Integrated design of smart rotor and robust control system

Vibration and noise are two long-standing problems that have limited the expansion of military and commercial applications of rotorcraft. The source of these interrelated phenomena is the main rotor, which operates in an unsteady and complex aerodynamic environment. The trailing edge flap concept for smart blade control has been investigated by several researchers for possible use in noise and vibration reduction, and shows promise. The flaps are actuated using piezo-stack, bimorph or magnetostrictive actuators. It is however still unclear if there is a single actuation mechanism that addresses both noise and vibration reduction, while still having enough control authority available to act as an extra control effector in its own right. The uncertainty about the actuation mechanism, about the precise amount of flap deflection available, and about the accuracy of current constitutive models of the actuators lead to significant difficulties in analyzing the potential of the concept for helicopter applications. In this study we propose and execute an innovative approach to the above problem that consists of modeling the smart actuation mechanism using a simple low order linear model that matches test data (with an associated variation or uncertainty). We use this model in association with a helicopter flight dynamic model for carrying out an optimization of flap sizing and placement for minimum fixed frame vibration. Finally, we use the model to carry out an analysis of the effectiveness of the flap in reducing inter-axis coupling, and as a redundant control effector in case of primary actuator failure.