Design of an integrated control system for flutter margin augmentation and gust load alleviation, tested on a dynamic windtunnel model

Since 1981 the National Aerospace Laboratory NLR has been involved in a research program to study the aeroelastic effects of active control systems. This research program was concentrated on the performance of a number of windtunnel tests with a dynamic windtunnel model, exhibiting "hard" flutter characteristics, lightly damped rigid body modes and equipped with active ailerons, tailplanes, spoilers and rudder. These windtunnel tests were carried out in a subsonic windtunnel under normal flow conditions as well as in a simulated discrete or random gust environment. This paper describes the design method and shows some results from windtunnel tests of a digitally implemented, integrated control system for both flutter margin augmentation and gust load alleviation. The control system was designed using optimization techniques applied to a "reduced order output controller". Either the ailerons or the spoilers were used as control surfaces, while tailplanes and rudder were used additionally for rigid body mode control.