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Holden’s EFIJY
Show Car
Powered by V8, controlled by PICAXE
The Holden EFIJY show car was one of the most popular
vehicles on display at the 2005 Sydney International Motor
Show. While the stunning looks and technology drew the
crowds, few people would have been aware that the majority
of the electrical systems in the vehicle were controlled by
PICAXE microprocessors.
By JEFF BROWN*
8 Silicon Chip
siliconchip.com.au
H
OLDEN INNOVATION IS Holden’s research and development
centre and one of its functions is
to develop and demonstrate new
technologies and concepts. Vehicle
design is moving more and more into
the virtual world but technology still
needs to be demonstrated to allow
people to decide if they want this in
a future vehicle.
Invariably, this requires a demonstration or concept vehicle. The
concept vehicle may be based on a current production car and have the new
technology integrated into it or in the
case of EFIJY, it became a completely
new vehicle.
With the increasing complexity
of today’s vehicle electrical systems
and the integration of mechanical
and electronic control systems, it can
be quite difficult to adapt or modify
the base vehicle to accept the new
technology, even with the benefit of
having detailed information about the
vehicle’s architecture.
Traditionally, first-tier suppliers
provide the components and in some
cases the technology used in a given
subsystem.
Typical development of a component for production involves a number
of charges from the supplier; including design and development charges,
tooling charges and, of course, piece
cost. When a prototype is produced,
the supplier incurs many of the same
costs. It costs almost the same to write
software for a one-off prototype as
a production system. In the case of
the production system, the software
may be more complex to increase the
robustness of the code but most of the
requirements will be the same.
A similar issue occurs with hardware. In the case of PC boards, design
work still needs to be done, again perhaps not to the same extent as production, but still a significant percentage
of the work.
This all leads to significant expense
to produce a single working prototype.
A simple change to add a customer
feature may result in charges of $5$10,000. A more complex system can
see the cost escalate to $250,000 to
demonstrate a new technology. Therefore, significant budgets are required.
By developing a low-cost prototyping
system in-house, Holden is able to
investigate and demonstrate new systems at much lower costs and ensure
any intellectual property remains with
Holden.
Why PICAXE?
LCD panels are used for the large instrument panel screen and for the central
touch-screen display.
siliconchip.com.au
Many of the engineers at Holden are
readers of SILICON CHIP magazine and
recent articles about the PICAXE range
of microcontrollers sparked some interest due to our previous experience with
the Microchip range. The need arose
for a relatively simple project and the
PICAXE looked like it might be suitable, while giving us the opportunity
to evaluate the product.
Our initial selection was the 18X
processor and in the target application, it proved to be very competent;
the simple interface and relatively
January 2006 9
screens are LCD panels, each controlled by compact PCs with embedded
Windows XP operating systems.
The on-screen images for the touch
screens were created by Holden’s
Design Department specifically for
EFIJY and are running in Macromedia
Flash. The touch screens interface
with Flash and communicate with the
outside world via the PC’s serial port.
This results in each “button press”
on the touch screen being transferred
to the subsystem the driver intends
to control.
A dedicated module based on an Atmel Mega16 programmed in BASCOM
handles all serial traffic with the PCs
and sends and receives commands
from the modules that control most
subsystems. A second Atmel micro
handles communications with the
engine and transmission CAN (Controller Area Network) networks for
data such as RPM and vehicle speed
for display on the instrument panel
and also controls the ignition and
start systems.
CM4 control module
Developed especially for the EFIJY, the CM4 is a general-purpose control
module for use in a variety of applications. It uses a PICAXE 40X running
at 16MHz and includes a high-current H-Bridge for controlling motors,
high-current FET outputs for switching lights, solenoids etc, analog inputs,
and digital inputs with jumper selectable pull-ups or pull-downs.
simple BASIC language resulted in
very fast prototyping of a concept.
Holden Innovation has now used the
PICAXE 08, 08M, 18A, 18X and the
40X in numerous applications. Over
time the complexity of the projects in
which we have utilised the PICAXE
for has increased and we now base
most projects on the 40X running at
16MHz.
The most interesting aspect of the
PICAXE is the number of users, some
of whom do not have an electrical
background. We have found that the
simple interface and language has
been readily adopted by students
10 Silicon Chip
and engineers, and even by hardcore
programmers.
EFIJY electronics
With the exception of the engine
and transmission control modules,
the electronic systems in the EFIJY are
unique and are not based on production components. They use a total of
11 microcontrollers: nine PICAXEs
and two Atmel AVRs.
