3 edition of Application of higher harmonic control to hingeless rotor systems found in the catalog.
Application of higher harmonic control to hingeless rotor systems
1991 by National Aeronautics and Space Administration, Ames Research Center, For sale by the National Technical Information Service in Moffett Field, Calif, [Springfield, Va .
Written in English
|Statement||Khanh Nguyen and Inderjit Chopra.|
|Series||NASA technical memorandum -- 103846|
|Contributions||Chopra, Inderjit., Ames Research Center.|
|The Physical Object|
"Vibrations of rotary-wing aircraft may derive their energy from the rotation of the rotor rather than from the air forces. A theoretical analysis of these vibrations is described and methods for its application are explained herein" (p. 1). Information about self-excited speed range and shaft-critical speed are provided for any rotor with more than two by: harmonic drive operation can be found in , . Construction of harmonic drives with gear meshing at two diametrically opposite ends improves the contact ra-tio of gear teeth by at least twice that of conventional transmissions. Because of this harmonic drives have higher gear reduction, lower (almost zero) backlash and higher. Here are some Record rainfalls How often are weather records broken? The harmonic series gives the answer. Suppose we have a list of rainfall figures for a hundred years. How many record-breaking falls of rain do you expect have taken place over t.  S. Panza, M. Lovera, Rotor state feedback in helicopter flight control: robustness and fault tolerance, IEEE MultiConference on Systems and Control, Antibes, France,  F. Riccardi, M. Lovera, Robust attitude control for a variable-pitch quadrotor, IEEE MultiConference on Systems and Control, Antibes, France,
the natural frequencies for rotating systems can help to avoid system failure by giving the safe operating speed range. In the present work, finite element method has been used to find these natural frequencies for different possible cases of multi-rotor and gear-branched systems.
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APPLICATION OF HIGHER HARMONIC CONTROL TO HINGELESS ROTOR SYSTEMS Khanh Nguyen* t Inderjit Chopra tRotorcraft Aemmechanics Branch, NASA Ames Research Center, Moffett Field CA $ Center for Rotorcraft Education and Research, Department of Aerospace Engineering, University of Maryland, College Park, Maryland File Size: 1MB.
COVID Resources. Reliable information about the coronavirus (COVID) is available from the World Health Organization (current situation, international travel).Numerous and frequently-updated resource results are available from this ’s WebJunction has pulled together information and resources to assist library staff as they consider how to handle.
To alleviate these drawbacks of helicopters, active rotor control technologies have been investigated for a long time. Many different approaches have been investigated and most of them are not being followed any more.
First investigations started with so-called Higher Harmonic Control (HHC) which has been replaced by Individual Blade Control (IBC).Cited by: the rotor swashplate to actively control vibration in this way is generally referred to as higher harmonic control (HHC).
However, it is clear that HHC systems for vibration reduction can also utilize airframe control surfaces such as flaps, ailerons, elevators, and rudders, airframe-mounted devices such as seismic masses andFile Size: 88KB.
closed-loop stability properties of higher harmonic control, based on a simulation study of the coupled rotor-fuselage dynamics of a four-bladed hingeless rotor helicopter. Application of higher harmonic control to hingeless rotor systems [microform] / Khanh Nguyen and Inderji Aeroelastic simulation of higher harmonic control [microform] / Lawson H.
Robinson and Peretz P. Friedmann; Comprehensive analysis of helicopters with bearingless rotors [microform]: status report / by V.R. Murthy. A higher harmonic control (HHC) investigation was conducted on a full-scale, isolated XV Rotor in helicopter mode in the NASA Ames by Foot Wind Tunnel to independently control noise, vibra-tion, and trim.
The higher harmonic blade root pitch was generated using swashplate oscillations. The ra-File Size: 1MB. Higher harmonic control (HHC) is one of the several active control concepts that have the goal of reducing helicopter vibration. HHC has been researched, flight and wind tunnel tested by several investigators and organiza- tions.l'15 To date, due to various adverse considerations (weight, cost, reliability, complexity, etc.), HHC has not.
Higher Harmonic Control (HHC) has been considered for many years a valid approach for the design and the implementation of active rotor control Author: Christoph Keßler.
