torque -~ T
`
`Vehicle--~l I
`speed Ih___j
`
`B
`
`Gear ratio
`R
`
`’uel mass
`
`Air mass
`A
`
`Electric
`current
`I
`
`Fig. 2 Control system
`
`As shown in Figure 2, the target drivetrain torque T
`is calculated as a function of the torque set point and
`the vehicle speed in block1 (B1). The upper and lower
`limits of the equivalent gear ratio Rh and RI are
`calculated as a function of the vehicle speed in B2.
`The equivalent gear ratio R, fuel mass F, and air
`mass A are simultaneously calculated as a function of
`the target torque T, taking the limit Rh and RI in
`consideration in B3. Some control strategies such as
`the dynamic compensation described in section 3.7
`are executed in B4. Fuel mass F is delivered with an
`electronically controlled fuel injector as shown
`elsewhere [10]. Fuel is injected directly into the
`cylinders. Therefore, the system is free from transient
`fuel compensation which is commonly in port injection
`systems [8]. The air mass A is controlled with an
`electronically controlled throttle valve and air bypass
`valve as described later. The fuel mass may be set by
`the target torque directly, as in diesel engines. But the
`estimation of the air mass by the accelerator position
`is not accurate. Therefore,the fuel mass is controlled
`
`Page 8 of 151
`
`FORD 1110
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`

`

`by the air mass which is generally measured by the
`air flow meter, to control the air-fuel ratio precisely
`[12].
`Under stratified charge conditions, the accelerator
`pedal opening angle, rather than the intake manifold
`pressure, is the most important information for
`determining the quantity of injected fuel. But,
`information about the amount of intake air has also
`importance in actual engine operation to control the
`air-fuel ratio A/F precisely.
`The gear ratio R is controlled with an electronically
`controlled transmission [13-16]. The command
`electronics for an electrically excited synchronous
`drive can be easily accomplished. In the case of a
`synchronous drive, an inverter provides optimal
`control of rotor excitation, stator current amplitude I,
`and stator current phase. A power inverter with
`insulated gate bipolar transistors transforms the
`battery voltage into the rotating voltage system for the
`motor driving of the electric machine. An additional
`chopper controls the DC current for the rotor. Then,
`the drivetrain output torque is obtained, which is equal
`to the target torque T if there are neither calculation
`nor control errors.
`
`2.3 Air-fuel ratio control
`As the target torque T increases, the drivetrain
`switched from the electric machine to the engine. The
`fuel mass F, air mass A of the engine and the electric
`current I are changed stepwise.
`
`The air mass and fuel mass of the engine are
`changed frequently as the target torque changes. The
`air-fuel ratio must be controlled during the transient
`conditions precisely to reduce exhaust emissions and
`improve driveability. It was determined that the
`volumetric efficiency during and immediately following
`a transient, at any engine temperature, was not equal
`to the staedy-state value. The transient volumetric
`efficiency was found to be as large as 10% different
`from the steady-state value. The volumetric efficiency
`is dependent upon instantaneous cylinder wall and
`valve temperature. To control the the air-fuel ratio A/F
`during transients accurately, the engine controller
`needs precise predictions or measurements of the
`amount of intake air, and the amount of fuel injected
`that will go directly in-cylinder [12].
`The intake system of the engine is equipped with a
`compressor for supercharging and an exhaust gas
`recycle system, as shown in Figure 3. Wt, Wc, Wb,
`Wh, Wr, and We are the air or gas mass flow rate at
`the upstream throttle valve, at the outlet of the
`compressor, at the bypass valve, at the downstream
`throttle valve, at the exhaust gas recycle valve, and at
`the intake port of the engine, respectively. In
`conventional engine control systems, the air flow into
`the cylinders should be predicted based on the
`movement of the throttle plate [12]. The air intake
`process is modeled through the manifold abusolute
`pressure observer model. The observer is based on
`the estimated throttle opening [12]. With stratified
`
`Bypass valve
`
`,Air flow meter
`
`/
`
`/
`
`Engine
`
`Intake manifold
`
`m[--
`
`W.--~
`
`I
`
`1
`
`Compressor
`
`Intercooler
`
`Throttle valve
`
`Throttle valve
`
`\
`
`Exhaust gas
`recycle valve
`
`Fig. 3 Intake system
`
`Page 9 of 151
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`

