An overview of the effects of aeroservoelasticity on the design of flight control systems

The key elements in aeroservoelasticity, the dynamics of the flexible aircraft, actuator dynamics and the effects of digital control have been identified. It is suggested that the effect of exciting the structural modes can be considered as measurement noise, resulting in the possible trade-off between system bandwidth and flexible mode attenuation. In addition, the effect of high frequency signal components on the performance of the actuator is highlighted. The current design methodology of designing the feedback filtering to meet a conservative clearance margin is discussed. This methodology assumes the in-phase addition of the control surface contributions to avoid the robustness problem associated with the need to consider variations in phase between the various signal paths. Although current work is concentrating on the effects of the nonlinear nature of the system, and not addressing the multivariable nature of the problem, it is clear that aeroservoelasticity is a current engineering problem in which multivariable methods may well have a role to play in the future