sports utility vehicle

Moolander Wisconsin’s Hybrid-Electric Sport Utility Vehicle Nicholas L. Woulf, Kathryn M. Orgish, Bradley J. Grzesiak, Katherine R. Edwards, Julie G. Marshaus, Glenn R. Bower University of Wisconsin–Madison ABSTRACT The University of Wisconsin – Madison FutureTruck team has designed and constructed a four-wheel drive, charge sustaining, parallel hybrid-electric sport utility vehicle for entry into the FutureTruck 2003 competition. This is a multi-year project utilizing a 2002 Ford Explorer as the base vehicle. Wisconsin’s FutureTruck, nicknamed the “Moolander,” weighs approximately 1905 kg and includes a prototype aluminum frame. The Moolander uses a high efficiency, 1.8 liter, common rail, turbo-charged, compression ignition direct injection (CIDI) engine supplying approximately 85 kW of peak power and an AC induction motor that provides an additional 60 kW of peak power. The 145 kW hybrid drivetrain will out-accelerate the stock V6 powertrain while producing similar emissions and drastically reducing fuel consumption. The PNGV Systems Analysis Toolkit (PSAT) model predicts a Federal Testing Procedure (FTP) combined driving cycle fuel economy of 16.05 km/L (37.8 mpg). The Moolander achieved 16.36 km/L (38.5 mpg) and Ultra Low Emission Vehicle (ULEV) emissions during initial dynamometer testing. Without sacrificing any interior space, the Moolander maintains the stock appearance and towing capacity of the Ford Explorer while reducing greenhouse Table 1. Moolander’s 2002 Results and 2003 Goals Competition Goals 2002 Results 45 % Tier 1 66 % reduction 11.33 240 km 907 kg 2068 kg 2003 Goals 75 % Calif. ULEV 75 % reduction 10.82 290 km 907 kg 1950 kg 1 Figure 1. Overview of the 2003 Moolander Layout. gas emissions by a factor of 4. INTRODUCTION FutureTruck is a student competition that challenges teams to build a sport utility vehicle (SUV) that maintains current safety standards, performance, comfort, utility, and affordability while improving fuel economy and reducing the greenhouse gas impact (GHGI). Fifteen universities from North America will compete in FutureTruck 2003, which is sponsored by the US Department of Energy and Ford Motor Company. The University of Wisconsin has improved the Moolander, their charge sustaining, parallel hybridelectric four-wheel drive SUV, after evaluating its performance in FutureTruck 2002. To optimize the design, the Wisconsin team used knowledge gained from the previous three years of SUV testing on the Moollennium and Moolander [1, 11,13], as well as testing the Aluminum Cow, a parallel hybrid sedan [2]. A smaller engine and lighter, more powerful electric motor replaced last year’s drivetrain (see Figure 1). An aluminum frame replaced the stock steel frame to help meet the team’s aggressive weight reduction goal of 150 kg. The Moolander’s 2002 results and 2003 goals are listed in Table 1. Parameter Combined FTP 25 % Fuel Economy improvement Emissions GHG Acceleration: 0.2 km Range Trailer Tow Vehicle Weight Calif. ULEV Reduce 11.5 No req. 907 kg 2100 kg Table 2. Wisconsin’s Team Composition by Major. 59 % 22 % 8% 3% 5% 3% FUEL REVIEW Reducing GHGI is a global initiative and a primary goal of the FutureTruck competition. The EPA has developed a standardized method to quantify the greenhouse gas impact, which uses the following formula: (1) GHGI = CO2 + 21*CH4 + 310*N2O Mechanical Engineering Electrical and Computer Engineering Industrial Engineering Materials Science Computer Science Other TEAM ORGANIZATION The University of Wisconsin FutureTruck team consists of seven groups – Mechanical, Electrical, Drivetrain, Controls, Telematics, Business, and Information – overseen by a faculty advisor and a student team leader. In addition, a team RADAR acts as a liaison between the competition organizers and the team. There are approximately 42 FutureTruck team members, with 14 enrolling for engineering course credit. Two team members are graduate students. Team composition is shown in Table 2. Each group has a leader in charge of planning and assigning projects as well as providing team members with guidance. Group leaders are also responsible for setting and meeting project deadlines. The team leader oversees the groups to facilitate communication between groups and ensure completion of multidisciplinary projects. The faculty advisor provides guidance, answers technical questions, and promotes relationships with industry. Figure 2 is a general timeline of the past two years showing deadlines set to prepare for competition in June of 2003; the team has successfully achieved the milestones depicted on the timeline. Energy consumed during fuel distillation or processing must be included in a “well to wheels” analysis. The additional upstream factors for crude oil are fairly straightforward: drilling, pumping, transporting, and refining. Energy Path Factor (EPF) is defined as the percent of energy that reaches the consumer as listed in Table 3. Liquid fuels such as gasoline and diesel fuel use approximately 1 unit of energy in the refining process to produce 4 units of fuel, hence an EPF of 0.8 [14,15]. Renewable resources are one way for the United States to reduce its dependence on foreign oil. The US Department of Energy defines a renewable resource as anything that can be regrown to its previous state within 7 years. Ethanol, a renewable resource, in comparison to gasoline, consumes 3 units of energy for every 4 units that are delivered (EPF = 0.57) [14]. Although ethanol is a renewable fuel, it consumes a majority of its upstream energy during processing. Another renewable fuel source, derived from soybeans, is biodiesel. Biodiesel’s Table 3. Energy Path Factor for Competition Fuels. FUEL 85% Ethanol Blend (E85) Gasoline Reformulated Gasoline EPF (%) 0.604 0.806 0.794 0.833 0.809 GHGI (g/km) 92 1710 1548 1330 -446 Competition '03 Diesel Fuel 35% Biodiesel Blend (B35) Summer '02 Spring '02 Deadline Spring '03 Fall '01 Fall '02 Task Design Build Aluminum Frame Choose Components Receive Components Integrate Components Test Design transesterification process consumes 1 unit of energy for every 3.2 produced, resulting in an EPF of 0.76 [15]. Because domestic energy sources such as coal and natural gas can be used to process ethanol and biodiesel, these fuels are a viable alternative to foreign oil. Although renewable fuels use significant amounts of energy during processing, overall they produce less GHGI because corn and soybeans eliminate CO2 from the atmosphere during photosynthesis. For instance, E85, a blend of 85% ethanol and 15% reformulated 2 Legend FT02 FT03 Figure 2. Wisconsin FutureTruck project timeline. Table 4. Crude Oil Refinery Product Percentages[16] Product Percent of Production (%) 33.9 10.6 33.2 10.7 11.6 Kerosene Gasoline Diesel Oils Fuel Oil Other Products “On the Road in 2020” [10], a study conducted by the Massachusetts Institute of Technology, provides a framework for defining the best future power source as the effects of global warming and local air quality standards are quantified. “Vehicles with hybrid propulsion systems using either ICE [Internal Combustion Engine] or fuel cell power plants are the most efficient and lowest emitting technologies assessed. In general, ICE hybrids appear to have advantages over fuel cell hybrids with respect to life cycle GHG emissions, energy efficiency, and vehicle cost, …” After reviewing relevant literature, Wisconsin eliminated natural gas hybrids from consideration because of their inability to store enough fuel to meet the team’s range goals. Series hybrids were also eliminated because they are not well suited for trailer towing. In