Differential Sweep Attitude Control for Swept Wing UAVs

A novel approach for attitude control of swept wing unmanned aerial vehicles (UAVs) is presented, involving the use of only differential wing sweep and rudder deflection. An analytic aerodynamic model of the aircraft based on simple sweep theory is derived in a first step. The prediction of a vortex lattice method is then compared to the initial model. Based on the body moment analysis of the two models, design constraints and a control structure are proposed and implemented on a small scale UAV with variable sweep wings. The control structure involves a cascaded PID controller with a nonlinear mapping from controller output to sweep angles. The obtained simulation results show that simultaneous bank and elevation inputs can be tracked successfully by the attitude controller. Tracking of step inputs and dynamic inputs in the roll direction using only wing sweep is demonstrated in flight tests. The results show that the nonlinear mapping achieves decoupling of the roll and pitch movement, but performance is limited by the inertia of the moving wings.