Hyper Seminar Original

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HYPERCAR SEMINAR REPORT 2014-2015

ABSTRACT Designing and making cars differently ± emphasizing ultra light weight,

ultralow drag, and integrated design ± can reduce required propulsive power by

about two-thirds. This can make direct-hydrogen fuel cells and commercially

available compressed-hydrogen-gas tanks practical and affordable even at

relatively high early prices. Coordinating such vehicles with deployment of fuel

cells in buildings permits a rapid transition to a climate-safe hydrogen economy

that is profitable at each step starting now.

New manufacturing and design methods can also make these radically more

efficient vehicles cost-competitive and uncompromised, as illustrated by a 2.38-

litre-equivalent-per-100-km midsize sport-utility concept car designed in 2000 by

Hyper car, Inc. Major reductions in the required capital, assembly, space, and

product cycle time can offer key competitive advantages to early adopters. These

changes are increasingly recognized as portents of unprecedented technological

and market transitions that can make cars climate-safe and the car and oil

industries more benign and profitable.

INTRODUCTION

DEPT. OF MECHANICAL ENGINEERING M.T.I THRISSUR

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The hypercar design concept combines an ultralight, ultra-aerodynamic

autobody with a hybrid-electric drive system. This combination would allow

dramatic improvements in fuel efficiency and emissions. Computer models predict

that near-term hypercars of the same size and performance of today’s typical 4–5

passenger family cars would get three times better fuel economy. In the long run,

this factor could surpass five, even approaching ten. Emissions, depending on the

power plant, or APU, would drop between one and three orders of magnitude,

enough to qualify as an “equivalent” zero emission vehicles (EZEV).

In all, hypercars’ fuel efficiency, low emissions, recyclability, and durability

should make them very friendly to the environment. However, environmental

friendliness is currently not a feature that consumers particularly look for when

purchasing a car. Consumers value affordability, safety, durability, performance,

and convenience much more. If a vehicle can not meet these consumer desires as

well as be profitable for its manufacturer, it will not succeed in the marketplace.

Simply put, market acceptance is paramount. As a result, hypercars principally

strive to be more attractive than conventional cars to consumers, on consumers’

own terms, and just as profitable to make.

HISTORY


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Since 1991, Rocky Mountain Institute, a 15-year-old, 43-person

independent non profit resource policy centre, has applied to cars its experience

from advanced electric end-use efficiency. In many technical systems, buildings,

motors, lights, computers, etc., big electrical savings can often be made cheaper

than small savings by achieving multiple benefits from single expenditures. The

marginal cost of savings at first rises more and more steeply (“diminishing

returns”), but then often “tunnels through the cost barrier” and drops down again,

yielding even larger savings at lower cost. RMI hypothesized that the same might

be possible in cars. By 1993, this concept had been established and published and

by 1995 it refined into papers advised by hundreds of informants; and by 1996,

expanded into a major proprietary study emphasizing manufacturing techniques

for high volume and low cost.

Most big changes in modern cars were driven either by government

mandate, subsidy, or taxation motivated by externalities, or by random

fluctuations in oil price. However, the more fundamental shift to hypercars can

instead be driven by customers’ desire for superior cars and manufacturers’ quest

for competitive advantage. Customers will buy hypercars because they’re better

cars, not because they save fuel—just as people buy compact discs instead of vinyl

records. Manufacturers, too, will gain advantage from hypercars’ potentially lower

product cycle time, tooling and equipment investment, assembly space and effort,

and body parts count. Since these features offer decisive competitive advantage to

early adopters, RMI chose in 1993 not to patent and auction its intellectual


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property, but rather, like the open- software development model, to put most of it

prominently into the public domain and maximize competition in exploiting it. In

late 1993, the concept won the Nissan Prize at ISATA (the main European car-

technology conference); in 1994, it was the subject of an ISATA Dedicated

Conference, and began attracting considerable attention. By late 1995, RMI was

providing compartmentalized and nonexclusive support, strategic and technical, to

about a dozen automakers and a dozen intending automakers from other sectors

(such as car parts, electronics, aerospace, polymers, and start-ups, including a

number of alliances and virtual companies).

