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`1997 FUtureCar
`
`Challenge
`
`SP-1359
`
`
`
`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, |nc.
`400 Commonwealth‘Drive
`
`Warrendale, PA 15096-0001
`-
`USA
`
`Phone: (724) 776-4841
`Fax: (724) 776-5760
`F b
`1998
`9 $6th 1218
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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. O-7680-0179-X/98$7.00.
`
`Any part of this publication authored solely by one or
`more US. 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 0-7680-0179-X
`SAE/S P-98/1359
`
`Library of Congress Catalog Card Number: 97-81274
`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
`
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`PREFACE
`
`The papers in this Special Publication, 1997 FutureCar Challenge (SP-1359), were
`originally written to fulfill competition requirements from the 1997 FutureCar
`Challenge. These papers document the design, construction, and performance of ten
`advanced technology vehicles, which represent the second year of the FutureCar
`Challenge sponsored by the US. Department of Energy and the US. Council on
`Automotive Research (Chrysler, Ford, and General Motors). The sponsors invited
`these universities to use the most advanced vehicle technologies available to them to
`modify a mid-size vehicle that approaches 80 miles per gallon (mpg) while still
`offering the same comfort, safety, and affordability that consumers expect from
`conventional vehicles. The goals of the competition mirror those set by the
`Partnership for a New Generation of Vehicle program, a cooperative effort between
`the federal government and the domestic automobile industry.
`
`Beginning with a conventional Lumina, Intrepid, or Taurus, each university team
`made whatever modifications were necessary within the constraints of the existing
`vehicle to approach 80 mpg. Most teams made dramatic changes to the powertrain,
`added energy storage capability, improved aerodynamics, and attempted to reduce
`vehicle weight. Safety, energy efficiency, improved emissions characteristics,
`affordability, and the use of advanced technologies are the cornerstones of the
`FutureCar Challenge. These vehicles represent some of the most innovative
`advanced technology vehicles ever attempted. The technical reports that were a
`scored event in this competition are presented in this volume to record design
`rationale, engineering features, and performance of these unique vehicles. The
`vehicle’s technical specifications and performance summary from the competition are
`shown in Table A; the results summary is shown in Table B.
`
`These teams competed in a series of dynamic and static events at the GM Technical
`Center in Warren, Michigan. Emissions testing and fuel economy assessment took
`place at the US. Environmental Protection Agency National Vehicle and Fuel
`Laboratory in Ann Arbor, Michigan. The teams then embarked on an over-the-road
`endurance event from Warren to Washington, DC, where they participated in a
`vehicle display and awards ceremony on Capitol Hill.
`
`The papers in this publication cannot fully convey the dedication and considerable
`effort demonstrated by the students and faculty to design and build not only an
`advanced car, but a concept for a new generation of vehicles. On behalf of all the
`participants and organizers of these competitions, we extend many thanks to those
`companies that made these competitions possible through financial contributions, in-
`kind support, and the dedication of their staffs.
`
`Key Sponsors of the 1997 FutureCar Challenge included the US. Department of
`Energy, United States Council for Automotive Research, Chrysler Corporation, Ford,
`and General Motors. Other sponsors included the US. Environmental Protection
`
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`Agency, Allied-Signal Automotive, Natural Resources Canada, Detroit Edison, and
`National Science Foundation. Acknowledgments go to the American Society for
`Engineering Education and the Center for Transportation Research at Argonne
`National Laboratory for organizing the competition.
`
`Shelley Launey
`Office of Advanced Automotive Technologies
`US. Department of Energy
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`TABLE OF CONTENTS — gm -— i 3 S “I
`
`1997 FutureCar Challenge
`
`California State University Northridge ............................................. 1
`Concordia University ..................................................................... 13
`Lawrence Technological University ............................................... 29
`Michigan Technological University ................................................ 41
`University of California, Davis ........................................................ 53
`University of Illinois, Chicago ........................................................ 67
`University of Maryland ................................................................... 75
`University of Wisconsin ................................................................. 87
`Virginia Tech ................................................................................. 99
`West Virginia University .............................................................. 115
`
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`Design and Development of Hyades, a Parallel Hybrid
`Electric Vehicle for the 1997 FutureCar Challenge
`
`James Swan, Jenny Spravsow, Greg Davis, Nick Brancik, Eric Beattie, John Dombrowski,
`Brenda Settle, Robert Day, Paul Kornosky, Fabio Okubo, Richard Silas, Richard Johnson,
`Craig Hoff
`Lawrence Technological University
`
`Copyright © 1998 Society of Automotive Engineers, Inc.
