hy-wire car

Hy-wire

ABSTRACT

In this seminar, we will look at one interesting vision of the

future, General Motors’ remarkable concept car, the Hy-wire.

General Motors (GM) may never actually sell the Hy-wire to the

public, but it is certainly a good illustration of various ways cars

might evolve in the near future.

Instead of an engine, Hy-wire car has a fuel cell stack,

which powers an electric motor connected to the wheels. Instead

of mechanical and hydraulic linkages, it has a drive by wire

system where a computer actually operates the components that

move the wheels, activate the brakes and so on, based on input

from an electronic controller. By combining fuel cell and drive

by wire technology, the Hy-wire car has opened a new world of

chassis architectures and customized bodies for individual

expression. The development is a significant step towards a new

kind of automobile that is substantially friendlier to the

environment and provides consumers positive benefits in driving

dynamics, and freedom of individual expression.

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INTRODUCTION

Cars are immensely complicated machines, but when you

get down to it, they do an incredibly simple job. Most of the

complex stuff in a car is decided to turning wheel, which grip the

road to pull the car body and passengers along. The steering

system tilts the wheel side to run the car, and brake and

acceleration system control the speed of the wheel. Given that the

overall function of the car is basic (it just needs to provide rotary

motion to the wheel), it seems a little strange that almost all cars

have the same collection of complex crammed under the hood

and the same general mass of mechanical and hydraulic linkages

running throughout.

Why do cars need necessarily need a steering column, brake

and acceleration pedals, a combustion engine and the rest of it?

This question led the automotive engineers at the General Motors

Company to design and develop a new breed of cars.

FIGURE 1 GM'S SEDAN MODEL HY-WIRE

Hy-wire

HY-WIRE BASICS

The two basic elements that largely dictate car design today

are: the internal combustion engine and mechanical and hydraulic

linkages. If we look under the hood of a car, we can see that an

internal combustion engine requires a lot of additional equipment

to function correctly. The designers trying to bring out new

luxurious and environment-friendly cars into the market always

have to make room for this equipment.

The same is the case with the mechanical and hydraulic

linkages. The basic idea of using the linkages is that the driver

can maneuver the various actuators in the car more or less

directly, by manipulating driving controls connected to those

actuators by shafts, gears and hydraulics. For example, in a rack

and pinion steering system turning the steering wheel rotates a

shaft connected to a pinion gear, which moves a rack gear

connected to the car’s front wheels.

The defining characteristic of the Hy-wire is that it doesn’t

have either of those two things. Instead of an engine, it has a fuel

cell stack, which powers an electric motor connected to the

wheels. Instead of mechanical and hydraulic linkages, it has a

drive by wire system where a computer actually operates the

components that move the wheels, activate the brakes and so on,

based on input from an electronic controller. By combining fuel

cell and drive by wire technology, the Hy-wire car has opened a

new world of chassis architectures and customized bodies for

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individual expression. The development is a significant step

towards a new kind of automobile that is substantially friendlier

to the environment and provides consumers positive benefits in

driving dynamics, and freedom of individual expression.

FIGURE 2 THE HY-WIRE HAS WHEELS, SEATS AND WINDOWS LIKE A

CONVENTIONAL CAR, BUT THE SIMILARITY PRETTY MUCH ENDS THERE. THERE

IS NO ENGINE UNDER THE HOOD AND NO STEERING WHEEL OR PEDALS

INSIDE.

The result of the two substitutions is a very different type of

car and a very different driving experience. There is no steering

wheel, there are no pedals and there is no engine compartment. In

fact, every piece of equipment that actually moves the car along

the road is housed in an 11-inch-thick (28 cm) aluminum Chassis

—also known as the skateboard – at the base of the car. This

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maximizes the interior space for five occupants and their cargo.

Everything above the chassis is dedicated solely to driver control

passenger comfort.

