As part of the AP50, the team decided to try to simulate the flight. This would provide the capability for the team to get a better approximation of the gains used for the PID (Proportional, Integral, Derivative) controller. There are 8 PID control loops that are referenced in the AP50 manual provided by UAV Flight Systems, Inc., which are mentioned in the AP50 section of the website.
The initial goal was to relate airspeed error with elevator deflection. To solve for this, the team manipulated basic equations used for lift and inertia. When the equations were analyzed, a relationship was made. However, a problem existed in this process and the simulation results were incorrect.
The team decided to solve the problem using a different method where the control derivatives are found and placed in a state-space model that is found in any flight dynamics book.
This alternative solution included using an old program used by the AirForce called Digital Datcom. Inputs neccessary are the geometry of the airplane and flight conditions The output that it will provide are the control derivatives that can be placed into a state-space model. Using the manual for the Datcom program, proper measurements were made on the RC aircraft, and an input code was produced. See below for example of input file:
From here, the next step in the process involved taking the outputs (coefficients) and using those values to input them into a MATLAB code provided by a team mentor. This code will create a state-space model for use in Simulink. Once modeled in Simulink, the controller gains can be found.