1. Page 1 of 14
Optimizing the University of Wisconsin's
Parallel Hybrid-Electric Aluminum Intensive
Vehicle
J. Bayer, M. Koplin, J. Butcher, K. Friedrich, T. Roebke, H. Wiegman, G. R. Bower
University of Wisconsin–Madison
Copyright © 1999 Society of Automotive Engineers, Inc.
ABSTRACT
The University of Wisconsin – Madison FutureCar Team
has designed and built a lightweight, charge sustaining,
parallel hybrid-electric vehicle for entry into the 1999
FutureCar Challenge. The base vehicle is a 1994
Mercury Sable Aluminum Intensive Vehicle (AIV),
nicknamed the “Aluminum Cow,” weighing 1275 kg. The
vehicle utilizes a high efficiency, Ford 1.8 liter, turbo-
charged, direct-injection compression ignition engine.
The goal is to achieve a combined FTP cycle fuel
economy of 23.9 km/L (56 mpg) with California ULEV
emissions levels while maintaining the full
passenger/cargo room, appearance, and feel of a full-
size car. Strategies to reduce the overall vehicle weight
are discussed in detail. Dynamometer and experimental
testing is used to verify performance gains.
INTRODUCTION
The FutureCar Challenge (FCC) is a student competition
that has adopted the goals of the Partnership for a New
Generation Vehicle (PNGV) program. Those goals are
to build a mid-sized car that maintains current standards
of safety, performance, comfort and price, while at the
same time achieving 80 miles per gallon with California
ULEV emission levels. Thirteen universities from North
America annually compete in the FCC which is
sponsored by the US Department of Energy and the US
Consortium of Automotive Research (USCAR).
Table 1. UW FutureCar 1999 Performance Goals.
Parameter 1999 Goals
Combined FTP Fuel Economy 23.9 km/L (56 mpg)
Emissions ULEV
Acceleration: 0–100 kph <10 seconds
Range 970 km (600 mi)
Vehicle Weight 1275 kg (2805 lbs)
The University of Wisconsin has designed a charge
sustaining, parallel hybrid-electric vehicle for the 1999
FutureCar challenge (Figure 1). After extensively testing
our 1998 FFC vehicle [1] on a chassis dynamometer,
areas for improving the vehicle were obvious and
extensive changes have been made to the Aluminum
Cow over the past year. The vehicle performance goals
for this year are listed in Table 1. With a goal of 1275
kg, a large emphasis was placed on weight reduction of
each component in the vehicle.
12
kW
Motor
Fuel
Tank
39L
8.0 A-hr
286V Nom
Ni-Cad
Battery
50
Figure 1. The University of Wisconsin’s 1999 parallel-
assist hybrid electric vehicle layout.

2. Page 2 of 14
VEHICLE ENERGY CONSUMPTION MODELING
The road power demand equation represents the energy
consumption of a vehicle over a period of time. This
equation defines how power is used in a vehicle as it
travels down the road [2]. This equation is the basis for
both the vehicle simulation developed by Wisconsin and
also for all the components and modifications integrated
into the vehicle. The equation to calculate road power
demand for a given driving condition is shown in
Equations 1-6. (Symbol list at end of paper.)
Proad = Proll + Phill + Paero + Paccel + Paux (1)
Proll = m g V Crr cos θ (2)
Phill = m g V sin θ (3)
Paero = 0.5 ρ A V3
Cd (4)
Paccel = d Ekinetic / dt = m V dV / dt (5)
Paux = f(alternator, power steering, etc.) (6)
The road power demand Equation (1) identifies the
vehicle design aspects that could be changed to improve
the overall energy efficiency. Using reported efficiencies
for vehicle components and modeling this equation for a
vehicle driving on the FTP 75 driving cycle, a fuel
economy modeling study was completed. The relative
importance of reducing each of the equation parameters
can be seen in Figure 2. [3]
0 10 20 30 40 50
1.0
1.1
1.2
1.3
Mass
Aero
Tires
Accessories
EPACombinedFuelEconomyMag.
Parameter Reduction (%)
Figure 2. Fuel Economy gain vs. parameter reduction.
In order to increase the fuel efficiency of the vehicle, the
road power demand must be decreased. With vehicle
mass affecting 3 of the 5 terms in Equation 1, it is clearly
the dominant factor in vehicle energy consumption (see
Figure 2). Therefore, the design focus was on weight
reduction in an effort to take advantage of the
indisputable efficiency gains that come with lighter
vehicles.
1998 FUTURECAR CHALLENGE RESULTS
As part of the 1998 FutureCar Challenge, each vehicle
was evaluated on the FTP 75 driving cycle at the EPA
laboratory in Ann Arbor, Michigan. The fuel economy
results are shown in Table 2. These fuel economy
numbers were very encouraging because the hybrid
mode was not operating during the FTP-75
dynamometer cycle (EPA City).
Table 2. 1998 FutureCar Challenge Fuel Economy.
Fuel Mileage Test 1998 Fuel Economy
(RFG equivalent)
EPA City 34.7
EPA Highway 51.9
Chrysler’s Test Track 75.0
Emissions levels measured at FCC98 are presented in
Table 3. In this case, the limiting emission was NMHC,
and the emission bracket would be Federal Bracket 13.
The engine used was a prototype from Europe and the
Engine Gas Recirculation (EGR) system was not
operating. The EGR would drastically reduce the NOx
emissions while also increasing the engine’s thermal
efficiency. (Appendix B)
Table 3. Emissions from 1998 FutureCar Challenge.
Regulated
Emissions
Emission
Levels
(g / mile)
Federal
Emissions
Bracket
NOx 1.836 15
CO 1.468 35
NMHC 0.551 13
PM10 0.125 21
Reviewing the emission data of Table 3, one would not
expect a compression ignition engine to have high non-
methane-hydrocarbon (NMHC) emissions. This
prototype engine had not yet been optimized. The
engineers responsible for the development of this engine
indicated that the combustion bowl and fuel injectors
have since been modified for their production engine.
The mixing of the fuel and air in the combustion chamber
was inefficient and thus created incomplete combustion.
Replacing the prototype engine with a production version
will decrease particulate, NMHC and CO emissions.