`
`ABSTRACT
`
`The task given to the twelve universities in the 1997
`FutureCar Challenge was
`to modify
`an
`existing
`production mid-sized vehicle to me the goals set for the
`Partnership for a New Generation of Vehicles (PNGV).
`These goals included achieving a fuel economy of 34 km
`per liter, 3 range of 400 kilometers, and space for five
`passengers.
`The Lawrence Technological University
`entry is a charge depleting parallel hybrid electrical
`vehicle, built on a 1996 Ford Taurus chassis. The power
`train consists of a 32 kW Unique Mobility brushless DC
`motor with a Nickel Metal Hydride (NiMH) battery pack
`and a 1.9 L Volkswagen TDl engine, coupled to a Ford
`Taurus SHO manual transmission. The transmission is
`shifted automatically using an electro-hydraulic control
`unit developed by team.
`
`INTRODUCTION
`
`Lawrence Technological University was one of twelve
`universities selected to compete in the 1996/1997
`FutureCar Challenge. The FutureCar Challenge is the
`premiere, inter-collegiate engineering design competition
`to date and is sponsored by the US. Department of
`Energy (DOE) and the United States Council for
`Automotive Research (USCAR). Twelve competing
`universities received a 1996 Chevrolet Lumina, a 1995
`Dodge Intrepid, or a 1996 Ford Taurus. The vehicle was
`modified to meet the goals of the Partnership for a New
`Generation of Vehicles (PNGV) program; to develop
`enabling technologies leading to the production of
`mid-sized vehicles, to achieve three times the current
`average fuel economy, and to maintain the performance,
`utility, and affordability of modern sedans. To try to meet
`these goals LTU will implement a parallel Hybrid Electric
`Vehicle in a 1996 Ford Taurus.
`
`A Hybrid Electric Vehicle (HEV) is defined as a vehicle
`that can draw propulsion power from both of the
`following sources of energy: (1) consumable fuel and (2)
`an energy storage system (e.g., batteries) that is
`
`capable of being charged by an on-board generator or
`an off-board source. The systems may be combined in
`any configuration (e.g., series or parallel). An HEV is
`considered to be charge depleting (SAE Draft J1711) if
`during vehicle operation over a given driving schedule,
`electrical energy originally supplied from an off-board
`source is depleted during the same time that the
`on-board consumable fuel is used.2
`
`VEHICLE DESIGN
`
`The overall design goals were to produce a vehicle with
`increased fuel efficiency and reduced emissions while
`retaining the reliability and driveability of a conventional
`vehicle.
`in order to achieve this, every effort was made
`to improve sub-system efficiencies and to reduce vehicle
`weight and aerodynamic drag. The largest gains were
`made by replacing the powertrain with one that is more
`energy efficient. Additional benefits were achieved
`through the use of lightweight materials and by reducing
`the vehicle drag and rolling resistance.
`
`Computer Simulation - To determine the best possible
`control strategy, computer programs were developed to
`analyze both the city and highway cycles of the Federal
`Test Procedure (FTP).
`The analysis
`focused on
`instantaneous energy used by the vehicle power plant.
`Vehicle speed and acceleration were tabulated in one-
`second intervals. These two knowns, coupled with the
`vehicle weight and drag, were used to calculate the
`tractive force, revolutions per minute at the wheels and
`energy consumption in kWh/ km. Additional analysis
`focused on maximizing the overall drivetrain efficiency
`by experimenting with various operating scenarios. For
`example, during the city—cycle,
`the vehicle is at
`rest
`approximately 420 seconds out of 1878 seconds. The
`decision to shut
`the diesel engine down during 'idle
`periods resulted in reduction of fuel consumption by
`approximately 20%.
`
`predicted the amount of
`simulation
`The computer
`electrical
`assist necessary to
`provide
`acceptable
`
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`performance during the FTP city and highway cycles.
`The power assist from the electric traction motor was
`defined as the percent of
`total power needed to
`accelerate the car during the driving cycle. The amount
`of electrical assistance is continuously modulated to
`obtain the best possible engine efficiency based on the
`power output,
`engine revolutions per minute,
`and
`accelerator pedal position. This simulation indicated that
`on average 15%-20% electrical assist during the FTP
`city cycle,
`5%—7°/o electrical assist during the FTP
`highway cycle, no electrical assist at
`idle, and no
`electrical assist above 70 kph would yield the best
`efficiency and driveablility.
