On a Strong Robust-Safety Notion for Differential Inclusions

TL;DR

This paper introduces a stronger notion of robust safety for differential inclusions, using barrier functions to characterize safety under continuous perturbations, and distinguishes between strong and uniform strong robust safety.

Contribution

It defines a new, stronger robust safety concept for differential inclusions and provides barrier function-based conditions for verifying this safety.

Findings

Strong robust safety is characterized by barrier functions.

Equivalence established between strong robust safety and smooth barrier certificates.

Conditions for uniform strong robust safety are also provided.

Abstract

A dynamical system is strongly robustly safe provided that it remains safe in the presence of a continuous and positive perturbation, named robustness margin, added to both the argument and the image of the right-hand side (the dynamics). Therefore, in comparison with existing robust-safety notions, where the continuous and positive perturbation is added only to the image of the right-hand side, the proposed notion is shown to be relatively stronger in the context of set-valued right-hand sides. Furthermore, we distinguish between strong robust safety and \textit{uniform strong robust safety}, which requires the existence of a constant robustness margin. The first part of the paper proposes sufficient conditions for strong robust safety in terms of barrier functions. The proposed conditions involve only the barrier function and the system's right-hand side. Furthermore, we establish the equivalence between strong robust safety and the existence of a smooth barrier certificate. The second part of the paper proposes scenarios, under which, strong robust safety implies uniform strong robust safety. Finally, we propose sufficient conditions for the latter notion in terms of barrier functions.