addition, the extra space and weight required for series implementation would reduce the vehicle’s cargo capacity. Therefore, the University of Wisconsin utilized a parallel design. The team has chosen GHGI reduction as its major priority; hence, working within the team’s budget, the Moolander utilizes a compression ignition engine. In order to strive for ULEV emission compliance, two senior members have been dedicated to prototype emission controls equipment. gasoline, provides almost no upstream GHGI compared to reformulated gasoline (EPF = 0.8) despite having an EPF of 0.57. Because biodiesel has a relatively high EPF, a 35% biodiesel blend (35% biodiesel, 65% diesel fuel) actually provides an upstream credit. Biodiesel has such a GHGI advantage over the other competition fuels that the competition organizers have limited its blending percentage to 35%. Because crude oil is a mixture of hundreds of different hydrocarbon molecules, crude oil must be refined to produce fuel. Longer hydrocarbons can be thermally or catalytically “cracked” into shorter molecules. It is not economically feasible to convert 100% of crude oil into gasoline, so several different fuel grades including kerosene, diesel fuel, and fuel oil are produced. The percent of each distillate is listed in Table 4. From the table, crude oil is refined primarily into gasoline and diesel fuel. To minimize crude oil dependence and domestic fuel costs, development of gasoline and diesel hybrids is necessary until a hydrogen society is established. KEYS TO INCREASING FUEL ECONOMY A very simple model that gives insight into how the major vehicle parameters affect fuel economy, but does not include engine or electric motor efficiency, was developed [3]. Wisconsin also used the PSAT model, which is an all-inclusive model including individual component efficiencies. Fuel economy modeling done with PSAT will be discussed later. ENERGY AND EMISSION REVIEW In conjunction with the PNGV program, several renowned scientists have examined viable power sources for personal transportation. These “well to wheels” analyses consider the global impact of each energy source and the local impact from the tailpipe emissions. A 1998 study, “Societal Impact of Fuel Options of Fuel Cell Vehicles” [5], considered various fuels and vehicle configurations. It concluded that there were no clear winners, that “The optimum fuel and optimum vehicle depend on the priority given to societal objectives…. If reduced greenhouse gases is the sole criterion, then the clear winners are natural gas or diesel parallel hybrids, with diesel parallel hybrids providing almost 15% lower greenhouse gas emissions than a direct hydrogen FCV [Fuel Cell Vehicle],…” EPA Combined Fuel Economy Magnitude 1.30 1.25 1.20 Mass Aero Tires Accessories 1.15 1.10 1.05 1.00 0 10 20 30 40 50 Parameter Reduction (%) Figure 3. Fuel economy gain vs. parameter reduction. 3 (2) (3) (4) (5) (6) (7) Proad = Proll + Phill + Paero + Paccel + Paux Proll Phill = m g V Crr cos θ = m g V sin θ 3 domestically manufacturing the Moolander. Throughout the selection process, appropriately sized components were chosen to maximize energy efficiency and minimize weight. A packaging diagram of the Moolander is shown in figure 4. 125 5% grade, zero head wind, with 907 kg Trailer 1% grade, 48 km/hr head wind, with 907 kg Trailer Lynx Engine Power Peak (85 kW) 100 Paero = 0.5 ρ A V Cd Paccel = d Ekinetic / dt Paux = f (alternator, power steering, etc.) Required Power (kW) The road power demand, Equation (2), identifies the vehicle design aspects that can be changed to improve the overall energy efficiency of the vehicle. The relative effect of reducing each parameter in terms of the fuel economy impact over the FTP 75 cycle for a conventional vehicle is depicted in figure 3 [4]. It is clear from the figure that vehicle mass is the dominant factor in vehicle energy consumption; therefore, weight reduction was given the highest design priority. 75 50 25 CONVENTIONAL DRIVETRAIN COMPONENTS Components exactly matching “ideal” specifications are rarely obtainable; therefore, component availability was a dominating constraint as the team searched for a desirable combination of engine, transmission, and electric drive system. Wisconsin researched and identified viable component options for integration into their FutureTruck in the fall of 2001. Many of the desired components could not be obtained in time for the 2002 competition and alternatives had to be selected. However, those components were obtained in time for the 2003 competition and have been integrated into the Moolander. When searching for components, American manufacturers were considered first. This was done to minimize lead times and increase the feasibility of 0 20 40 60 80 100 120 Vehicle Speed (km/hr) Figure 5. Power requirements for the Moolander to tow a 907 kg trailer up a 1% grade and into a 48 km/hr headwind. ENGINE With the aforementioned constraints in mind, Wisconsin searched for an acceptable common rail compression ignition direct injection (CIDI) engine for its 2003 FutureTruck. The IC engine must be sized to meet the largest continuous power demand the vehicle will experience. Two different loading scenarios were investigated. The first case considers the power needed to pull a 907 kg trailer up a 5% grade. In the second case, Wisconsin considered driving the Moolander up a 1% grade and into a 48 km/hr wind. Figure 5 was generated using the power equations described in the “Keys to Increasing Fuel Economy” section. It was determined that the engine’s peak continuous power must be at least 75 kW. Traditional transmissions have discrete gear ratios, and engines cannot be operated at peak power under all conditions. Therefore, it is imperative that the peak trailer tow power required must be delivered throughout the upper 25% of the engine’s operating range (1000 rpm band). Due to the torque-rise characteristic of the CIDI engine, a 10% peak power margin will ensure that power demands can be achieved during extended hill climbs. Figure 4. Isometric view of the Moolander’s packaging diagram (same color scheme as figure 1). 4 Ideal midrange (1.8 – 3.0 liter) CIDI engines that provide the desired power are currently unavailable domestically. Oversized engines would consume more fuel and increase vehicle weight, lowering the vehicle’s fuel economy. Therefore, a midsize European CIDI engine would best suit Wisconsin’s hybrid powertrain design. The 2.5L Land Rover used in the 2001 Moollennium and 2002 Moolander provided 325 Nm of torque and 100 kW of power; however, at 249 kg, its weight is a significant disadvantage. Recent advancements in CIDI technology have increased the power to weight ratio while simultaneously reducing engine noise, vibration, and harshness (NVH). After a rigorous search, it was determined that the Ford 1.8L Lynx PS115 engine almost matched design specifications. The Lynx weighs 158 kg and has enough torque to meet the FutureTruck 2003 competition requirements. Utilizing a Delphi common rail injection system, the engine actively controls pilot injection quantities to minimize low speed NVH using an engine-mounted accelerometer. A variable nozzle turbocharger is responsible for increasing low speed engine torque and reducing turbo lag. The engine is also cleaner – it is certified for Euro IV emission levels. A complete list of the engine specifications is shown in Table 5. is readily available. The top-load shifter aligns with the stock Explorer shifter access panel and produces a quiet, smooth shift. The gear ratios are shown in Table 6. Lower gear ratios st th were selected for 1 – 4 gears to