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GM’s HyGeneral Motors has unveiled the Hy-wire
concept car, the world’s first drivable vehicle that
combines a hydrogen fuel cell with by-wire technology.
The heart of the Hy-wire is an innovative “skateboard” chassis, which
contains all of the sedan’s propulsion,
transmission, steering and braking
components within its 279mm high
frame and provides a single electrical
connection to the body.
In essence, fuel cells enable a
skateboard chassis and this flat plane
provides unprecedented freedom for
designing the vehicle body.
8 Silicon Chip
Complementing this, the by-wire systems allow a single docking connection
between the skateboard chassis and
the body, and this creates great opportunities for reinvesnting the interior
layout.
Hy-wire was literally designed from
the inside out, with form following
function. The flexibility of the chassis
accommodates multiple interchangeable “snap on” body styles that can be
customised to meet customers’ various
lifestyles.
Fuel Cell Propulsion System
Inside, between the aluminium
beams of the skateboard chassis, GM
engineers have integrated an impressive technology package. A 3-phase
electric motor, mounted transversely,
drives the front wheels via a single-stage planetary gear with a transwww.siliconchip.com.au
mission ratio of 8.67:. It generates a
maximum power of 60kW and delivers
a maximum torque of 215Nm. Maximum
speed is 12,000 rpm.
The fuel cell stack consists of 200
single fuel cells connected in series and
is roughly the size of a PC tower. It is
located in the rear of the skateboard chassis and is cooled
using a conventional
radiator.
The stack, which
operates under a
pressure of 1.52.7 Bar, has a
power density of 1.60kW/l
and produces
94kW continuously, with
a peak power
of 129kW. This
delivers between 125V and 200V DC,
depending on the load. This is boosted
to 250-380V and then converted to
3-phase AC to drive the electric motor.
Unlike other fuel cell vehicles, there
is no battery in Hy-wire to provide extra
power for peak loads. It uses only the
fuel cell to provide power, thus simplifying the development and integration.
The fuel cells obtain the hydrogen
fuel from tanks mounted securely in the
centre of the skateboard. The three cylindrical compressed hydrogen storage
tanks are made of carbon composite
material, have a total weight of only
75kg and store a total of 2kg of gaseous
hydrogen at 350 Bar.
Yes, you read that correctly – 350 Bar,
about 5,000 pounds per square inch!
Incidentally, the next stage of development will increase the tank pressure
from the current 350 Bar to 700 Bar.
GM and QUANTUM Fuel Systems
Technologies Worldwide received
certification from the top
German safety
-wire
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institute for a 700 Bar (10,000 psi)
hydrogen storage system that could
ultimately allow fuel cell vehicles to drive
300 miles depending on the storage
volume.
Drive-By-Wire, BrakeBy-Wire, Steer-By-Wire,
Docking Connection
Developed by Swedish-based SKF,
the “by-wire” technology enables all of
Hy-wire’s major driver-control functions,
including steering, accelerator and
brakes, to be consolidated into a flexible,
hand-controlled unit called the X-drive.
It is similar to today’s advanced aircraft controls, where commands are
transmitted digitally from the cockpit
through electrical cables, or “by wire”,
to the various parts of the plane.
Hy-wire uses the same technology,
allowing the driver to easily control the
vehicle with either the right or left hand
from the X-drive unit. Drivers also have
the option of driving from the left or right
driving position because the X-drive is
located in a centre console that shuttles
from left to right.
Because it uses fully electronic
connections and controls, the by-wire
system simply plugs into the docking
connections on the Hy-wire chassis.
At the heart of the by-wire system
March 2003 9
are smart electro-mechanical actuating units, which convert the driver’s
commands from electronic signals to
motion. The by-wire system also provides dynamic feedback to the driver
via electronic signals.
The advantages of by-wire technology in automobile applications include
the elimination of steering columns and
foot pedals and allows greater design
freedom, simplified production of left
and right-hand drive models and improved passive safety for
the driver.
The elimination
of mechanical
and hydraulic
linkages saves
weight and simplifies maintenance because
there are fewer
moving parts that
can wear out.
By-wire is more environmentally friendly because hydraulic fluids required for steering
and braking are eliminated. Software
allows the driver to personalise the
handling characteristics of the vehicle
by adjusting the feel of steering, braking
and acceleration. Adjusting them is as
simple as loading a new program.
10 Silicon Chip
The Hy-wire’s X-Drive replaces the
usual round steering wheel and pedals,
giving drivers the option to brake and
accelerate with either the right or left
hand. The driver accelerates by gently
twisting either the right or left handgrip
and brakes by squeezing the handgrips.
The handgrips glide up and down for
steering, somewhat different
than today’s vehicles
where the steering
wheel revolves
around a steering
column.
The X-Drive also incorporates an electronic monitor for rear-
view and vital
car functions and
shuttles easily from
side-to-side on a horizontal
bar that stretches across the full
width of the vehicle.
The steering system highlights
the basic functions of the by-wire
controls. A conventional vehicle
uses a direct mechanical or hydraulic
connection between the driver’s control
www.siliconchip.com.au
Specifications: GM Hy-Wire
Vehicle:
Seating capacity:
Fuel storage system:
device and
the relevant component. For example,
the commonly used rack-and-pinion
steering system uses a small toothed
wheel (the pinion) to engage the rack
and to shift it left or right. Tie rods then
carry the motion to the steering arms
at the wheel.
