STRATEGIES IN
`
`Engine
`
`Transaxle
`
`Main Batteries
`
`Traction Motor
`Inverter & MCU
`
`\
`\
`\
`\ Generator Motor
`’,Inverter & GCU
`
`SP.1156
`
`1 of 15
`
`FORD 1372
`
`

`
`Strategies in Electric and
`Hybrid Vehicle Design
`
`SP-1156
`
`GLOBAL MOBILITY 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: (412) 776-4841
`Fax: (412) 776-5760
`February 1996
`
`2 of 15
`
`FORD 1372
`
`

`
`Permission to photocopy for internal or personal use, or the internal or personal use of specific
`clients, is granted by SAE for libraries and other users registered with the Copyright Clearance
`Center (CCC), provided 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.
`1-56091-786-5/9657.00.
`
`Any part of this publication authored solely by one
`or more U.S. Government employees in the course
`of the, ir o, mnlnxtrn~nt ic r, nr~ciA~v~A ~,", 1.,,~ ;,,. ~ .... 1..1"~
`domain, and is not subject to this copyright.
`
`No part of this publication may be reproduced in any form, in an electronic retrieval system or
`otherwise, without the prior written permission of the publisher.
`
`ISBN 1-56091-786-5
`SAE/SP-96/1156
`
`Copyright 1996 Society of Automotive Engineers, Inc.
`
`Positions and opinions advanced in this pa-
`per are those of the author(s) and not neces-
`sarily those of SAE. The author is solely
`responsible for the content of the paper. A
`process is available by which discussions will
`be printed with the paper if it is published in
`SAE Transactions. For permission to pub-
`lish this paper in full or in part, contact the
`SAE Publications Group.
`
`Persons wishing to submit papers to be con-
`sidered for presentation or publication through
`SAE should send the manuscript or a 300
`word abstract of a proposed manuscript to:
`Secretary, Engineering Meetings Board, SAE.
`
`Printed in USA
`
`3 of 15
`
`FORD 1372
`
`

`
`PREFACE
`
`Electric and hybrid vehicle technology is rapidly progressing worldwide in an attempt
`to lessen the air quality impacts of personal transportation and to reduce dependence
`on petroleum fuels. Strategies in electric and hybrid vehicle design seek to optimize
`vehicle performance, fuel economy, and emissions, and keep cost and complexity
`within consumer-acceptable limits.
`
`This SAE special publication, Strategies in Electric and Hybrid Vehicle Design
`(SP-1156), is a collection of papers presented for sessions at the 1996 SAE
`International Congress and Exposition, co-organized by the Advanced Powerplant
`Committee/Powerplant Activity and the Electric Vehicle Committee/Passenger Car
`Activity.
`
`One session, Engine and Fuel Technology for Hybrid Vehicles, focuses on engine and
`fuel strategies for fuel efficient, low emission hybrid vehicles. Hybrids employing
`either mechanical energy storage or electrical energy sources are covered. Longer-
`range concepts employing novel engines and hydrogen and compressed natural gas
`alternative fuels are also discussed. The reader will find that hybrid strategies taken
`by European, Japanese, and North American developers differ. While technology is
`evolving rapidly, it is clear that the definitive hybrid strategy has not yet been
`developed.
`
`Strategies covered in the above session can be divided into three general
`classifications: series, parallel, and dual system (combined series-parallel). Each
`strategy places different demands on the engine. Typically, parallel operation,
`favored by the Europeans, has the advantage that the operation of the internal
`combustion (IC) engine is just as efficient as the operation of a conventional vehicle.
`However, the IC engine in a parallel arrangement must contend with transients.
`Controlling a parallel hybrid is critical, because each power source can provide
`traction to the wheels independent of the other system. Series operation has the
`advantage of allowing the engine to operate at a constant speed in the vicinity of its
`optimum (in terms of efficiency and emissions) operating point. However, the series
`configuration has an efficiency penalty, as energy must be converted several times.
`Dual systems appear promising because they have the advantages of both the parallel
`and series systems. It is hoped that this session will spark interest in research and
`development on engine systems tailored specifically for hybrid vehicle application.