DYNAMOMETER RESULTS
In the fall of 1998, the Aluminum Cow was tested on a
chassis dynamometer on two different occasions. Both
tests were completed with a fully functioning hybrid
vehicle. City fuel economy results are listed in Table 4.

3. Page 3 of 14
TABLE 4. Dynamometer FTP 75 City Fuel Economy
Results using the 1998 Hybrid Design.
Vehicle Testing Mode
(94 Sable-AIV)
FTP-75 Fuel Economy
(RFG Equivalent)
No Hybrid Mode - FCC 98
(Electric Motor Removed)
34.7
No Hybrid Mode - Fall 98
(Unique Motor Spinning)
29.0
Hybrid Mode - Fall 98 35.8
Load Leveling - Fall 98 35.6
The FTP 75 city cycle was used to compare the
effectiveness of the hybrid drivetrain as the highway
cycle rarely uses the hybrid mode. The inclusion of an
uncontrolled permanent magnet electric motor into the
drivetrain of the Aluminum Cow produced a 16.4%
decrease in fuel economy. After experimenting with two
different control strategies, the best hybridized strategy
had a 3.2% fuel economy advantage over the same
vehicle with no electric motor.
0
500
1000
1500
2000
2500
79675749444239363228241916129641
Vehicle Speed (MPH)
Loss(W)
Measured Data
UQM Prediction
Figure 3. Drag force generated by the Unique Mobility
permanent magnet electric motor.
The permanent magnet free-spinning drag losses (see
Figure 3) add to the drivetrain’s resistance and is
analogous to a 20% increase in the dynamometer’s
aero drag setting. The higher efficiency of the
permanent magnet motor offsets its drag during non-
utilized periods during the city cycle, but the drag grossly
exceeds the benefits during the FTP 75 highway cycle
causing similar reductions in fuel economy.
The dynamometer testing results from the fall of 1998
were closely scrutinized and were the dominant factor in
deciding to modify the hybrid drivetrain for this year. The
permanent magnet motor was replaced with a
comparable induction motor - following is the reasoning
and documentation of the 1999 Aluminum Cow.
COMPONENT SELECTION
Once the vehicle drag requirements are minimized, and
past performance data is reviewed, drivetrain
components must be appropriately selected to process
the power flow in the hybrid as efficiently as possible.
The selected drivetrain components could potentially
achieve an overall fuel efficiency in excess of our 23.9
km/L (56 mpg) [4] fuel economy goal.
Because components that exactly match theoretical
specifications are rarely obtainable, component
availability had to be considered while the team
searched for a desirable combination of engine,
transmission, and electric drive system.
When searching for components, American
manufacturers were considered first. This was done to
both minimize component lead times and also to
increase the feasibility of manufacturing the FutureCar
locally.
A packaging diagram of the Wisconsin FutureCar is
shown in Figure 4. Throughout the selection process,
appropriately sized components were chosen to
maximize energy efficiency and minimize weight.
Modified
Fuel
Tank
High
Voltage
Battery
Pack
Ford TDI
Engine
Solectria
Electric
Motor
Ford FWD
Transmission
Figure 4. UW vehicle packaging diagram.
Engine - Depending on the size of the electric drivetrain,
the engine in a power-assist parallel hybrid vehicle
should have a power capability in the range of 50-80 kW
(70-110 hp). This is based on the power required to
accelerate the vehicle from 0-100 kph (0-60 mph) in 12
seconds and sustained hill climbing requirements. A 5-
passenger vehicle that weighs 1500 kg (3300 lbs)
requires 75 kW (100 hp) to accomplish this performance,
while it requires 35 kW (50 hp) to maintain 100 kph on a
6% grade [3].

4. Page 4 of 14
1000 1500 2000 2500 3000 3500 4000 4500
0
10
20
30
40
50
60
70
Engine Speed (rpm)
Power(kW)
200
210
220
230
240
250
260
270
280
290
Figure 5. Characteristics for the Ford 1.8L TDI
compression ignition engine - LYNX 90PS [5].
A search of economically viable engines revealed two
engine alternatives – spark-ignited (SI) or compression
ignited (CI). A recent study by Thomas et al. [4],
concluded that natural gas hybrid and diesel hybrid
vehicles produce the lowest overall greenhouse (CO2)
gas emissions – even lower than hydrogen fuel cell
vehicles. It also concluded that among these two
powertrains, a diesel hybrid was 14% more fuel efficient
than a natural gas hybrid. The diesel hybrid is the most
fuel efficient piston powered option considered by this
study. For the aforementioned reasons, the Wisconsin
team chose a direct-injection compression ignition (CIDI)
engine for its 1999 FutureCar. After a lengthy search,
Ford Motor Company agreed to donate a 66 kW (88 hp),
1.8 liter, 4-cylinder, turbo-charged, direct-injection
compression ignition engine (see Figure 5 and Table 5)
with a maximum thermal efficiency of 42%.
TABLE 5. Engine Build Details for the Ford 1.8L Turbo
CIDI LYNX 90 PS Engine [5].
Engine Component Specification
Rated Power 66 kW at 4000 rpm
Maximum Torque 200 Nm @ 2000 rpm
Speed Range 800 - 4800 rpm
Bore 82.5 mm
Stroke 82.0 mm
Displacement 1753 cc
Compression Ratio 19.34 : 1
Swirl Ratio 2.4
Fuel Injection Pump Bosch VP30
EGR valve diameter 16 mm
Turbocharger Garrett T15
Control System EEC V
After-Treatment - Historically, exhaust after-treatment
has been developed for SI engines. These engines
used closed-loop controls to keep the air/fuel ratio
stoichiometric, where the 3-way catalyst operates
effectively. If the engine were operated lean, the NOx
conversion efficiency would drop drastically while rich
combustion would cause excessive CO and HC
emissions. In the case of CI engines, the engine is
always operated lean, and 3-way catalyst technology is
not applicable.
The LYNX 90PS engine is equipped with a platinum
loaded catalyst. The catalyst is mainly designed to
reduce hydrocarbon (HC) and carbon monoxide (CO)
emissions but it also slightly reduces particulate and
nitric oxide (NO) emissions as shown in Figure 6. From
the four different catalyst tested, Ford chose a
production catalyst loading of 40 g / ft3.