utilize the engine’s low-end torque to aid in towing capabilities. High-end th gearing for 5 gear were chosen to optimize engine efficiency during highway driving. The placement of the transmission in the Wisconsin FutureTruck is displayed in the packaging diagram (figures 1 & 4). Table 6. Gear Ratios for the Borg Warner World Class T5 Transmission in the Moolander. Gear st 1 nd 2 rd 3 th 4 th 5 Reverse Differential Ratio 3.97:1 2.34:1 1.46:1 1.0:1 0.79:1 3.70:1 3.73:1 Table 5. Specifications for the 1.8L Ford Lynx PS115 Common Rail Engine. Engine Characteristic Specification Rated Power 85 kW at 3800 rpm Maximum Torque 250 Nm @ 1850 rpm Speed Range 900 – 4500 rpm Bore 82.5 mm Stroke 82.0 mm Displacement 1753 cc TRANSFER CASE Four-wheel drive engagement for the 2003 Moolander will be supplied by a Borg Warner model 13-54 transfer case. This transfer case uses a drive chain and has a low-range gear ratio of 2.48:1 and a drop angle of 27.12 degrees. It adapts directly to the Borg Warner T5 and uses the same engagement motor as the stock Explorer. A double Cardan constant velocity (CV) assembly will connect the transfer case output to the electric motor. Decoupling the motor from the transfer case significantly decreases the overall powertrain NVH providing a smooth, quiet ride. FUEL TANK TRANSMISSION Wisconsin has chosen to use a manual transmission because of its inherent high efficiency and low mass. Since all drivers do not desire manual transmissions, an auto-shift unit could be an option in a production vehicle. The auto-shift manual transmission is a proven design that has been incorporated into many “high-end” vehicles. Wisconsin chose not to integrate an autoshifting feature into the Moolander to reduce drivetrain control complexity. The Borg Warner World Class T5 transmission was chosen as the best option for the 2003 Moolander. The T5 was utilized last year without incidence. This transmission has been in service for over 20 years and 5 Based on the 2002 FutureTruck on-road fuel economy, the fuel tank capacity was reduced from 30.28L to 27.44L, providing a 290 km range. An L-shaped aluminum fuel tank was constructed to optimize underbody packaging. It was prototyped using 5052 H34 1.27 mm thick sheet aluminum with all seams joined and sealed using tungsten inert gas welding. The Delphi injection system requires no tank pump, which minimizes couplings to an inlet, outlet, and fill port. The fuel system is compatible with both conventional diesel fuel and biodiesel blends. ELECTRIC DRIVE SYSTEM Motor Output Power (Kw) 65 60 To optimize fuel economy while minimizing the cost of a hybrid SUV, the electric drive components must have the ability to capture most of the energy normally lost during friction braking. During dynamometer testing at the 2002 FutureTruck competition, current into and out of the high voltage battery was monitored, and the results are tabulated in Table 7. The results show significant assist and regenerative events only utilize the electric motor during 4% of the FTP cycle. After evaluating the 2002 Moolander’s performance shown in figure 6, the team decided that an electric motor with more high-speed (50–100 km/hr) torque was needed to ensure satisfactory performance with the smaller, slightly less powerful engine. In choosing the Moolander’s 2003 electric drive components, the traction motor was chosen first. Next, it was decided to reuse the Solectria DMOC445LC, which had been successfully used in 2002. It is capable of providing 60 kW of peak power for assist events and 78 kW of regenerative braking power. The hybrid battery pack was sized to utilize the full capabilities of the motor controller. TRACTION MOTOR Previous experience led to the conclusion that a permanent magnet motor was not well suited to a mild hybrid. Since the motor is only significantly utilized 4% of the time, the parasitic loss of the permanent magnets during idle operation negates any efficiency gains from machine utilization [2]. Therefore, the Moolander was fitted with an AC induction electric motor. After the 2002 competition, Wisconsin reevaluated the electric motor. For 2003, the Delphi EV1 motor was chosen because of its additional power and increased 55 50 45 40 35 30 25 20 15 10 5 0 0 10 20 30 40 50 60 70 80 90 EV1 - 280 Amp DC max 2002 Custom Motor Vehicle Speed (mph) Figure 6. Comparison of 2002 and 2003 Moolander motors’ peak power output versus vehicle speed. efficiency. Comparing the Moolander’s 2002 axle-speed custom electric motor to the EV1 motor, the latter motor delivers significantly more power over all operating speeds when a second battery pack is available, as illustrated in figure 6. Since last year’s custom motor was already magnetically saturated, an additional battery would not have increased its performance. Once integrated, the EV1 motor and Lynx engine combination provides the most power of any of the options considered for the 2003 Moolander hybrid drive. In an 1/8 mile acceleration, the 2002 powertrain achieved a minimum time of 11.33 seconds. Delivering 25 more kW to the ground, it is estimated that the 2003 powertrain should reduce the 1/8 mile acceleration time to 10.82 seconds. Table 7. Analysis of Electrical Power Demands on the 2002 Moolander During the FTP Cycle Using a 6.5 Amp-hr Battery. Seconds of Use I = 1/10C (seconds) 85 64 36 185 Utilization Percentage I = 1/10C (%) 9.8% 12.7% 4.7% 8.7% Seconds of Use I = 1C (seconds) 25 30 29 84 Utilization Percentage I = 1C (%) 2.9% 5.9% 3.8% 3.9% Seconds of Use I = 4C (seconds) 7 13 13 33 Utilization Percentage I = 4C (%) 0.8% 2.6% 1.7% 1.5% FTP Cycle UDS (866 sec) Hot 505 (505 sec) Highway (767 sec) Combined (2138 sec) 6 150 125 100 been tuned for operation with Wisconsin’s EV1 motor. The DMOC is equipped with a Controller Area Network (CAN) bus and is controlled and monitored digitally by the hybrid controller. The inverter is liquid-cooled, 98% efficient, and weighs 10.58 kg. The unit is rated for a nominal battery input voltage of 312 V and has a 280 Arms limit. BATTERY Lynx and EV1 Motor 2002 Powertrain Lynx 115 PS EV1 (280 Amp DC Max) Max Accel on FTP 75 Power (kW) 75 50 25 0 0 20 40 60 80 100 120 140 160 Vehicle Speed (km/hr) Figure 7. Power versus speed curves for the Lynx engine, EV1 motor, and 2002 and 2003 powertrain configurations compared to the FTP 75 cycle. A summary of the characteristics of available battery chemistry is shown in Table 8. Nickel Cadmium (NiCd) batteries were ruled out due to the difficulties of recycling heavy metals. Spiral wound lead acid batteries were eliminated because their low cycle life would require battery pack replacement during the expected life of a production vehicle. Reviewing this information, Wisconsin decided that a nickel metal hydride (NiMH) pack would be the best alternative for the Moolander. Historically, appropriately-sized nickel based batteries for mild hybrid designs have not been commercially available. Wisconsin has previously addressed this The electric motor utilized in the Moolander is a copper bar rotor design that was developed for General Motor’s electric concept vehicle, the EV1. A Ballard planetary gearset, which provides a 3.18:1 speed reduction, has been integrated into a custom motor case. As seen in figure 8, a very light and compact through-shaft motor was fabricated using a hollow rotor shaft. The electric motor is mounted between the back of the transfer case and the rear differential. MOTOR CONTROLLER The Solectria DMOC445LC motor controller/inverter has Table 8. Battery Comparison. Selection Criteria Battery Chemistry NiMH Economically Recyclable Cycle Life Cost Power Density (kW/kg) Energy Density (MJ/kg) Yes 100,000 + High 0.984 0.143 NiCd No 100,000 + High 0.582 0.160 Spiral Wound Pb Acid Yes 10,000 + Low 3.0 0.100 issue by custom packaging NiMH sub-C cells into “sticks” and then connecting them in series and parallel to produce an acceptable hybrid battery. To increase the Moolander’s performance, the electric drive system must be capable of supplying 60 kW across normal vehicle operating speeds. In order to meet the increased demands of the electrical system, two Panasonic prismatic battery packs, originally produced for the Toyota Prius, are utilized in a parallel configuration. Both batteries have been repackaged to fit within the structure of the Ford Explorer while ensuring uniform and adequate cooling. One Panasonic pack was utilized successfully in the Moolander for FutureTruck 2002. Figure 8. Exploded view of Moolander’s 2003 throughshaft motor utilizing an EV1 motor and a Ballard planetary gear reduction. 