Retrofit Control with Approximate Environment Modeling

TL;DR

This paper introduces a retrofit control method that uses approximate environment models to ensure robust stability in network systems, even with modeling errors, and demonstrates its effectiveness through numerical experiments.

Contribution

It presents a novel retrofit control approach that guarantees stability despite modeling inaccuracies, enhancing modular control design in network systems.

Findings

Robust stability is maintained despite environment model errors.

Control performance can be improved by increasing model accuracy.

Numerical experiments validate the proposed method's effectiveness.

Abstract

In this paper, we develop a retrofit control method with approximate environment modeling. Retrofit control is a modular control approach for a general stable network system whose subsystems are supposed to be managed by their corresponding subsystem operators. From the standpoint of a single subsystem operator who performs the design of a retrofit controller, the subsystems managed by all other operators can be regarded as an environment, the complete system model of which is assumed not to be available. The proposed retrofit control with approximate environment modeling has an advantage that the stability of the resultant control system is robustly assured regardless of not only the stability of approximate environment models, but also the magnitude of modeling errors, provided that the network system before implementing retrofit control is originally stable. This robustness property is practically significant to incorporate existing identification methods of unknown environments, because the accuracy of identified models may neither be reliable nor assurable in reality. Furthermore, we conduct a control performance analysis to show that the resultant performance can be regulated by adjusting the accuracy of approximate environment modeling. The efficiency of the proposed retrofit control is shown by numerical experiments on a network of second-order oscillators.