A nonlinear flight controller design for a UFO by trajectory linearization method. I. Modeling

We present the development of a nonlinear dynamic model of a 3 degrees-of-freedom (3 DOF) flight control experiment apparatus, the "Quanser UFO", which is a helicopter with three propellers driven by DC motors. The modeling includes determination of the geometric and physical properties of the airframe, control derivatives, static stability, as well as closed-loop attitude control performance specifications. The location of the center of gravity (CG) and the mass moments of inertia are determined by both experimental approaches and by means of a three-dimensional computer aided design (CAD) software package Solid Edge. The control effectiveness derivative matrix is determined from the nominal DC motor and propeller parameters. Closed-loop flying quality specifications are also derived, assuming the UFO is a 1:9 scale model of a real aircraft. The nonlinear dynamic model was then implemented and validated in SIMULINK.