7 12 10 8 6 4 2 300 Table 9. Pack Voltage 290 280 270 260 250 String Current (A) 0 -2 -4 -6 -8 240 String 1 String 2 String 3 String 4 220 230 240 250 260 270 230 220 210 200 280 Specification of Panasonic Prismatic Cells. Panasonic Battery Characteristic Prismatic Battery Mass [kg] 44.7 Voltage [V] 273 Capacity [A-h] 6.5 Energy [kW-h] 1.78 Power Density [kW/kg] 0.984 Energy Density [MJ/kg] 0.143 Pack Voltage (V) -10 210 Time (s) Figure 9. Pack voltage and individual string’s current levels for 4 parallel strings in a hybrid vehicle being tested on the FTP 505 cycle. water. It has 32 analog inputs, 6 digital inputs, 20 low side driver power outputs, 8 logic level outputs, and a dual 2.0B CAN interface. CONTROL STRATEGY The PCM is programmable in C/C++ allowing utilization of Wisconsin’s previously successful control strategy code. In addition, programming libraries developed by MotoTron support adjusting control strategy parameters tables in real-time using an attached laptop. The control strategy uses the vehicle conditions, battery state, and driver inputs to optimize the CIDI engine and electric motor operation. Wisconsin estimates state of charge (SOC) using an ensemble averaged pack voltage. This averages the transient voltage pulses from assist and regenerative braking, which yields a real-time estimate of the SOC. This lagging SOC indicator is well suited to the wide hysteresis bands associated with the voltage deviations of a mild hybrid battery pack. The result is smooth vehicle operation with a feel similar to a conventional vehicle. The software is restricted to run in only one of four states at a time. Each state can be tested, debugged, and tuned separately. The four states are as follows: State 1: Engine-Only In this state, the vehicle operates without using the electric motor and is used when the clutch is depressed or when the transmission is in neutral. The accelerator input goes directly to the diesel engine, and the motor provides zero torque. In everyday driving, this state is primarily entered briefly during shifting or when driving at a constant speed for extended periods, as with highway driving. State 2: Regenerative Braking From previous experimental data acquired during operation of Wisconsin’s hybrid sedan, recirculating currents between four parallel sub-C strings were never observed, as illustrated in figure 9. Furthermore, the packs will be isolated during non-operation. Each pack is composed of 38 prismatic cells and mounted on an aluminum support structure that doubles as a ventilation plenum. An aluminum cover will mimic the original enclosure while integrating the required mounting structure for the Moolander. Figure 10. Side view of several prismatic cells. HYBRID CONTROL CONTROL HARDWARE The Moolander uses a Motorola MPC555 Powertrain Control Module (PCM) embedded controller specifically designed for automotive applications. The PCM, which utilizes software developed by MotoTron, is hermetically sealed and suitable for the under-hood environment. It can withstand temperatures from -40°C to 130°C, acceleration up to 18 g’s, and submersion in 3 m of 8 Regenerative braking (regen) uses the mechanical energy from the wheels to drive the motor, generating electricity for storage in the batteries. This process recharges the battery while decreasing the vehicle speed. The vehicle goes into the regen state if the brake pedal is depressed and the battery pack is not excessively charged. The brake pedal travel is split into two portions. The first 2 cm of travel does not engage the hydraulic brakes – only regenerative braking is used. After 2 cm, regenerative braking is fully saturated and the stock hydraulic brakes engage to help slow the vehicle. This allows the driver to recapture large amounts of kinetic energy during braking, which increases fuel economy in stop-and-go driving. At the same time, “hard” braking must still cause the conventional brakes to invoke the ABS system. The goal of the regen brake system is to maintain “normal” brake pedal feel during regen events. Small orifices were added to the internal bore of the master cylinder with relief to the brake fluid reservoir. Relief holes were added to the front and rear chambers so that the original brake biasing is maintained. The holes were positioned so that a slow depression of the brake pedal allows 2 cm of pedal travel before the conventional brakes are activated. Because this restricts fluid flow, rapid activation of the brake pedal causes the brake line pressure to rise during the first 2 cm of travel. Under slow depression, the fluid will be relieved and the regenerative system will provide the majority of the braking. The control system measures the brake pedal position using a rotary potentiometer mounted on the pedal and adjusts the regenerative braking level accordingly. State 3: HEV The HEV state contains the battery SOC regulating control code that attempts to keep the battery SOC between 20% and 80% for optimal operation (below 20% the battery is incapable of delivering useful assist power, above 80% the battery cannot efficiently absorb adequate regen power). The HEV state implements an internal hysteresis-based state machine that, based on SOC and battery temperature, switches between several curves specifying engine/motor torque versus pedal position. As shown in figure 11, when the battery temperature is in the normal operating range (less than 50°C), the motor torque increases linearly with pedal position from the assist point. The assist point is determined by adding a small offset value to the ensemble averaged pedal position. At temperatures between 50°C and 60°C, the assist algorithm becomes quadratic. At higher temperatures, the quadratic function is multiplied by a de-rating scale factor that decreases linearly from 1 at 60°C to 0 at 70°C. This strategy reduces the load on the motor and requires a larger difference between the average and current pedal positions for motor assist when the batteries are hot. Safety is ensured by range checking all inputs and outputs. If a value entering or leaving the hybrid control system is too low or too high, the control system will adjust the value to the closest bound. Or, if the values are far out of range, indicating a serious hardware error, 9 1 0.9 Temperature<50C Temperature between 50C and 60C Temperature at 65C Temperature at 70C Requested Motor Torque 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.2 0.4 0.6 0.8 1 Current Pedal Position Figure 11. Effect of temperature on the torque assist algorithm assuming an ensemble averaged pedal position of 0.3. the control strategy will disable the electric motor to prevent hazardous operation. State 4: Low Speed ZEV