PRINCIPLES OF HYPERCAR DESIGN


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After a century’s devoted effort by excellent engineers, only ~15–20%

of a modern car’s fuel energy reaches the wheels, and 95% of that moves the car,

not the driver, so only 1% of fuel energy moves the driver. This is not very

gratifying. Its biggest cause is that cars are conventionally made of steel—a

splendid material if mass is either unimportant or advantageous, but heavy enough

to require for brisk acceleration an engine so big that it uses only 4% of its power

in the city, 16% on the highway. This mismatch halves an Otto engine’s

efficiency. Rather than emphasizing incremental improvements to the driveline,

the hypercar designer starts with platform physics, because each unit of saved road

load can save in turn ~5–7 units of fuel that need no longer be burned in order to

deliver that energy to the wheels.

Thus the compounding losses in the driveline, when turned around

backwards, become compounding savings. In typical flat-city driving (Fig. 2),

road loads split fairly evenly between air resistance, rolling resistance, and

braking. Hypercars could have lower curb mass, lower aerodynamic drag, ´ lower

rolling resistance, and lower accessory loads than conventional production

platforms. In a near-term hypercar, irrecoverable losses to air and road drag

plummet. Wheel power is otherwise lost only to braking, which is reduced in

proportion to gross mass and largely regenerated by the wheel motors (70%

recovery wheel-to-wheel has been demonstrated at modest speeds). The hybrid

decouples engine from wheels, eliminating the part-load penalty of the

Otto/mechanical drive train system, so the savings multiplier is no longer 5–7%


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but only ~2–3.5%. Nonetheless, even counting potentially worse conditions in

high-speed driving (because aero drag rises as the cube of speed and there’s less

recoverable braking than in the city), the straightforward parameters illustrated

yield average economy ~41 km/l.7

ULTRALOW DRAG

Hypercars would combine very low drag coefficient CD with compact

packaging for low frontal area A. Several concept cars and GM’s productionized

EV-1 have achieved on-road CD 0.19 (vs. today’s production average ~0.33 and

best production sedan 0.255, or Rumpler’s 0.28 in 1921). With a longer platform’s

lesser rear-end discontinuity; Ford’s 1980s Probe concept cars got wind-tunnel CD

0.152 with passive and 0.137 with active rear-end treatment. Some noted

aerodynamicists believe £0.1, perhaps ~0.08, could be achieved with passive

boundary-layer control analogous to the dimples on a golf-ball. Between that

idealized but perhaps ultimately feasible goal and the 1996 reality of 0.19 lie many

linked opportunities for further improvement without low clearance or excessively

pointy profile.3, 7 Thin-profile recumbent solar race cars illustrate how well side

wind response can be controlled, as in the Spirit of Biel III’s on-track CD of 0.10

at 0° yaw angle but just over 0.08 at 20°.

Production cars have A £2.3 (US av.) to 1.8 m2 (4-seat Honda DX);

well-packaged 4-seat concept cars, 1.71 (GM Ultralite) to 1.64 (Renault Vesta II).

For full comfort, we assume 1.9 for 4–5 or 2.0 for 6 (3+3) occupants. Rolling

resistance is reduced proportionally to both gross mass and coefficient of rolling


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resistance r0. Steel drum test values of r0 are 0.0062 for the best mass produced

radial tires, 0.0048 for the lowest made by 1990 (Goodyear), and the low 0.004s

for the state of the art. On pavement, with toe-in but not wheel-bearing friction, we

assume the EV-1’s empirical 0.0062 (Michelin), which might be further reduced

without sacrificing safety or handling. Such tires are typically hard and relatively

narrow, increasing pressure over the contact patch to help compensate for the car’s

light mass. The wheel motors, being precise and ultra strong digitally controlled

servos, could also be designed to provide all-wheel anti-slip traction and antilock

braking superior to those now available.

ULTRALIGHT MASS

Today’s production platforms have curb mass mc ~1.47 t (RMI’s

simulations add 136 kg for USEPA test mass). Some 1980s concept cars made of

light metal achieved mc <650 kg (Toyota 5-seat AXV diesel 649 kg, Renault 4-

seat Vesta II 475, Peugeot 4-seat ECO 2000 449). But advanced composites can

do better, with carbon-fibre composites acknowledged by Ford and GM experts to

be capable of up to a 67% body in- white (BIW) mc reduction from the 273-kg

steel norm without/372 kg with closures—to ~90/123 kg, vs. the 5- seat Ultra

Light Steel Auto Body’s 205/– kg or the 5–6- seat Ford Aluminium-Intensive

Vehicle’s 148/198 kg. RMI assumes near-term advanced-composite 4–5-seat

BIWs not of 90/123 kg but ~130/150.3,4 In contrast, the 4-seat Esoro H301’s BIW

weighed only 72/150 (using lighter-than-original bumper and door designs for

comparability) far below the carbon GM Ultralite’s 140/191, even though 75% of


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the Esoro’s fiber was glass, far heavier than carbon fibre.2 Of carbon-and-aramid