10 20 30 40 50 60 70
0
10
20
30
40
50
60
70
80
90
100
Production Catalyst Loading
Hydrocarbons
Carbon Monoxide
Particulates
Nitric Oxide
ConversionEfficiency(%)
Catalyst Loading (g / ft
3
)
Figure 6. Platinum loading levels versus conversion
efficiency for exhaust constituents for the LYNX 90PS
catalyst.
In addition to the production catalyst, Deguzzi, the
supplier for the LYNX 90PS catalyst, will be furnishing a
lean NO catalyst with an estimated efficiency of 40% in
addition to a NO trap. The trap actual cause the NO to
adhere to the surface of the catalyst. Once the catalyst
surface is loaded with NO, a small injection of fuel into
the exhaust stream (2-3 % fuel economy penalty)
causes a slightly fuel rich exhaust gas stream. In the
absence of oxygen, the NO converts to diatomic nitrogen
and oxygen and the NO trap is ‘regenerated’.
Regeneration is usually done every 30-60 seconds
during normal operation in order to keep the catalyst
efficiency above 75%.
Transmission - A transmission that would couple the
engine to the road efficiently had to be selected as well.
To perform this coupling, a Ford MTX-75, manual front-
wheel drive transmission manufactured for use with a
LYNX 90 PS engine was selected. A manual
transmission was selected for its low throughput losses
(> 90% efficiency). Its gear ratios are shown in Table 6.
These gear ratios were designed for use in 1300 kg
vehicle similar to the Aluminum Cow.

5. Page 5 of 14
Figure 7. The modified transmission case for the Ford
MTX-75 FWD transmission.
Table 6. Gear ratios for Ford MTX-75 transmission.
Gear Ratio
1
st
3.666
2
nd
2.047
3
rd
1.258
4
th
0.864
5
th
0.674
Differential 4.060
A custom designed gearbox was develop to couple the
electric motor to the engine/road. This was
accomplished by modifying the secondary transmission
shaft (see Figure 7), which then makes the transmission
a durable and efficient torque splitter. This gearbox is a
second generation design. The new gear box was
fabricated on a Milltronics fix-bed CNC mill from 6061-T6
aluminum billet. The gear box, seen in Figure 8, was
originally drawn in AutoCAD which supplied the
geometric traces to the CNC controller. Subsequently,
the gearbox was solid modeled in ProE so that it could
be analyzed using ANSYS (see Figure 9). Before
manufacturing the gear box, extensive stress analysis
were performed to ensure design’s reliability.
Figure 8. Computer numerically controlled machined
gearbox.
Figure 9. Stress plot from ANSYS analysis of hybrid
gearbox.
The transmission placement in the Wisconsin FutureCar
is displayed in the packaging diagram (Figure 4). The
gear selector and clutch are typical of those found in
conventional vehicles. In addition the complete hybrid
drivetrain (engine, transmission, and electric motor) was
designed to be pre-assembled on the engine cradle sub-
frame and subsequently placed into the vehicle as a unit.
Fuel – The 1999 Wisconsin FutureCar has adopted
Fischer-Troups fuel for compression ignition engines.
Fischer-Troups is considered an alternate fuel as it is
derived from natural gas or coal. Similar to synthetic
oils, Fischer-Troups contains no impurities. This
produces a predominantly straight-chained, clear, clean
fuel. Typically it has a cetane number of 70 while
containing no sulfur or aromatics. The elimination of
sulfur will extend catalyst life while reducing particulate
emissions.
ELECTRIC DRIVE SYSTEM
Motor/Inverter - The 1999 UW FutureCar uses a 12 kW
induction electric motor with a peak power of 30 kW
(battery limited). The motor can supply a maximum
torque of 100 N-m and a maximum speed of 12,000 rpm.
The motor weighs 32 Kg, and delivers 94% peak
efficiency. The motor is part of Solectria's prepackaged
electric drive system which includes a microprocessor
vector control unit, the UMOC 340. The 98% efficient
control unit is rated for input voltages ranging from 200-
350 V and has a 210 Arms limit.
The AC induction motor and controller were selected in
place of the permanent magnet motor and controller
used in last year for numerous reasons. As discussed
earlier, the permanent magnet motor adds unnecessary
drag to the driveline when not in use and therefore is not
desirable in a parallel-assist hybrid vehicle where electric
motor utilization is low during steady state driving.
These drag losses are converted to heat and require an
additional radiator/pump/coolant system in the vehicle.
Switching to a lower power AC induction motor the drag
loss were eliminated while realizing a 32 kg weight
savings.

6. Page 6 of 14
Figure 10. System efficiency map for the Solectria
Acgtx20 motor using a UMOC 340 controller operating
from 270Vdc.
The motor is coupled to the secondary transmission
shaft of the 2WD transmission via a custom gear box.
The gear box supports the electric motor and includes a
2.30:1 gear ratio (9.34 overall to axle) to decrease the
motor speed. This allows the motor to spin in its
optimum range of 3000-6000 rpm (37-75kph) (see
Figure 10).
Battery – The 1998 energy storage system used in the
UW-Madison FutureCar was based on high power
density Nickel Cadmium C-cells. The technology was
capable of delivering 400W/kg (10 sec, 20% voltage
variation), thus providing a lightweight system which was
near optimal for the charge-sustaining, parallel assist
hybrid design.
To improve upon the design, and to move to a more
optimal overall vehicle efficiency, the energy storage
system was re-evaluated for the 1999 competition.
Three battery technologies were tested and compared.
PNGV style power pulse testing was applied in order to
objectively evaluate the relative electrical
performances.[9,10] The three chemistries tested were;
Thin-Metal Film Lead Acid (TMF Pb), Nickel Cadmium
(NiCad), and Nickel Metal Hydride (NiMH). A overview
of the technologies are compared in Table 7.
Table 7. Battery performance improvement summary
Feature TMF Pb NiCad NiMH
Disadvntg. cost,
sulfation
Envirnmnt.
Impact
Only
moderate
power
dens.
Advantage Highest
power dens.