and Engine Off To further improve fuel economy in city driving and reduce emissions, the control strategy implements intermittent engine operation. When the driver does not need the engine, for example when coasting or stopped at a red light, the control strategy shuts the engine down. The engine is automatically restarted when it is needed again. A low speed ZEV mode has also been implemented for speeds less than 16 km/hr. When regenerative braking events are started, the control computer integrates the amp-hrs that are stored in the battery pack. Then, this energy will be used to power the vehicle using only the electric motor until 80% of the previous braking events energy has been consumed. This allows the engine to remain off during low speed “creeping” and will lower emissions while increasing fuel economy. ENVIRONMENTAL IMPACT GREENHOUSE GAS For any IC engine, CO2, the dominant GHGI contributor, is directly related to the quantity of fuel consumed. Once a fuel is determined, the most effective way to minimize CO2 emissions from an engine is to maximize fuel economy. This was one of the primary reasons for selecting a CIDI engine. In an effort to reduce the tailpipe GHGI, idle stop operation was tested on the Aluminum Cow during an FTP test cycle and resulted in a 2-3% improvement in fuel economy. Modal CO2 emissions were recorded and compared. Figure 12 shows a comparison of the instantaneous CO2 emissions from normal and idle stop operation during a portion of the FTP cycle. Between 120 and 160 seconds of the “hot 505” cycle the engine would ordinarily be at idle. With idle stop operation, the CO2 Emissions 5 4 Engine On (Hot & EGR) - Friday Engine Off (Hot & EGR) - Friday drastically, while rich combustion would cause excessive CO and HC emissions. In the case of CI engines, the engine is always operated lean, so 3-way catalyst technology is not applicable. 3 2 Table 10. Efficiency of Emission Control Equipment Emission Total Particulate Matter 110 120 130 140 150 160 170 180 1 0 100 Reduction 90 - 95% >98% >90% >90% >75-80% Fine Particulate Matter CO HC NOx Figure 12. Comparison of modal CO2 emission data recorded during a “Hot 505” FTP chassis dynamometer experiment. engine is shut down during this period so there are no CO2 emissions. When the engine is restarted at 162 seconds, no CO2 spike is observed. The Moolander should experience a 1-3% reduction in GHG emissions when utilizing idle stop and ZEV operation. The other technique for reducing GHG is to use an alternative fuel source that has a large GHG credit. The GHG credit accounts for CO2 recaptured annually by soybeans, corn, or rape seed used in producing the fuel. For CIDI applications at the 2003 competition, the only allowed renewable alternative is a blend of 35% biodiesel. Since biodiesel is an oxygenated fuel, there is a slight energy density penalty. When comparing standard diesel fuel to a typical soybean based B35 blend [8], the engine power will be reduced by only 3.1% while decreasing the GHGI by 25%. For the aforementioned reasons, the Moolander is a ‘grain-fed’ hybrid SUV. EMISSION CONTROL Because catalytic reactions can only reduce pollutants by a set percentage, the first step to reducing tailpipe emissions is to minimize raw engine emissions. The hybrid controller can blend the torque of the electric and IC machines to avoid high pollutant regimes of engine operation. For the CIDI engine, the limiting pollutant that is most difficult to reduce catalytically is NOx. This year, Wisconsin is utilizing a selective catalytic reduction (SCR) system to obtain ULEV, or possibly SULEV, emission levels. High NOx occurs at low engine speed (1000-1400 rpm) and high loads. When not operating in ZEV mode, the hybrid controller heavily assists during launch and the shift schedule has been adjusted to maintain engine RPMs above 1400 rpm, minimizing engine-out NOx. Historically, exhaust emission control has been developed for spark ignition (SI) engines. These engines use closed-loop controls to keep the air to fuel ratio stoichiometric, in a region where the 3-way catalyst technology operates effectively. If the engine was operated lean, the NOx conversion efficiency would drop 10 The Lynx’s original close-coupled direct oxidation catalyst (DOC) reduces approximately 90% of emitted CO, HC, and the soot’s soluble organic fraction. Immediately after the DOC, urea is injected into the exhaust pipe. It is uniformly mixed along 1.5 m of exhaust pipe containing two 90-degree elbows. A lowangle diffusion cone uniformly distributes urea onto the SCR unit. Two Engelhard Corporation SCR units, 11.4 cm and 15.2 cm long, are utilized in the system, as shown in figure 13. The hybrid controller manages the mass flow of urea. Using thermocouples in the exhaust stream, urea is only injected when the SCR catalyst are within their operating region. The engine’s mass air flow sensor and an NTK heated NOx sensor are used to actively control the urea injection quantity. A commercially developed injector, SOBRIS, delivers the urea into the exhaust stream without plugging. The SOBRIS system uses compressed air to transfer the relatively small quantities of urea into the exhaust pipe. The exhaust finally exits the vehicle after it flows through a passive carbon soot filter. The soot filter is PARTICULATE TRAP SCR SCR DIFFUSION CONE Figure 13. Urea system schematic. automatically regenerated when exhaust temperature exceeds 350°C. This system reduced soot levels to 0.0427 g/mile in the 2002 competition. Utilizing the cleaner Lynx engine, Wisconsin estimates soot emissions of 0.03 g/mile in 2003. Overall estimated emission control reduction efficiencies are listed in Table 10 – the Moolander is ULEV compliant. COMPONENT SUMMARY Table 11 provides a summary of the mechanical and electrical components used in the Moolander. The combined hybrid power is 145 kW (198 hp), almost equivalent to the stock Explorer power output of 157 kW (210 hp). The broad torque characteristics of the diesel engine and electric motor will provide smooth, quick acceleration. Table 11. Moolander Component Summary. Component Engine Transmission Motor Manufacturer Ford Borg Warner Delphi Specifications 1.8L CIDI 85 kW at 3800 rpm 250 Nm @ 1850 rpm 5-speed 3.73:1 Diff. Ratio 103 kW peak 40 kW continuous 78 kW ≤ 280 Arms 312 Vdc NiMH 273.6 V (nominal) 1.78 kWhr Direct Oxidation Catalyst and Carbon Soot Filter TELEMETRY SYSTEM A National Instruments FieldPoint cFP-2020 module monitors and records environment variables including battery pack temperature, fuel consumption, speed, torque, and electrical load. For development and testing purposes, this system was installed to provide comprehensive data recording for the vehicle performance and the state of its systems under various loads. Other computers can communicate with the module over a local area network or serial cable link. Figure 14 illustrates the Moolander’s telemetry layout. Inverter Solectria Battery (single pack) Emission Control Panasonic Engelhard Corporation Figure 14. 