BIWs, Viking 23’s (1994) weighed 93 kg with closures, while Esoro composites

expert Peter Kägi’s 1989 2-seat OMEKRON’s weighed only 34 kg without

closures. Though these examples differ in spaciousness and safety, they confirm

carbon fibre’s impressive potential for BIW mass reduction. A 115-line-item mass

budget benchmarked to empirical component values indicates that a 130/150-kg

BIW corresponds to mc ~521 kg. Near-term values for a full-sized 3+3 sedan

range upwards to ~700 kg but can be reduced at least to ~600 kg with further

refinement.

Advanced composites are used in Hypercars they offer the greatest

potential for mass reduction. Reducing a vehicle's mass makes it peppier and/or

more fuel-efficient to drive, nimbler to handle, and easier to stop. Experts from

various U.S. and European car companies have estimated that advanced composite

auto bodies could be up to 67 percent lighter than today's steel versions. In

comparison, aluminium is estimated to be able to achieve a 55-percent mass

reduction, and optimized steel around 25-30 percent. So for mass reduction and

fuel economy, advanced composites look especially promising. Their superior

mechanical properties allow them largely to decouple size from mass enabling cars

to be roomy, safe, and ultralight.

HYBRID-ELECTRIC DRIVE


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Hypercars build on the foundation of recent major progress in electric

propulsion, offering its advantages without the disadvantages of big batteries.

Batteries’ deliverable specific energy is so low (~1% that of gasoline) that, as P.D.

van der Koogh notes, “Battery cars are cars for carrying mainly batteries ,but not

very far and not very fast, or else they’d have to carry even more batteries.” This

nicely captures the mass compounding snowballing of weight that limits battery

cars, good though they’re becoming, to niches rather than to the general-purpose

family-vehicle role that dominates at least North American markets. It is

unimportant to this discussion whether Hypercars use series or parallel hybrids.

Both approaches, and others, may offer advantages in particular market segments.

Either way, an onboard auxiliary power unit (APU) converts fuel into electricity as

needed; the APU can be an internal- or external-combustion engine, fuel cell,

miniature gas turbine, or other device. The electricity drives special wheel motors

(conceivably hub motors, but at least in early models probably mounted inboard to

manage sprung/unsprung mass ratios).

The motors may be direct drive or use a single gear, though some designs

might benefit from two gear ratios. A load-levelling device (LLD) buffers the

APU, temporarily stores recovered braking energy, and augments the APU’s

power for hill climbing and acceleration. The LLD can be a high specific- power

battery, ultracapacitor, superflywheel, or combination, typically rated at ~30–50

peak kW. High braking-energy recovery efficiency and reducing the APU map

nearly to a point require high kW/kg plus excellent design and controls.


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Fuel cells are also used as APU because they're very efficient,

produce zero or near-zero emissions (depending on the type and origin of the fuel

used), could be extremely reliable and durable (since they have almost no moving

parts), and could offer a high degree of packaging flexibility. Currently, however,

they're very expensive because they're not produced in volume, and a widespread

refuelling infrastructure doesn't yet exist for some of the fuels considered for their

use. Fuel cells generate electricity directly by chemically combining stored

hydrogen with oxygen from the air to produce electricity and water. The hydrogen

can be either stored onboard or derived by "reforming" gasoline, methanol, or

natural gas (methane). Reforming carbon-containing fuels generates more

emissions than using hydrogen created directly with renewable energy, but these

fuels are much more readily available and may be used as a transitional step until a

hydrogen infrastructure develops. Fuel-cell technology has advanced significantly

in the past few years, and a handful of automakers have shown prototype fuel-cell-

powered vehicles. However, these prototypes have been quite heavy, requiring

large (and therefore expensive) fuel-cell power plants, which have led some

observers to predict that it may take 15 to 20 years for fuel cells to become

economical. Yet Hypercar® vehicles could accelerate the adoption of fuel cells,

because the Hypercar® vehicle's much lower power requirements would require

far less fuel-cell capacity than a heavy, high-drag conventional car.

