APPLICATION OF THE AERODYNAMIC ENERGY CONCEPT TO FLUTTER SUPPRESSION AND GUST ALLEVIATION BY USE OF ACTIVE CONTROLS

摘要

The effects of active controls on flutter suppression and gust alleviation of two different types of subsonic aircraft (the Arava twin turboprop STOL transport and the Westwind twin-jet business transport) are investigated. The active control surfaces are introduced in pairs which include, in any chosen wing strip, a 20-percent chord leading-edge (L.E.) control and a 20-percent chord trailing-edge (T.E.) control. Each control surface is driven by a combined linear-rotational sensor system located on the activated strip. The control law is based on the concept of aerodynamic energy and utilizes previously optimized control law parameters based on two-dimensional aerodynamic theory. The best locations of the activated system along the span of the wing are determined for bending-moment alleviation, reduction in fuselage accelera¬tions, and flutter suppression. The effectiveness of the activated system over a wide range of maximum control deflections is also determined. Two control laws are investigated. The first or basic control law utilizes both rigid-body and elastic contributions of the motion. The second or extended control law employs primarily the elastic contribution of the wing and leads to large increases in the activated control effectiveness as compared with the basic control law.nThe results indicate that flutter speed can be significantly increased (over 70 percent increase) and that the bending moment due to gust loading can be almost totally eliminated by a control system of about 10 to 20 percent span with reasonable control-surface rotations. Large reductions in fuselage accelerations can also be obtained by a small number of activated L.E.-T.E. control systems.