2003 Moolander telemetry schematic. TELEMATICS The Clarion Joyride provides voice-activated entertainment and navigation capabilities for the driver and passengers of the Moolander. The Joyride includes a radio, CD audio player, and DVD video player, complete with color LCD screen featuring an adjustable viewing angle. In addition, the Joyride is capable of playing MP3s and can provide navigational aid via GPS and point-to-point navigation software with voice recognition. Communication features of the Moolander include an interchangeable cell phone cradle with a connection to the vehicle’s existing stereo system. A TRW Electrically Powered Hydraulic Steering (EPHS) pump was integrated into the Moolander. Eliminating belts, pulleys, and all direct connections to the engine, this system combines an electric motor, pump, electronic control unit, and reservoir into one unit. The flow rate of this unit is between 3.0 L/min and 6.3 L/min, matching the 5.1 L/min demand of the stock rack and pinion steering. The unit runs off the 12-volt system and draws 13-85 amps, depending on load. The EPHS connects to the hybrid controller through the Moolander CAN bus. The controller reduces EPHS power consumption as vehicle speed increases, providing speed-sensitive power steering. VACUUM The Moolander uses an electrically-powered vacuum pump, originally developed for the electric Chevrolet S10 pickup. The mechanical vacuum pump has been removed from the engine to reduce parasitic losses and to ensure power-assisted braking during engine idle stop. AIR CONDITIONING Instead of a conventional belt-driven air conditioning compressor, the Moolander uses a prototype highvoltage electric compressor manufactured by Masterflux. The system includes a permanent magnet brushless DC motor and a variable speed controller to match output to load. The unit uses 200 to 1200 watts of energysignificantly less than a belt-driven compressor. 12-VOLT SYSTEM AUXILIARY SYSTEMS For the 2003 Moolander, a number of parasitic, beltdriven loads were removed from the engine and replaced with electrically powered accessories. This allows the rest of the vehicle to continue functioning when the engine has been shut down during idle stop or low speed ZEV and improves overall system efficiency. POWER STEERING Major components of the 12-volt system in the Moolander include a DC-DC converter and lightweight 11 Table 12. Comparison of FEA and Experimental Frame Results UW-Madison Ford UW-Madison Aluminum Frame Steel Frame Experimental FEA Results FEA Results Results 138.73 lbs 692 N/mm 913 N*m/° 27.70 Hz 28.60 Hz 31.31 Hz 43.45 Hz 299.15 lbs 1981 N/mm 2371 N*m/° 30.76 Hz 34.54 Hz 31.75 Hz 56.51 Hz 195 lbs 904 N/mm 1410 N*m/° 30.7 Hz 36.4 Hz 32.3 Hz 53.6 Hz Weight Vertical Stiffness Torsion Stiffness Mode Shape Torsion Bending In-Plane Matchboxing Lateral starter battery. The Solectria DC-DC converter will serve as the sole 12-volt power source during idle stop and ZEV operation. The Solectria unit is packaged to withstand an under-vehicle environment and was easily integrated into the Moolander. The starter battery is a Johnson Controls Inspira battery that utilizes spiralwound lead acid technology. It delivers up to 2000 A to quickly start the engine in a very light 3 kg package. quenched shortly after being heated to 50-100°C below its melting temperature. Once in the retrogression state, the aluminum can be yielded 25-30%. Pre-bending the material, the aluminum could then be hydroformed into conventional frame rails with front and rear kick-ups. Wisconsin prototyped this idea by having the non-linear frame sections projected into 2-dimensional profiles. These sections were then waterjet cut. Clamping the four sides simultaneously until they touched, the curved frame rails were joined by metal inert gas welding the intersecting corners. The front cross member was fabricating using the same technique. Extrusions developed from this Alumax project were used for the straight frame sections. All mounting brackets were fabricated using 6061-T6 aluminum stock. The initial design was validated by the Budd Company using NASTRAN software (see Table 12). Once fabricated, static deflection and torsional rigidity were measured using dial indicators and vehicle scales. In addition, the frame was suspended from the shock towers by ropes and the frame was excited using a dead-blow hammer. The natural frequencies were determined by using a fast Fourier transform on accelerometer data recorded on an oscilloscope. Several excitation and accelerometer points were recorded and the resultant data is shown in Table 12. The fabricated frame was stiffer and more rigid than FEA analysis predicted. The aluminum frame reduced the vehicle mass by roughly 90 kg. WEIGHT REDUCTION In an effort to reduce the weight of the vehicle, many components were either redesigned using lightweight materials, such as aluminum, or replaced with lighter stock components from other vehicles. According to the aluminum industry, a 20% weight reduction will increase fuel economy 12-16%. Over its lifetime, an aluminumintensive vehicle would save 2,270 to 3,180 liters (500 to 700 gallons) of fuel, worth about $800 in the U.S. and three to four times that in Europe and Japan. ALUMINUM FRAME An aluminum frame was fabricated through a cooperative effort between the University of Wisconsin and ALCOA. The UW AL152 is the completion of an aluminum frame project started by the Alumax Corporation that was since purchased by ALCOA. Using the retrogression heat treating process, a temporary “soft”, high-yield state is produced in 6061-T6 material. Within a few hours it re-ages to a T4 condition and then ages to its original T6 over the next few days. Typically heated using an induction coil, the aluminum is water Figure 15. The front of the UW AL152 frame designed for the 2003 Moolander. 12 Figure 16: 3-D model of the Ford Explorer steel frame from used for FEA modeling. ALUMINUM BUMPERS AND TRAILER HITCH Alcoa Automotive supplied aluminum extruded bumper beams for the front and rear of the vehicle. The trailer hitch has been integrated into the rear bumper, as on the stock Explorer. To reduce the risk of failure in the receiver body, a press-bonded sheet of aluminum and steel was utilized. This cladded material, supplied by Al Metals, facilitates joining of steel and aluminum by welding like materials to their respective sides. In this case, the steel increases the shear capability of the draw pin-hole, while the aluminum allows it to be welded to the bumper. ALUMINUM DRIVESHAFT An aluminum driveshaft minimizes driveline weight and rotating inertia. DynaTech supplied the rear driveshaft, which has an 89 mm aluminum tube and a 1350 series u-joint. The estimated weight reduction will total 3 kg for the driveshaft. Figure 18 illustrates that FEA done in ANSYS verified that the maximum stress within the rotor for a onewheeled landing produces peak stresses 5 to 6 times lower than the yield strength of the 7075-T6 material. Implementing this spindle design not only eliminated a significant source of rotating drag losses but also reduced the vehicle mass by 4.5 kg. Coastdown testing in the fall of 2002 showed that disengaging the front axles and differential reduced rolling resistance by 1.5%. Figure 18. ANSYS analysis of spindle and rotor, with maximum and minimum stresses shown for a load representing all of the vehicle weight on one wheel. Figure 17. “Cookie Cutter” design of the front spindle and brake rotor. WEIGHT REDUCTION SUMMARY Table 13 summarizes the weight reduction achieved in the Moolander. Table 14 summarizes the material content of the Moolander compared to PNGV vehicles. SPINDLE/ROTOR The front spindle design was modified to reduce the mass and rotating losses of the front driveline. Using 7075-T6 aluminum, a ‘cookie-cutter’ design, shown in figure 17, allows the brake rotors to transmit shear forces directly from the brake rotor to the spindle rather than through the wheel studs. The cast aluminum steering knuckle of the 2002 Explorer was modified to accept the steel wheel bearing from a 1999 Ford Ranger. Its auto-locking hub mechanism allows the front driveline to completely disengage at the hubs. By disengaging the hubs when not in four-wheel drive, the