Proven
technology
Promising
Technolog
y
The final battery selection was based upon probability of
success, low cost, and electrical performance. Today,
Ni-Cad batteries are utilized in the hand-held battery
power tool industry. Huge gains in NiCad power density
and reliability have been accomplished through the
developments of companies such as Milwaukee Tool
and Sanyo Inc.
The battery system was adjusted slightly in order to
obtain high power capability and processing efficiency. A
battery performance improvement summary for the 1999
vehicle is shown in Table 8.
Table 8. NiCad battery performance improvement.
Battery Characteristics 1998 1999
Total Cell Mass [kg] 49 53
Bat. Box Mass [kg] 6 6
Voltage [V] 272 286
Capacity [A-h] 7.5 8.0
Energy [kW-h] 2.0 2.3
Power [kW] # +/- 22 +/- 24
Cycle Efficiency [-] * 0.87 0.89
# - 10 seconds, +/- 20% voltage variation
* - at +/- 4kW rate, 30 seconds, 50% SOC
The PNGV style power pulse testing revealed the
maximum power capability and efficiency characteristic
of the battery. Sample testing was instrumental in
improving the battery system design for the 1999 effort.
Figure 11. shows the 30 second capabilities of the 1999
battery system. The 10 second power capability is higher
due to a lack of diffusion effect during the short duration
pulses, hence it was not used as a realistic test of the
batteries. The efficiency characteristic as shown in
Figure 11 revealed a relatively flat and broad operating
range vs. SOC, showing the flexibility of the high power
density cell design.
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0
2
4
6
Power Capability and Efficiency vs. SOC
Power
[pu]
30 sec discharge and charge
Pdis = solid
Pchrg = dash
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
0.8
0.85
0.9
0.95
1
Eff.
[pu]
SOC [pu]
30 sec, Pow = 2 pu
Eff.dis = solid
Eff.chrg = dash
Eff.cycle = da-dot
Figure 11. Per-unit power and efficiency vs. SOC for the
NiCad battery system under 30 second pulse testing.
(Pbase=2.3kW, Efficiency rated at 2 per unit power)

7. Page 7 of 14
Computer – The Wisconsin FutureCar team has been
successful in past competitions partly due to the
flexibility of the control system. The control strategy is
run on a custom-built computer system consisting of a
Computer Dynamics single-board pentium machine with
a touch-screen user interface. The computer's Micro
Industries data acquisition boards are connected to a
custom-designed board that collects input signals from
sensors throughout the car and distributes control
signals to actuators and controllers. The data
acquisition boards have a maximum capability of 48
digital inputs and outputs, 16 analog inputs, and 16
analog outputs. By using a computer, the team can
program in common languages (C/C++) and remain
flexible in the hardware and software designs.
Control Strategy - The Wisconsin team has developed
a hybrid control strategy that is state of voltage (SOV)
regulating. A SOV regulating strategy will monitor the
battery voltage and maintain that voltage within a
prescribed range, resulting in a battery which avoids full
and empty regions.[12] Transient emissions caused by
changes in the engine load are reduced by using the
motor to meet rapid increases in road power demands.
The engine power output is then gradually increased
while the motor power output is simultaneously
decreased. Buffering the engine from the road in this
manner also increases the vehicle fuel economy.
The UW control strategy has only one mode of
operation. This results in a FutureCar that operates
similarly to a conventional automobile. There are no
added modes, switches, pedals, or dials with which the
driver might be concerned.
The control strategy is designed as a state machine with
three states. By developing the control strategy as a
finite state machine, the software is restricted to run in
only one state at a time. Since the current vehicle state
can always be determined, each state can be tested,
debugged, and tuned separately. Each of the states are
reviewed in the following sections.
State 1: Engine Only – The first state is engine only. In
this state, the vehicle operates as if the electrical system
were not present. This state is used at low speeds, when
the clutch is in, when the car is in neutral, or when the
battery is so low that attempting to use it could cause
damage. In this state, the accelerator input goes directly
to the engine, with the motor providing no torque.
State 2: Regenerative Braking – The second state is
the regenerative braking state. Regenerative braking
(regen) is the act of using the mechanical energy from
the wheels to drive the motor, generating electricity for
storage in the battery. This process recharges the
battery while decreasing the vehicle speed.
The vehicle goes into the regenerative braking state only
if the brake pedal is depressed and the battery pack is
not fully charged. The brake pedal travel is split into two
portions as seen in Figure 12. The first 2 cm (0.75in) of
travel only enables regenerative braking. After 2 cm,
regenerative braking is saturated and the stock hydraulic
brakes engage to help slow the vehicle. This allows a
conservative driver to regenerate large amounts of
energy during anticipated breaking, but retains the ability
to break hard when needed.
For previous competitions, the Wisconsin FutureCar
used a rotary potentiometer attached to the brake pedal
to produce an analog signal based on the first small
amount of brake pedal travel; however, no resistance
was incorporated for this regen travel distance. As a
result, the first few centimeters, the regen portion, was
traversed through quickly until resistance was felt in the
form of hydraulic fluid actuating the friction brakes. The
speed with which the regen portion was traveled through
reduced the effectiveness of the regenerative braking
capability. In order to improve its effectiveness, a new
sensor with hydraulic resistance was designed.
0 10 20 30 40 50 60
0
10
20
30
40
50
60
70
80
90
100
Master Cylinder
Reservoir Closes
Brake Switch
Activated
Regenerative Braking System
Conventional Braking System
BrakingSystemCapacityApplied(%)
Brake Pedal Depression (mm)
Figure 12. Depiction of the application of the
regenerative and conventional braking systems in the
vehicle.
An instrumented hydraulic piston is attached to the end
of the existing master cylinder. As the brake pedal is
depressed, the brake fluid forces this hydraulic piston to
compress a resistive spring. Initially, a brake line
pressure of 100 kPa (14.5 psi) is needed to initiate the
movement of the piston while a mechanical stop is used
to limit the piston’s stroke at a pressure of 350 kPa (see
Figure 12). A position sensor attached to the piston is
used by the control computer to adjust the amount of
regenerative braking. After the piston contacts the stop,
the disc braking system operates normally. The 350 kPa
preload causes a very smooth transition between the
regenerative and conventional braking systems.
