كاهش ارتعاشات پره اصلي هلي كوپتر به روش IBC

چكيده انگليسي :

Vibration Reduction of Helicopter Main Rotor with IBC Method Mohsen Razouei m razooee@me iut ac ir Date of Submission 2012 03 12 Department of Mechanical Engineering Isfahan University of Technology 84156 83111 Isfahan IranDegree M Sc Language FarsiSupervisor Hassan Nahvi hnahvi@cc iut ac irAbstract Rotor Vibration is of utmost problem in helicopter industry Reducing vibration levels of the helicopter havemany benefits such as reducing maintenance cost by increasing the fatigue life of critical structuralcomponents reducing crew fatigue improving crew awareness and reliability and improving communityacceptance by increasing passenger comfort In this thesis a modified Myklestad method for rotating beamshas been developed and represent the helicopter blade by lamped mass system which includes effects of rotaryinertia blade geometric pitch and inertial and elastic coupling among the five degrees of freedom at each massstation radial motion is not included Shear deformation and aerodynamic effect are not considered Discretespanwise variation of blade properties and various hub configurations are modeled in the program In order tobe able to determine blade lift drag flapping moment and ultimately rotor vibratory loads it is necessary aswith axial flight to determine the induced velocity In the aerodynamic chapter aerodynamics are modeledwith an approximation method named classical actuator disc theory mangler squire method used to modelinduced velocity within rotor disk classical theory The dynamics of the blades and rotor are equallysusceptible to simple approaches based on straight forward ideas of induced velocity aerofoil characteristicsand blade modeling At last vibration solution coupled with aerodynamic loads for modeling blade vibrationsand then a control method is proposed to reduce vibrations in helicopters using individual blade control on themain rotor blades The problem of stabilization of hub vibratory loads in a front fight subject to externaldisturbances is addressed Robust control is a branch of control theory that explicitly deals with uncertainty inits approach to controller design Robust control methods are designed to function properly so long asuncertain parameters or disturbances are within some typically compact set Robust methods aim to achieverobust performance and or stability in the presence of bounded modeling errors In contrast with an adaptivecontrol policy a robust control policy is static rather than adapting to measurements of variations thecontroller is designed to work assuming that certain variables will be unknown Necessary and sufficientconditions are presented for static output feedback control of linear time invariant systems using the H Infinityapproach The novelty of the method is that each blade is controlled independently taking into account possibleuncertainty such as helicopter velocity etc and develop the equations of motion for the structural andaerodynamic forces and moments of a rotor blade using five degrees of freedom This is different fromprevious control approaches that assumed blades were identical and generated a single control input which isapplied with adequate phase shift to each blade Keywords IBC Robust control Helicopter vibration reduction Rotating blade

رضوئي، محسن

كاهش ارتعاشات پره اصلي هلي كوپتر به روش IBC

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