front wheel drive components are completely isolated and all spinning losses from the front driveshafts and differential are eliminated. Table 13. Summary of Mass Reduction Stock 177.8 kg 20.83 kg 19.96 kg 333.4 kg 1548.01 kg 2100 kg Moolander 88.9 kg 2.95 kg 3.13 kg 203.4 kg 1606.62 kg 1905 kg Component Frame Starter Battery Fuel Tank Drivetrain Other Total Mass 13 Summary of Materials in the Moolander versus a PNGV Vehicle. % in PNGV % in UW Material UW Mass (kg) by Mass by Mass Ferrous Metals 24.0 58.9 1122 Aluminum 36.7 19.2 365 Magnesium 4.3 0.04 0.8 Titanium 0.6 0.10 2 Plastic 13.5 12.6 240 Other 11.1 2.1 39.8 Rubber 6.2 4.2 79.5 Glass 1.8 2.8 52.4 Lexan 1.5 0.07 1.3 Carbon Fiber 0.4 0.12 2.2 Total Mass 100 100 1905 DRAG REDUCTION As shown in Equation (4) of the “Keys to Increasing Fuel Economy” section, the second most significant factor that contributes to a vehicle’s power demand is aerodynamic drag. This loss is dependent on several factors; however, frontal area profile, drag coefficient, and rolling resistance are the only factors that can be influenced by design. AERODYNAMIC DRAG At the time of modeling, the competition rules did not allow modification to the overall vehicle length or width, thus limiting potential aerodynamic improvements. Nevertheless, the vehicle was modeled in FLUENT, a computational fluid dynamics analysis package. Using a 2-dimensional representation of the Explorer, shown in figure 16, FLUENT was used to investigate front and rear spoilers. Unfortunately, no significant drag reductions were found. Force (N) 30 Table 14. P255/70R16 tires reduced the vehicle rolling resistance by 5% over the stock Michelin P235/70R16 tires. 40 35 25 20 Goodyear Goodyear Engaged Michelin Michelin Engaged 15 0 10 20 30 40 50 Vehcile Speed (m/s) Figure 20. Coastdown data comparing Goodyear and Michelin tires with and without the front axles and differential spinning. PSAT MODEL Wisconsin utilized PSAT to estimate the performance characteristics of the Moolander. PSAT is a zerodimensional, forward-looking vehicle model, which operates within MATLAB v5.3 and Simulink v3. Each vehicle component and parameter is characterized using a separate module. This allows each module to be modified and verified independently as parametric changes are implemented. MODELING APPROACH To verify the accuracy of PSAT, a stock V-6 four-wheel drive Explorer was modeled. As reviewed in Table 14, the PSAT urban fuel-economy prediction almost 14 Figure 19. Aerodynamic drag modeling of the Ford Explorer using FLUENT. TIRES Equation (3) shows that the vehicle power loss is directly proportional to the tires’ rolling resistance. Wisconsin has opted to use Goodyear’s low rolling resistance tires. Recording coastdowns using a radar gun at a local airport, it was determined that the Goodyear matched the published EPA values. The highway prediction was 12.8% low. Once the accuracy of the PSAT architecture was verified, a hybrid model of the Moolander was developed. MODELING RESULTS After a PSAT model was developed for the Moolander, the model was exercised to study the effects of different vehicle masses and shift schedules on fuel economy. The 2003 configuration was modeled at a vehicle mass of 1905 kg (4200 lb) with the appropriate components. The 2003 Moolander is estimated to achieve a combined fuel economy of 16.05 km/L, nearly double the stock vehicle fuel economy. required safety feature for competition. Inline fuses protect against serious battery faults, and an inertia switch will isolate the high voltage system in the event of a crash. A Bender ground fault detection system continuously monitors for a high voltage ground fault condition. If this hazardous condition occurs, the system signals an audible alarm inside and visible alarm outside the vehicle and disables the hybrid drive. BATTERY THERMAL CONSIDERATIONS The battery pack for the 2003 Moolander utilizes the OEM blower and cooling system. Battery pack temperatures are continuously monitored; blower speed is controlled by the hybrid controller and is proportional to battery temperature. Additionally, a redundant thermostatically controlled system, independent of the hybrid controller, will also activate the blower if the battery temperature is excessive. The blower is operated continuously during charging. CONTROL STRATEGY CONSIDERATIONS The control strategy has been designed with a safety state—any abnormal signal levels will cause it to activate the safety state. For example, the gas pedal signal is typically between 0.9 V and 4.2 V. If there were a lowside fault, the signal would go up to 5 V, and it would be apparent that a failure has occurred. The control strategy will recognize this discrepancy and hybrid operation would be disabled. Similarly, if the battery voltage ever approaches an extreme value or if the motor controller stops providing feedback to the hybrid control system, the strategy automatically defaults to a safety state disabling the electric drive and alerting the driver. The Moolander CAN bus also demonstrates the robustness and safety of the vehicle. Many critical vehicle variables, such as driver inputs and electric drive control commands, are communicated over the CAN bus. In addition to the error checking built into the CAN protocol, the Moolander uses a dual CAN system. Identical signals are transmitted over each CAN bus, providing for a highly reliable data transmission. DFMEA ANALYSIS In designing the Moolander, appropriate design techniques were used to minimize component failures and insure the safety of persons both inside and outside the vehicle. MECHANICAL CONSIDERATIONS Safety factors were considered in all components, and FEA analysis was performed for any structural parts that were modified. Splines were used instead of keyways on all rotating components and locking devices— locknuts, safety wire, or threadlocker—were used on all critical fasteners. Coated fasteners and rivets were used to minimize galvanic reactions with the aluminum frame. ELECTRIC DRIVE SYSTEM The temperatures of the inverter, electric motor, and battery pack are continuously monitored. Power levels are limited as values approach unsafe levels. If the temperatures exceed extreme limits, the electric drive will be totally disabled and the driver alerted. ELECTRICAL CONSIDERATIONS The Moolander has two emergency disconnect switches (EDS), one in the dashboard and one on the rear bumper, that will isolate the entire high voltage system and shut down the engine when depressed. These would not be installed in a production vehicle but are a Table 15. PSAT Fuel Economy Results Urban (km/L) Stock Explorer Published Stock Explorer PSAT Moolander PSAT 7.09 Highway (km/L) 10.90 EPA Composite (km/L) 8.41 INTENDED MARKET The intended market for the Moolander is similar to that of a typical light-duty SUV. SUVs are designed for consumers desiring a stylish vehicle with good power and traction for towing heavy loads, traveling in poor weather, or traversing rough terrain. Because of its low emissions and high fuel economy, this vehicle will be especially attractive to environmentally conscious and forward-thinking consumers. In addition to retaining the original look and feel of the Explorer, several features have been incorporated to enhance the consumer acceptability of the vehicle. A 15 7.06 15.05 9.50 17.05 7.98 16.05 DVD player and LCD screen have been integrated for use by passengers in the second and third rows of seating. An infotainment system including navigation (GPS), voice recognition, radio, CD player, and handsfree cell phone has been installed for the driver. In modifying the vehicle, care was