State 3: HEV – HEV state is the third and most
common state in the control strategy. This state contains
the SOC regulator control code which manages the
battery voltage as previously described. To optimally
control the vehicle systems in the HEV state, the control
laws for this state will involve fuzzy logic.

8. Page 8 of 14
The hybrid diesel-electric propulsion state uses fuzzy
logic to synthesize accelerator pedal, battery state-of-
charge and vehicle speed sensor inputs into commands
to the diesel engine and electric motor. Using a small
number of rules, the basic relationships between inputs
and desired outputs will be described using fuzzy sets.
For example, an increased accelerator pedal
measurement will result in an increased command to the
motor to increase available torque while the engine
command is increased slowly to control soot emissions.
Safety is insured by range checking all inputs and
outputs. If a value entering or leaving the computer is too
low or too high the computer will adjust the value to the
closest bound, or shutdown.
AUXILIARY SYSTEMS
For the 1999 Wisconsin FutureCar a number of the
parasitic loads were removed from the engine including
the air conditioning, power steering and alternator. Self-
contained units that run independently of the engine
replaced these systems. Systems which are electrically
driven can be easily controlled to match demand periods
and are easily controlled. The implementation of the
new systems also allowed for optimization of these
systems.
Air Conditioning - The air conditioner compressor is
Matsushita LRA 71. 115 Vac, single phase self
contained rotary compressor. The system is capable of
removing 16000 BTU/hr. The compressor is run off of a
1.5 hp adjustable speed motor controller, Reliance
model SP200. With the removal of its dependence upon
the engine speed the new air conditioner can run at
required speeds and can even be throttled back. This
prevents the air conditioner from having to blend warm
outside air to achieve an intermediate temperature
improving the efficiency of the system.
Power Steering - The LYNX 90PS power steering pump
was replaced by a DELPHI Electro-Hydrolic (EH)
steering module. The EH module contains a 12 volt
motor which is directly coupled to a hydraulic pump. The
module also contains a controller which adjusts the
current to the electric motor proportional to the pumps
output pressure. The EH module uses 15 watts during
standby compared to 150 watts for the LYNX 90 PS
pump. At peak load, it requires 750 watts. The new
steering system reduces power draw by up to 80% [11].
12 Volt System - The 12 Volt system was totally
redesigned with the objective of removing redundant
systems and excess component weight. The
conventional 12 V alternator (9 kg) was removed from
the vehicle and replace with two 600 Watt Vicor DC to
DC converters (1 kg). In addition, the traditional
automotive SLI battery (18 kg) was replaced with a small
Bolder thin-metal film lead acid battery (1 kg). The DC-
DC converters use the high voltage battery pack to
supply up to 100 amps of current to the 12 V system
which contains the Bolder battery for starting current
demands. The Bolder battery is capable of supplying
500 cranking amps for approximately 10 seconds and it
can be recharged from the high voltage battery pack in
under 60 seconds.
Table 9. Aluminum Cow Component Summary.
Component Manufacturer Rating
Engine
Ford
1.8 L TDI
66 kW @ 4000 rpm
200 N-m @ 2000
210 g/kW-hr @ 2000
Transmission
Ford
MTX-75
5-speed w/ Reverse
4.06 Diff. Ratio
Motor
Solectria
AC gtx 20
12 kW continuous
≤100 N-m
≤12,000 rpm
Inverter
Solectria
UMOC 340
56 kW
≤ 210 Arms
200 - 350 Vdc
Battery
Sanyo
Sealed NiCad
+/- 24 kW
2.3 kWh
WEIGHT REDUCTION
In and effort to reduce the weight of the vehicle many
components were reconstructed of Aluminum. A more
complete description of the benefits and uses of
aluminum is discussed in Appendix A.
Battery Box – The physical size of the battery box is
comparable to the volume of the spare tire well. For this
reason, the spare tire well was removed so the battery
box could be suspended from the trunk floor without
sacrificing any trunk space.
Figure 13. 2.3kWh NiCad battery with 15 cell strings.

9. Page 9 of 14
Figure 13 shows a picture of the high voltage (HV)
battery box. In order to hold the 56 modules in place,
four sets of machined acetyl strips were clamped
together around the modules. Each battery module is
held in the center and at both ends by these sets of
acetyl strips, which also serve as excellent insulators.
Additional electrical insulation is provided by the shrink-
tube which covers each of the 56 modules. This design
requires a minimum amount of support material while
completely restraining the cells. Aluminum structural
angle beams 5 cm (2 in) on each side and 3.2 mm (.125
in) thick are used to anchor the acetyl strips together and
to mount the entire pack to the vehicle.
The large void in the battery box is used to enclose the
entire high voltage switch gear and DC-DC converters.
By combining all the HV components and removing
redundant systems, a modular HV unit was created. A
clear polycarbonate box, for protection, will enclose the
battery. The total weight of the battery box is 59 kg (130
lbs).
Brakes/Suspension – To reduce the weight and brake
drag, CNC 4-piston aluminum brake calipers were
installed in place of the Sable stock brake calipers.
Typical brake calipers employ a single piston. The brake
pads slide on pins when the brakes are released in order
to retract the brake pads. Over time, the pin/caliper
interface becomes corroded, preventing sliding. When
this occurs, the calipers do not fully disengage resulting
in a disk drag force which decreases overall efficiency.
The 4 piston calipers do not rely on this sliding and
actively minimize the residual drag force on the disk. In
addition, at 1.1 kg (2.5 lbs) each, they save 3.2 kg (7 lbs)
per side over the standard brakes. The AIV was
supplied with DurAlcan metal matrix composite
aluminum rotors each weighing 2.3 kg (5 lbs) less than
the stock steel rotors.
In order to adjust for a lighter chassis and modified
weight distribution, the team installed Koni coil-over
struts on all 4 corners. The struts allow for the
adjustment of ride height, camber, caster, toe, and
rebound damping. Not only have they allowed us to
optimize the handling of the FutureCar, but they will also
save about 0.9 kg (2 lbs) per wheel since they have
aluminum strut bodies.
To fit the newer engine cradle design, the front steel
spindles were upgraded to cast aluminum spindles
which save 1.4 kg (3 lbs) per front wheel. In addition, the
new spindles facilitated the mounting of the new
calipers. Through the use of all these aluminum
components, the overall vehicle weight will be reduced
by 23 kg (50 lbs).
