Safety Guardrails in the Sky: Realizing Control Barrier Functions on the VISTA F-16 Jet

TL;DR

This paper presents Guardrails, a control barrier function-based safety mechanism implemented on an F-16 jet, ensuring real-time safety during autonomous and human-controlled flight tests.

Contribution

It introduces Guardrails, a novel runtime safety assurance method that blends human or AI commands with safe control actions on high-performance autonomous systems.

Findings

Guardrails successfully enforced safety constraints during flight tests.

The system minimally modified unsafe pilot inputs to maintain safety.

Flight tests demonstrated effective supervision of a human pilot by Guardrails.

Abstract

The advancement of autonomous systems -- from legged robots to self-driving vehicles and aircraft -- necessitates executing increasingly high-performance and dynamic motions without ever putting the system or its environment in harm's way. In this paper, we introduce Guardrails -- a novel runtime assurance mechanism that guarantees dynamic safety for autonomous systems, allowing them to safely evolve on the edge of their operational domains. Rooted in the theory of control barrier functions, Guardrails offers a control strategy that carefully blends commands from a human or AI operator with safe control actions to guarantee safe behavior. To demonstrate its capabilities, we implemented Guardrails on an F-16 fighter jet and conducted flight tests where Guardrails supervised a human pilot to enforce g-limits, altitude bounds, geofence constraints, and combinations thereof. Throughout extensive flight testing, Guardrails successfully ensured safety, keeping the pilot in control when safe to do so and minimally modifying unsafe pilot inputs otherwise.