An active control concept for reducing helicopter vibration levels, in which the control system Application of higher harmonic control to hingeless rotor systems book vibrations originating with aerodynamic forces acting on the rotor blades, and applies high-frequency pitch motion to the rotor blades at very small.
active control of structural response (ACSR). Within the ﬁrst category of active control, where the pri-mary objective is to reduce vibrations in the rotor, two approaches have emerged. These are (1) higher harmonic control (HHC) where the blades are activated in.
The rigid rotor system shown in Figure is mechanically simple, but structurally complex because operating loads must be absorbed in bending rather than through hinges.
In this system, the blade roots are rigidly attached to the rotor hub. Rigid rotor systems tend to. Conventional, Compound, and Coaxial Helicopters Using Higher Harmonic Control by Eli B. Giovanetti Department of Mechanical Engineering and Materials Science Duke University Date: Approved: Kenneth C.
Hall, Supervisor Earl H. Dowell. 30th Structures, Structural Dynamics and Materials Conference. 03 April - 05 April Mobile,AL,U.S.A. Application of higher harmonic control (HHC) to hingeless rotor systems. Forward flight aeroelasticity of a hingeless rotor blade. Prescribed wake formulations are much faster than free-wake codes, Application of higher harmonic control to hingeless rotor systems book they require simplified á priori information of the induced velocity field within the rotor disk to compute the wake.
SummaryThe application of second harmonic control on a helicopter rotor causes a redistribution of the loading over the disc. This can be utilised to postpone the forward speed limitations imposed by stalling of the retreating blade.
This report develops the theory for secondharmonic Size: KB. Based on the harmonic vibration response coupling action of nonlinear vibration system, the harmonic vibration synchronization transition rule of dual excitation sources has also been analyzed. At the end, the validity of the harmonic vibration synchronization phenomenon analysis was verified by numerical simulation and application experiments.
: Xiaohao Li, Tao Shen. Complex harmonic analysis for rotor systems has been proposed from the strict complex modal analysis based upon Floquet theory. In this process the harmonic balance method is adopted, effectively associated with conventional eigenvalue analysis.
Also, the harmonic coefficients equivalent to dFRFs in harmonic mode has been derived in by: 1. convergence for the higher harmonic control application.
Results from the simulation demonstrate that the HLMS approach is far superior to the standard multifrequency, filtered-x LMS algorithm in adaptive, feedforward, higher-harmonic control.
PACS numbers: Vn INTRODUCTION Higher-harmonic control has been a subject of interest. Stability of hingeless and bearingless rotors in forward flight lead-lag deflection and w the flap deflection.
Then the blade undergoes a rotation 0. about the deformed elastic axis: 0, = + and = _ ~` VV dx, (1) 0 where 0 is the pretwist, is the geometric twist, and Cited by: 6. Identification of the Harmonic Transfer Functions of a Helicopter Rotor by Afreen Siddiqi Submitted to the Department of Aeronautics and Astronautics on February,in partial fulfillment of the requirements for the degree of Master of Science Abstract.
We present a method for computing the optimal aerodynamic performance of conventional and compound helicopters in trimmed forward flight with a limited set of design variables and control inputs, including conventional and higher harmonic blade control, and radial twist and chord distributions.
The first active rotor approach, tested in the s (Warnicke and Drees) on a 2-bladed UH-1 relied upon oscillating the existing main rotor blades through the rotor control system; a method known as Higher Harmonic Control (HHC).
Typically, helicopters have three hydraulic servos that move the swashplate which, in turn, steers the main rotor Author: William A.
Welsh. A Harmonic Balance Approach for the Analysis of Flexible Rotor Bearing Systems on Non-Linear Support M.A. Rezvani1 Abstract. The purpose of this article is to describe the theoretical background to the Harmonic Balance approach; adopted and further developed for the analysis of general multi degree of freedom rotor bearing systems with Author: M.A.
Rezvani. The Rigid Rotor The rigid rotor is a simple model of a rotating diatomic molecule. We consider the diatomic to consist of two point masses at a fixed internuclear distance.
We then reduce the model to a one-dimensional system by considering the rigid rotor to have one mass fixed at the origin, which is orbited by the reduced mass, at a distance. Higher harmonic blade pitch control: a system for helicopter vibration reduction.
Author(s) Shaw, John. DownloadFull printable version (Mb) Other Contributors. Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. by: and adjusted to model a multilayer. rotor. Positive- and negative-sequence currents have been taken into account and impedances for forward- and backward-travelling field have been found.