Aluminum Wheels – Another opportunity for weight
reduction appeared in the wheel rims. The original
aluminum alloy rims weighing 10.5 kg (23 lb.) each were
replaced with lighter, American Racing aluminum alloy
rims weighing only 8.2 kg (18 lb.) each. This exchange
results in a savings of nearly 9.2 kg (20 lb.) total.
Engine Cradle - In a joined effort with Tower Automotive
the Wisconsin FutureCar team replaced the stock steel
engine cradle with a prototype Aluminum cradle. The
original steel engine cradle weighed 22.7 kg (50 lbs)
and was replaced by a all Aluminum engine cradle that
weighed in at a little over 9kg (20lbs).
Figure 14. Finite element analysis displacement results
for a Ford Taurus aluminum engine cradle with a 6 kN
load.
When replacing stamped steel with aluminum, the
strength of the steel can be matched by heat treating the
6061aluminum component to a T6 state. However, the
deflection of the aluminum is still approximately 3 times
greater than its steel counter-part. Figure 14 illustrates
the predicted displacement on the engine cradle for a 6
kN load applied to the bottom of the engine cradle. This
load simulates the vehicle cornering with a lateral
acceleration of 10 m/s
2
. Because the static support of
the engine is directly onto the uni-body frame in the
Aluminum Cow, the maximum stress strain and
displacement of the aluminum engine cradle are well
within acceptable limits.
A-Arms - The A-arms were also replaced with lighter,
stiffer aluminum counterparts. Tubular aluminum with a
31.8 mm diameter and 6.4 mm wall were bent and
welded in a triangular pattern. In this instance, the
volume of material was almost doubled in an effort to
create a stiffer yet lighter replacement. Figure 15 shows
the completed arms. The steel A-arms weighed 3.7 kg,
the Aluminum A-arms weighed only 2.2 kg.

10. Page 10 of 14
Figure 15. Aluminum A arms constructed from thick
wall aluminum tubing.
Engine Mounts- The engine mounts were another item
with the possibility for improvement in design. The
engine mounts were redesigned out of aluminum and
were also examined under finite element analysis to
make certain there was not a potential for failure.
Figure 16 shows the results of a finite element analysis.
Figure 16. Engine Mount finite element stress analysis.
DRAG REDUCTION
As shown in Equation 4 of the Vehicle Energy
Consumption section, some power loss of a vehicle can
be attributed to aerodynamic drag. This loss is
dependent on several factors, of which only the frontal
area profile and drag coefficient can be changed.
The following steps were taken to reduce the Wisconsin
FutureCar's frontal area profile, drag coefficient, and
coefficient of rolling resistance.
Wind Tunnel Testing – An aerodynamic study of the
vehicle was performed via wind tunnel testing. Three
different Ertel®
1/25-scale Ford Taurus models were
assembled (see Figure 17). The first vehicle was left in
its stock configuration. An underbody panel was
installed on the second model; this model also included
smaller rear view mirrors and a round-corner trunk lid.
The second and third models were identical with the
front underbody panel being replaced with a air dam on
the third model. A slippery smooth finish was applied to
each model by spraying them with a lacquer enamel
finish.
A wind tunnel at the University of Wisconsin was used to
perform the study. It was capable of producing wind
speeds up to 45 meters per second (100 mph). The
cross-sectional area of the tunnel's measurement
section was approximately 900 cm2
. A plate was
installed parallel to the air flow to simulate ground
effects. An instrumented arm extended into the bottom
of test section to measure both drag and lift on the
vehicle. An airfoil shrouded the arm to ensure accurate
drag measurements.
Figure 17. A still frame image of a 1/25 scale Ford
Taurus during wind tunnel testing.
A pitot tube was used to measure the air velocity in the
test section. During the experiment, the pitot tube
pressure was randomly varied from 2 inches of water to
5 inches of water in 0.25 inch increments and 20 data
points were collected for each vehicle test. 8 different
test sets were collected to ensure repeatability in the
experiment.
After post-processing, results were plotted as drag
coefficient versus wind tunnel velocity. The results from
the 5th
data set are plotted in Figure 18. It was observed
that at slow speed, the models have the same relative
drag coefficient. As the velocity increases, the model
with the underbody panel measured the lowest drag
coefficient. Compared to the stock model, the
underbody panel provided a 6% lower drag coefficient
while the spoiler increased the drag coefficient by 4%.
This relationship was observed in all 8 data sets.
Although the Reynolds numbers for the wind tunnel test
are an order of magnitude lower than for the real vehicle,
similar or exaggerated relations are expected for over-
the-road Reynolds numbers.
From the wind tunnel results, the Wisconsin FutureCar
Team concluded that the greatest reduction in
aerodynamic drag would be realized by streamlining the
underbody of the AIV Sable.

11. Page 11 of 14
0.59
0.61
0.63
0.65
0.67
0.69
0.71
0.73
0.75
15 20 25 30 35 40 45 50
Wind Tunnel Speed (m / s)
DragCoefficient(Cd)
Stock
Air Dam
Belly
Linear
Figure 18. Wind tunnel test data indicates that the use
of an underbody panel will reduce the drag coefficient
whereas the use of a spoiler will increase it.
Aerodynamic Simulation - In an effort to find a way to
reduce the drag force of the 1999 FutureCar a 2-D
profile of the car was modeled and tested in a finite
element program, Fluent 5.0. Different locations and
designs of spoilers were simulated to determine which
designs were worth pursuing in physical testing.
Figure 19. Fluent analysis of car profile at 30 [m/s].
Figure 19 shows the results of a simulation on the base
car profile. The spoiler designs with the smallest drag
force were used for physical testing.
Underbody Panel – Since approximately 10% of all
vehicle drag comes from underneath the car, the
Wisconsin team has made a panel that shelters the
underbelly. Reinforced, 24 gauge aluminum sheet metal
provides a smooth underbody surface which decreases
the drag coefficient.