`
`Frank Stodolsky
`Argonne National Laboratory
`
`Session Organizer and Chair
`
`Bradford Bates
`Ford Motor Co.
`
`Session Organizer
`
`4 of 15
`
`FORD 1372
`
`

`
`960229
`
`960230
`
`960231
`
`960232
`
`960233
`
`960234
`
`960254
`
`960255
`
`TABLE OF CONTENTS
`
`Duty Cycle Operation as a Possibility to Enhance the Fuel
`Economy of an SI Engine at Part Load .................................................... 1
`Martin Ender and Philipp Dietrich
`Swiss Federal Institute of Technology
`
`Engine Control Strategy for a Series Hybrid Electric Vehicle
`Incorporating Load-Leveling and Computer Controlled Energy
`Management ............................................................................................ 11
`Clark G. Hochgraf, Michael J. Ryan, and Herman L. Wiegman
`University of Wisconsin-Madison
`
`Development of a New Hybrid System - Dual System .......................... 25
`Kozo Yamaguchi, Shuzo Moroto, Koji Kobayashi, Mutsumi Kawamoto, and
`Yoshinori Miyaishi
`Equos Research Co., Ltd.
`
`Evaluation of the Hydrogen-Fueled Rotary Engine for Hybrid
`Vehicle Applications ............................................................................... 35
`Paul A, Salanki and James S, Wallace
`University of Toronto
`
`Robust Control of a Parallel Hybrid Drivetrain with a CVT .................. 47
`Thomas Mayer and Dierk Schroeder
`Technical University of Munich
`
`Optimization of a CNG Series Hybrid Concept Vehicle ........................ 55
`Salvador M. Aceves, J. Ray Smith, L. John Perkins,
`Scott W. Haney, and Daniel L. Flowers
`Lawrence Livermore National Lab.
`
`Ride, Handling and Overall Chassis Development of GM
`Impact Electric Vehicle ........................................................................... 65
`Clive A. Roberts
`Lotus Engrg.
`Mark A. Rushbrook
`Delphi Chassis Systems
`
`Efficiency Considerations in the GM Impact Electric Vehicle:
`Ride, Handling, and Steering Function .................................................. 77
`Richard J. Kowalczyk
`Delphi Chassis Systems
`William L. Shepard, Jr.
`GM Electric Vehicles
`Jarett M. Smith
`Delphi Saginaw Steering Systems
`Ronald G. Williams
`Sachs Automotive of America
`
`960256
`
`Switched Reluctance Drives for Electric and Hybrid Vehicles ............ 91
`Ajay Yelne
`EA Engineering, Science, and Tec=,nology, Inc.
`Kenneth Heitner
`U. S. Department of Energy
`
`5 of 15
`
`FORD 1372
`
`

`
`960259
`
`960445
`
`960446
`
`960447
`
`Dielectric Breakdown Sensing for Electric Vehicle Applications ...... 103
`Min Sway-Tin
`Chrysler Corp.
`Sandeep Dhameja
`VI Engineering, Inc.
`
`Power Improved ZEBRA Battery for Zero Emission Vehicles ........... 113
`C.-H. Dustmann
`AEG Corp.
`R. Tilley
`Beta Research and Development
`
`Fast |ntelligent Battery Charging for Automotive Applications
`Using Neural-Fuzzy Technology .......................................................... 121
`Zafar Ullah, Brian Bufford, Sayeed Rahman, Dilip S, and Roger Miller
`National Semiconductor Corp.
`
`Ni-MH Battery Charger with a Compensator for Electric
`Vehicles ................................................................................................. 125
`Hae-Woo Park, Chang-Seok Han, Chul-Soo Kim, Bong-Ho Lee,
`and Young-Woo Kim
`Hyundai Motor Co.
`Paul R. Gifford
`Ovonic Battery Co.
`
`960448
`
`An Empirically B~s~d El~-etrn~o,_Jrge Horizo~ Le_~d=A¢id
`Battery Model ........................................................................................ 135
`Stephen Moore and Merhdad Eshani
`Texas A&M Univ.
`
`6 of 15
`
`FORD 1372
`
`

`
`960231
`Development of a New Hybrid
`System - Dual System
`
`Kozo Yamaguchi, Shuzo Moroto, Koji Kobayashi,
`Mutsumi Kawamoto, and Yoshinori Miyaishi
`Equos Research Co., Ltd.
