PFR - Aerospace Engineering Sciences Senior Design Projects ...

Project Final Report – CUDBF April 30 th , 2009
ASEN 4028: Aerospace Senior Projects
Figure 89: Wing Geometry Determination Flow Diagram
The stability derivatives calculated from AVL were then used to determine the dimensional
stability of the aircraft under different loading conditions for the chosen geometry. MATLAB
code was created to convert the non-dimensional derivatives provided by AVL into dimensional
derivatives. These were then entered into Equation 15 and Equation 16 along with the inertias
from SolidWorks for each loading case and mission. The eigenvalues of the system were then
plotted to determine the stability of the spiral divergence, dutch-roll, and roll subsidence in the
lateral direction, along with short and long period in the longitudinal direction. The flow
diagram is seen in Figure 90.
Figure 90: Stability Determination Flow Diagram
Finally, drag analysis was needed to establish that the propulsion subsystem provides enough
thrust for the aircraft to perform as expected. The geometry of the aircraft developed in AVL
was created as a three-dimensional model in SolidWorks. The model was then subjected to
Powerflow, and the drag on the body determined.
Figure 91: Drag Calculation Flow Diagram
10.2 Avionics Microcontroller Software
The following explains the software that was programmed to the microcontroller. All coding
was written in C and MPLAB was used to compile the code and generate a hex file, so it could
be programmed to the circuit board via a USB cable.
The microcontroller was programmed such that the pilot had to arm the microcontroller when he
was ready to release the payload. To activate the microcontroller, the pilot simply flipped a
switch on the transmitter. The switch on the transmitter produced two different PWM signals
each with a period of 20.0 ms. One position of the switch produced a signal with a 10% duty
cycle and the other position produced a signal with a 5% duty cycle. The signal was read into the
microcontroller and based on the duty cycle, the microcontroller either did nothing (no
deployment required) or allowed signals to be sent to the payload servos (when deployment was
required). The logic for arming the PIC can be seen in Figure 92. The microcontroller was able
to differentiate between the duty cycles by using the capture module associated with the CCP
pin. In software, it was written such that a flag was set when the CCP pin read a rising edge of
the signal. After setting a flag, a timer was initiated. Once the microcontroller found the falling
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