`
` i
`
`I
`an o———————
`_.
`..._..__.,.__ua,g m..........“.4
`
`Figure 1: Hyades Powertrain Layout
`
`Powerfrain Selection - The design chosen was a parallel
`HEV powertrain, shown in Figure 1, which coupled a 32
`kW phase advanced brushless DC electric traction motor
`via an aluminum bridge assembly to a small 67 kW
`turbocharged direct
`injection diesel
`engine.
`The
`combination provides tractive energy to the front wheels
`through a manual transmission, which is mechanically
`shifted by the on-board computer, rather than by the
`driver. The electric assist enables the vehicle to operate
`at an equivalent power level of a conventional vehicle,
`while maintaining lower emission levels and improved
`fuel economy. The estimated increase in fuel economy
`due to the new powertrain is about 100% compared to
`the standard Taurus as shown in Table 1.
`
`Table 1: Fuel Economy of Hybrid Compared to Stock
`
`Highway Fuel
`
`City Fuel
`Economy
`(km/L)
`
`Economy (km/l.)
`
`Three powertrain configurations were compared: a heat
`engine, a series HEV, and a parallel HEV. The heat
`engine option was quickly dismissed. To meet the fuel
`economy goal the engine would be sized too small to
`
`Page 11 of 20
`
`acceleration
`the
`provide adequate performance for
`requirement. A series configuration employs an engine,
`which produces electric power for the electric motor and
`batteries through a generator. The series HEV offers
`better efficiency at low speeds because the engine is
`decoupled from the drivetrain and can thus operate at or
`near peak efficiency regardless of vehicle speed.
`In a
`parallel configuration, both the engine and the electric
`motor are used for propulsion, At higher speeds, the
`parallel drive is often more efficient since the engine can
`be sized so that
`it
`is operating near peak efficiency.
`Further, because the engine is directly coupled to the
`drivetrain, two of the energy conversion processes of the
`series HEV are not required (engine to electric, and from
`electric back to mechanical), making the parallel system
`more efficient. Over a range of speeds, the parallel and
`series HEV configurations' overall
`fuel economy are
`comparable. Despite the complexity of
`the parallel
`system.
`it offers greater reliability than a series system
`due to a limp home mode using either the engine or the
`motor. Further, the parallel configuration provides better
`acceleration and passing abilities,
`and thus better
`maintains the performance of a conventional vehicle.
`This
`led
`to
`the decision to
`choose the parallel
`configuration, where the electric motor is used to assist
`the engine in meeting heavy load demands. The level of
`assist is adjusted in order to keep the diesel engine
`operating in it's most efficient range.
`In order to best
`utilize the electric energy storage and to achieve
`maximum normal range, Team Hyades has modified a
`1996 Ford Taurus producing a charge depleting parallel
`HEV in Normal Mode.
`
`Motor Selection - The electric, or traction, motor is a 32
`kW phase advanced brushless DC design.
`The
`advantages of
`the brushless DC motor are: higher
`efficiency, higher power density, better heat dissipation,
`and increased motor life compared to a conventional
`brushed motor. The brushless DC motor experiences no
`losses due to brush friction while having two to three
`times more torque than a brushed DC of equivalent size
`and weight. The electric motor utilizes high efficiency,
`liquid cooled, 18 pole neodymium iron boron permanent
`magnets,
`with
`four-quadrant
`operation,
`and
`a
`microprocessor-based
`controller.
`The
`controller
`incorporates closed loop torque control, which allows the
`motor to be used with conventional
`throttle based
`
`operator control. The peak efficiency of the motor alone
`is 95%. However, when the power generation and line
`transmission efficiency of 37.27% is accounted for, the
`electrical efficiency drops to 37.4%.
`
`Engine Selection - The 1.9-liter diesel engine was
`chosen from a pairwise comparison of several engines
`including IC engine, gas turbine, and Stirling engine.
`The
`selection
`criteria
`investigated
`performance
`characteristics,
`which
`included
`emissions,
`fuel
`consumption, acceleration, and endurance. The Stirling
`and gas turbine engines were not used due to extremely
`limited availability. Additionally,
`the gas turbine was
`found to be inferior during the transient Speed and load
`conditions experienced in the parallel design.
`The
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`and longevity. The Nickel Metal Hydride (NiMH) battery
`has the best power to weight ratio compared to available
`alternatives. Each module has a nominal voltage of 13.2
`volts with a maximum voltage of 16 volts after charging.
