Modeling of Engine and Driveline Related Disturbances on the Wheel Speed in Passenger Cars
The aim of the thesis is to derive a mathematical model of the engine and driveline
in a passenger car, capable of describing the wheel speed disturbances related
to the engine and driveline. The thesis is conducted in order to improve the
disturbance cancelation algorithm in the indirect tire pressure monitoring system,
TPI developed by NIRA Dynamics AB.
The model consists of two parts, the model of the engine and the model of the
driveline. The engine model uses an analytical cylinder pressure model capable
of describing petrol and diesel engines. The model is a function of the crank
angle, manifold pressure, manifold temperature and spark timing. The output is
the pressure in the cylinder. This pressure is then used to calculate the torque
generated on the crankshaft when the pressure acts on the piston. This torque is
then applied in the driveline model. Both a two wheel and a four wheel driveline
model are presented and they consist of a series of masses and dampers connected
to each other with stiff springs. The result is a 14 and 19 degrees of freedom
system of differential equations respectively.
The model is then validated using measurements collected at LiU during two
experiments. Measurements where conducted of the cylinder pressure of a four
cylinder petrol engine and on the wheel speed of two different cars when driven in
a test rig. The validation against this data is satisfactory and the simulations and
measurements show good correlation.
The model is then finally used to examine wheels speed disturbance phenomenon
discovered in the huge database of test drives available at NIRA Dynamics
AB. The effects of the drivelines natural frequencies are investigated and
so is the difference between the disturbances on the wheel speed for a petrol and
diesel engine. The main reasons for the different disturbance levels on the front
and rear wheels in a four wheel drive are also discussed.
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Last updated: 2019-12-02