`
`Copyright 1996 Society of Automotive Engineers, Inc.
`
`ABSTRACT
`
`A new hybrid vehicle system has been developed, the Dual
`System, which combines the series and parallel hybrid
`systems.
`Combination with a motor has reduced the engine size,
`only using the most efficient range of the engine. A transaxle
`employing a generator motor and a traction motor in one
`compact package is applicable to currently produced vehicles
`with little modification. Use of the generator as a motor
`realizes multiple control functions.
`A prototype vehicle with this new Dual System was built
`and tested. Its driving performance and the fuel economy
`were measured, and the fuel economy results were analyzed.
`
`INTRODUCTION
`
`Toward the 21st century, energy conservation has keen
`global interest due to an expected sharp increase in energy
`demands according to ever increasing population and global
`warming caused by an increasing volume of generated CO2.
`To decrease the energy used for vehicles, there are activities
`in various countries to find ways to greatly reduce the fuel
`consumption of vehicles, such as the "80 mpg Super Car
`Concept" in the U.S. It is required to adapt a completely new
`system, not just make a simple modification to the current
`system, to realize a dramatic improvement in fuel economy.
`It is recognized that one promising field is hybrid systems.
`Both series and parallel hybrid systems are well known.
`This paper discusses a new hybrid system based on the "split"
`system which splits energy from the engine using a planetary
`gear [1] [2] [3], the new system being called the Dual System.
`
`COMPARISON OF VARIOUS HYBRID SYSTEMS
`
`Not only used as a range extender of electric vehicles, the
`hybrid system, employing both an engine and an electric
`motor, can improve fuel economy using the engine through
`
`its combination with the motor [4]. The hybrid system can
`improve fuel economy in light of the following:
`1. Operation of the engine in optimum efficiency range
`2. Transmission efficiency between the engine and the
`driving wheels is improved
`3. Regeneration of deceleration energy
`Figure 1 shows the four different hybrid systems.
`
`(A) SERIES SYSTEM - This system supplements
`electricity generated by the engine. It is most commonly used
`as a range extender for electric vehicles. Since the engine is
`not mechanically connected to the drive wheels; this system
`has an advantage of controlling the engine independently of
`the driving conditions. Accordingly, the engine is used in its
`optimum efficiency and low emission range. This system is
`particularly suited to engines which are hard to mechanically
`connect to the drive wheels such as gas turbine engines.
`Disadvantages, however, include large energy conversion
`losses because of the necessity of full electricity conversion
`of the engine output. Further, a generator large enough to
`convert the maximum engine output is required.
`
`(B) PARALLEL SYSTEM - With the parallel system, an
`electric motor which supplements the engine torque, is added
`to the conventional driveline system of the engine and
`transmission. Accordingly, operations of the engine are quite
`similar to those of an engine in a normal vehicle. This system
`requires no generator, and there is a direct mechanical
`connection between the engine and the drive wheels, providing
`an advantage of less energy being lost through conversion to
`electricity.
`On the other hand, this system requires a transmission
`because no speed adjustment mechanism is installed, though
`the motor supplements the torque. When an automatic
`transmission is used, a torque converter, oil pump, and other
`auxiliary components can reduce the transmission efficiency.
`Although the engine torque can be controlled by the motor,
`the engine speed is determined by gear ratios like a
`
`25
`
`7 of 15
`
`FORD 1372
`
`

`
`(A) SERIES
`
`(B) PARALLEL
`
`i
`u
`m
`
`(C-1) SWITCHING
`
`(C-2) SPLIT
`
`L===n===~.~..g.~’
`
`I
`
`w
`
`+ |
`
`l
`
`R
`|
`
`(C- 1) SWITCHING SYSTEM - Application and release
`of the clutch switches between the series and parallel systems.
`For driving as by the series system, the clutch is released,
`separating the engine and the generator from the driving
`wheels. For driving with the parallel system, the clutch is
`engaged, connecting the engine with the driving wheels.