Spoiler - From the simulations a trunk mounted spoiler
was designed in an effort to reduce the pressure drag of
the vehicle. The spoiler is made of Aluminum and is
designed as a reversed airfoil, 4 inches long and .5
inches tall. The spoiler will be mounted 5 inches above
the edge of the trunk. The addition of the spoiler creates
small-scale turbulence which causes the streamline to
recollect sooner behind the vehicle. This decreases the
dead zone behind the vehicle and reduces drag. Based
on simulation results the spoiler should reduce the
overall drag of the vehicle by about 8%.
Tires – Equation 2 shows that vehicle power loss is
directly related to the tire’s rolling resistance. The UW
FutureCar Team has opted to use Goodyear’s
experimental low rolling resistance tires. This particular
tire has the best available coefficient of rolling resistance
- less than 0.00625.
ALTERNATIVE ENERGIES
Solar Array- The 1999 FFC will have two solar arrays,
both mounted upon the roof. Each panel is made up of
36 Kyocera 4" square polycrystalline silicon cells
connected in series to produce 12Vdc. The two panels
are connected in parallel to the cars 12V system. Each
panel should be able to supply 50 Watts. This is
sufficient to supply the diesel engine's electronics as well
as the touch screen computer and other steady state
driving loads. During long periods of storage the solar
cells will be able to maintain the vehicle's batteries.
INTENDED MARKET
Producing a hybrid vehicle that has a high level of
consumer acceptability was a high priority for the
University of Wisconsin FutureCar Team. Accordingly,
the team entered the FutureCar Challenge committed to
maintaining full passenger and cargo room in the
vehicle, to producing a seamless appearance similar to
the original, and to retaining the driving feel of a stock
Mercury Sable. The 1999 Wisconsin FutureCar
accomplishes all of these goals. The intended market for
this car includes drivers looking for a mid–size sedan
with the following characteristics:
• Enhanced performance
0-100 kph in < 10 seconds
145 kph (90 mph) maximum speed
970 km (600 mi) range
• Impressive fuel economy
23.9 km/L (56 mpg)
1.1 cents/km (1.8 cents/mi) travel cost
• Creature comforts
Turn-key start up
Air conditioning
Cruise control
Power windows
AM/FM radio & cassette player
Touch screen computer interface
Televisions in both headrests
The UW FutureCar has a clean body and passenger
compartment. The interior of the vehicle maintains the

12. Page 12 of 14
size, shape and amenities of the original Mercury Sable
with the addition of a touch screen computer console.
The design of this vehicle makes it simple to operate,
with a conventional turn–key start. No extra switches or
buttons are required to start or drive the vehicle. The
advanced control strategy allows an operator to achieve
the same performance after traveling 970 km (600 mi)
that they experienced at the beginning of the journey,
and only a five minute fueling service in order to travel
another 970 km.
COST ANALYSIS
The estimated total cost of the 1999 UW FutureCar at
high volume production is $28,000. This cost estimate is
based upon a Mercury Sable list price of $21,000, an
additional cost of $11,000 for new engineering, and a
$4000 savings from replacing the conventional
drivetrain. In order to estimate these costs, several
assumptions were made.
• The cost of manufacturing the aluminum
unibody and enclosure panels is 1.4 times that
of manufacturing steel [5].
• Components that are not “off the shelf” can be
mass produced at a cost of 20-30% of the price
that the Wisconsin team paid.
• All other vehicle components are the same as
those found in a stock Mercury Sable.
• 100,000 vehicles are manufactured each year.
• The cost of labor is negligible.
• All costs have been assessed in 1999 dollars.
The cost for a single prototype FutureCar is estimated to
be $54,000. This estimate assumes that the cost of a
prototype AIV is $31,000. The remainder of the cost is
obtained from the special order prices of the hybrid
components.
MANUFACTURING POTENTIAL
The Wisconsin FutureCar component selection and
packaging has been chosen for ease of procurement,
access, and maintenance. This design inherently favors
obtaining components and assembling the vehicle in
mass production.
The current trend in automotive manufacturing is to use
common platforms – the use of common components
on multiple vehicles (i.e. engines, transmissions, and
frames). Adapting to the methods of Ford, GM and
Chrysler, the Wisconsin FutureCar team adopted this
methodology in 1998. This vehicle could be easily
integrated into a conventional vehicle production line and
would need supplemental tooling only for installation of
the battery pack. The electric motor would simply bolt
onto a standard transmission fitted with a special
secondary shaft. Additional components would be
minimal and could be installed by the regular assembly
line workers onto existing hardware.
A compact design not only aids in manufacturing but
also minimizes the number of serviceable parts. If
needed, threaded fasteners are conveniently located so
that disassembly is quick and easy.
Just as any prototype vehicle must be modified before it
is put into production, the following features of the
Wisconsin FutureCar would be changed in preparation
for mass production.
• Replace the Pentium control computer with an
embedded computer.
• Design the battery pack to fit behind the rear
seat back.
Combining these modifications with the existing design
before incorporating the FutureCar into the assembly
line would significantly reduce the time and cost of
production.
SUMMARY
The Wisconsin FutureCar Team has successfully
converted a prototype 1994 Mercury Sable AIV into a,
power assist, charge sustaining parallel hybrid-electric
vehicle. The UW FutureCar was designed to exceed the
stock Sable fuel economy and emissions standards
without sacrificing performance or consumer
acceptability. This was accomplished by using advanced
technologies as well as existing automotive science.
The team used traditional hybrid-electric components;
including an AC induction electric motor with matched
inverter; a high power density Ni-Cad battery pack; and
a compression ignition internal combustion engine in an
attempt to reach the FutureCar Competition fuel
economy goal of 80 miles per gallon.
In addition, the Wisconsin team incorporated several
advanced technologies into its 1999 FutureCar. The use
of computer simulation to optimize control software
coupled with an aggressive fuzzy logic control strategy
helped realize team goals. Finite element analysis such
as Fluent and ANSYS were used to minimize vehicle
testing time while verifying the integrity of using
aluminum and polycarbonate to reduce the vehicle
weight. All while keeping the vehicle design cost
effective and modular so that it could be implemented
into an automotive production line.

13. Page 13 of 14
ACKNOWLEDGMENTS
The outstanding contributions of Advisor Dr. Glenn
Bower regarding sound engineering, student education,
and professional conduct have been invaluable to the
UW FutureCar Team. His dedication, along with the
financial support and enthusiasm of the UW College of
Engineering, has given team members the ability to
flourish with new opportunities and experiences.
