| The last few years have been very challenging for
everyone in the automotive business. A general economic malaise has led
to losses at many of the major OEMs that have, in turn, dramatically re-shaped
their buying policies especially when it comes to outsourcing. One particular
branch of the industry that has been badly hit has been the testing one,
with proving grounds and those providing test services having to tighten
their belts in order to survive. Millbrook, the proving ground located
in the Midlands of England, has had its own share of belt-tightening,
but after a rather difficult patch, especially in 2002, is now coming
the other side in a stronger position. Partly this is because of some
wise decisions that were made when the clouds were gathering overhead,
and partly due to some inspired investment that is now paying dividends.
These include the Variable Temperature Emissions chamber that can simulate
real-world usage patterns for almost any type of road vehicle and an Engine
Technology Centre, the latest additions to which have been a couple of
transient engine dynamometers.
Commissioned late last year, these new dynos are said to cut development
times for a new engine variant by up to 30% and reduce costs during the
test phase by up to half. This is because they also allow engineers to
run their powertrain through may different drive cycles and climatic conditions
without the cost of prototype vehicles, engineering support and the need
to test around the world.
With cold fluids and air that can be cooled to –15°C, and using
data that has been captured directly from vehicles, including vehicle
mass, aerodynamics, inertial effects and transmission parameters, the
desired drive cycle can be programmed into the control systems so that
emissions performance can be repeatedly measured. The number of iterations
can be reduced using Millbrook’s Design of Experiment techniques,
a carefully selected subset of the millions of configurations to deliver
sufficient data to converge quickly on the optimum solution.
“Millbrook’s new techniques capture drive data directly from
vehicles,” says Peter Adams, principal engineer with Millbrook’s
powertrain division, “allowing us to model real road routes accurately,
at either Millbrook or the customer’s proving ground, where an engine’s
‘real-world’ behaviour can be analysed in a controlled environment.
“Achieving the optimum balance between emissions, refinement and
driveability is always challenging,” says Adams. “Laboratory
simulations allow their interactions to be studies more quickly and in
greater depth, delivering a superior solution even before the vehicle
is built. We have also found that this also allows us to feed useful information
back to those responsible for other parts of the vehicle design early
enough to allow cost-effective revisions.”
As far as the data is concerned, although it is technically possible,
Millbrook does not yet offer it in ‘real-time’ yet as there
is a built-in validation phase and there are security issues. However,
says Adams, “the data is generated on an hourly basis which the
customer receives first thing in the morning, even if they are in a different
time zone.”
Adams also believes that these transient engine dynos will be useful in
the development of powertrain programmes as it will enable OEMs to develop
niche market engine variants.
“We see tremendous potential for this new technique in a wide range
of areas,” says Adams. “It’s a significant step forward
in powertrain development that has already proved its value. Historically,
engines are calibrated in a steady-state environment with the transient
environment used to validate its steady-state calibration. The way forward,
though, is to look at transient engine behaviour and maybe calibrate some
of the transients.
“These dynos are unique in the commercial test industry as far as
I am aware, although there are other a few labs around that are very expensive,
but in terms of being to correlate against real-world drive cycles on
the dyno, they are unique.”
“Emissions tests is probably the area where Millbrook is strongest
technically,” says managing director Rod Calvert, “but we’re
still strong in crash, components testing and clearly the tracks.” On its 285 hectare (700 acre) site is a network of roads, hill routes
and off-road and cross-country tracks, but there was still room for improvement.
Keeping in step with the military
”We could see that the military test facilities were closing down
or being taken out of service for one reason or another so we set ourselves
a strategy of trying to get hold of a significant part of the whole vehicle
tests,” says Calvert. “We felt we were very well equipped
as an all-round facility to handle military Type Approval – it goes
right back through our heritage to the approval of the Bedford military
trucks. However, it was when we hosted the DVD – Defence Vehicle
Dynamics – exhibition last July, where the industry has the opportunity
to pedal its wares to the Ministry of Defence, that we realised that we
lacked one of the extreme facilities. We decided we must add some cross-country
and off-road facility enhancements as a strategic move to make Millbrook
the dominant site in the UK and probably Europe for military vehicle approval.
It’s a USP for us.”
Development work prior to the DVD exhibition included adding 10 hectares
of new development that complemented the existing cross-country and extreme
off-road areas. The course included 12 special features ranging from a
dried river bed to a simulated muddy wallah and a 10 metre concrete 1
in 1 incline.
“We already have Europe’s leading commercial test and development
facilities for most classes of vehicles, including some pretty tough off-road
and military rources,” says Julian Bryan, Millbrook’s head
of strategic marketing. “However, we felt that only a purpose-built
Extreme Service Area would be able to meet the needs of the military and
specialist vehicle industries fully.”
“We worked closely with the specialist vehicle manufacturers to
ensure that the new facility provides some of the most challenging conditions
their vehicles are likely to meet anywhere in the world,” says Cliff
Robertson, Millbrook’s head of facilities. “This isn’t
just a tough set of hills, it is an outdoor laboratory, carefully designed
and maintained to allow consistent results.”
A leader in rollover crash testing
nother area in which Millbrook regards itself as the global leader is
in rollover crash testing.
“We were involved in a pioneering research programme with Delphi
and Saab, which supplied the test vehicles, in the different type of rollovers,”
says Calvert. Millbrook’s engineers can now simulate more than 90%
of all rollover scenarios with a high degree of reproducibility. All but
one of the nine test configurations can be undertaken at Millbrook in
its indoor crash laboratory, where the vehicle can be decelerated to a
constant speed on a specially developed sled. Roll is initiated in a number
of ways to simulate contact with kerb, gravel, soil, impacted gravel,
high-friction surfaces, posts and banks – the most common form of
rollover in real-world accidents. Sideways roll down an embankment is
simulated in a specially constructed outdoor facility, where the vehicle
can roll safely down a calibrated gradient.
“Having defined the types of rollover, we then looked at how the
occupants could be best protected. The rollover itself then needed to
be modelled mathematically so that we could understand its threshold values,
the rate of rollover and the phasing of the occupant protection device.
Millbrook’s bit of the project – and it was world leading
– was to devise all the test protocols so that the tests could be
reproduced in a reliable fashion again and again. The protocols were subsequently
released and have now become a world standard. Typically now a programme
from a car manufacturer includes rollover tests.”
Prior to this work, there were not any truly representative rollover test
procedures available to development engineers addressing this challenge.
The US FMVSS208 test uses a barrel roll while the German ADAC test specifies
a corkscrew roll, both of which are spectacular but represent only a small
proportion of real-world rollover events.
“We believe that this is the only suite of commercially available
tests that accurately reflects the vast majority of real-world rollover
events,” says Phil Glyn-Davis, Millbrook’s engineering manager,
crashworthiness. “It will be tremendous value to engineers investigating
critical areas such as occupant kinematics, occupant interactions with
restraint systems, sensing requirements and system calibrations.
“We have paid particular attention to ensuring that each test is
repeatable, even to the extent of developing special calibration techniques
for the soil and gravel surfaces. Our technique is to build on field data
to allow specific interactions within a high-security controlled environment.”
In a tough environment, Calvert and his team have worked hard to enhance
Millbrook’s worldwide reputation for confidentiality, service and
competitiveness. Future developments will continue to focus on providing
test solutions well in advance of planned legislation, on reducing costs
and timescales, particularly for world-car programmes, and on developing
test techniques for new technologies such as roll-over protection, integrated
electronics and highly integrated cockpit modules.
|
|
