Since you already have the equations of motion for the pitch angle, it would be helpful if you could demonstrate how basic control theory is applied to design a simple PID controller in MATLAB code. Your PID gains do not need to be optimal, as long as the control system remains stable with your chosen gains.
PSO experts/users in the forum can extend your code by simply incorporating the PSO component to demonstrate how to optimize the PID gains. This approach saves users the time required to search for textbook materials and to write the code for the pitch angle model and the PID controller components.