`The module has 1.25 kWh of energy and a weight of
`17.8 kg. The physical dimensions of each module are
`102 mm by 179 mm by 412 mm. The performance
`specifications are described in Table 2. The operating
`temperatures of the NiMH are: less than 45 C to achieve
`maximum life.
`less
`than
`55 C to
`obtain
`80%
`performance. and less than 65 C to avoid damage. The
`United States Advanced Battery Consortium has
`identified the NiMH as having the potential
`to meet
`mid-term criteria
`It has outlasted other battery
`
`technology because the material to produce the battery
`is readily available.
`
`Table 2: NiMH Performance Specifications
`
`Specific Energy
`165 Wh/L
`
`Energy Density
`
`250 W/kg @ 50% soc
`
`220 W/kg @ 20% soc
`
` L
`
`Specific Power
`
`
`
`stroke,
`four
`cylinder.
`four
`a
`is
`engine
`chosen
`injected (TDI) diesel engine. The
`turbocharged direct
`turbocharger provides an extra boost and excess air for
`minimum particulate emissions. This engine boasts a
`peak thermal efficiency of 43% and is capable of
`meeting strict emission standards. Further. this engine
`has better part-load efficiency characteristics
`than
`gasoline engines.
`
`Transmission Selection - A Ford model RBE-AR fve-
`speed manual transmission was selected to replace the
`stock automatic because it reduced weight
`improved
`efficiency, and packaged well
`in the stock chassis and
`cradle.
`The transmission half-shafts were utilized
`because they matched the existing vehicle track width.
`The transmission weight
`is 42.6 kg to give a weight
`advantage of 34.5 kg and decreased rolling resistance of
`20% compared to the stock system.
`In order to maintain
`the consumer acceptability of an automatic transmission.
`a hydraulic shifting mechanism was designed and
`implemented. Research shows that this system offers
`efficiency advantages over other alternatives
`
`Control System Hardware - The Programmable Logic
`Controller (PLC) with digital and analog input/output
`(I/O) cards. is responsible for real-time processing of all
`input commands and updating outputs in order to control
`the
`powertrain.
`The
`PLC takes
`inputs
`from
`Analog/Digital
`(AID) converters (used to sense throttle
`position and vehicle speed) and from the user control
`panel The PLC power supply requirement of 24 VDC is
`supplied from the traction battery pack via 00-DC
`converters. All
`I/O cards are grounded to the vehicle
`common ground.
`The PLC is capable of being
`programmed in ladder logic. Boolean. and statement list
`languages. The Hyades control program is written in the
`ladder
`logic programming language because of
`its
`graphic. self-explanatory nature. The PLC utilizes a
`main program. which cycles continuously.
`From this
`main program. all subroutines. or "function blocks" are
`called.
`A separate function block was created for
`initialization of variables upon startup. The startup block
`runs only once. before the first execution of the main
`block. The program for Hyades consists of the main
`block and 12 function blocks. A conditional return to the
`main block is contained in each subroutine depending on
`the mode of vehicle operation selected and whether a
`gearshift is in process.
`
`via
`input
`takes user
`The operator control panel
`This unit has memory
`user-defined function keys.
`storage. which is
`independent of the PLC. A backlit
`liquid crystal display and a serial data stream. which
`allows communication with the PLC. are the available
`
`control panel outputs. The control panel outputs are a
`backlit
`liquid crystal display and a serial data stream.
`which allows communication with the PLC. The control
`
`panel
`PLC.
`
`is powered by the same 24 VDC supply as the
`
`Fuel Selection - Dimethyl Ether was initially considered
`because it
`is the most environmentally benign choice.
`Emaust from a DME-driven diesel engine contains no
`sulfur. almost no soot. and only about 20% of
`the
`nitrogen
`oxides
`that
`a
`diesel
`produces.
`The
`hydrocarbons
`in
`the exhaust are also dramatically
`reduced. However. DME is a gas at room temperature
`and in order to be used as a liquid fuel,
`it has to be
`bottled under pressure. There is less energy in a given
`amount of DME than in the same amount of diesel;
`therefore. bigger fuel tanks are needed. The cost. the
`distribution. and the availability of DME also dims the
`use of DME in the near future because producing DME
`means more expensive equipment for more chemical
`processes and several years to build production plants.
`
`Biodiesel used in a 20 percent blend of soybean oil with
`petroleum diesel was chosen as the fuel. Combined
`with the catalytic converter it will reduce air pollution.
`Particulate matter
`is
`reduced 31
`percent.
