Safe Drone Flight with Time-Varying Backup Controllers

TL;DR

This paper introduces time-varying backup controllers (TBCs) that enhance safety and operational freedom in drone flight by generating safe reference trajectories, applicable to multi-agent systems and verified through experiments with quadrotors.

Contribution

The paper presents TBCs, a novel approach that reduces conservatism in safety control for nonlinear systems, especially in high-speed drone applications, and demonstrates their effectiveness in multi-agent scenarios.

Findings

TBCs guarantee safety while reducing conservatism.

TBCs improve operational freedom in drone control.

Experimental results show robustness and efficiency in multi-quadrotor safety filtering.

Abstract

The weight, space, and power limitations of small aerial vehicles often prevent the application of modern control techniques without significant model simplifications. Moreover, high-speed agile behavior, such as that exhibited in drone racing, make these simplified models too unreliable for safety-critical control. In this work, we introduce the concept of time-varying backup controllers (TBCs): user-specified maneuvers combined with backup controllers that generate reference trajectories which guarantee the safety of nonlinear systems. TBCs reduce conservatism when compared to traditional backup controllers and can be directly applied to multi-agent coordination to guarantee safety. Theoretically, we provide conditions under which TBCs strictly reduce conservatism, describe how to switch between several TBC's and show how to embed TBCs in a multi-agent setting. Experimentally, we verify that TBCs safely increase operational freedom when filtering a pilot's actions and demonstrate robustness and computational efficiency when applied to decentralized safety filtering of two quadrotors.