The method of the performance calculation for a multilayer rotor induction motor, including current assymetry and higher space harmonics, has been worked out.
Mast moment measurement in hingeless rotors I want clarification with reference to the mast moment measurement in 4-bladed hingeless rotor (Example like in BOEC, BK and ALH from India).
The measurement of mast moment was done on rotating mast with reference to main rotor blade through strain gauge/slip rings. Cons of the higher harmonics, 'the first order effects are eliminated in the generalised forms 91 + a, longitudinally and -AI + bl laterslly.
The definition of h perpendicular to the rotor diso is required for the evriluation of a, anti of the control angles if required. Differentiating equation (3) nFile Size: 1MB. Response Control (SRC) algorithms, were developed – .
Previously, such controllers have mainly been used for rotor-bearing systems, Active Magnetic Bearings (AMBs) and helicopter rotors, for instance. The SRC has proven to be advantageous in AMBs  but has not previously been demonstrated in rotor vibration attenuation by using a self.
the number of rotor blades. Im et al.7 developed an implicit harmonic balance method to accelerate the solution convergence, and the convergence of this method was an order of magnitude faster than that of an explicit time-marching computation.
Thus, in our study, the implicit harmonic balance method was used to resolve the open rotorCited by: 7. EFFECT OF HARMONICS ON A SOLID-ROTOR INDUCTION MOTOR A. Saleh and A. Radhi air-gap flux the rotor impedance at the fundamental supply frequency can be expressed in terms of the air-gap voltage, E, [A.
Saleh, ] as below Z2f = 2 2 3 θ ρ ∠ K DEs AmL N B f e s (2) Equivalent CircuitFile Size: 3MB. This paper deals with analyzing the operating modes peculiarities of induction motor equipped with ACS frequency converter. Great attention is given to the study of higher current harmonics behavior at changing rotation velocity and momentum of the induction motor.
Advantages and disadvantages of frequency converter application are discussed in by: 5. Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation by: American Institute of Aeronautics and Astronautics Sunrise Valley Drive, Suite Reston, VA Higher Harmonic Flapping Motion Profile Power and Radial Flow Flap Motion with a Hinge Spring Flap Hinge Offset Hingeless Rotor Gimballed or Teetering Rotor Pitch-Flap Coupling "Helicopter Force, Moment, and Power Equilibrium" Lag Motion Reverse Flow Compressibility Tail Rotor Brand: Dover Publications.
Theoretical analysis and practical application experiments demonstrate that the higher the harmonic vibration response order of nonlinear vibration system is, the more difficult it is for the dual excitation rotors to realize the harmonic vibration synchronization, and the smaller the driving torque difference Δ T and damping coefficient c 1 Author: Xiaohao Li, Tao Shen.
of harmonic linearization in its application to systems with "strong" nonlinearity. By writing the given equation (1) in.t;he form of equation (8) all the variants of the method of harmonic balance in control theory and all generalizations of the method also become easily understandable.
The harmonic drive gear is the subject of continuous development, due to new market requirements from each of the major application areas. Common requirements are the desire for higher power density, higher torsional stiffness and lower ratios.
There are therefore four key themes driving current product development • Reduced size • Reduced File Size: KB. Harmonic Balance in Rotor/Stator Contact Problems 2 lems, the HBM is essentially a frequency-domain method.
It is not only convenient for purposes of linearisation of systems with small non-linearities , but can can also be applied to large non-linearities . Kim et. New material is included on blade tip design, flow characteristics surrounding the rotor in forward flight, tail rotors, brown-out, blade sailing and shipborne trating on the well-known Sikorsky configuration of single main rotor with tail rotor, early chapters deal with the aerodynamics of the rotor in hover, vertical flight.A summary of rotor-hub bending moments encountered by a high-performance hingeless-rotor helicopter during nap-of-the-earth Application of higher harmonic blade feathering on the OH-6A helicopter for vibration Aerospace Laboratory, Inc Systems Control Technology, and United States.
Federal Aviation Administration.The Harmonic Oscillator as a Control System The classical harmonic oscillator is an example of a primitive control system where there is no representation of the controlled system S as distinct from S itself.
Information flows directly from S to the controller C. A hydrogen molecule can be treated as a harmonic oscillator.