Abstract:
Aircraft is a complicated structure with numerous automated systems that must work
together to provide the desired functions. Aircraft fuel tank control system is implemented
to maximized the fuel system performance. The adoption and integration of a control
system for an aircraft’s fuel system is a complex series of interconnected devices in the
aerospace industry, that are required to supply fuel in proportion to an engine’s effective
and efficient throughput. The analysis in this thesis involves calculating the fuel flow rate
of a model flight cycle while taking into account all of the aircraft’s static and dynamic
factors. A mathematical model of the system has been created, and the model was validated.
In this Thesis, aircraft fuel tank control system is highly affected by disturbance and
parameter variation. Sliding Mode Control (SMC) method was studied for controlling the
fuel flow because of its robustness against model uncertainties and external disturbances.
In this method, using high control gain to over come uncertainties lead to occur chattering
phenomena in control law which can excite unmodeled dynamics and may harm the
plant. As a result various approaches were proposed to reduce chattering. Among
those intelligent methods like, Fuzzy Logic Controller (FLC) was used to reduce the
sliding mode switching control law effect. Then, a sliding mode fuzzy logic controller
(SMFLC) was constructed to connect with a light-wing two-engine aircraft fuel system.
The proposed controller guarantees that the actual motor speed tracks the reference
speed slightly faster than the proportional-integral-derivative controller. The speed
difference between the actual and the reference for a PID speed controller is 0.0034
while for the SMFLC is 0.0014 which implies the PID has larger steady state error. In
all cases, the proposed SMFLC controller has better performance than conventional PID
controller in controlling speed of aircraft fuel tank system. SMFLC was also robust
against external disturbance. The performance of the system have been simulated using
the MATLAB-Simulink program. The performance of the proposed controller profile was
plotted, and the extracted findings from the proposed controller was compared to similar
(like PID controller) plots.
Key Words: Aircraft Fuel System, Mathematical model, MATLAB-Simulink, Sliding
Mode Fuzzy Logic Controller