The patient work of the FutureCar organizers to create
and facilitate the Challenge is also greatly appreciated
by the members of the Wisconsin team. The funding for
such organization, as well as the availability of
competition facilities, seed money, and platform
vehicles, is made possible by the generous contributions
of USCAR, USDOE, USEPA, ANL, Chrysler Corp., Ford
Motors, and General Motors. We would especially like to
thank Ford with whom we have maintained a close
working contact, and from whom we have received much
knowledge and help dating back to the initial designs of
the 1998 FutureCar. We would like to extend our thanks
to all of these organizations who have been instrumental
to the FutureCar Challenge and the promotion of energy
efficient vehicles.
Finally, the authors of this report wish to recognize all of
the members of the Wisconsin FutureCar Team who
have contributed to the success of the “Aluminum Cow”
and elevated the engineering standards at the University
of Wisconsin.
REFERENCES
1. Thiel, M.P., et al., “The Development of the University of
Wisconsin’s Parallel Hybrid-Electric Aluminum Intensive
Vehicle,” SAE Publications February 1999, SAE .
2. Bower, G.R., et al. , “Design of a Charge Regulating,
Parallel Hybrid Electric FutureCar,” SAE Publications
February 1998, SAE 980488.
3. Johnston, Brian, et al. , “The Continued Design and
Development of the University of California, Davis
FutureCar,” SAE Publications February 1998, SAE
980487.
4. Thomas, C.E., et al., “Societal Impacts of Fuel Options for
Fuel Cell Vehicles,” SAE Publications October 1998, SAE
982496.
5. "1.8L DI TCI LYNX 90 PS in Focus - Engine and Vehicle
Performance Data", Ford of Dunton, England, November
1998.
6. Cuddy, Matthew R. and Wipke, Keith B. "Analysis of the
Fuel Economy Benefit of Drivetrain Hybridization," SAE
970289.
7. Mariano, S. and Tuler, F. and Owen, W., "Comparing
Steel and Aluminum Auto Structures by Technical Cost
Modeling." JOM, 45(6):20-22, 1993.
8. Gallopoilos, N.E., “Environmental Vehicle,” EDS,
Dearborn, MI, 1996.
9. USABC Electric Vehicle Battery Test Procedures Manual,
Revision 2, U.S. DOE, Idaho National Engineering
Laboratory, DOE/ID-10479, Jan. 1996
10. PNGV Battery Test Manual, U.S. DOE, Idaho National
Engineering Laboratory, DOE/ID-10597, Jan. 1997
11. http:www.delphiauto.com, 5-3-99
12. Wiegman, H., Vandenput, A., "Battery State Control
Techniques for Charge Sustaining Applications," SAE
Publ. 981129, SP-1331, 1998, pp 65-75 , and 1999 SAE
Transactions
SYMBOLS
m = mass of vehicle (kg)
g = gravitational acceleration (9.8 m/s^2)
V = velocity (m/s)
θ = inclination of road (rad)
ρ = density of air (~ 1.3 kg/m^3)
A = frontal area of car (~2 m^2)
Cd = drag coefficient (~.30)
Crr = coefficient of rolling resistance (~.008)
Note: Appendix follows on next page.

14. Page 14 of 14
APPENDIX
A. ADVANTAGES OF ALUMINUM - Aluminum is a
versatile and useful metal with many advantages,
including its light weight, resistance to environmental
conditions, high elasticity, ease of working and forming,
and the high strength of aluminum alloys (up to and
exceeding the strength of steel). For an equal volume of
material, its strength is equivalent to that of mild steel.
However, its stiffness is lower by a factor of three,
requiring the designer to increase the cross sectional
area of critical parts or to reevaluate their structure.
Aluminum is easily machinable and can be cast as well.
The material properties are compared in Table A.1.
Because of the global need for reduced fuel
consumption, the automotive industry is interested in
exploring the possibility of substituting aluminum for
steel in passenger vehicles. For example, the Audi
5000s had an aluminum frame with a 48.6% lower
weight (as part of a joint project between Audi and
ALCOA). Other examples of aluminum body construction
include US Postal mail cars, the US Army HMMWV
multi-purpose vehicles, and semi truck trailers such as
those produced by Freightliner Corporation. In all these
applications, the use of aluminum has saved money by
improving fuel mileage through weight reduction. Its
strength has improved the overall designs, while its
corrosion resistance prolonged the life of the vehicles.
(Aluminum forms a protective oxide coating which
prevents rust related failures.)
Companies such as ALCOA and BMW are developing
new manufacturing processes for aluminum. The BMW
500 series axles were hydroformed for higher stiffness
and fatigue strength, and then GMA welded together.
Aluminum tends to respond well to GMA and GMA-
impulse welding. For high-quality joints, TIG welding is
also used.
Table A.1 - Material properties for aluminum and steel.
Alloy & Temper Ultimate
Strength
(ksi)
Yield
Strength
(ksi)
Modulus of
Elasticity
(ksi)
Alum. 2014-T6,
T651
70 60 10.6
Alum. 6061-T6,
T651
42 37 10.0
Alum. 7075-T6,
T651
83 73 10.4
Steel 1020 HR 66 42 30
Steel 1018 A 49.5 32 30
B. EXHAUST GAS RECIRCULATION
One of the main drawbacks of compression ignition (CI)
engines is the high oxides of nitrogen emission levels.
CI engines utilize high compression ratios (15-18:1) to
achieve high thermal efficiency. Unfortunately, high in-
cylinder temperatures promote the formation of NOx
during combustion. It has been found that NOx
emissions can be reduced by introducing exhaust gas
into the intake charge. This practice is known as
exhaust gas recirculation (EGR). NOx emissions can
further be reduced by cooling this recirculated exhaust
gas.
The Ford engine was originally equipped with an EGR
intercooler. This heat exchanger lowers the temperature
of the EGR stream by using the cooling system as its
heat sink. This exchange of heat results in two
advantages. First, cooling of the exhaust gas produces
lower NOx emissions from forming. Second, the coolant
that is heated is then pumped directly to the heating
system for the vehicle. This will provide heat to the cabin
much more quickly and efficiently than the stock heating
system