Optimization-Free Constrained Control with Guaranteed Recursive Feasibility: A CBF-Based Reference Governor Approach

TL;DR

This paper introduces a new constrained control framework combining ERG and CBF that guarantees safety and recursive feasibility without online optimization, using a closed-form reference update law.

Contribution

It develops a novel CBF-based reference governor that ensures safety constraints are always feasible by design, avoiding online optimization.

Findings

Guarantees recursive feasibility through a closed-form reference update law.

Ensures safety constraints are maintained by design using barrier functions.

Achieves performance comparable to traditional ERG methods in simulations.

Abstract

This letter presents a constrained control framework that integrates Explicit Reference Governors (ERG) with Control Barrier Functions (CBF) to ensure recursive feasibility without online optimization. We formulate the reference update as a virtual control input for an augmented system, governed by a smooth barrier function constructed from the softmin aggregation of Dynamic Safety Margins (DSMs). Unlike standard CBF formulations, the proposed method guarantees the feasibility of safety constraints by design, exploiting the forward invariance properties of the underlying Lyapunov level sets. This allows for the derivation of an explicit, closed-form reference update law that strictly enforces safety while minimizing deviation from a nominal reference trajectory. Theoretical results confirm asymptotic convergence, and numerical simulations demonstrate that the proposed method achieves performance comparable to traditional ERG frameworks.