Adaptive Output-Feedback Control with Closed-Loop Reference Models for Very Flexible Aircraft

This paper proposes a model reference adaptive controller for a class of multi-input/multi-output plants where the number of outputs is larger than the number of inputs: an example of which is very flexible aircraft. A dominant presence of model uncertainties and actuator anomalies necessitates an adaptive approach for control of very flexible aircraft. The proposed controller, denoted as the adaptive strictly positive real/loop transfer recovery controller, combines a baseline observer-based design with loop transfer recovery properties and an adaptive design based on strictly positive real transfer functions. In addition to accommodating the absence of full-state measurements, the controller includes a reference model that also plays the role of an observer through a closed-loop component. Conditions are delineated under which this controller can guarantee asymptotic reference tracking, and the control design is validated using a very flexible aircraft model around a single equilibrium flight condition with 707 states, 12 outputs, and 2 control inputs. Simulation results show that the adaptive controller not only ensures stability but also recovers a nominal performance in both the time domain and frequency domain, despite the presence of varying wing shapes and actuator anomalies.