`For example, since city driving requires low loads for
`driving and low emissions, the series system is selected with
`the clutch released. For high speed driving where the series
`system would not work efficiently due to higher drive loads
`and consequently higher engine output is required, the parallel
`system is selected with the clutch applied.
`
`(C-2) SPLIT SYSTEM - This system acts as the series
`and parallel systems at all times. The engine output energy is
`split by the planetary gear into the series path (from the engine
`to the generator) and the parallel path (from the engine to the
`driving wheels). It can control the engine speed under variable
`control of the series path by the generator while maintaining
`the mechanical connection of the engine and the driving
`wheels through the parallel path.
`Correlation between the vehicle speed V and the engine
`speed NE is shown in Figure 2. When the engine is operating
`at a relatively constant torque in an optimum efficiency range,
`the energy from the engine is almost proportional to the engine
`speed NE. Accordingly, Figure 2 also indicates correlation
`between the vehicle speed and the engine output energy. In
`
`2, ti.~ ~1J~’u ,r. ,~
`NE = NEP + NES
`where NEP is the engine speed by the parallel path and NES
`the engine speed by the series path. As the parallel path engine
`speed NEP increases in proportion to the vehicle speed, the
`output energy from the engine increases as the vehicle speed
`becomes higher. The higher the speed, the more energy is
`required for driving, it being appropriate that the parallel path
`energy becomes larger for higher speeds. For high speed
`
`50O0
`(rpm)
`
`Mechanical Connection
`
`...... Electrical Connection
`
`EG : Engine G : Generator M : Motor B : Battery
`TM : Transmission C : Clutch PG : Planetary Gear
`
`NE
`
`Figure 1: Four Different Hybrid Systems
`
`4000
`
`3000
`
`200(
`
`100(
`
`conventional vehicle. Accordingly, the engine operation is
`linked to the driving conditions.
`
`(C) SERIES-PARALLEL COMBINED SYSTEM - This
`combined type, having a generator and a motor, features
`characteristics of both the series and parallel systems, and the
`following two systems are possible:
`
`20 40
`
`60
`V
`
`80
`
`1 oo 120
`
`(km/h)
`
`Figure 2: Engine Speeds in Split Hybrid System
`
`26
`
`8 of 15
`
`FORD 1372
`
`

`
`driving, most of the output from the engine is supplied by the
`parallel path; consequently the energy conversion is small and
`not such a large generator as for the series system, is required.
`Since the engine speed NES with the series path is variable
`within the generator capacity, it is possible to control the
`engine conditions into ranges favorable for engine efficiency
`and lower emissions. It is also possible to control the amount
`of electricity charging the batteries.
`
`OBJECTIVES OF THE DUAL SYSTEM
`
`The maximum efficiency of the conventional reciprocating
`engine reaches 35% [5] and this could be increased to 40%
`through combination with a hybrid system. Other engines,
`for example, a gas turbine engine, may not easily exceed
`such an efficiency. We therefore consider it more realistic to
`take advantage of very developed reciprocating engine
`technologies so that the system can maximize the advantages
`of such engines.
`Based on the comparison of various hybrid systems,
`recognizing that the split type has the largest potential among
`the hybrid systems, we developed the Dual System which
`maximizes the advantages of the split hybrid system. Features
`of this system are:
`
`1. Compact Transaxle package design requires minimal
`modification of vehicles currently available.
`2. Combination with a motor enables the engine to be small
`and lightweight. The engine can be operated in an
`optimum efficiency range.
`3. The motor can operate as a generator, realizing a variety
`of control functions.
`
`CONSTRUCTION
`
`The complete schematic of the Dual System is shown in
`Figure 3. Figure 4 depicts the positions of major components
`within the vehicle. The vehicle is a modified "Corolla"
`production model, the vehicle weight being increased by 305
`kg from the production weight of 1,040 kg, to 1,345 kg.
`
`ENGINE - Since a small engine can meet requirements
`as the drive motor adds the torque, a 660cc engine for a
`commuter vehicle was used. Although a normal vehicle can
`rarely operate in the optimum efficiency range of the engine,
`engine downsizing should make it possible at all times. The
`engine throttle was disconnected from the accelerator pedal
`and computer-controlled by a throttle actuator motor.
