PFR - Aerospace Engineering Sciences Senior Design Projects ...

More documents

Recommendations

Info

Project Final Report – CUDBF April 30 th , 2009 ASEN 4028: Aerospace Senior Projects 10.0 Software Design Elements Author: Brett Miller Co-Author: Mark Findley, Jarryd Allison The Buff-2 Bomber had two main software components. The first allowed the team to iterate their wing design in order to optimize the aircraft’s wing geometry. The second controlled the aircraft’s payload through the microcontroller. These two components detailed in the following sections below. 10.1 Aerodynamic Design Software The aerodynamics sub-team focused on minimizing weight, configuring the aircraft to be able to fit within the dimensions of the storage container, and most importantly being able to fly all missions. It was important to choose a geometry without negatively affecting the stability of the aircraft. Therefore, analysis was performed to select the optimal geometry configuration, while still adhering to project requirements. First the airfoil was selected, and the program XFOIL was used to determine certain airfoil properties such as lift characteristics, drag, and the moment coefficients. Flying wing airfoils documented in the University of Illinois, Urbana-Champaign airfoil database were assessed along with the Osborne Design/Build/Fly airfoil collection. From this collection, the drag polars were used to select the airfoils to be used. Figure 88: Airfoil Selection Flow Diagram To analyze the effect on static margin for a given center of gravity location with varying leading edge sweep angle and taper ratio, MATLAB code was then created to iterate between many different geometries at once, and output files that were compatible with AVL. The output geometries from MATLAB were run through the AutoIT program which entered the geometries along with commands into AVL. This process yielded the stability derivatives for every combination produced in the MATLAB iteration, and these stability derivatives were then reentered into a different MATLAB code to determine the static margin of the selected geometry. This MATLAB code stored the different sweep, taper, and static margin values, and the results plotted in order to observe how sweep and taper affect the static margin. In this way, the ideal static margin and final geometry of the Buff-2 Bomber was selected. Figure 89 shows this flow diagram. 112
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 113
Page 1:
University of Colorado Design/Build
Page 4 and 5:
Project Final Report - CUDBF April
Page 6 and 7:
Page 8 and 9:
Page 10 and 11:
Page 12 and 13:
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
Page 22 and 23:
Page 24 and 25:
Page 26 and 27:
Page 28 and 29:
Page 30 and 31:
Page 32 and 33:
Page 34 and 35:
Page 36 and 37:
Page 38 and 39:
Page 40 and 41:
Page 42 and 43:
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
Page 54 and 55:
Page 56 and 57:
Page 58 and 59:
Page 60 and 61:
Page 62 and 63:
Page 64 and 65: Project Final Report - CUDBF April
Page 164 and 165:
Page 166:
show all

PFR - Aerospace Engineering Sciences Senior Design Projects ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?