REVOLUTION CONCEPT CAR DESIGN


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OVERVIEW

The Revolution fuel-cell concept vehicle was developed by Hypercar, Inc. in

2000 to demonstrate the technical feasibility and societal, consumer, and

competitive benefits of holistic vehicle design focused on efficiency and

lightweighting. It was designed to have breakthrough fuel economy and emissions,

meet US and European Motor Vehicle Safety Standards, and meet a rigorous and

complete set of product requirements for a sporty five-passenger SUV crossover

vehicle market segment with technologies that could be in volume production

within five years (Figure 1).

Fig. 1 Revolution concept car photo and layout

The Revolution combines lightweight, aerodynamic, and electrically and

thermally efficient design with a hybridized fuel-cell propulsion system to deliver

the following combination of features with 857 kg kerb mass.2.

Seats five adults in comfort, with a package similar to the Lexus RX-300

(6% shorter overall and 10% lowers than a 2000 Ford Explorer but with

Slightly greater passenger space)

1.95-m3 cargo space with the rear seats folded flat


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2.38 L/100km (99 miles per US gallon) equivalent, using a direct-hydrogen

fuel cell, and simulated for realistic US driving behaviour

530-km range on 3.4 kg of hydrogen stored in commercially available 345-

bar tanks

Zero tailpipe emissions

Accelerates 0±100 km/h in 8.3 seconds

No body damage in impacts up to 10 km/h (crash simulations are described

below)

All-wheel drive with digital traction and vehicle stability control

Ground clearance adjustable from 13 to 20 cm through a semi-active

suspension that adapts to load, speed, location of the vehicle's centre of

gravity, and terrain

Body stiffness and torsional rigidity 50% or more higher than in premium

sports sedans

Designed for a 300 000á-km service life; composite body not susceptible to

rust or fatigue

Modular electronics and software architecture and customizable user

interface

Potential for the sticker price to be competitive with the Lexus RX-300,

Mercedes M320, and BMW X5 3.0, with significantly lower lifecycle cost.

LIGHTWEIGHT DESIGN


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Every system within the Revolution is significantly lighter than

conventional systems to achieve an overall mass saving of 52%. Techniques used

to minimize mass, discussed below, include integration, parts consolidation, and

appropriate application of new technology and lightweight materials. No single

system or materials substitution could have achieved such overall mass savings

without strong whole-car design integration. Many new engineering issues arise

with such a lightweight yet large vehicle. While none are showstoppers, many

required new solutions that were not obvious and demanded a return to

engineering fundamentals.

For example, conventional wheel and tyre systems are engineered

with the assumption that large means heavy. The low mass, large size and high

payload range relative to vehicle mass put unprecedented demands on the

wheel/tyre system. Hypercar, Inc. collaborated with Michelin to design a solution

that would meet these novel targets for traction and handling, design appeal, mass,

and rolling resistance. Another challenge in this unusual design space is vehicle

dynamics with a gross mass to kerb mass ratio around 1.5 (1300 kg gross

mass/857 kg kerb mass). To maintain consistent and predictable car-like driving

behaviour required an adaptive suspension. Most commercially available versions

are heavy, energy-hungry, and costly. Hypercar, Inc. collaborated with Advanced

Motion Technology, Inc. (Ashton, MD) to design a lightweight semi-active

suspension system that could provide variable ride height, load levelling, spring

rate, and damping without consuming excessive amounts of energy. Other unique


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challenges addressed included crosswind stability, crashworthiness, sprung-to-

unsprung mass ratio, and acoustics.

EXTERIOR STYLE AND AERODYNAMICS

The Revolution concept vehicle is designed as a mid-sized, entry-level luxury

sport- utility crossover vehicle (i.e., combining sport-utility with passenger car

characteristics). Its design is contemporary and attractive but aerodynamic.

Fig. 2 An Example Of Aerodynamic Analysis

Some of the aerodynamic features include:

a smooth underbody that tapers up toward the rear to maintain neutral lift

underbody features that limit flow out of the wheel wells

tapered roofline and rear `waistline'

clean trailing edge

rounded front corners and A-pillar

gutter along roofline to trip crosswind airflow

radiator intake at high-pressure zone on vehicle nose

wheel arches designed to minimize wheel-induced turbulence


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aerodynamic door handles.