`

`Table 2
`
`Calculation conditions
`
`Type
`
`Cylinder volume per cylinder
`
`Maximum air mass per cylinder at atmospheric pressure A0
`
`Maximum exhaust gas recycle ratio
`
`Maximum exhaust recycle mass per cylinder GO
`
`Sum of A0 and 60 Gv0
`
`Maximum fuel mass per cylinder at atmospheric pressure F0
`
`Maximum air-fuel ratio
`
`Atmospheric pressure
`
`Maximum pressure ratio of compressor
`
`Torque T
`
`Cylinder volume per cylinder
`
`Thermal efficiency of engine
`Maximum output power of electric machine
`
`4-stroke 4 cylinder
`
`4× 10-~
`4.8× 10-~
`
`1.9X 10-4
`6.7× 10-4
`4.8 × 10-s
`
`9.8 × 104
`
`m3
`
`kg
`
`%
`kg
`
`kg
`
`kg
`
`Pa
`
`4O
`
`40
`
`1.92× 10~×F-19.2 Nm
`4 × 10-4
`m3
`30 %
`10.5 kW
`
`charge engines, nearly unthrottled operation is
`realized. Under these conditions, the estimation of the
`air flow based on movement of the throttle plate is not
`accurate due to the small pressure differential
`accross the throttle plate. Therefore, the model based
`on the air flow meter was investigated in this paper.
`
`3. ANALYSIS
`
`-3.1 Simulation conditions
`A 4 cylinder, 4-stroke engine with a cylinder
`volume of 4 ×10-4 m3 was used for testing. The
`engine was equipped with a direct injection stratified
`charge system [10], a supercharger and an exhaust
`gas recycle (EGR) system. The air-fuel ratio A/F was
`set between 11 and 40. The maximum ratio of the
`EGR was 40 %. The maximum pressure ratio of the
`superchager was 2. The air mass A was controlled by
`opening and closing of the throttle valve or the bypass
`valve in Figure 3. The relevant gear ratios from lst-
`5th for a stepped transmission were 3.5, 2.0, 1.3, 1.0
`and 0.73, respectively. Fuel mass F was controlled
`with electronically controlled fuel injectors. Table 2
`shows the calculation conditions. The output power of
`the electric machine was 10.5 kW, and the torque
`was 50 Nm at the speed of 2000 rpm.
`
`3.2 Smooth switching of power source
`As the target torque T increases in Figure 4
`
`drivetrain switches from the electric machine to the
`engine. The sw!tching is carried out by simultaneously
`decreasing the power of the electric machine and
`increasing the engine power. At T=50 Nm in Figure 4,
`the power source is switched from the electric
`machine to the engine. The fuel mass F, air mass A
`and the exhaust recylce mass G ’are increased
`stepwise simultaneously to keep the air-fuel ratio 15
`and the EGR ratio 40 %. As the target torque T
`increases further, the supercharger starts, the air
`mass A is increased more than A0, and the EGR
`mass is also increased. At T=162 Nm, the air mass A
`and the EGR mass G becomes doubled,
`
`2
`1.8
`1.6
`1.4
`!.2
`
`2 o.a
`
`0.4
`cZ 0.2
`
`0
`
`0
`
`1
`
`2
`T/IO0 Nm
`
`3
`
`Fig.4 Fuel mass F, air mass A and
`
`EGR mass G versus target torque
`
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`FORD 1110
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`

