Collision Avoidance and Geofencing for Fixed-wing Aircraft with Control Barrier Functions

TL;DR

This paper presents a control framework using control barrier functions to ensure fixed-wing aircraft safely perform collision avoidance and geofencing tasks with formal safety guarantees, demonstrated through simulations.

Contribution

It introduces a novel safety filter based on control barrier functions for fixed-wing aircraft, enabling simultaneous collision avoidance and geofencing with formal safety assurances.

Findings

Control barrier functions effectively enforce safety constraints.

The framework ensures safe operation in both simulation models.

Simulations demonstrate the controller's ability to prevent collisions and boundary crossings.

Abstract

Safety-critical failures often have fatal consequences in aerospace control. Control systems on aircraft, therefore, must ensure the strict satisfaction of safety constraints, preferably with formal guarantees of safe behavior. This paper establishes the safety-critical control of fixed-wing aircraft in collision avoidance and geofencing tasks. A control framework is developed wherein a run-time assurance (RTA) system modulates the nominal flight controller of the aircraft whenever necessary to prevent it from colliding with other aircraft or crossing a boundary (geofence) in space. The RTA is formulated as a safety filter using control barrier functions (CBFs) with formal guarantees of safe behavior. CBFs are constructed and compared for a nonlinear kinematic fixed-wing aircraft model. The proposed CBF-based controllers showcase the capability of safely executing simultaneous collision avoidance and geofencing, as demonstrated by simulations on the kinematic model and a high-fidelity dynamical model.