Safe Output Regulation of Coupled Hyperbolic PDE-ODE Systems

TL;DR

This paper develops a robust control strategy for coupled hyperbolic PDE-ODE systems that ensures safe output regulation, disturbance rejection, and exponential convergence, demonstrated on a UAV payload delivery example.

Contribution

It introduces a nonovershooting backstepping control method combined with disturbance estimation for safe regulation of coupled PDE-ODE systems with safety guarantees.

Findings

Guarantees safety if initially safe, or rescues to safety within a prescribed time.

Achieves exponential convergence of output tracking error.

Ensures accurate disturbance and state estimation with exponential error decay.

Abstract

This paper presents a safe output regulation control strategy for a class of systems modeled by a coupled $2\times 2$ hyperbolic PDE-ODE structure, subject to fully distributed disturbances throughout the system. A state-feedback controller is developed by the {{nonovershooting backstepping}} method to simultaneously achieve exponential output regulation and enforce safety constraints on the regulated output that is the state furthest from the control input. To handle unmeasurable states and external disturbances, a state observer and a disturbance estimator are designed. Explicit bounds on the estimation errors are derived and used to construct a robust safe regulator that accounts for the uncertainties. The proposed control scheme guarantees that: 1) If the regulated output is initially within the safe region, it remains there; otherwise, it will be rescued to the safety within a prescribed time; 2) The output tracking error converges to zero exponentially; 3) The observer accurately estimates both the distributed states and external disturbances, with estimation errors converging to zero exponentially; 4) All signals in the closed-loop system remain bounded. The effectiveness of the proposed method is demonstrated through a UAV delivery scenario with a cable-suspended payload, where the payload is regulated to track a desired reference while avoiding collisions with barriers.