`

`which is limited by the pressure ratio of the
`supercharger. At T=243 Nm, the EGR mass G is
`decreased and the air mass A is doubled. When the
`target torque increases further, A/F becomes lower
`than 15, and the air mass must be controlled by using
`the throttle valve and the bypass valve.
`
`3.3 Lean burn control by supercharging
`Figures 5 (a), (b) and (c) show the simulation
`results with high supercharging and lean burn. When
`the target torque is more than TI= 50 Nm, the power
`source switched from the electric machine to the
`engine. When the air mass ratio A/A0 becomes more
`than 1 , the supercharge starts, the air mass ratio
`A/A0 is finally doubled. In Figure 5(a), at T=50 Nm,
`the supercharger starts simultaneously with the
`switching to the engine. When the target torque
`becomes higher than T2, The air-fuel ratio A/F
`becomes lower than 40. In Figure 5(b), the
`supercharger starts at T= 78 Nm. The air-fuel ratio
`A/F is increased temporally from 20 to 40. When the
`target torque becomes T3, the air mass A is
`decreased by decreasing the air-fuel ratio from 20 to
`15 stepwise ,without passing into the high nitorogen
`oxide emission region.
`Figure 5 (c) shows the result with high
`supercharging when pressure is controlled by the
`bypass valve proportionally to keep the air-fuel ratio at
`15. When the target torque becomes T2, the air mass
`is decreased slightly to decrease the air-fuel ratio
`from 20 to 15 by controlling the throttle valve. When
`the target torque increases further, the supercharger
`starts again and the pressure is controlled by the
`bypass valve.
`
`3.4 Smooth gear shift with exhaust gas recycle
`control
`Figures 6 (a)-(d) show the results when the gear
`is shifted from 4th to 2nd at the target torques are
`Tg=100 Nm, 170 Nm, 238 Nm, and 300 Nm,
`respectively. The engine torque must be changed
`simultaneously, so that the output torque remains the
`same during the shift operation. The engine torque is
`controlled by decreasing the mass of fuel. The air
`mass and EGR mass are decreased simultaneously
`to keep the air-fuel ratio at 15 and EGR ratio at 40%.
`The air mass is controlled by opening and closing the
`
`4
`
`3.5
`
`o 3
`
`f .................... <.ii ............................................................
`
`~2.5
`
`i
`
`~ 2
`
`~ 1.5
`
`1
`
`0.5
`
`0
`
`’"’"’"’"-.. T3
`
`-- F/70
`
`A,:F
`
`T/IO0 Nm
`
`(a) Early supercharging
`
`4 ,,- .......
`
`3.5
`
`o
`
`3
`
`",.,
`
`".
`
`2.5 ’". ",
`" T3
`2 ’,
`v
`T2
`
`~
`
`~ 1.5
`
`1
`
`0.5
`
`T1
`\
`
`~
`
`F/FO:
`A/AO
`AiF
`
`2
`TilO0 Nm
`
`Co) Late supercharging
`
`2.5
`
`2
`
`<~ 1.5
`
`1
`
`0.5
`
`i
`
`2
`T/IO0 Nm
`
`(c) Proportional supercharging
`
`Fig. 5 Fuel mass F, air mass A and EGR mass G
`
`versus target torque T
`
`throttle valve and the bypass valve. When the target
`torque becomes higer than T3 (Figures 6 (a)-(c)), the
`ass G decreases. When the target to
`
`Page 11 of 151
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`FORD 1110
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`

`

`and air-fuel ratio A/F versus traget torque T
`
`Fig. 6 Fuel mass F~ air mass A, EGR mass
`
`5 6
`
`.... G/GO
`...... A/F
`
`AIAO
`
`(d) Tg= 300 Nm
`
`TIIO0 Nrn
`2 3 4
`
`0 1
`
`T1
`
`5 6
`
`I
`
`%,.
`
`.... G/go
`...... A/F
`A/AO
`FIFO
`
`T4
`
`(b) Tg= 170 Nm
`I’/100 Nm
`3 4
`
`2
`
`0 1
`
`T3
`
`0.2
`
`0.4
`
`o 0.6
`0.8
`1
`
`O
`
`;2
`¯ -~ 1.2
`
`1.4
`
`1.6
`
`1.8
`
`0.2
`
`0.4
`o 0.6
`o 0.a
`
`1.2
`1.4
`1.6
`
`1.8
`
`(c) Tg= 238 Nm
`
`T/IO0 Nm
`3 4
`
`T1
`
`(a) Tg= 100 Nm
`
`5
`
`T/IO0 Nm
`3 4
`
`\
`
`o
`
`r~
`
`r~
`
`0.2
`
`0.4
`
`o 0.6
`0.8
`
`~ 1.2
`
`"< 1
`
`1.4
`
`1.6
`
`1.8
`
`Page 12 of 151
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`FORD 1110
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`

