Robust Nonlinear Tracking Control for Unmanned Aircraft with Virtual Control Surfaces

The flight trajectory of unmanned aerial vehicles (UAVs) can be significantly affected by external disturbances such as turbulence, upstream wake vortices or wind gusts. These effects present challenges in ensuring UAV flight safety. Hence, addressing these challenges is of critical importance for integration of unmanned aerial systems (UAS) into the National Airspace System (NAS), especially in terminal airspace. This paper presents a robust nonlinear control method that can be proven to achieve altitude regulation in the presence of unmodeled external disturbances and actuator parametric uncertainty. Proof of the theoretical result is summarized,

and detailed numerical simulations are provided. Side-by-side simulation comparisons with a standard linear control method are provided for completeness. These simulations are focused on applications involving small UAVs equipped with arrays of synthetic jet actuators (SJA). The results demonstrate the capability of the proposed nonlinear controller to asymptotically reject wind gust disturbances and the parametric uncertainty inherent in the SJA model. In addition, the nonlinear controller is designed with a computationally simplistic structure. This computational structure does not require complex calculations or function approximators in the control loop. Hence, the proposed controller is a great choice for small UAV applications with limited

computational resources.