Design and real time testing of a trajectory linearization flight controller for the "Quanser UFO"

In this paper, the design and real-time testing of an attitude controller for a 3-DOF flight control experiment apparatus, the "Quanser UFO," is presented. The UFO is an educational and research test bed for multi-input, multi-output (MIMO) nonlinear tracking and decoupling control techniques. Changes in the roll, pitch and yaw attitude are affected by differential thrust and differential reactive torque using three propellers. The dynamics and control of the UFO are highly nonlinear and coupled. The controller presented here is designed by the trajectory linearization method. It consists of two components: a pseudo-inverse of the plant that computes the nominal control (open-loop control), and a linear time-varying feedback regulator that stabilizes and decouples the tracking error dynamics (closed-loop control). For regulating the attitude and the body rate tracking errors, inner and outer loop PI controllers are employed, which are designed by time-varying bandwidth PD-eigenstructure assignment. The controller was implemented and tuned in both SIMULINK and the real-time UFO simulator. The modeling and controller design procedures are outlined. Design, implementation, simulation and real-time testing results are presented.