`An average maximum cruising speed which does not drain
`electricity from the batteries is determined according to the
`
`-- SIGNAL
`
`................. 12V
`
`288V
`
`PEDALS, LEVER
`
`& SWITCHES
`
`--ivcu ,o,sPLAY,
`
`CABIN
`
`TRUNK
`
`D/C D/C
`CONVERTER
`
`I i ................................ )i) .......................
`
`....................... "~’"’:’: ................................................. i
`
`OR
`
`rL~ ~OLER3ONTR
`/ L,,-"
`
`ENGINE
`COMPARTMENT
`
`THROTTLE
`ACTUATOR
`
`BATTER ~ I RELA
`
`©
`
`Figure 3: Complete Dual System Schematic
`
`27
`
`9 of 15
`
`FORD 1372
`
`

`
`Main Batteries
`
`Traction Motor
`Inverter & MCU
`
`Generator Motor
`Inverter & GCU
`
`Engine
`
`Transaxle
`
`vcu
`
`Figure 4: Major Components Positions in Vehicle
`
`engine size. This discussed system provides an average
`cruising speed in the range of 90 to 100 km/h.
`
`TRANSAXLE - A sectional view of the transaxle is shown
`in Figure 5 and its picture in Figure 6.
`The transaxle is for a FWD transversely mounted engine
`and is a package of a traction motor and generator motor. Its
`total length is 359 ram, shorter than the replaced production
`4-speed automatic transaxle.
`The weight of the transaxle, including the flywheel and
`damper assembly and transmission fluid, is 90 kg, 8 kg more
`than the production 4-speed transaxle. The small engine used
`eliminates both the starter and the alternator in addition to the
`oil cooler of the transaxle. The total weight of the engine and
`the transaxle is 30 kg tess than those used in current production
`model.
`Layout - The layout of the transaxle is of a 4-axle
`construction. On the first axle, which is on the same axis as
`the engine axle, is mounted the flywheel and damper, planetary
`gear set, generator motor and generator brake, while on the
`second axle, the traction motor. The counter gear is mounted
`on the third axle and the differential gear on the fourth.
`Installation of the traction motor on an axle different from
`the engine axle results in a reduced total length. This also
`enables independent design of gear ratios of the engine and
`those of the traction motor, which permits optimum gear ratio
`designs for both. The designed engine gear ratio (including
`the planetary gear ratio) is 4.19 and the traction motor gear
`ratio, 7.99.
`
`Planetary Gear
`
`Generator Motor (6kW
`
`Flywheel & Damper
`
`Y
`
`Traction Motor (40kW)~
`
`Differential Gear
`
`Figure 5: Sectional View of Transaxle
`
`28
`
`10 of 15
`
`FORD 1372
`
`

`
`prevent hard brake engagement.
`Hydraulic Circuits - ATF (Automatic Transmission Fluid)
`is used, affecting cooling, lubrication and engaging pressures
`of the generator brake. The valve body is small, having only
`one solenoid for the brake. Cooling of the transaxle is realized
`by radiating heat using transaxle case fins along with the
`internal circulation of the ATF which equalizes thermal
`distribution within the transaxle. No oil cooler is installed
`such as a radiator, outside the transaxle. Cooling of the motors
`is, done with the ATF being showered on the stator coil ends.
`
`BATTERIES - In the hybrid vehicle using a small engine,
`acceleration and deceleration are done by discharging and
`charging of the batteries. As a result, the batteries require
`power density more than energy density. The prototype
`vehicle involved is mounted with lead-acid batteries which
`are low in cost and relatively high in power density. Those
`used are Cyclon-25C VRLA batteries, their capacity being
`25Ah each. The number of batteries used is 24 with a total
`voltage of 288V and a total weight of 240 kg.
`
`DISPLAY - The display connected to the vehicle
`controller enables monitoring vehicle conditions including the
`energy flows of each component and engine conditions, on a
`real-time basis.
`
`SYSTEM CONTROL
`
`ROLE OF EACH CONTROL UNIT - The Dual System
`has four control units, including one for the engine. VCU
`(vehicle control unit) gives instructions, depending on driving
`conditions, to ECU (engine control unit), GCU (generator
`motor control unit), and MCU (traction motor control unit).