`

`becomes higher than T4 ( Figures 6 (a)-(c)), the air-
`fuel ratio becomes lower than 15. As the target torque
`at the gear shift Tg becomes higher, the region of
`supercharging increases. In Figure 6 (d),the air-fuel
`ratio becomes less than 15 at T=230-300 Nm,
`resulting in the increase of carbon monoxide
`emission.
`Figures 7 (a) and (b) show the total mass Gv (the
`sum of air mass and EGR mass) as a function of the
`target torque T. Tg is the target torque at gear
`shift .The gear is shifted from 4th to 2nd. The total
`mass ratio Gv/Gv0 is lowered when the Tg becomes
`lower. Thus, the target torque T when the
`supercharger ¯ starts :, becomes higher. When
`Tg is 100 Nm, the supercharger starts at the target
`torque T of tess than 100 Nm.
`
`3.5 Smooth gear shift with lean burn control
`Figures 8 (a)-(c) show the results when the gear is
`shifted from 4th to 2nd at the target torque Tg=70 Nm,
`170 Nm and 238 Nm, respectively. As Tg becomes
`higher, the target torque when the superchager starts,
`becomes lower. The engine torque must be changed
`so that the output torque remains the same during the
`shift operation. The engine torque can be controlled
`by controlling the fuel mass only. The air mass
`remains the same during the shift operation.
`
`4 -
`
`¯
`
`,
`
`.T2
`3.5 , ".., T3
`}’rl i": ....................
`3~\ :\,
`~2.5 ~ , .....
`
`’’,....,
`
`--
`
`1
`
`.........................................///.t:(
`
`/
`
`:
`
`/"
`
`,.~
`
`"~.
`
`o.51
`i
`0
`
`O ’ ....
`
`:= >5;
`5
`6
`
`1
`
`2
`
`4
`3
`T/IO0 Nm
`
`(a) Tg= 70 Nm
`
`I n., ..i: ’,.... ,.,..i:: ""\" ........
`%
`2.5
`"" ....
`T4
`i:., "’..
`I
`i
`
`2
`
`I :"
`1.5
`
`4
`
`3.5
`
`!,X ......
`i, w2i .....
`
`3
`
`i T3
`
`i
`
`0.5
`
`0
`
`o
`
`o
`
`...... AiF
`
`3 4
`Ti100 Nm
`
`(b) Tg= 170 Nm
`
`! ~ FRO’
`- A/AO
`...... A/F
`
`3 4
`T/IO0 Nm
`
`5
`
`(c) Tg= 238 Nm
`
`Fig. 8 Fuel mass F, air mass A, EGR mass
`
`as a function of the target torque T
`
`1.8
`1.6
`c= 1.4
`
`1.2
`1
`-~. 0.8
`
`>
`
`c= 0.6
`"~" 0.4
`
`0.2
`
`1.8
`¢= 1.6
`1.4
`
`~ 1.2
`
`>
`
`1
`-~ 0.8
`0.6
`0.4
`
`il //
`r! ,’ /
`i;2/,.///
`iA/ /
`_/"
`
`I A/AO
`i
`,,~
`
`"F
`
`ff 1
`,1 ....
`,
`3 4
`1
`2
`T/IO0 Nm
`
`0
`
`",,~4\J,.:
`
`5
`
`6
`
`(a) Tg= 70 Nm
`
`/
`/
`,1
`/
`/
`
`T4
`
`0.2
`
`0
`
`0
`
`3 4
`T/IO0 Nm
`
`5
`
`6
`
`(b) Tg= 100 Nm
`
`Fig. 7 Total mass Gv as a function of
`
`the target torque T
`
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`FORD 1110
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`

`

`Figures 9 (a) and (b) show the results when gear
`is shifted from 4th to 2nd at the target torque Tg=70
`Nm, 171 Nm, respectively. As the target torque at
`gear shift Tg becomes higher, the region of
`supercharging becomes wider, the region of the air-
`fuel ratio A/F of more than 20 becomes narrower.
`
`T4
`f
`
`T5
`I
`
`--F/FO! .....
`
`2.5
`
`1.5
`
`0.5
`
`f.z.,
`
`0
`
`i
`
`2
`
`4
`3
`T/IO0 Nm
`
`5
`
`6
`
`(a) Tg= 70 Nm
`
`:’,,
`
`T4
`1
`
`T5
`I
`
`F/FOI
`~--a/AOl
`A/F
`
`4
`3
`T/IO0 Nm
`
`(b) Tg= 170 Nm
`
`Fig. 9 Fuel mass F, air mass A. EGR mass
`
`as a function of the target torque T
`
`3.6 Air-fuel ratio control
`As mentioned before, the fuel mass is controlled
`by the air mass which is generally measured by the
`air flow meter. During switching from the electric
`machine to the engine, the air mass increases
`stepwise against the target torque T to maintain the
`air-fuel ratio adequately. The accuracy of maintaining
`the air-fuel ratio for operation during transient
`conditions depends on the accuracy of the estimated
`air mass entering the engine cylinders. It is ne
`
`to estimate this air mass in advance of fuel injection
`timing and before placing l the fuel in the cylinders. In
`case of gasoline direct injection the fuel injection is
`free from compensation for the fueling dynamics.
`When the capacity of the compressor, the surge tank
`and the intercooler in the intake system [17] is larger
`in Figure 3, the air mass going through the air flow
`meter increases temporarily to fill the surge tank and
`intercooler during throttle opening and the
`compressor starting. The air mass must be
`compensated also according to the response lag of
`the air flow meter and the filling lag of the EGR.
`The filling spike must be compensated to reduce
`fluctuation of the air-fuel ratio which is apt to increase
`exhaust emissions. This compensation is attained by
`using the aerodynamic model of the intake system
`[13]. The air mass into the cylinder is calculated by
`using the intake manifold filling dynamics and the
`compressor dynamics. Then, the model of the intake
`system to predict future air mass is applied. Some
`simulation results, obtained by the method mentioned
`above, are shown in Figure 10 which has samples of
`the traces for air mass flow rate Wa, Wc, Wb, Wh,
`and We and the pressure pi (105 Pa) at the
`intercooler when the compressor is started during 0-
`0.2 s and the bypass valve is closed during 0.3-0.4 s.
`Wa is the measuring value by the air flow meter. The
`estimated air mass, We, is close to the air mass
`
`0.03
`
`0. 025
`
`5_
`
`0.02
`
`O. 015
`
`0.01
`
`0.005
`
`°
`
`/
`/
`4/
`r,/
`
`"x
`
`K e
`Wa
`m Wc
`
`...... Wh
`
`.... Wb
`p~/100
`
`0.2
`
`0.4 0.6 0.8
`
`Time s
`
`Fig. 10 Air flow during bypass v
`
`Page 14 of 151
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`