The most visible systems when
sitting in the vehicle are the large
instrument panel screen and the central display, revealed when the centre
compartment opens. The two touch
Holden Innovation developed the
CM4 module as a general purpose
control module that could be used for
a variety of demonstrator applications.
It’s called CM4 because it is the fourth
in a family of control modules developed by Holden Innovation.
The heart of the CM4 is a PICAXE
40X running at 16MHz. This module
has a high-current H-bridge with
current measurement for controlling
motors, high-current FET outputs for
switching lights and solenoids, etc,
plus analog inputs and digital inputs
with jumper-selectable pull-ups or
pull-downs.
In addition, a resistor network is
employed for resistor-encoded switching to further increase the number of
available inputs. This is achieved using one of the 40X’s analog inputs and
a resistor ladder; by switching points
on the ladder to ground, 10 steps at
0.5V per step is achieved. Therefore,
the 40X can process 10 different inputs
on the one analog input.
The power supply is capable of
providing 5V for various sensors and
the PICAXE has the ability to control
and switch its own power supply off
for any house-keeping required before
a controlled system shutdown. This
is very handy for functions that need
to be controlled after the ignition has
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been turned off. The usual PICAXE
features such as serial communications, I2C, etc, are also available.
PC board design and fabrication of
the CM4 was conducted in-house by
Holden’s Instrumentation department.
EFIJY uses four CM4 modules for the
following subsystems.
ePark Brake
EFIJY is fitted with an electric park
brake which offers a number of features, including removing the need for
a large and bulky lever. The pushbutton is pressed to apply and pressed
to release the parking brake. In the
event the parking brake is required as
an emergency brake, the rate of brake
application limits the vehicle deceleration to 0.3G.
Operation of the system is via an
actuator operating on a conventional
park brake system located within the
rear wheels. This actuator is controlled
via the H-bridge and uses both positional feedback and current through
the H-bridge. This allows the system
to be self-adjusting and provides the
control algorithm with a measure of
load applied.
Entry and exit
Entry and exit from the vehicle is
interesting, since there are no door
handles in or outside the vehicle.
Pushbutton switches for the doors and
boot use the resistor encoded inputs
to the CM4 module to control release
solenoids.
There is also a custom remote control based on a surface-mount version
The driver selects the gear by pushing one of the buttons located on the centre
console. These buttons use the resistive encoded inputs on one of the CM4
modules, while the actuator (which controls the transmission) is controlled via
the H-bridge output.
of the PICAXE 08M. This operates on
433MHz and has three pushbuttons
that release the doors and boot in a
conventional manner. The vehicle
responds to the command from the
remote and starts a power-up sequence
to ensure all systems are ready for
operation when the driver enters the
vehicle.
The third method of entry is via a
passive entry system. The operator
walks up to the car, holds out his/her
hand and the door pops open to meet
it. In this mode, the vehicle detects the
presence of a valid remote.
This is achieved using a multi-axis
motion sensor controlling the power
supply in the remote. This allows the
remote to power up for brief periods.
A unique message is then transmitted
but only if the remote is moving. This
significantly increases battery life – if
the remote is in storage or not in use,
the power supply to the 08M is off.
When this message is received by
the CM4, the door proximity sensors
are enabled. These use a capacitance
type proximity sensor based on the
The central display is revealed when the centre compartment opens. It displays touch-screen images (controlled by
compact PCs) to control functions such as the radio and the suspension settings.
siliconchip.com.au
January 2006 11
The headlamps use 20 high-brightness
LEDs in the centre, while the outer
rings use 36 pairs of white and amber
devices (the latter for turn indication).
A 6-litre LS2 V8 fitted with a supercharger sits in the engine bay. It develops
480kW of power and 775Nm of torque.
velops 480kW of power and 775Nm
of torque.
You start the engine with the large
pushbutton on the left of the instrument cluster. Starting is controlled by
one of the Atmel Mega16 microcontrollers, which provides interface to
the power control and engine management systems of the vehicle.
When a valid remote transmitter is detected within the passenger
compartment, the start button flashes
to indicate that the engine can be
started. Pushing the button for a brief
period then starts the engine. To stop
the engine, the start button is pushed
again. Various interlocks ensure that
the engine is not cranked if it is already
running.
Alternatively, a key can be used to
turn on the ignition and the start button used to crank the engine.
ePRNDL
When a valid remote transmitter is detected inside the passenger compartment,
the engine can be started by briefly pressing the large Start button to the left of
the steering column. Pressing it again stops the engine.
QT110 IC which provides a digital
output when an object is detected.