FUEL CELL –ON HY-WIRE

A fuel cell is an electrochemical energy conversion device

that converts hydrogen and oxygen into water, producing

electricity and heat in the process. A fuel cell provides a DC

(direct current) voltage that can be used to power motors, lights

or any number of electrical appliances. One can continually

recharge a fuel cell by adding chemical fuel- hydrogen for an

onboard storage tank

The type of fuel cell that is used in the Hy-wire car is the

Proton exchange membrane fuel cell.

Proton exchange membrane

The four basic elements of a PEM fuel cell are:-

The anode, the negative post of the fuel cell, conducts the

electrons that are freed from the hydrogen molecules so

that they can be used in an external circuit. It has channels

etched into it that disperse the hydrogen gas equally over

the surface of the catalyst.

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The cathode, the positive post of the fuel cell, has channels

etched into it that distribute the oxygen to the surface of the

catalyst. It also conducts the electrons back from the

external circuit to the catalyst, where they can recombine

with the hydrogen ions and oxygen to form water.

The electrolyte is the proton exchange membrane. This

specially treated material, only conducts positively charged

ions. The membrane blocks electrons.

The catalyst is a special material that facilitates the reaction

of oxygen and hydrogen. It is usually made of platinum

powder very thinly coated onto carbon paper or cloth. The

catalyst is rough and porous so that the maximum surface

area of the platinum can be exposed to the hydrogen or

oxygen. The platinum-coated side of the catalyst faces the

PEM.

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The working of PEMFC

FIGURE 3 FUEL CELL

The pressurized hydrogen gas (H2) enters the fuel cell on

the anode side. This gas is forced through the catalyst by the

pressure. When an H2 molecule comes in contact with the

platinum on the catalyst, it splits into two H+ ions and two

electrons (e-). The electrons are conducted through the anode,

where they make their way through the external circuit (doing

useful work such as turning a motor) and return to the cathode

side of the fuel cell.

Meanwhile, on the cathode side of the fuel cell, oxygen gas

(O2) is being forced through the catalyst, where it forms two

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oxygen atoms. Each of these atoms has a strong negative charge.

This negative charge attracts the two H+ ions through the

membrane, where they combine with an oxygen atom and two of

the electrons, from the external circuit to form a water molecule

(H2O).

Chemistry of a Fuel Cell

Anode side:

2H2 => 4H+ + 4e-

Cathode side:

O2 + 4H+ +4e- => 2H2O

Net reaction:

2H2 + O2 => 2H2O

PEMFCs operate at a fairly low temperature (about 176

degrees Fahrenheit, 80 degrees Celsius), which means they warm

up quickly and don’t require expensive containment structures.

FIGURE 4 THE HYDROGEN TANKS AND FUEL-CELL STACK IN THE HY-WIRE

Hy-wire

The gaseous hydrogen fuel needed to power this system is

stored in three cylindrical tanks, weighing about 165 pounds (75

kilograms) total. The tanks are made of a special carbon

composite material with the high structural strength needed to

contain high-pressure hydrogen gas. The tanks in the current

model hold about 4.5 pounds (2kg) of hydrogen at about 5000

pounds per square inch (350 bars). In future models the Hy-wire

engineers hope to increase the pressure threshold to 10000

pounds per square inch (700 bars), which would boost the car’s

fuel capacity to extend the driving range.

DRIVE BY WIRE TECHNOLOGY

The Hy-wire’s “brain” is a central computer housed in the

middle of the chassis. It sends electronic signals to the motor

control unit to vary the speed, the steering mechanism to

maneuver the car, and the braking system to slow the car down.

The central computer is connected to an array of advanced

sensors. Based on input from the driver, the computer activates

the different actators to control the motion of the vehicle. The

driver doesn’t actually drive the car directly: He or she gives

instructions and the computer decides how to carry them out. The

computer constantly makes adjustments on it to improve the

driving performance the computer artificially creates a relatively

smooth ride. The computer is connected to the body’s electronics

through universal docking ports. The UDP transmits a constant

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stream of electronic command signals from the car controller to

the central computer, as well as feedback signals from the

computer to the controller. Additionally, it provides the electric

power needed to operate all of the body’s onboard electronics.

