The pursuit of lightweight structures and high-aspect-ratio wings in modern aircraft design enhances aerodynamic efficiency but inherently reduces structural stiffness, thereby decreasing flutter speeds. To safely exploit such configurations, future designs may benefit from active flutter suppression (AFS). Designing effective AFS controllers is challenging due to the large number of sensor signals to be considered, the spatial distribution of sensors and actuators, and the coupling of multiple aeroelastic modes. The input/output blending method provides a systematic means to reduce this complexity by isolating individual modes. Modes of the system are decoupled through appropriately selected linear combinations of inputs and outputs. The controllers then consist of an output blending vector, an input blending vector, and a scalar gain with which the designer can tune (usually increase) the damping of the target mode without affecting its frequency and without affecting other modes.
This paper introduces new generalizations of the input/output blending method using linear inequality constraints. The new capabilities are leveraged to introduce new parameters allowing the designer to tune the trade-off between decoupling robustness and actuator effort, which the original method did not allow. The original input/output blending is a special case of this generalized method. Furthermore, a damping lower bound constraint is introduced, which relaxes the decoupling constraints and leads to a lower feedback gain than previous methods.