Optimal Selection of Control Surfaces for Active Aeroelastic Control of Prescribed Modes

Abstract

Efficient distribution of control through actuating control surfaces plays a critical role in designing the optimal active aeroelastic control. A wing planform may consist of multiple control surfaces which may be used to facilitate certain desired control objectives such as suppression of flutter instabilities, flutter boundary extension and gust load alleviation. This leads to the design of control surfaces for facilitating the desired control while still satisfying the sizing constraints of the control surfaces and other cost functions i.e. controller norms and actuator saturation. Wing configurations having multiple control surfaces also present an opportunity to select “an optimal combination of control surfaces” which can satisfy the control objective. Moreover, the aeroelastic structures have an inherently large number of modes, therefore it is desired to design a controller for some targeted modes without affecting any other aeroelastic modes. In this research, these two aspects of active aeroelastic control are considered. An investigation of the optimal placement of control surfaces is considered such that a prescribed flutter boundary extension is achieved for a given flight envelope by controlling only a few targeted modes. A multi-input state feedback controller based on the method of receptances is designed for controlling the targeted modes of interest. Several performance measures are developed for identifying the optimal placement of control surfaces which also satisfies the dynamic constraint of pole placement for a desired flutter boundary extension. Numerical examples involving multi-mode wing models having multiple control surfaces are presented to highlight the effectiveness of a controller with the optimal placement of control surfaces.