`The engine is so controlled as to follow the optimum efficiency
`curve. The generator motor controls the engine speed, and
`the output torque is controlled by the traction motor.
`Engine Control - VCU controls the throttle actuator by
`determining throttle openings from the engine speed so that
`the optimum efficiency curve be followed. It also turns the
`ECU on and off, turning the engine on and off.
`Generator Motor Control - VCU gives instructions as to
`the desired generator motor speed, NG*, to GCU on the basis
`of accelerator pedal movement, vehicle speed and battery SOC
`(state-of-charge).
`GCU uses feedback control for the generator torque in
`order to make the actual generator motor speed NG NG*. PI
`(Proportional-Integral) feedback control is applied for high
`responsiveness and compensation of steady-state error.
`Traction Motor Control - VCU determines the output
`torque of the traction motor from accelerator pedal movement
`and vehicle speed. Further, it computes the generator motor
`torque to determine influence of the engine torque on the
`output torque (because the torque of the engine, generator
`motor and output reaction are proportional to each other), and
`then compensates the output torque of the traction motor so
`that the output torque remains constant whatever the engine
`
`Figure 6: Picture of Transaxle
`
`The counter gear of the third axle transmits the torque of
`the first and second axles to the fourth axle.
`Planetary. Gear - The planetary gear splits the engine output
`to the generator motor and output shaft. The planetary carrier
`is connected to the engine and the ring gear to the output shaft.
`The sun gear is connected to the generator motor.
`The planetary gear also works as a speed increasing and
`torque reducing device for the generator motor, enabling the
`latter to be small. The speed increasing gear ratio is 3.21.
`Generator Motor - The generator motor is a DC brushless
`motor with a maximum output of 6 kW. Using a motor with
`8 poles, which is more than usual, the generator brake and the
`planetary gear are arranged inside the coil ends, causing the
`total length to be shortened.
`The generator motor is used as a motor, leading to it being
`the center of multiple control functions of the Dual System;
`when functioning as a generator, it eliminates the necessity
`of an alternator, and a starter as well since it also functions as
`an engine starter. It functions as a starting device, clutch and
`a kind of CVT together with the traction motor, resulting in
`not requiring a transmission.
`Traction Motor - The traction motor, outputting a
`maximum 40 kW, is a 4-pole DC brushless motor. It functions
`as the engine torque leveling device of the parallel hybrid
`system.
`Generator Brake - Under low load conditions such as
`constant speed cruising, the system used is the parallel hybrid
`one with the brake engaged, preventing the generator motor
`from causing energy conversion losses. The cooling oil of
`the brake plate is also used for cooling the generator motor.
`The generator motor uses "soft-landing" control for which a
`cushion plate is simply applied instead of an accumulator to
`
`29
`
`11 of 15
`
`FORD 1372
`
`

`
`conditions are. When the brake pedal is applied, the engine
`is released, with regeneration torque of the traction motor is
`determined according to the amount of brake pedal application
`and the vehicle speed.
`MCU controls the traction motor to make the traction
`motor torque, TM, equal to the desired torque, TM*, from
`VCU.
`
`ENGINE CONTROL STRATEGIES - For high efficiency
`and low emissions of the engine, the throttle openings are so
`designed to be a constant 35% for NE for values of 2,000 rpm
`and greater. The fixed point control of the engine can be
`applied for an optimum efficiency point, while it increases
`losses due to energy conversion of motors and batteries. As
`the production engine efficiency is not so sensitive with respect
`to the engine speed, the engine speed of the Dual System is
`controlled depending on the driving load.
`When the load increases, the generator motor speed is
`raised to supplement the energy from the engine. This control
`reduces the electricity passing through the batteries,
`consequently reducing the energy conversion losses of the
`batteries and also protecting the batteries from excessive
`discharge. As the accelerator pedal is depressed, the engine
`speed increases, and the driving feeling is natural to the driver.
`Battery current accumulation is used as SOC, maintaining
`the initial value by generator motor control. If the SOC lowers
`
`STOP
`
`’~
`
`a) STOP MODE
`
`from the initial value, the generator motor speed increases,
`making the engine speed increase for higher engine output
`energy. If SOC becomes higher, the generator motor speed is
`decreased.
