Viscosity CBFs: Bridging the Control Barrier Function and Hamilton-Jacobi Reachability Frameworks in Safe Control Theory

Fuente: arXiv
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Main Authors: Hirsch, Dylan, Fisac, Jaime Fernández, Herbert, Sylvia
Format: Preprint
Published: 2025
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author Hirsch, Dylan
Fisac, Jaime Fernández
Herbert, Sylvia
author_facet Hirsch, Dylan
Fisac, Jaime Fernández
Herbert, Sylvia
contents Control barrier functions (CBFs) and Hamilton-Jacobi reachability (HJR) are central frameworks in safe control. Traditionally, these frameworks have been viewed as distinct, with the former focusing on optimally safe controller design and the latter providing sufficient conditions for safety. A previous work introduced the notion of a control barrier value function (CB-VF), which is defined similarly to the other value functions studied in HJR but has certain CBF-like properties. In this work, we proceed the other direction by generalizing CBFs to non-differentiable ``viscosity'' CBFs. We show the deep connection between viscosity CBFs and CB-VFs, bridging the CBF and HJR frameworks. Through this bridge, we characterize the viscosity CBFs as precisely those functions which provide CBF-like safety guarantees (control invariance and smooth approach to the boundary). We then further show nice theoretical properties of viscosity CBFs, including their desirable closure under maximum and limit operations. In the process, we also extend CB-VFs to non-exponential anti-discounting and update the corresponding theory for CB-VFs along these lines.
format Preprint
id arxiv_https___arxiv_org_abs_2510_09929
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Viscosity CBFs: Bridging the Control Barrier Function and Hamilton-Jacobi Reachability Frameworks in Safe Control Theory
Hirsch, Dylan
Fisac, Jaime Fernández
Herbert, Sylvia
Systems and Control
Control barrier functions (CBFs) and Hamilton-Jacobi reachability (HJR) are central frameworks in safe control. Traditionally, these frameworks have been viewed as distinct, with the former focusing on optimally safe controller design and the latter providing sufficient conditions for safety. A previous work introduced the notion of a control barrier value function (CB-VF), which is defined similarly to the other value functions studied in HJR but has certain CBF-like properties. In this work, we proceed the other direction by generalizing CBFs to non-differentiable ``viscosity'' CBFs. We show the deep connection between viscosity CBFs and CB-VFs, bridging the CBF and HJR frameworks. Through this bridge, we characterize the viscosity CBFs as precisely those functions which provide CBF-like safety guarantees (control invariance and smooth approach to the boundary). We then further show nice theoretical properties of viscosity CBFs, including their desirable closure under maximum and limit operations. In the process, we also extend CB-VFs to non-exponential anti-discounting and update the corresponding theory for CB-VFs along these lines.
title Viscosity CBFs: Bridging the Control Barrier Function and Hamilton-Jacobi Reachability Frameworks in Safe Control Theory
topic Systems and Control
url https://arxiv.org/abs/2510.09929