In addition to the `fixed' design features, other systems also contribute to

the Revolution's aerodynamic performance. For example, the suspension system

lowers ride height during highway driving to minimize frontal area. Also, the

suspension and driveline components do not protrude significantly below the floor

level; this maintains smooth underbody airflow and minimizes frontal area.

Having the rear electric motors in the wheel hubs also eliminates the need for a

driveshaft and differential under the vehicle.

POWERTRAIN

The Revolution powertrain design integrates a 35kW ambient pressure

fuel cell developed by UT Fuel Cells, 35kW nickel metal hydride (NiMH) buffer

batteries, and four electric motors connected to the wheels with single-stage

reduction gears. Three 34.5MPa internally regulated Type IV carbon-fibre tanks

store up to 3.4 kg of hydrogen in an internal volume of 137 L (Fig 3).

The fuel cell system's near- ambient inlet pressure replaces a costly and

energy-intensive air compressor with a simpler and less energy-intensive blower,

raising average fuel efficiency and lowering cost. The commercially available foil-

wound NiMH batteries provide extra power when needed and store energy

captured by the electric motors during regenerative braking. The _3kWh of stored

energy is sufficient for several highway-speed passing manoeuvres at gross


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vehicle mass at grade, and can then gradually taper off available power until the

batteries are depleted, leaving only fuel-cell power available for propulsion until

the driving cycle permits recharging.

Fig3: Revolution Component Packaging

The front two electric motors and brakes are mounted inboard,

connected to the wheels via carbon-fibre half shafts. This minimizes the unsprung

mass of the front wheels and saves mass via shared housing and hardpoint

attachments for the motors and brakes. The front motors are permanent magnet

machines, each peak-rated at 21kW. The rear witched reluctance motors are each

10 peak kW, so they're light enough to mount within the wheel hubs without an

unacceptable sprung/unsprung mass ratio. Hubmotors also allow a low floor in the

rear, and improve underbody aerodynamics by eliminating driveshaft, differential,

and axles. The switched reluctance motors also have low inertia rotors and no

electromagnetic loss when freewheeling, improving overall fuel economy


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especially at high speed. More efficient four-wheel regenerative braking is also

possible with this system, further increasing fuel economy.

Proprietary innovations within the Revolution manage and distribute

power among the drive system components. Powertrain electronics are currently

expensive, and typical fuel cell systems require extensive power conditioning

(using a DC -- DC converter) to maintain a consistent voltage, since at full power,

the stack voltage drops to approximately 50% of its open circuit voltage.

Hypercar, Inc. developed a power electronics control methodology that simplifies

power conditioning while optimally allocating power flows under all conditions.

This cuts the size of the fuel cell DC -- DC converter by about 84%, reducing

system cost, and improves power distribution efficiency, increasing fuel economy.

The normal doubling of radiator size for a fuel cell vehicle doesn't handicap the

Revolution because its tractive load, hence stack size, are reduced more than that

by superior platform physics. The Revolution's cooling system efficiently

regulates the temperature of each powertrain component without resorting to

multiple cooling circuits, which would add weight and cost.

The common-rail cooling has a branch for each main powertrain

component and a small secondary loop for passenger compartment heating. This

loop also includes a small hydrogen-burning heater to supply extra start-up heat

for the passengers when required (though this need is minimized by other aspects

of thermal design). The variable-speed coolant pump, larger-diameter common rail


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circuit, and electrically actuated thermostatic valves ensure sufficient cooling for

all components without excessive pumping energy.

The Revolution's fuel economy was modelled using a second-by-

second vehicle physics model developed by Forschungsgesellschaft

Kraftfahrwesen mbH Aachen (`FKA'), Aachen, Germany. All fuel-economy

analyses were based on the US EPA highway and urban driving cycles, but with

all speeds increased by 30% to emulate real-world driving conditions. Each

driving cycle was run three times in succession to minimize any effect of the

initial LLD state of charge on the fuel economy estimate. In addition to fuel

economy, Hypercar, Inc. simulated how well the Powertrain would meet such load

conditions as start-off at grade at gross vehicle mass, acceleration at both test and

gross vehicle mass, and other variations to ensure that the vehicle would perform

well in diverse driving conditions. Illustrating the team's close integration to

achieve the whole-vehicle design targets, the powertrain team worked closely with

the chassis team to exploit the braking and steering capabilities allowed by all-

wheel electric drive to create redundancy in these safety-critical applications. The

powertrain, packaging, and chassis teams also worked closely together to

distribute the mass of the Powertrain components throughout the vehicle in order

to balance the vehicle and keep its centre of gravity low.