`carbon
`mon0xide by 21 percent and total hydrocarbons by 47
`percent.
`It also reduces sulfur emissions and aromatics.
`While its emissions are radically lower. biodiesel can be
`substituted for diesel with no engine modifications, and
`maintains the payload capacity and range of diesel.
`In
`addition. biodiesel has about the same energy content
`as diesel: 128,800 Btu/gallon. compared to 130,500
`Btu/gallon of diesel.
`Production cost of biodiesel
`is
`60-80 cents per gallon more than diesel alone. and it
`requires no special storage facilities.
`In fact.
`it can be
`stored wherever petroleum diesel
`is stored. except
`in
`concrete-lined tanks, due to the adverse chemical
`reactions.5
`
`Battery Selection - The selection criteria for the batteries
`included weight, power storage. charging rate. safety,
`
`31
`
`Page 12 of 20
`
`FORD 1218
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`Emission Control - The emission control target was to
`achieve the California ULEV emission level when the
`
`vehicle operates in Normal Mode. The stock two-way
`catalytic converter reacted with carbon monoxide and
`unburned hydrocarbons. To reduce all emissions. the
`original two—way catalytic converter was replaced with a
`three-way converter equipped with an absorber. The
`cold-start gases from the engine are stored in
`the
`absorber until the temperature of the catalyst
`is high
`enough to burn the gases within it's ceramic substrate.
`Additionally, the engine is shut down during extended
`coastdowns and when the vehicle is stationary. This
`reduces fuel consumption and helps to maintain catalytic
`converter temperatures above the levels required for
`acceptable
`conversion efficiencies
`during
`the
`idle
`portions of the federal California Vehicle Standard (CVS)
`emission test. This is possible because the engine is no
`longer pumping large quantities of lean exhaust gas
`through the catalyst.
`
`in the area
`A phenolic resin spacer has been put
`between the intake manifold and engine block. The
`phenolic intake manifold spacer was utilized to minimize
`heat conduction from the cylinder head to the intake
`manifold. This was done to cool the intake charge in
`order to lower nitrogen oxide emissions. The exhaust
`spacers were fabricated for packaging concems since
`the phenolic intake spacer pushed the intake manifold
`away from the cylinder head,
`towards the exhaust
`manifold.
`
`Finally, an exhaust gas recirculation (EGR) cooling
`system was implemented. The heat exchanger uses
`engine coolant to cool the EGR as it flows between the
`exhaust and intake manifolds.
`This helps to further
`reduce combustion temperatures, leading to lower NOx
`formation. Additionally, this system also provides faster
`engine warm-up, further reducing cold start emissions.
`
`POWERTRAIN CONTROL STRATEGY
`
`The PLC maintains control of the vehicle powertrain,
`which determines the percentage electric assist to the
`diesel, starts and stops the engine, and shifts the
`transmission. The percent of motor assist is dependent
`on accelerator pedal position and vehicle speed, which
`are accurate indicators of the load requirements for the
`powertrain.
`
`Operating Modes - There are three modes of operation:
`Normal (parallel HEV), Motor or Zero Emission Vehicle
`(ZEV), and Recharge. These modes were chosen to
`fully utilize on-board electrical energy storage.
`The
`normal mode is charge depleting, providing full range
`capabilities before recharge. ZEV mode can be used in
`urban situations where
`no
`emissions
`should
`be
`produced. Finally, Recharge Mode operates in charge
`sustaining mode so that vehicle range is only limited by
`the fuel storage capabilities. Thus a vehicle could be
`driven extended distances requiring only to be refueled.
`
`Page 13 of 20
`
`Normal Mode - The Normal Mode of operation for the
`vehicle is parallel HEV. The diesel engine and electric
`motor, operating simultaneously, provide the motive
`power. The maximum combined peak power is 115.8
`kW@ 4000 RPM with a peak torque of 427 Nm @ 2000
`RPM. Based on the combined Federal Test Procedure
`(FTP)
`city
`and
`highway
`drive
`cycles,
`computer
`projections predict
`that
`the vehicle
`is capable of
`accelerating 1/5 of a kilometer in less than 14 seconds.
`Consumption of 17 liters of diesel fuel and 16 kWh of
`electrical energy are predicted based on a 400-km
`extrapolation of the FTP drive cycle. The advantages of
`the normal mode include achieving the maximum power
`provided by the two sources.
` ,_
`
`.I
`
`
`
`Figure 2: Hyades powertrain operating map for
`electric assist modulation.
