Coordinated Standoff Flights for Multiple UAVs via Second-Order Sliding Modes

Abstract

This study focuses on guidance associated with coordinated standoff flight for fixed-wing uninhabited aerial vehicles against a fixed or slowly moving ground target. A novel guidance law is first proposed for a single standoff-flying vehicle. Although the proposed guidance law is quite simple, it can incorporate desired properties such that the guidance law provides smooth transfer from an approach to a standoff flight. Furthermore, the proposed guidance law along with a proposed guidance-related equation guarantees a pre-specified directional (right or left) turn at the final phase of the standoff flight. The structure of the proposed guidance law forms a sliding surface for a sliding mode approach. Coordination with other UAVs is made with a decentralized velocity control that avoids central computing. A second–order sliding mode (SOSM) is selected to develop guidance schemes. The potential of the proposed method is demonstrated through multiple UAVs’ coordinated standoff flight guidance simulation where each UAV keeps a standoff position around a stationary target or a slowly moving target with coordination.