Model Reference-Based Control with Guaranteed Predefined Performance for Uncertain Strict-Feedback Systems

TL;DR

This paper presents a new model reference-based control framework for uncertain strict-feedback systems, ensuring predefined performance with robustness and stability, validated on an electromechanical actuator with significant uncertainties.

Contribution

Introduces a novel MRBC framework with homogeneous adaptive estimators and controllers using barrier Lyapunov functions for guaranteed performance in uncertain SFF systems.

Findings

Achieves exponential stability under uncertainties.

Ensures prescribed transient and steady-state performance.

Validated experimentally on an electromechanical system.

Abstract

To address the complexities posed by time- and state-varying uncertainties and the computation of analytic derivatives in strict-feedback form (SFF) systems, this study introduces a novel model reference-based control (MRBC) framework which applies locally to each subsystem (SS), to ensure output tracking performance within the specified transient and steady-state response criteria. This framework includes 1) novel homogeneous adaptive estimators (HAEs) designed to match the uncertain nonlinear SFF system to a reference model, enabling easier analysis and control design at the level, and 2) model-based homogeneous adaptive controllers enhanced by logarithmic barrier Lyapunov functions (HAC-BLFs), intended to control the reference model provided by HAEs in each SS, while ensuring the prescribed tracking responses under control amplitude saturation. The inherently robust MRBC achieves uniformly exponential stability using a generic stability connector term, which addresses dynamic interactions between the adjacent SSs. The parameter sensitivities of HAEs and HAC-BLFs in the MRBC framework are analyzed, focusing on the system's robustness and responsiveness. The proposed MRBC framework is experimentally validated through several scenarios involving an electromechanical linear actuator system with an uncertain SFF, subjected loading disturbance forces challenging 0-95% of its capacity.