Performance and Robustness Assessment for a Robust Port-Hamiltonian Flight Controller

Abstract

Those conducting research in the field of nonlinear control of unmanned air vehicles are constantly searching to improve robustness and performance of flight control systems through new control laws. A control law can be designed to provide robustness guarantees due to the structure of the aircraft dynamics. This work presents an implementation of a novel control law which simultaneously transforms the nonlinear fixed-wing aircraft dynamics into a port-Hamiltonian structure using feedback linearization, from which input-to-state stability guarantees follow. This novel control law is compared to two industry standard methods, linear quadratic regulator and nonlinear dynamic inversion, which provide a baseline for comparing robustness and performance. To replicate flight, measurement noise, model mismatch, wind, and discretization with time delay were implemented in a collection of simulation studies to understand which disturbances the novel control law was most sensitive to. Due to the non-additive nature and magnitude of the applied disturbances, the novel control law was most sensitive to combinations of disturbances of wind, discretization with time delay, model mismatch, and measurement noise in order of greatest to least sensitivity. The novel control law performed as expected, and much better than both competitors, when the disturbances applied did not include wind. This result was due to a particular interaction between the wind disturbance and the construction of the novel control law that was not present with other disturbances. Future work includes flight testing and extending the robustness guarantees to non-feedback linearized systems.