An eigenvector orientation approach for detection and control of panel flutter

A basic eigenvector orientation approach has been used to evaluate the possibility of controlling the onset of panel flutter using a flat panel (wide beam) as an illustrative example. The onset of flutter can be defined as the instance when two modes coalesce. Since eigenvectors for two consecutive modes are usually orthogonal, an indication of the onset of flutter condition can be observed earlier when they start to lose their orthogonality. Using eigenvector orientation method for the prediction of the flutter boundary (indicated by a gradual loss of orthogonality between two eigenvectors) was developed in a previous study and thus can provide a 'lead time' for possible flutter control. In this study, a basic simple beam element is used to model the panel (wide beam). As a first step, piezoelectric layers are assumed to be bonded on the top and bottom surface of the panel to provide counter-bending moments at joints between elements. The standard linear quadratic control theory is used for controller design and full state feedback is considered for simplicity. The controllers are designed to modify the system stiffness matrix in such a way to restabilize the system at the onset of flutter; as a result, flutter occurrence is offset to higher flutter speed. Controllers based on different control objectives are considered and the effects of control moment locations are studied as well. Potential applications of this basic method can be straightforwardly applied to plates and shells of laminated composites using finite element method.