taken to preserve the full passenger capacity and cargo room found in the stock Explorer. Turnkey start up, air conditioning, cruise control, and power windows are a few of the many attractive vehicle features. The Moolander can also haul 907 kg and is equipped with four-wheel drive. COST ANALYSIS Depending on manufacturer and dealer markup, the cost of the Moolander to the consumer could be competitive with that of a stock Explorer. Wisconsin projects the volume production cost of the Moolander to be $35,975. Price estimates are based on current Explorer retail prices, with an MSRP of $34,500. Table 16 lists the assumptions and prices used to calculate the production cost of the Moolander. The following is a list of assumptions made in the cost analysis. • • • • • Labor costs would be comparable All costs have been assessed in year 2003 dollars 10,000 vehicles are manufactured each year on an existing vehicle platform The cost of the Moolander’s conventional drivetrain is equal to that of a stock Explorer All other components are stock Explorer parts MANUFACTURING POTENTIAL Component selection for the Moolander was based on functionality, ease of procurement, maintainability, and manufacturability. This vehicle can be produced using existing production line technology, and the drivetrain can be installed as a single unit, much like today's current truck production techniques. To further improve manufacturability, some features of the Moolander would be implemented differently in a mass produced vehicle. Some components could be manufactured lighter and less costly using mass production techniques. Incorporating these modifications into the existing design prior to developing the assembly line would significantly reduce the time and cost associated with production. Table 16. Moolander Production Cost Estimates. UW Prototype Production Cost Cost Stock Vehicle Motor/Inverter Controller Batteries Al. Components Entertainment System Total 1 2 3 $24,500 $10,000 $500 $7,000 $500 $5000 $47,500 $24,500 $3,500 $350 $3,800 1 2 3 $1825 $2000 $31,275 40% net manufacturer – dealer markup assumed for stock Explorer. 75% mass production discount for all electronic components. $3100 battery pack cost to dealer. 44% manufacturer markup assumed. 16 SUMMARY Wisconsin has successfully converted a 2002 Ford Explorer into an electric assist, charge-sustaining, fourwheel drive parallel hybrid-electric vehicle. Utilizing a 1.8L CIDI engine (85 kW), a five-speed transmission, a two-speed transfer case, and an EV1 traction motor (60 kW), Wisconsin has minimized components and complexity in creating a unique hybrid powertrain. In an effort to minimize greenhouse gas emissions, mass was reduced, the drivetrain was hybridized to maximize city fuel economy, and B35 fuel was utilized to minimize upstream greenhouse gas factors. Aluminum components were used whenever possible, including the frame, to minimize weight. Matching the capacity of the traction motor, motor controller, and the high voltage battery has resulted in a lightweight, fuel-efficient hybrid design. Using the PSAT model, it is estimated that the hybrid powertrain will double the Moolander’s fuel economy compared to its stock counterpart from 7.98 km/L to 16.05 km/L. During initial dynamometer testing, the Moolander achieved 16.36 km/L. A chemi-luminsecnt NOX analyzer was used to test initial SCR effectiveness at steady state engine loads. The SCR system reduces NOX emissions between 70-80%. Wisconsin has one month to optimize the hybrid design and to dynamically test the SCR system. The Moolander is a highly recyclable, highly manufacturable, prototype hybrid SUV that is capable of achieving one-fourth the GHGI of the stock vehicle. Figure 21. Moolander during initial dynamometer testing in the Phil Meyers Student Automotive Laboratory at the University of Wisconsin. Figure 22. Moolander exiting the off-road course at Ford Arizona Proving Grounds. 17 REFERENCES 1. Marshaus, Ramnarine, et al., “Development of the University of Wisconsin's Parallel Hybrid-Electric Sport Utility Vehicle,” SAE Special Publications March 2000, SAE. 2. Bayer, Koplin, et al., “Optimizing the University of Wisconsin’s Parallel Hybrid-Electric Aluminum Intensive Vehicle,” SAE Publications March 1999, SAE. 3. Bower, G.R., et al., “Design of a Charge Regulating, Parallel Hybrid Electric FutureCar,” SAE Publications February 1998, SAE 980488. 4. Johnston, Brian, et al., “The Continued Design and Development of the University of California, Davis FutureCar,” SAE Publications February 1998, SAE 980487. 5. Thomas, C.E., et al., “Societal Impacts of Fuel Options for Fuel Cell Vehicles,” SAE Publications October 1998, SAE 982496. 6. PNGV Battery Test Manual, U.S. DOE, Idaho National Engineering Laboratory, DOE/ID-10597, Jan. 1997. 7. 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. 8. Scholl, K. and Sorenson, S., “Combustion of Soybean Oil Methyl Ester in a Direct Injection Diesel Engine,” 1993, SAE 930934. 9. Tree, D., et al; “Emission Tests of Diesel Fuel with NOx Reduction Additives,” 1993, SAE 932736. 10. Weiss, M.A., et al., “On the Road in 2020: A lifecycle analysis of new automobile technologies,” 2000, Energy Laboratory Report #MIT EL 00-003. 11. Rowe, R.F., et al., “Design and Optimization of the University of Wisconsin's Parallel Hybrid-Electric Sport Utility Vehicle” SAE Publications March, 2002, SAE 2002-01-1211. 12. Marshaus, J.G., et al., “Safety Aspects Related to the Development of a Full Aluminum Frame for the year 2000, 1500 Series Chevy Suburban,” Crashworthiness of Composites and Light Weight Structures, AMD Vol. 205 MD Vol. 96, ASME 2001. 13. Helgren, J.M., et al., “Design and Development of the University of Wisconsin’s Parallel Hybrid Electric Sport Utility Vehicle” SAE Publications March, 2003, SAE 2003-01-1259. 14. Andress, D., “Ethanol Energy Balances,” Nov. 2002. 15. Sheehan, J., et al., “An Overview of Biodiesel and Petroleum Diesel Life Cycles,” May 1998, NREL/TP580-24772. 16. www.shelloil.com APPENDIX A. SYMBOL LIST 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 truck (~4.169 m^2) Cd = drag coefficient (~.446) Crr = coefficient of rolling resistance (~.006) APPENDIX B. USE OF ALUMINUM Aluminum provides many advantages over alternative materials in vehicle production. Beneficial characteristics of aluminum include desirable energy absorption and crashworthiness, versatility in design, high elasticity, high strength-to-weight ratio, reduced noise and vibration, and resistance to corrosion and rustrelated failures. In the manufacturing process, lighter aluminum can mean easier mobility of material. In addition, dies used for aluminum are less expensive than those used for harder steel due to the ease of working and forming aluminum. Production and development of aluminum-intensive vehicles have generated the following results: • • • • • 45-55% body structure weight reduction 25-35% increased torsional rigidity Up to 50% assembly parts consolidation Improved crash performance Dramatic reduction in tooling costs Issues to address with aluminum include the higher cost of raw material and lower stiffness (by a factor of three) in comparison to steel. 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 MIG welded together. Aluminum tends to respond well to MIG and MIGimpulse welding. For high-quality joints, TIG welding is also used. Table A.1. Material Properties for Aluminum and Steel. Alloy & Temper Ultimate Yield Modulus of Strength Strength Elasticity (ksi) (ksi) (ksi) Alum. 2014-T6, T651 Alum. 6061-T6, T651 Alum. 7075-T6, T651 Steel 1020 HR Steel 1018 A 18 70 42 83 66 49.5 60 37 73 42 32 10.6 10.0 10.4 30 30