Eliminating Persistent Boundary Residence via Matrosov-Type Auxiliary Functions

TL;DR

This paper introduces an auxiliary function framework inspired by Matrosov arguments to eliminate persistent boundary residence in safety-critical control, ensuring trajectories do not remain on the boundary indefinitely while maintaining safety.

Contribution

It proposes a novel auxiliary function approach that guarantees boundary-level liveness without compromising safety or requiring controller modifications.

Findings

The method prevents infinite boundary residence in safety systems.

It preserves forward invariance while ensuring boundary liveness.

Numerical examples demonstrate effective boundary sticking removal.

Abstract

Control barrier functions enforce safety by guaranteeing forward invariance of an admissible set. Under standard (non-strict) barrier conditions, however, forward invariance alone does not prevent trajectories from remaining on the boundary of the safe set for arbitrarily long time intervals, potentially leading to boundary sticking or deadlock phenomena. This paper studies the elimination of persistent boundary residence under forward-invariant barrier conditions. Inspired by Matrosov-type arguments, we introduce an auxiliary function framework that preserves forward invariance while excluding infinite-time residence within boundary layers. Sufficient conditions are established under which any trajectory can only remain in a prescribed neighborhood of the boundary for finite time, thereby restoring boundary-level liveness without altering forward invariance. The proposed construction does not rely on singular barrier formulations or controller-specific modifications, and can be incorporated into standard safety-critical control architectures. Numerical examples illustrate the removal of boundary sticking behaviors while maintaining safety across representative systems.