Mercedes Benz has announced its use of a computer simulation model to determine
optimal climate conditions in vehicles’ interiors. Using data from years of accumulated research on large numbers of
drivers, the automaker has developed “TIM”, or ‘Thermo-physiological Interior Model’. TIM is subjected to various virtual climates to
see how a real human being would react with the goal to determine if “he” is comfortable.
[Source: Mercedes-Benz]
[Press release after the jump]
OFFICIAL PRESS RELEASE
Mercedes-Benz SLK-Class: The latest computer
models for climate
control: Virtual driver tests climatic comfort in wind and weather
Stuttgart,
Mar 02, 2006
Mercedes engineers are using an innovative process to optimise the
climatic comfort
of car occupants. With the aid of computer
simulations, they send new models on virtual test drives and
calculate the air and temperature distribution in the interior under
different weather
conditions. This computer model is based on
research carried out with a large number of male and female
drivers,
who provided information about their personal comfort and the
temperatures at which
they felt most comfortable. The SLK Class was
the first Mercedes passenger car to embark on such a
computer-based
climate test.
Controlling the climate in the interior is one of the most complex
tasks in automobile development. Since the vehicle speed,
temperature, level of sunlight and
humidity change constantly when on
the move, a car air conditioning system must respond very rapidly and
flexibly if the occupants are to experience a uniform standard of
comfort – neither
feeling cold if the outside temperature suddenly
falls nor perspiring if it increases. People only feel
really
comfortable if their climatic surroundings remain pleasantly constant.
In order to ensure
this under all driving and weather conditions,
climate control engineers must commence their tests as soon
as
possible during the development of a new car model. They are not able
to wait for the first
prototypes or pre-series vehicles, as the
technology and design have been almost completely finalised by
this
stage.
This led to the development of “TIM” – the Thermo-physiological
Interior Model, which allows the climatic comfort of future Mercedes
models to be calculated
and optimised in advance. At an early
development stage it enables the engineers to establish the ideal
output for the heating and air conditioning systems, how many
ventilation vents are required
and how large these should be in order
to ensure the constant climatic comfort which is typical for a
Mercedes.
“TIM”: a virtual driver with almost every body function
“TIM” is
the result of many years of work by DaimlerChrysler
researchers on human thermal comfort levels. For
example, a large
number of male and female drivers provided the basic data for the so-
called
“equivalence temperature”, which corresponds to the
temperature “felt” by car occupants
and enables the actual, perceived
climatic comfort to be defined for each part of the body. Specialists
for example found that 80 percent of the individuals tested felt most
comfortable in summer
when the equivalence temperature at the torso
and arms was between 19 and 28 degrees Celsius, while the
comfort
range for the lower legs and feet is between 23 and 27 degrees Celsius.
The
“TIM” computer model is based on these and other findings about
the sub-jective perception of
comfort. It simulates most of the human
body in a total of 14 areas, also taking into account the blood
circulation and relative heat generation. The result is a virtual but
certainly representative
car occupant, who is sent to all the
climatic zones of the world by computer and supplies Mercedes
engineers with a mass of data. These are intended to answer only one
question: does he feel
comfortable?
Airflow: comfort test at four million points of the interior
The SLK-Class is the
first Mercedes model whose heating and automatic
climate control systems were developed both by computer
and by
practical testing. “TIM” absolved test drives of many hours duration
under the
most varied driving and weather conditions in this sporty
two-seater. In addition, “TIM” was
linked to other computer
programmes which for example divided the interior into up to four
million spatial units and measured the airflow, temperature and other
comfort parameters at each of these
points.
On-screen readouts enabled the engineers to establish when the
respective feel-good
temperatures were reached, and whether “TIM”
indicated the right comfort level. If required, a
few key strokes at
the computer were enough to adjust the climate control system until
the two
virtual vehicle occupants began to transmit satisfactory data.
Climate control: thousands of key data for
all driving and weather
situations
In this way the engineers fed thousands of key data into the
control
unit of the THERMOTRONIC automatic climate control system,
subsequently verifying and
refining these in practical trials. Once
the computer recognises a certain situation on the basis of sensor
data, it accesses the programmed values and adjusts the air
conditioning accordingly. This
activates up to five electric motors
inside the air conditioning unit, which automatically open or close
the air vents to adjust the air distribution. At the same time the
fan speed is increased and
the output of the compressor is adapted to
the new conditions.
The results obtained from this
computer simulation not only provide
the basis for the key data in the climate control system, but also
help developers to design the dashboard. The computer model gives
them a precise indication of
where the air vents should be located,
and how large they should be, to ensure an effective i.e. draught-
free air distribution. The larger the cross-section of the vent, the
lower the air speed and
therefore the less draught to disturb the
occupants. The striking air vents in the dashboard of the SLK
sports
car follow this principle, thereby combining form with function in an
exemplary way.
Although they are not obvious, the six footwell vents on the
underside of the dashboard are no less
important for climatic
comfort. Their location is likewise mainly based on the “TIM”
simulation and other computer models. When the heating is on, 80
percent of the air volume flows through
these vents to warm the
thermo-physiologically most sensitive body areas of the occupants,
namely the feet.
Open-air experience: good heating performance even with the vario-
roof open
The intelligent climate control system of the SLK-Class also works
when the vario-roof is open. As
soon as the occupants decide to enjoy
open-air driving, the automatic climate control system switches to
special characteristic values and adjusts both the air distribution
and temperature control.
The basic settings for this are also
supplied by computer models such as “TIM”: the computer, for
example,
simulates an open-air drive on a fine day at an ambient temperature
of ten degrees
Celsius, calculating the airflow over and inside the
Roadster at 80 km/h.
At an early
development stage, this enables Mercedes engineers to
achieve the right comfort (equivalence) temperatures
at head level:
for example by reducing the air speed with the help of the standard
draught-stop
and large air vents which direct warm air precisely at
the car occupants. In conjunction with the unique
AIRSCARF neck-level
heating system, this achieves a level of thermal comfort unrivalled
by any
other convertible in this vehicle class.