`During transient conditions for turning the engine and
`brake on and off, the generator motor controls the engine speed
`so that changes are gradual in order to prevent any excessive
`change in engine operation.
`
`VEHICLE CONTROL OF EACH STATE - As shown in
`Figure 7, each control mode is specifically applied depending
`on driving conditions:
`a) Standstill Mode - When the vehicle is stopped at a
`standstill, the engine stops.
`b) Motor Mode - Until the vehicle reaches a speed of 8
`km/h after starting or it decelerates to 5 km/h or lower when
`driving, the engine stops and the motor alone works.
`c) Parallel Mode - The generator brake is engaged and the
`system drives using the parallel hybrid system. The generator
`motor does not operate during this time.
`d) Split Mode (Positive) - Accelerator pedal movement
`and the SOC determine the generator motor speed NG. The
`engine speed NE is obtained from the formula:
`NE = NEP + 3.212 o NG
`where NEP is the engine speed of parallel path which is
`proportional to the vehicle speed. NE should be increased by
`
`(CREEPING SPEED)
`.~
`MOTOR DRIVE
`
`b) MOTOR MODE
`
`1
`
`VEHICLE
`CONTROL
`
`¯
`~
`
`DRIVE
`
`il
`
`I
`
`ORDINARY I-----I c/PARALLEL I
`OPERAT,ON 11 MODE I
`
`,,,BeNoo!
`
`H,GH LOADor I___1 d SPL,TMODE I
`
`LOW SOC Jl (POSITIVE) I
`
`HIGH SOC
`
`._~
`
`(NEGATIVE)
`
`[ e) SPLITMODE
`
`1
`
`--" [ ORDINARY
`k OPERATION )
`ENGINE DRIVE ?
`
`~GINE STOP i
`
`-- DRIVE ~,i
`
`CONTROL
`
`g) ENGINE START
`CONTROL
`
`--1 DECELERATE
`
`f) REGENERATION
`MODE
`
`I
`
`Figure 7: Vehicle Control
`
`3O
`
`12 of 15
`
`FORD 1372
`
`

`
`increasing NG according to the degree of low SOC. This
`leads to an increase of energy supply from the engine. As the
`accelerator is depressed, NE is increased, raising the energy
`supply from the engine.
`As the efficiency of the generator motor reduces in a low
`speed range, the generator brake is engaged to change to
`parallel mode when calculated NG* reaches 1,500 rpm or less.
`The parallel mode is not applied when the vehicle speed is
`lower than 25 km/h because the engine speed becomes too
`low. To avoid any possible worsening of emissions due to a
`sharp change in the engine speed, the maximum rate of the
`generator motor speed change is limited to 300 rpm!second
`while in the split mode.
`e) Split Mode (Negative) - When the SOC becomes too
`high, the generator motor functions as a motor and not a
`generator, with the generator motor rotating in the negative
`direction, controlling the engine speed to be lower than the
`parallel speed NEP.
`f) Regeneration Mode - When the brake pedal is applied,
`the regeneration mode comes on. The regenerated electricity
`depends on the degree of pedal application. The upper limit
`of the regeneration is 20 kW for battery protection, almost
`taking care of LA#4 (Los Angeles No.4: Federal Urban
`
`Driving Cycle) mode deceleration. The engine stops to
`eliminate its resistance and consequently the regeneration
`energy is maximized.
`g) Engine Start Control - The generator motor starts up
`the engine, at which time the output torque is compensated
`for by the traction motor using the generator motor torque.
`h) Engine Stop Control - The engine is stopped by cutting
`the fuel.
`i) B-ON Control - In order to prevent harsh shock and
`emissions upon generator brake engagement, the generator
`motor gradually reduces its own speed until it is zero for "soft
`landing".
`j) B-OFF Control - The generator motor controls its own
`speed from zero to ensure "soft taking off" to prevent harsh
`shock and emissions upon generator brake release.
`
`VEHICLE PERFORMANCE
`
`DRIVING PERFORMANCE - The traction performance
`of the Dual System vehicle is shown in Figure 8. The total
`power of the engine and the traction motor is comparable to
`approx. 50 kW. In particular, at medium and low speeds, it is
`confirmed that most of the drive torque of the vehicle is
`supplied by the traction motor, and the engine works as an
`energy supply source. The maximum speed is 125 km/h.
