Designing active flutter suppression for high-dimensional aeroelastic systems involving a control delay

Many linear control laws, such as optimal controllers and classical controllers, have seen their applications to suppressing the aeroelastic vibrations of the high-dimensional aeroelastic system. However, those conventional control laws may not work effectively if the high-dimensional aeroelastic system involves a control delay. The paper reveals the effect of input time delay on the stability of a controlled high-dimensional aeroelastic system in an incompressible flow field and presents a new optimal control law to suppress the flutter of the high-dimensional aeroelastic system with an input time delay in the control loop. The procedure of designing the proposed control law includes three steps as follows. The first step is to convert the system described by a set of differential equations with a time delay into a set of difference equations involving discrete delay terms by using zero-order holder. The second step, exhibiting the novelty of the study, is to transform the difference equations with delay terms into a set of delay-free difference equations via a state transformation. The third step is to use the theory of linear control, say, the theory of Linear Quadratic Gaussian (LQG), to complete the design of controller by solving an equivalent Riccati equation. The paper demonstrates the efficacy of proposed method in designing the flutter suppression controller for a wind-tunnel model of Multiple-Actuated Wing. The new method works much better than classical feedback and conventional LQG controllers, both of which do not take the input time delay into account and may induce instability, when the input time delay becomes significant.