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Prof. Hall's main research interests are the control of flexible structures, especially space structures; and control of helicopter rotor dynamics, especially using piezoelectric actuators. In the flexible structure control area, the main focus is the development of methods for designing high performance controllers which are robust to model uncertainty. In the rotor control area, the emphasis is on the development of blade-mounted actuators for high-frequency control of vibration, noise, etc. Some recent and current projects are described below.
Blade-Mounted Actuators for Rotor Control: Development of actuators that can fit within a helicopter rotor blade and produce useful actuation effort at high frequency. Research is focusing on the use of a piezoelectric ceramic bender to control a trailing edge flap. We have developed a scaled bench-top article demonstrating the feasibility of the concept. Future plans are to demonstrate the concept on a spinning model rotor.
Mixed H2/H° Control Techniques: Develop methodologies for the analysis and synthesis of control systems to minimize the H2 (root-mean-square) performance of systems subject to H° (worst-case) modeling errors. The topic is primarily theoretical, with possible application to flexible space structures, among others.
Multiplier Methods for Robust Control Design: Recent developments have made connections between modern robust control techniques (i.e., H°) and multiplier methods (i.e., the Popov test) of the 1960Õs. The goal is to further develop these connections, and in the process extend the types of problems that can be handled in robust control theory.
Analysis of the Effectiveness of Blade-Mounted Actuation for Rotor Control: Determine the effectiveness of blade-mounted actuators for rotor control. The problem is that rotors are highly flexible, so that control surface actuation produces a complex response in the rotor, including blade twist, flapping, and other effects.
Also pursuing research in: Extensions of optimal lifting theories to helicopters and birds.