In operation, the device continuously adapts to its environment and
only reacts to step changes in capacitance. An output from the proximity
sensor is generated by the presence of
the driver’s hand at a range of approximately 80-100mm from the top rear
edge of each door. The combination of
a valid remote in range and the driver’s
12 Silicon Chip
hand allow the door to be released.
In addition, various interlocks in the
code determine if door operation is
permitted, based on door position,
vehicle speed, ignition status, etc.
Naturally, the occupants still need
to manually close the doors!
Starting
EFIJY has a 6-litre LS2 V8 engine
fitted with a supercharger. It de
ePRNDL stands for “electronic Park
Reverse Neutral Drive Low” – the electronic transmission selector located
in the centre console. EFIJY uses a
4-speed GM automatic transmission,
the 4L60E, with the cable control replaced by an actuator.
The driver selects the gear by pushing one of the buttons located on the
centre console. The buttons use the
resistive encoded inputs on one of
the CM4 modules, while the actuator
is controlled via the H-bridge output
and utilises positional feedback from
both the actuator and the transmission’s internal controls.
The CM4 is also responsible for
siliconchip.com.au
switch illumination, and selected gear
position feedback, both to the driver
and to other subsystems. Naturally, a
number of interlocks are employed to
ensure accidental operation is avoided,
to prevent damage to the vehicle.
Proportional speed control of the
actuator is used to ensure fast response
as well as accurate selection of the
correct gear position
Air suspension
The car is fitted with integral airbag and damper assemblies and each
wheel has an analog suspension height
sensor. Compressed air is supplied via
an onboard compressor and storage
tank. A manifold with eight solenoid
valves, four for lift and four for lower,
together with the CM4 module, controls the air supply to each airbag to
maintain the desired trim height, regardless of load in the vehicle. There
are three settings: show, drive and
load and the height can be controlled
to within approximately 1mm.
The CM4 receives the target height
request from the central touch screen.
Using the EEPROM in the PICAXE,
the last requested suspension height
is tracked to allow for system power
loss.
In a show vehicle, there is usually an
isolator switch for the vehicle battery.
This is turned off when the vehicle is
in storage or on display. But because
of the non-volatile memory (EEPROM)
in the PICAXE, the control module
knows what height it should be at
when power is reapplied. The software
inhibits control of height when the
vehicle is moving and includes error
detection and reporting.
Steering column lock
Setting the suspension to the show
position requires the front wheels to be
centred inside the front wheel arches.
If this does not happen, the wheels
will make contact with the fenders
and result in body damage.
This problem was solved using an
analog steering angle sensor, similar to
the type used for stability control systems. This allowed the CM4 module
to determine if the steering wheel was
centred and if not, allow the central
display to indicate not only the need to
centre the wheel but also the direction
the wheel needs to be turned. When
the wheel is in the correct position, a
locking actuator is engaged to prevent
the steering wheel being turned when
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Eight high-brightness red LEDs are used in the stop indicator housing that’s
mounted on the boot lid.
the car is in the lowered position.
The locking actuator is a rack type
and requires an H-bridge to drive it to
the lock and unlock positions, while
integral position switches provide
lock status. Again, various interlocks
are employed to ensure the steering
column is not allowed to lock when
the vehicle is in motion.
Lighting
The headlamps use Osram Ostar
LEDs. These consist of a cluster of
five 1W LEDs mounted on a single
substrate. With four of these clusters
per lamp, there is approximately 20W
of LED illumination per side. The outer
rings contain 36 pairs of LEDs, one
white 50mA device and one amber
150mA device per aperture.
The tail lamps consist of 32 dual
colour LEDs and a single blue 1W
Dragon LED. The dual colours provide
stop and tail functions by control of
the current through the red elements.
When a turn signal is required, the
amber LEDs are strobed to provide the
flash function.
A 40X PICAXE running at 4MHz is
used in each tail lamp assembly.
LED lighting is also used for interior
illumination, as well as for switches
and warning lamps.
Collaboration
The electronic systems in EFIJY
were the result of a collaboration of
several departments within Holden,
The tail lamps use 32 dual-colour
(red and amber) LEDs to provide the
stop and turn indicators.
as well as a number of suppliers who
contributed components or assemblies
to allow EFIJY to be a fully functioning,
fully-drivable demonstration of future
vehicle technologies.
About the author*
Jeff Brown is the Technology Leader –
Flexible Architecture at Holden Innovation. During his 19 years with Holden,
amongst other duties, he has been
responsible for powertrain management
systems, vehicle networks and electrical
SC
systems architecture.
January 2006 13
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