Energy Perspectives in Aeroelastic Control

Energy conversion/transfer forms the basis of all aeroelastic phenomena. Future aircraft are likely to depend on active control using multiple integrated actuators and sensors. The practical implementation of active control strategies will require new approaches to control design that consider the energetics of the system. The present work takes a step in that direction by proposing controller synthesis techniques based on the energy transfer mechanisms responsible for aeroelastic flutter. Two special cases are presented, viz., an active damping controller, and a mode shape controller. An active damping controller maintains all the system characteristics except for the damping of the unstable mode. Thus, control design either adds of removes energy from the mode of interest. The mode shape controller, on the other hand, changes the mode shape of the mode being controlled such that the mode shape is unable to extract energy from the flow. The damping of the mode is changed to be consistent with the aerodynamic energy loss of the modified mode shape. Thus, the controller does not add or remove energy, but only changes the energy transfer characteristics of the mode. Both the control designs are implemented on a 2-D airfoil problem and compared with optimal control designs. The two control design techniques are found to have performance comparable to optimal controllers.