`entering the cylinder. It is seen that the air mass can
`be estimated at the beginning of the intake stroke,
`resulting in the fuel supply without any delay, thus a
`precise air-fuel ratio control.
`3.7 Control strategies
`(1) Dymamic compensation
`Good acceleration performance will require some
`modification for the strategy mentioned in section 3.6.
`The output torque is reduced during the change in
`gear ratio and the power source (engine, electric
`machine) because part of the engine torque is used to
`accelerate the engine itself. The power is controlled
`by compensating the fuel mass and air mass through
`dynamic models, resulting in smooth switching and
`reduced drivetrain vibration.
`(2) Damping of the torque oscillation
`The torque of the engine is controlled during
`acceleration by monitoring differences between
`engine and wheel speeds in order to provide a
`measure of phase differences in the event of engine
`torque oscillating. The difference between the engine
`and wheel signals is integrated and fed to an ignition
`angle correction circuit in order to damp out the
`torque oscillations [18]. Or, the fuel mass is
`compensated in place of the ignition angle. In the
`case of the transmission without power shift, the
`oscillation will irlcrease when the fuel mass is
`increased stepwise after the gear engagement. The
`fuel mass is controlled, taking the oscillation into
`consideration or, the control is executed by estimating
`the torque by engine speed signal [19].
`(3)Block of the shift
`The control system compares and calculates the
`difference between two stationary torques calculated
`at different times. Then it recognizes whether the
`vehicle is on the crest of a hill or in a valley, and
`whether the vehicle is traveling uphill or downhill over
`the crest of the hill or through a valley. The gear shift
`is blocked according to this information to avoid
`frequent gear shifts.
`(4) Integration of brake control
`Full utilization of regenerative braking increases
`electric machine operating range by 25% [20]. The
`engine brake, wheel brake, and regeneration by the
`electric machine are controlled optimally during
`downhill travel. However, available regenerative
`braking methods vary for several operating conditions
`such as state of battery charge and vehicle speed.
`
`Regeneration cannot be executed when the battery
`charge is full. Integration of brake and drivetrain
`controls allows maximum energy recovery with
`minimal friction braking. This dynamic interaction
`between the vehicle’s brake and drivetrain systems
`also improves driveability.
`(5) Power assist with electric machine
`The electric machine is connected between the
`engine and transmission or between the transmission
`and the wheel. In the former, the electric machine can
`assist synchronization of the gear sets during the shift
`operation in the synchromesh transmission. The
`operating force becomes unnecessary, and the
`friction cones for synchronism are eliminated.
`Therefore, the gear shift mechanism in the
`synchromesh transmission becomes very simple. In
`the latter, the electric machine can assist power
`supply to the wheel during the shift operation in the
`resulting
`in better
`synchromesh transmission,
`driveability.
`
`3.8 Future outlook
`The system mentioned above is a concept,
`although some components and subsystems have
`oeen tested already. More detailed analysis would be
`conducted to demonstrate the magnitude of the
`efficiency gains by introducing all components and
`subsystems in a testing vehicle.
`
`4. SUMMARY
`
`A fuel efficient engine drivetrain control system
`was proposed which combines a lean burn engine
`with a supercharging, an exhaust gas recycle, an
`electric machine for power assist, and an
`electronically controlled trasmission. The smooth
`switching of power source, the lean burn control with
`supercharging, the smooth gear shift with exhaust
`gas recycle control and lean burn control, and the air-
`fuel ratio control by using an air flow meter were
`anal