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STRUCTURE

ALUMINIUM AND COMPOSITE FRONT END

The front end of the Revolution body combines aluminium with

advanced composites using each to do what it does best (Fig 4). The front bumper

beam and upper energy-absorbing rail are made from advanced composite. The

rest of the front-end structure is aluminium, with two main roles: to attach all the

front-end Powertrain and chassis components, and as the primary energy-

absorbing member for frontal collisions greater than 24 km/h. Aluminium could

do both tasks with low mass, low fabrication cost (simple extrusions and panels

joined by welding and bonding), and avoidance of the more complex provision of

numerous hardpoints in the composite structure.

Fig4: Aluminium And Composite Front End


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COMPOSITE SAFETY CELL

The overarching challenge to using lightweight materials is cost-

effectiveness. Since polymers and carbon fibre cost more per kilogram and per

unit stiffness than steel, their structural design and manufacturing methods must

provide offsetting cost reductions. Hypercar, Inc.'s design strategy minimized the

total amount of material by optimal selection and efficient use; simplified and

minimized assembly, tooling, parts handling, inventory, scrap, and processing

costs; integrated multipurpose functionality into the structure wherever practical;

and employed a novel manufacturing system for fabricating the individual parts.

OCCUPANT ENVIRONMENT

The occupant environment typically accounts for 30% of the mass and cost of a

new vehicle. Since it is also what users most intimately experience, automakers

pay close attention to design for aesthetic appeal, ergonomics, and comfort. The

Revolution development team was challenged to provide a lightweight interior that

would still meet aggressive safety, comfort, acoustic, thermal, and aesthetic

requirements. The result: much of the inner surface of the carbon-fibre safety cell

is exposed to the interior, and energy-absorbing trim is applied only where needed

to meet FMVSS requirements (Fig 5). The carbon fibre `look' is becoming

increasingly popular in several automotive and non-automotive markets, so this

feature should meet all requirements (light weight, aesthetically appealing, low

cost, and safe) though it may not fit the tastes of all market segments. Other


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interior safety features integrated into the Revolution include front and side

airbags, pretension seatbelts, and sidestick control of steering, braking, and

acceleration. While using a sidestick to control automobiles may take some time to

gain wide consumer acceptance, its safety benefits are compelling. It gets rid of

the steering column and pedals -- the leading sources of injury in collisions

because they are the first things that the driver hits. Without these obstacles, the

seat belt and airbag system have more room to decelerate the driver more gently.

This is especially important for short drivers who typically have to pull their seat

far forward in order to reach the pedals, putting them dangerously close to the

airbag in conventional vehicles.

Fig5 : Revolution Interior

In the Revolution, the seat does not adjust forward and back, only

vertically, so drivers of all sizes will be the same distance from the airbags,


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improving its deployment-speed calibration and increasing overall safety.

Sidesticks also improve accident avoidance. Studies have shown that after a short

familiarization period, sidestick drivers are much better at performing emergency

evasive manoeuvres than are stick-and-pedal drivers, due to finer motor control in

hands than in feet, and greater speed and ease of eye-hand than of eye-hand-foot

coordination. Clearly, more work would be required in this area for sidesticks to

be feasible, but for the purposes of this concept vehicle, the team could

demonstrate sufficient safety benefits to keep them in the final design.

DaimlerChrysler, BMW, and CitroÈ en appear to share this view.

Another user interface safety feature is the LCD screen that replaces

numerous traditional gauges and displays. Placing the screen at the base of the

windshield, centred on the driver's line of sight, allows the driver to change any

vehicle settings via a common interface without greatly shifting the driver's

viewline or focal distance. The multi-function display and the software-rich design

of the vehicle also add such non-safety benefits as the ability to customize the

interface and add new software-based services without adding new hardware.

