A New Model for Rolling Resistance of Pneumatic Tires
Rolling resistance of inflated tires is a factor that contributes to
the total load and fuel consumption of a vehicle. Therefore, models of
rolling resistance is an important area within computer simulations of
vehicles used to predict fuel consumption and emissions. In these
applications the coefficient of rolling resistance is usually
described as a function of velocity. We have earlier shown that this
is not a satisfactory solution.
In this paper, it is demonstrated that the temperature of the tires is
a dominating factor for rolling resistance in real driving. The tires
typically start at ambient temperature and are then warmed up by the
heat generated in the tire. As the temperature increases the rolling
resistance decreases (to some limit). After a long period (2 hours for
truck tires) of driving at constant conditions, a stationary
temperature (and rolling resistance) is reached. In real driving there
are usually also other (faster) changes in conditions, like a speed
change, that affects the rolling resistance as described in the
traditional velocity models.
These aspects are demonstrated and lead to a proposal of a new model
for rolling resistance. The new model is based on the relation between
rolling resistance and tire temperature at stationarity. A
differential equation for the tire temperature uses the relation
between momentary temperature and stationary temperature as input. A
speed dependent term is used to model fast changes of speed. In this
way both fast and slow phenomena can be described.
The new model is in good agreement with results published by
others. Further, in our own experiments with a heavy truck the new
model has shown a very good ability to calculate the true dynamic
rolling resistance.
Lars Nielsen and Tony Sandberg
SAE Transactions, Journal of Passenger Cars: Mechanical Systems,
2003
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