`Table 1 shows the acceleration performance of the vehicle.
`
`FUEL ECONOMY - Regarding LA#4 in the U.S. and the
`Japanese city 10o15 mode, fuel economy tests were conducted
`on a chassis dynamometer with one vehicle having a
`production 4-speed automatic transmission and the other being
`the Dual System vehicle.
`
`7000
`
`6000!
`
`5000!
`
`4000
`
`30OO
`
`200O
`
`1000
`
`Z
`v
`
`O
`£
`O
`I J_
`g
`
`.B
`
`O
`
`I-
`
`(km/I)
`
`[] LA#4
`
`Q ~O-15mode
`
`FUEL
`ECONOMY
`
`20
`
`15
`
`10
`
`Engine
`
`0%
`
`,~_~J
`
`0
`0 20 40 60 80 100 120 140
`
`Vehicle speed
`
`(km/h)
`
`Figure 8: Vehicle Traction Performance
`
`0--* lOOkm/h [ 17.2sec
`1 ......... ..........
`
`(km/I)
`(+%)
`(km/I)
`(+%)
`(kg)
`
`LA#4
`
`10o15mode
`
`Vehicle Weight
`Engine
`System
`
`12.4
`
`12.5
`
`1140
`1.5L
`4AT
`
`16.3
`31.2
`19.6
`57.2
`1455
`660cc
`DUAL
`
`Table 1: Acceleration Performance
`
`Chart 1: Fuel Economy Results
`
`31
`
`13 of 15
`
`FORD 1372
`
`

`
`Effect of Vehicle Weight
`
`Effect of Engine Efficiency
`
`Vehicle Weight (kg)
`
`lOO
`
`lOOO
`ot
`
`1200 1400
`i
`i
`i
`
`i
`
`Effect of Transmission
`Efficiency
`
`50
`
`--LA#4
`40 - - - 10.15mode ss
`
`’,
`
`-5
`
`E o -lO
`
`O
`O
`w
`
`LL
`
`-15
`
`-2O
`
`30
`
`2O
`
`10
`
`>,
`E
`o
`C
`0
`0
`w
`
`LL
`
`30
`
`Engine Efficiency (%)
`
`0
`
`8;
`
`/
`-10 L T/M Efficiency (%)
`
`i
`100
`
`W (kq)
`LA#4 110.15
`1140
`1450
`
`Engine Efficiency (%)
`LA#4
`110.15
`23.0
`20.2
`27.1
`27.0
`
`I
`
`II
`4AT
`J I
`/ DUAL
`
`I
`I
`I
`I
`I
`I
`I
`4AT
`4AT
`[ DUAL
`| DUAL
`/
`|
`/-Fue,-i+;,;i ...... -i7-.0- .... I .... ..... l-Fu7’7+ ;S-1 .... ..... I ..... 34:2 ..... I I- ue’-i+°Zi-1
`
`Transmission Efficiency (%)1
`LA#4
`!10.15
`71.5
`67.7
`I
`71 2
`69.9
`3.4
`
`--a:4
`
`-I
`
`I
`
`Chart 2: Relationship between Each Factor and Fuel Economy
`
`The Dual System is controlled so that the electricity
`balance of the battery is met before and after the test. Any
`.t-_ _lA-.~:,_ Oitli:llllJ~ O~lOI~ k[II(.l lzllI.Cl- [[lC [es[ 1s
`
`compensated for by the use of simulations.
`Fuel Economy Results - The measured results are
`summarized in Chart 1. The Dual System vehicle tested is
`305 kg heavier than the production 4-speed automatic
`transmission vehicle. The results show that the Dual System
`vehicle provided better fuel economy than the production
`vehicle by 31% for LA#4 and 57% for 10-15 mode.
`Analysis of the Results - The fuel economy results are
`analyzed using assumptions during simulations.
`Influence on fuel economy of each factor is shown in Chart
`2. The influence of each factor in this test is summarized in
`Table 2 based on Chart 2. The 10.15 mode, compared to
`LA#4, shows the greater improvements of engine efficien