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.

翻译：在航空航天控制领域，安全关键性故障往往导致致命后果。因此，飞行器控制系统必须确保严格满足安全约束，最好能提供安全行为的正式保证。本文针对固定翼飞机的避撞与地理围栏任务，建立了安全关键控制框架。该框架开发了一种运行时保证系统，可在必要时调节飞行器的标称飞行控制器，以防止其与其他飞行器相撞或穿越空间边界（地理围栏）。该运行时保证系统被构建为采用控制屏障函数的安全滤波器，并提供安全行为的正式保证。针对非线性运动学固定翼飞机模型，本文构建并比较了多种控制屏障函数。基于控制屏障函数的控制器展示了同时安全执行避撞与地理围栏任务的能力，这通过运动学模型和高保真动力学模型的仿真得到了验证。