`
`The diesel engine is capable of operating at a peak
`thermal efficiency of 43% for a limited load range at
`roughly 2000-RPM. The peak efficiency of the motor
`although lower,
`is available over a wider
`range of
`operating speeds. However, the engine rarely functions
`in it's most efficient range during normal driving. An
`operating map was developed and utilized to maintain
`the powertrain performance at or near peak efficiency by
`varying the motor assist with acceleration and vehicle
`speed. The map, shown in Figure 2, has been defined
`as a three dimensional surface plot with the vehicle
`speed on the X-axis,
`the accelerator position on the
`Y—axis, and the output voltage to the motor controller on
`the Z-axis. The operating map was developed in order
`to modulate motor assist
`to maintain
`powertrain
`operation at the highest possible efficiency at all times,
`while maintaining
`acceptable
`performance when
`needed.
`
`The PLC scans the operating map to calculate the
`percent of power assist to be supplied by the motor.
`Accelerator position is measured by a potentiometer,
`which is mounted in the engine compartment.
`The
`vehicle speed is determined using a sensor attached to
`the intermediate shaft. Under low load conditions, such
`as highway cruising, the accelerator voltage signal is low
`and the vehicle speed is high.
`in this scenario, the PLC
`sends zero voltage to the motor controller as an
`indication
`that
`no
`assistance
`is
`required, which
`corresponds to when the diesel engine is at or near it's
`
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`the dashboard. Many critical electrical and
`under
`mechanical
`indexing components for the switch were
`fabricated using existing hardware from the automatic
`transmission.
`
`Table 3: Transmission Gear Ratios
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`3.74 : 1
`
`Final Drive Ratio
`
`The shifting of the manual transmission is controlled by
`the PLC based on throttle position and vehicle speed
`during any driving mode. The current throttle position
`and vehicle speed are fed into the program. Based on
`these and the current gear selected, the program selects
`ranges of throttle position and vehicle speed whose
`' inputs are used in an interpolation of the vehicle speed
`at which a gear shift should be initiated. Figure 3 was
`used to determine actual shift points under full
`load
`conditions.
`
` 0
`
`20
`
`40
`
`60
`
`80
`
`Vehicle Speed (mph)
`
`— 1 st Gear ~ — 2nd Gear — -- 3rd Gear
`
`—4th Gear —- 5th Gear
`
`Figure 3: Combined torque curve -full motor
`assist, wide open throttle.
`
`The figure depicts combined torque curves by gear
`selection using vehicle speed in order to accelerate most
`quickly, the highest torque is desired. Thus full load up-
`shift speeds of 12, 25, 40, 60, and 80 mph were chosen
`for fastest acceleration.
`In order to provide maximum
`economy during
`very low load accelerations,
`shift
`speeds were chosen to maintain operation of the diesel
`engine near it's peak efficiency.
`Intermediate throttle
`position shift speeds were interpolated between these
`two extremes in order to provide a compromise between
`
`FORD 1218
`
`maximum efficiency. Utilizing these two inputs, the PLC
`recognizes a high load situation such as passing or hill
`climbing to call for full motor assist by sending a control
`voltage signal to the motor controller. At speeds above
`70 kph on level roads, the motor only provides assist if
`more torque is required, such as in a passing situation.
`
`For example, if the accelerator pedal has been released
`for more than
`1.5 seconds
`the diesel engine
`is
`de-clutched and shut off.
`if the vehicle comes to rest
`following an extended closed throttle deceleration, the
`ensuing acceleration employs the electric traction motor
`exclusively, until a calculated vehicle speed is reached.
`The vehicle is propelled initially with the traction motor,
`and the engine is subsequently restarted by the PLC
`during the next acceleration.
`At
`this programmed
`vehicle
`speed,
`the diesel engine is
`restarted and
`clutched to the transmission input shaft. This strategy
`improves fuel economy, while
`significantly reducing
`emissions.
`
`Zero Emission Vehicle Mode - The Zero Emission
`Vehicle Mode of operation is purely electric. The diesel
`engine is de-clutched from the transmission and turned
`off during the ZEV mode to meet zero emission
`requirements. All power to the driveshaft is therefore
`derived from the traction motor.
`The ZEV mode is
`selected when the driver elects
`to
`eliminate
`the
`consumption of diesel fuel and thereby eliminate exhaust
`emissions. The advantages of using the traction motor
`as the sole power source are smoothness,
`reduced
`noise, and zero emissions output. The disadvantages of
`this mode are