To adjust settings, the driver or passenger would use voice commands or a small

pod with four buttons and a jogwheel located in the centre console between the

front seat occupants..


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CLIMATE CONTROL

The climate control strategy illustrated in the Revolution design is

intended to deliver superior passenger comfort using one-fourth or less of the

power used in conventional vehicles. This required a systematic approach to

insulation, low thermal mass materials, airflow management, and an efficient air

conditioning compressor system. The foamcore body, the lower-than-metal

thermal mass of the composites, ambient venting, and spectrally selective glazings

greatly reduce unwanted infrared gain, helping cooling requirements drop by a

factor of roughly 4.5. Power required for cooling is then further reduced by heat-

driven desiccant dehumidification and other improvements to the cooling-system

and air-handling design.

Similarly, the Revolution was designed to ensure quick warm up,

controllability, and comfort in very cold climates. The heating system is similar to

that of conventional vehicles, but augmented by radiant heaters, a small hydrogen

burner for quick initial warm up if needed, and a nearly invisible heater/defroster

element embedded in the windshield.

CHASSIS

The chassis system combines semi-active independent suspension at

each corner of the vehicle, electrically actuated carbon-based disc brakes, modular

rear corner drive train hardware and suspension, electrically actuated steering, and

a high- efficiency run-flat wheel and tyre system. This combination can provide


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excellent braking, steering, cornering, and manoeuvrability throughout the

vehicle's payload range and in diverse driving conditions.

SUSPENSION

The Revolution's suspension system combines lightweight aluminium

and advanced-composite members with four pneumatic/electromagnetic linear-

ram suspension struts developed by Advanced Motion Technology, a

pneumatically variable transverse link at each axle, and a digital control system

linked to other vehicle subsystems (Figure 7). The linear rams comprise a variable

air spring and variable electromagnetic damper. The pressure in the air spring can

be increased or decreased to change the static strut length under load and to adjust

the spring rate. The resistance in the damper can be varied in less than one

millisecond, or up to 1000 times per vertical cycle of the strut piston. The overall

suspension system takes advantage of the widely and, in the case of damping,

rapidly tunable characteristics of these components. Thus the same vehicle can

pass terrain that requires high ground clearance, but also ride lower at highway

speeds to improve aerodynamics and drop the centre of mass.

Fig6: Revolution Chassis System


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Each strut is linked transversely (across the vehicle) to counter body roll.

The link itself is isolated so that a failure that might compromise anti-roll stiffness

would not compromise the pneumatic springs. Hydraulic elements connect the

variable pneumatic element at the center of the transverse link to the left and right

struts. The stiffness of the transverse link is adjusted by varying the pressure in the

isolated pneumatic segment. Oversized diaphragms reduce the pressure required in

the variable pneumatic portion of the roll-control link (normally at about 414 - 828

kPa), minimizing the energy required to tune the anti-roll characteristics. The anti-

roll system works in close coordination with the individual electromagnetic struts

to control fast transients in body roll and pitch during acceleration, braking,

cornering, and aerodynamic inputs. Many technologies can provide semi-active

suspension, but the linear rams best fit the Revolution's energy efficiency needs by

regenerating modest amounts of power when damping.

BRAKES

The Revolution's brakes combine electrical actuation with

carbon/carbon brake pads and rotors to achieve high durability and braking

performance at low mass. The front brakes are mounted inboard to reduce

unsprung mass. Carbon/carbon brakes' non-linear friction properties depending on

moisture and temperature are compensated by the electronic braking control,

because the caliper pressure is not physically connected to the driver's brake pedal,

so any nonlinearities between caliper pressure and stopping force are


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automatically corrected. Electrical actuation also eliminates several hydraulic

components, which saves weight, potentially improves reliability, and allows very

fast actuation of anti-lock braking and stability control. The brake calipers and

rotors should last as long as the car.

STEERING

The Revolution's steer-by-wire system has no mechanical link between

the driver and the steered wheels. Instead, dual electric motors apply steering force

to the wheels through low-cost, lightweight bell cranks and tubular composite

mechanical links.

This design permits continuously adjustable steering dynamics and maintains

Ackerman angle over a range of vehicle ride heights, in a modular, energy-

efficient, and relatively low cost package.