By-wire technology, in contrast,
translates the driver’s commands into
electrical impulses. If the driver turns
the handgrips of the X-Drive, sensors
capture this motion digitally and send a
signal to an electrical motor that moves
the steering rack as instructed.
Acceleration is similar to the throttle
on a motorcycle, except that a throttle
cable does not mechanically activate
the throttle valve of the power plant. The
by-wire system transmits an electronic
signal to the electric motor that drives
the Hy-wire’s front wheels.
Braking is achieved by squeezing
either the left or right hand grip. Grip
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Length/diameter:
Total capacity:
Total weight:
Fuel cell stack:
Voltage:
Length/width/height:
Pressure:
Continuous rating:
Power density:
Electrical traction system:
Operating voltage:
Maximum rating:
Maximum torque:
Maximum rpm:
Transmission ratio:
Total weight:
Skateboard chassis:
Body:
Length:
Vehicle weight:
Wheel base:
Fuel cell and by-wire technology, front-wheel drive,
luxury sedan
Five
Three cylindrical high-pressure tanks of carbon
composite material, mounted in the middle of the
skateboard chassis
1,161/241mm
2kg
75kg
200 single fuel cells; connected in a series
125-200 Volt
472/251/496 mm
1.5-2.7 Bar
94kW, peak of 129kW
1.60 kW/l, 0.94 kW/kg
3-phase asynchronous electric motor with
integrated power electronics and planetary gear
250-380 Volt
60kW
215Nm
12,000
8.67:1
92kg
Length/width/height: 4,357/1,670/ 279mm
Aluminium frame
Steel and fibreglass
5 metres
1,900kg
3,114mm
March 2003 11
sensors determine how much hand
pressure the driver is exerting and
these transmit a signal which applies
the brakes.
The system, developed together with
the Italian specialist, Brembo, works
with conventional brake calipers but
responds faster.
Maximum reliability and safety are
essential features of the data-transmission system in by-wire control. All safety
systems have built-in redundancy and a
back-up power supply similar to those
used in fly-by-wire systems.
Body and Interior
Since Hy-wire’s skateboard-like
chassis contains all of the propulsion
and control systems – a fuel cell and
by-wire technology – designers were
free to consider a number of body
styles and interiors with what amounts
to a fresh canvas to explore an endless
range of possibilities for the body style
and interior package.
GM wanted an obvious transition from
where vehicle design is now to where the
technology could take it and intentionally
designed a vehicle that will highlight the
openness in the interior and leave it to
the occupant’s imagination to consider
the possibilities.
The break with conventional automobile architecture is obvious on the
very first encounter with the car, which
is 5-metres long, 1.87-metres wide and
1.57-metres high.
Glass is used extensively, giving
12 Silicon Chip
passers-by a full view inside and the
passengers a perfect view of the world
outside.
The absence of a conventional engine
means there is no need for a grille up
front. So the question became what
to do with the open front face where
you’d typically put a grille. The designers
chose to enclose it with glass, allowing
the driver to have a view of the road
ahead that has never been possible
before.
You can see immediately that there
is no engine at the front, the pedals and
instrument panel are superfluous and
the floor is flat from front to back.
Hy-wire features large side windows
and no B-pillars (the traditional post
between the front and rear windows).
The rear doors are hinged at the back,
allowing the four doors to open very
wide, providing very easy access.
Anyone who accepts the invitation
aboard can look forward to a comfortable and exciting journey. Apart from
the unmatched panoramic view for the
driver and passengers and spacious
interior, Hy-wire offers several other
key features.
The fuel cell and by-wire systems
eliminate the need for a traditional engine bonnet and centre tunnel, resulting
in improved legroom. The lack of foot
pedals means the driver is not restricted
to a specific leg position.
Flexibility
The X-Drive can slide across for left or
right side driving, emphasizing Hy-wire’s
outstanding flexibility.
Pressing a button on the X-Drive
starts the Hy-wire vehicle. Buttons also
engage the vehicle’s forward, reverse,
and neutral drive conditions.
The X-Drive attaches to a very light
and transparent-looking centre console.
Integrated in this console is a second
15cm colour monitor which allows the
driver to view radio controls, heating,
ventilation, air conditioning and navigation systems.
The design team’s work was characterised by a feeling of freedom – freedom, for example, to position the seats
and control module where they wanted
to, without any restrictions.
They paid particular attention to the
seats when developing the Hy-wire’s
interior.
The five-passenger vehicle has front
and rear bucket seats; the centre rear
seat folds up to create a table.
Lightweight materials accentuate
the vehicle’s openness, and the overall environmental-friendly concept is
expressed by the choice of natural
colours.
The sporty yet elegant four-door vehicle has short overhangs, eight-spoke
light-alloy wheels with 20-inch tyres in
front, and 22-inch tyres in the rear.
Cameras have replaced the rearview mirrors and the headlamps and
tail-lamps feature LED technology. This
technology allows the lamps to be packSC
aged in a very small space.
www.siliconchip.com.au
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