Adaptive output-feedback control for relative degree two systems based on closed-loop reference models

In this paper, a new adaptive output-feedback controller for multi-input-multi-output (MIMO) linear plant models with relative degree two is developed. The adaptive controller includes a baseline design based on observers and parameter adaptation based on a closed-loop reference model (CRM). The overall design guarantees robust stability and tracking performance in the presence of parametric uncertainties that are commonly seen in aircraft applications.