Model based driveline control
A cars powertrain consists of everything that is needed for
its propulsion. The components in the driveline that transfer
the power from the engine to the driven wheels are not absolutely
stiff, hence they will wind up due to the torque and act as
torsion springs. If you suddenly demand a bigger torque by
stepping on the accelerator pedal, a so called tip in manoeuvre,
and that torque is acquired from the engine as quickly as possible,
the driveline will not be able to transfer that fast torque change
due to its weakness and as a result it will start to oscillate.
These oscillations will be transferred to the driven wheels and make
the car to accelerate jerkily which will be experienced as
uncomfortable by the passengers. Furthermore, there is a backlash
in the driveline that will make the weakness in the driveline
even more excited than it should have been if the backlash did not existed.
To avoid too big problems with these oscillations there is a
control system that controls the demanded torque. This control
system is today an open loop control system, i.e. a filtering
of the demanded torque. As the cars computer power is increasing
steadily there is an interest of investigating if it is possible
to get a higher performance control system by using a more advanced,
closed loop, model based control system.
In this thesis such a control system is developed. First a model of the
system is constructed; this model is used to design an observer that
estimates the non measurable states in the driveline.
The results show that this observer estimates these states fine
on the basis of the available signals. The observer is the base
for the driveline control system and simulations show that this
control system is a considerable improvement compared to the
control system used today.
Magnus Nordenborg
2005
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