FIGURE 5 THE HY-WIRE'S X-DRIVE

FIGURE 6 THE X-DRIVE CAN SLIDE TO EITHER SIDE OF THE VEHICLE

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The driver’s control unit, dubbed the X-drive has to

ergonomic groups, positioned to the left and right of a small LCD

monitor. To steer the car, you glide the gripes up and down

lightly, you don’t have to keep rotating a wheel to turn, and you

just have to hold the grip in the turning position. To accelerate;

you turn either grip, in the same way you would turn the throttle

on a motor cycle; and to brake you squeeze either grip. Electronic

motion sensors, translate the motion of the X-drive in to a digital

signal the computer can recognize. Buttons on the controller let

you switch easily from neutral to drive to rivers, and a starter

buttons turns the car on. Absolutely everything is hand

controlled.

The 5.8 inch (14.7 centimeter) color monitor in the center

of the controller displays all the stuff you‘d normally find on the

dashboard 9speed, mileage, fuel level). It also gives you rear-

view images from video cameras on the sides and back of the car,

in place of conventional mirrors. A second monitor, on a console

beside the driver, shows you stereo, climate control and

navigation information. Since it doesn’t directly drive any part of

the car, the X-drive could really go anywhere in the passenger

compartment. In the current Hy-wire sedan model, the X-drive

swings around to either of the front two seats, so you can switch

drivers without even getting up. It’s also easy to adjust the X-

drive up or down to improve driver comfort.

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One of the amazing things about the drive-by-wire system

is that you can fine-tune vehicle handling without changing

anything in the car’s mechanical components – all it takes to

adjust the steering, accelerator or brake sensitivity is some new

computer software. One fuel cell only puts out a little bit of

power, so you need to combine many cells into a stack to get

much use out of the process. The fuel-cell stack in the Hy-wire is

made up of 200 individual cells connected in series, which

collectively provide 94 kilowatts of continuous power and 129

kilowatts at peak power. The compact cell stack is kept cool by a

conventional radiator system that’s powered by the fuel cells

themselves. The fuel system delivers DC voltage ranging from

125 to 200 volts, depending on the load in the circuit. A

transformer in motor controller boosts this up to 250 to 380 volts

and converts it to AC current to drive the three-phase electric

motor that rotates the wheels.

The electric motor’s job is to apply torque to the front wheel

axle to spin the two front wheels. The control unit varies the

speed of the car by increasing or decreasing the power applied to

the motor. When the controller applies maximum power from the

fuel-cell stack, the motor’s rotor spins at 12000 revolutions per

minute, delivering a torque of 159 pound-feet. A single-stage

planetary gear, with the wheels, that’s enough torque to move the

4200 -pound (1905-kg) car 100 miles per hour (161 kph) on a

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level road. Smaller electric motors maneuver the wheels to steer

the car, and electrically controlled.

FIGURE 7 GM'S DIAGRAM OF THE AUTONOMY DESIGN

ADVANTAGES:

1. Fuel efficient - Since a fuel cell propulsion system is

about twice as efficient as an internal combustion engine, a fuel

cell vehicle could provide twice the fuel efficiency of a

comparably sized conventional vehicle, and an optimized fuel

cell vehicle like Hy-wire would be even more efficient.

2. Environment friendly - Since the reaction through which

the power is generated is 2H2+O2=>2H2O the only bi-product

formed is water, which is a non-pollutant. Since there is no burning

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or other oxidation process in the releasing of energy harmful

components like nitrogen oxides, hydrocarbons, carbon oxides and

other unburnt products are not produced. Hence these cars are

highly eco-friendly.

3. High stability - As all the technical elements have been

nicely blended into the chassis, most of the power train load has

been evenly distributed between the front and rear of the chassis.

