Helicopter rotor blade vibration reduction using active flaps

iHELICOPTER ROTOR BLADE VIBRATION REDUCTIONUSING ACTIVE FLAPS(Ph.D. Thesis)Uğur DALLIGAZI UNIVERSİTESİINSTUTE OF SCIENCE AND TECHNOLOGYFebruary 2007ABSTRACTA modeling and analysis study is presented to reduce helicopter rotor bladevibrations and rotor blade root loads using multiple trailing edge flaps. Acomphrehensive model for rotor blade with active trailing edge flaps isdeveloped. Rotor blade is modeled as an elastic system using the finite elementsmethod. Rotor blade root and hub loads are calculated using a non-linearquasi-steady aerodynamic model. Helirotor program is developed to calculatethe vibration characteristics, natural frequencies and mode shapes of anycomplex composite or metal helicopter rotor blade. Helisim program isdeveloped to calculate the system response, rotor blade root forces andmoments under aerodynamic forcing conditions. Rotor blade system responseis calculated using the proposed solution method and the developed programdepending on any structural and aerodynamic properties of rotor blades,structural properties of trailing edge flaps and properties of trailing edge flapactuator inputs. Rotor blade loads are determined first on a nominal rotorblade without multiple active trailing edge flaps and then the effects of theactive flap motions on the existing rotor blade loads are investigated. Multipleactive trailing edge flaps are controlled by using both open loop and closed loopcontrollers and the effects of the actuator signal output properties such asfrequency, amplitude and phase on the system response are analyzed. Effects ofusing multiple trailing edge flaps on controlling rotor blade vibrations areiiinvestigated and rules and design criteria are determined for the design oftrailing edge flap controller that will provide actuator signal outputs tominimize the rotor blade root loads. It is calculated that using the developedactive trailing edge rotor blade model, helicopter rotor blade vibrations can bereduced up to 36 % of the nominal rotor blade vibrations.Science Code : 914.1.091Key Words : Helicopter rotor blade vibrations, active trailing edgeflaps, active control of vibrations, aeroelastic rotor blademodelPage Number : 153Advisor : Assoc. Prof. Dr. Şefaatdin YÜKSEL