Robust and Synchronous Nonlinear Controller for Autonomous Formation Flight of Fixed Wing UASs

A robust and synchronous formation flight controller is developed for fixed wing unmanned aerial systems (UASs) in a leader-follower architecture. The controller is composed of a nonlinear dynamic inversion recently developed in literature and a robust sliding mode controller and takes into account exchanges of data among neighbor vehicles. A Lyapunov candidate function demonstrates the stability of the proposed controller. A simulation evaluates three configurations of the proposed controller: a non-synchronous configuration that uses the discontinuous and chattering generating sign function, a non-synchronous configuration using the continuous saturation function that avoids chattering at the cost of lower steady state performance and finally the synchronous version using the saturation function. These configuration variants are compared to a linear controller of the literature. It is shown that, for the proposed controller, the use of the saturation function provides significant chattering reduction without much performance penalty. It is also shown that the synchronous variant increases the performance of the formation shape error transient response at the cost of decreased formation position error transient response performance.