This provides a low center of gravity, giving the architecture both a

high stability and driving dynamics potential. This contributes to

the overall safety of the vehicle, by enabling superior handling,

while resisting rollover forces, with the tallest body attached.

4. Highly spacious - As there are no linkages and engine lot

of legroom space is available for the passengers.

5. Driver friendly - As the X-drive does not have any

physical linkages with the steering controller, it can be taken to

anywhere inside the car. Moreover as everything that drives the car

is housed in the chassis, the driver does not have to sit behind a

mass of machinery. This gives the driver a clear view of the road

and thus increases the drivability.

6. Freedom of individual expression - As the chassis would

be common for most the Hy-wire vehicles, one can easily remove

the entire passenger compartment and replace it with a different

one. This leads to the freedom of individual expression. For

example if one wants to switch from a van to a sports car, he does

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not need an entirely new car; he only needs a new body (which

would be a lot cheaper).

FIGURE 8 GM CONCEPT OF THE AUTONOMY WITH AND

WITHOUT A BODY ATTACHED

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DISADVANTAGES

1. Low safety - The big concern with drive-by-wire vehicles

is safety. Since there is no physical connection between the driver

and the car’s mechanical elements, an electrical failure would

mean total loss of control. In order to make this sort of system

viable in the real world, drive-by-wire cars will need back- up

power supply and redundant electronic linkages.

2. Storage and transportation of hydrogen fuels - The

other major hurdle for this type of car is figuring out energy-

efficient method for producing, transporting and storing hydrogen

for the on board fuel cell stack. With the current state of

technology, actually the production of the hydrogen fuel can

generate about as much pollution as using gasoline engines.

3. Pricing - With the current status of development,

manufacturing of the Hy-wire cars on a mass scale would not at all

be economical. According to the present accounts, the cost for

manufacturing even a single Hy-wire car would be about 1 to 2

crores.

FUTURE OF HY-WIRE

Looking in to the future, Burns says he thinks fuel cells offer

a promising alternative, but he recognizes that they need to be

compelling, affordable, and profitable. One area GM is tackling is

hydrogen storage. GM partnered with Quantum Technologies to

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develop a prototype tank that will give you a driving range of up to

300 miles before you have to refuel.

Burns says GM is looking into other ways it can store

compressed hydrogen, “There’s liquid for hydrogen and there’s

also metal hydrides when you’re storing hydrogen in a solid state,”

he said. Keebler says another solution could be to build a hydrogen

reformer into the car, which would enable it to turn other fuels into

hydrogen. You could also house these reforms at gas stations, he

says. Burns says you could distribute the gasoline the same way

you do today, but it would go through a reformer at the pump,

creating hydrogen from the gas. Burns sees a world where GM

overcomes those obstacles and your car becomes part of your

energy solution and not the problem.

“Let’s imagine a world in which you could come home at

night and pull your hydrogen fuel cell vehicle into your garage.

The first thing you do is connect it to some compressed hydrogen

tanks that are also in your garage and you put hydrogen into your

vehicle. You are refueling at home,” he said. At the end of the day,

if you have some leftover hydrogen in your tank, you could also

use it to power your home. He says he also envisions you being

able to plug your car into your city’s electric grid and selling back

fuel you don’t use. Keebler says he likes what he has seen from the

Hy-wire overall. He hasn’t been able to test-drive it yet. But he

said, “If they can pull that off, they will have indeed leaped over

the completion.”

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CONCLUSION

The Hy-wire concept has so profoundly brought about

changes in the automotive industry that GM and other auto makers

are planning to move beyond the conventional car, towards a

computerized environment friendly alternative. They are actually

planning to launch such a vehicle for the public usage by the year

2020, hoping that they can overcome all the drawbacks faced by

the Hy-wire car.

Anyway, in all likelihood life on the highway will see some

major changes within the next few decades.

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REFERENCES

1. www.popularmechanics.com

2. www.gm.com

3. www.motortrend.com

4. www.fuelcellonline.com

5. www.avista.com