Abstract

This paper presents implementation of a novel guidance logic for multi-agent fixed-wing unmanned aerial systems using a moving mesh method. The moving mesh method is originally designed for use in the adaptive numerical solution of partial differential equations where a high proportion of mesh points are placed in the regions of large solution variation and few points in the rest of the domain. In this work, the positions of the aircraft are considered as mesh nodes and connected to form a triangular mesh in two spatial dimensions. The outer aircraft, or the boundary nodes of the mesh, are moved with the velocities which are specified using the the relative distance from and the heading angle of a reference point while keeping the formation of the aircraft in a desired shape. The inner agents or the interior mesh nodes, on the other hand, are moved with a moving mesh technique to keep the whole mesh as uniform as possible. The moving mesh technique has built-in mechanisms to keep the mesh as uniform as possible and prevent nodes from crossing over or tangling. This property can be seen as an automatic collision avoidance mechanism. It also has explicit formulas for nodal velocities, which makes the technique easy to implement on computer. The centralized moving mesh guidance was complimented by a decentralized nonlinear predictive controller to control each aircraft. The mesh nodes are replaced by unmanned aerial systems with nonlinear six degrees of freedom dynamics. To increase flexibility of aircraft in the formation, the moving point concept is used to follow arbitrary linear or curvature shaped flight segments.