Flight Validation of a Global Singularity-Free Aerodynamic Model for Flight Control of Tail Sitters

This work validates through flight tests a pre- viously developed wide-envelope singularity-free aerodynamic framework, called φ-theory, for modeling dual-engine tail- sitting flying-wing vehicles for optimization-based control. The φ-theory methodology imposes a specific geometry on aerodynamic coefficients that leads to polynomial differential equations of motion amenable to semidefinite programming optimization. Through φ-theory, we illustrate a typical pre- dicted longitudinal and lateral flight envelope of a tail-sitting vehicle, which, while commonplace for fixed-wing aircraft in performance textbooks, is a novel figure that generalizes fixed- wing doghouse plots to tail-sitting vehicles. This flight envelope figure suggests a novel, natural and intuitive remote piloting interface that we validate in flight tests. Furthermore, we further validate φ-theory through the computation of flight features in simulation and their subsequent observation in flight tests.