Fig7 : Steer by Wire System


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WHEEL AND TYRE SYSTEM

Hypercar collaborated closely with Michelin on the design of the wheel

and tyre system for the Revolution. The PAX1 run-flat tyre system reduces rolling

resistance by 15%, improves safety and security (all four tyres can go flat, yet the

vehicle will still be driveable at highway speeds), and improves packaging (no

need for a spare). The PAX technology is slightly heavier per corner than

conventional wheel/tyre systems, but eliminating the spare tyre reduces total net

mass.

POWER DISTRIBUTION, ELECTRONICS, AND CONTROL SYSTEMS

The Revolution's electrical and electronic systems are network- and

bus-based, reducing mass, cost, complexity, failure modes, and diagnostic

problems compared with traditional dedicated point-to-point signal and power

wiring and specialized connectors. The new architecture also permits almost

infinite flexibility for customer and aftermarket provider upgrades by adding or

changing software. In effect, the Revolution is designed not as a car with chips but

as a computer with wheels.

POWER DISTRIBUTION

All non-traction power is delivered via a 42-volt ring-architecture

power bus, providing fault-tolerant power throughout the vehicle. Components are

connected to the ring main via junction boxes distributed throughout the vehicle,

via either a sub- ring (to maintain fault-tolerance to the device) or a simple branch


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line for non-fault- tolerant devices. The junction boxes are fused so that power can

be supplied to the branches from either leg of the ring main. The benefits of this

system include low mass, high energy efficiency, fault-tolerance, simplicity, and

cost-effectiveness.

COST ANALYSIS

Given the many new technologies in the Revolution, one might

wonder how much such a vehicle might cost to produce.. The engineering team

estimated the vehicle's production cost at a nominal volume of 50 000 units per

year, using extensive anonymous supplier price quotations (for 82% of the

components), plus some in-house and independent consultants' bottom-up cost

modelling for technologies not yet in production. As designed, the vehicle could

be sold profitably at standard mark-ups for US$ 40 -- 45 000 retail. With further

development, Hypercar, Inc. estimates that this price could be reduced to

approximately US$35000 competitive with existing vehicles of similar

performance, features, size, and amenity but lacking Revolution's exciting features

and quintupled fuel economy. This cost estimate is directly related to the starting

point the product requirements. Part of Hypercar, Inc.'s reason for designing a

vehicle for the entry-level luxury sport utility segment was that its price point

would make many of the advanced features affordable. If the product requirements

were instead for a small economy car, it would be designed differently to meet

those requirements, it may not include all the features of the Revolution, and cost

reduction requirements could become more stringent.


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CONCLUSION

The automobile industry is on the threshold of potentially dramatic

change in its materials use and platform design. Ultralight-hybrid hypercars, using

advanced composites for the auto body, may be more attractive to the consumer,

just as profitable to the producer, and much friendlier to the environment than

conventional cars. With careful design and the industrialization of recycling

technologies, hypercars may even increase the recyclability of cars in the future.

Hypercars’ reduced power requirements could make the drive system smaller and

simpler, enabling components to be modular for easy removal and upgrading.

Hypercars using fuel cells are very heavy and very expensive

nowadays. Therefore using composite materials for body parts may not reduce the

mass of the body to the desirable extent. Yet Hypercar vehicles could adopt the

fuel cells, because their much lower power requirements would require far less

fuel-cell capacity than a heavy, high-drag conventional car.


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REFERENCES

1) Lovins, A.B. (1995) `Hypercars: the next industrial revolution', 1993

Asilomar Summer Study on Strategies for Sustainable Transportation 75-95,

American Council for an Energy-Efficient Economy, Washington DC, Publ.

#T95-30.

2) Lovins, A.B. and Lovins, L.H. (1995) `Reinventing the wheels', Atlantic

275(1): 75-86 (Jan.), and `Letters', id. 275(4): 16-18 (Apr.), submitted in

1993, both available as Publ. #T94-29, www.rmi.org/images/other/HC-

ReinventWheels.pdf

3) Cramer, D.R. and Brylawski, M.M. (1996) `Ultra light-hybrid vehicles

design: implications for the recycling industry', Society of Plastics

Engineers Recycling Division,Proceedings 3rd Annual Recycling

Conference, Chicago, IL, 7-8 Nov., Publ. #T96-

4) Website: www.rmi.org, www.hypercar.com.


http://www.rmi.org/images/other/HC-

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