Download or read book Higher Harmonic Control Analysis for Vibration Reduction of Helicopter Rotor Systems written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: An advanced higher harmonic control (HHC) analysis has been developed and applied to investigate its effect on vibration reduction levels, blade and control system fatigue loads, rotor performance, and power requirements of servo-actuators. The analysis is based on a finite element method in space and time. A nonlinear time domain unsteady aerodynamic model, based on the indicial response formulation, is used to calculate the airloads. The rotor induced inflow is computed using a free wake model. The vehicle trim controls and blade steady responses are solved as one coupled solution using a modified Newton method. A linear frequency-domain quasi-steady transfer matrix is used to relate the harmonics of the vibratory hub loads to the harmonics of the HHC inputs. Optimal HHC is calculated from the minimization of the vibratory hub loads expressed in term of a quadratic performance index. Predicted vibratory hub shears are correlated with wind tunnel data. The fixed-gain HHC controller suppresses completely the vibratory hub shears for most of steady or quasi-steady flight conditions. HHC actuator amplitudes and power increase significantly at high forward speeds (above 100 knots). Due to the applied HHC, the blade torsional stresses and control loads are increased substantially. For flight conditions where the blades are stalled considerably, the HHC input-output model is quite nonlinear. For such cases, the adaptive-gain controller is effective in suppressing vibratory hub loads, even though HHC may actually increase stall areas on the rotor disk. The fixed-gain controller performs poorly for such flight conditions. Comparison study of different rotor systems indicates that a soft-inplane hingeless rotor requires less actuator power at high speeds (above 130 knots) than an articulated rotor, and a stiff-inplane hingeless rotor generally requires more actuator power than an articulated or a soft-inplane hingeless rotor. Parametric studies for a hingeless rotor operati...
Download or read book Higher Harmonic Control Analysis for Vibration Reduction of Helicopter Rotor Systems written by and published by . This book was released on 1994 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Smart Helicopter Rotors written by Ranjan Ganguli and published by Springer. This book was released on 2015-12-16 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Exploiting the properties of piezoelectric materials to minimize vibration in rotor-blade actuators, this book demonstrates the potential of smart helicopter rotors to achieve the smoothness of ride associated with jet-engined, fixed-wing aircraft. Vibration control is effected using the concepts of trailing-edge flaps and active-twist. The authors’ optimization-based approach shows the advantage of multiple trailing-edge flaps and algorithms for full-authority control of dual trailing-edge-flap actuators are presented. Hysteresis nonlinearity in piezoelectric stack actuators is highlighted and compensated by use of another algorithm. The idea of response surfaces provides for optimal placement of trailing-edge flaps. The concept of active twist involves the employment of piezoelectrically induced shear actuation in rotating beams. Shear is then demonstrated for a thin-walled aerofoil-section rotor blade under feedback-control vibration minimization. Active twist is shown to be significant in reducing vibration caused by dynamic stall. The exposition of ideas, materials and algorithms in this monograph is supported by extensive reporting of results from numerical simulations of smart helicopter rotors. This monograph will be a valuable source of reference for researchers and engineers with backgrounds in aerospace, mechanical and electrical engineering interested in smart materials and vibration control. Advances in Industrial Control aims to report and encourage the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rotorcraft Aeromechanics written by Wayne Johnson and published by Cambridge University Press. This book was released on 2013-04-29 with total page 949 pages. Available in PDF, EPUB and Kindle. Book excerpt: A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.
Download or read book Monthly Catalogue United States Public Documents written by and published by . This book was released on 1995 with total page 1638 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monthly Catalog of United States Government Publications written by and published by . This book was released on 1995 with total page 1632 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proceedings of the International Conference on Smart Materials Structures and Systems written by and published by Allied Publishers. This book was released on 1999 with total page 762 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rotorcraft Dynamics 1984 written by and published by . This book was released on 1985 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of the American Helicopter Society written by American Helicopter Society and published by . This book was released on 1999 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1963 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flexible Multibody Dynamics written by O. A. Bauchau and published by Springer Science & Business Media. This book was released on 2010-10-23 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt: The author developed this text over many years, teaching graduate courses in advanced dynamics and flexible multibody dynamics at the Daniel Guggenheim School of Aerospace Engineering of the Georgia Institute of Technology. The book presents a unified treatment of rigid body dynamics, analytical dynamics, constrained dynamics, and flexible multibody dynamics. A comprehensive review of numerical tools used to enforce both holonomic and nonholonomic constraints is presented. Advanced topics such as Maggi’s, index-1, null space, and Udwadia and Kalaba’s formulations are presented because of their fundamental importance in multibody dynamics. Methodologies for the parameterization of rotation and motion are discussed and contrasted. Geometrically exact beams and shells formulations, which have become the standard in flexible multibody dynamics, are presented and numerical aspects of their finite element implementation detailed. Methodologies for the direct solution of the index-3 differential-algebraic equations characteristic of constrained multibody systems are presented. It is shown that with the help of proper scaling procedures, such equations are not more difficult to integrate than ordinary differential equations. This book is illustrated with numerous examples and should prove valuable to both students and researchers in the fields of rigid and flexible multibody dynamics.
Download or read book Aeronautical Engineering A Cumulative Index to a Continuing Bibliography supplement 325 written by and published by . This book was released on 1995 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Whirl Flutter of Turboprop Aircraft Structures written by Jiří Čečrdle and published by Woodhead Publishing. This book was released on 2015-01-27 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: Whirl flutter is the aeroelastic phenomenon caused by the coupling of aircraft propeller aerodynamic forces and the gyroscopic forces of the rotating masses (propeller, gas turbine engine rotor). It may occur on the turboprop, tilt-prop-rotor or rotorcraft aircraft structures. Whirl Flutter of Turboprop Aircraft Structures explores the whirl flutter phenomenon, including theoretical and practical as well as analytical and experimental aspects of the matter. The first introductory part gives a general overview regarding aeroelasticity, followed by the physical principle and the occurrence of whirl flutter in aerospace practice. The next section deals with experiment research including earlier activities performed, particularly from the sixties, as well as recent developments. Subsequent chapters discuss analytical methods such as basic and advanced linear models, and non-linear and CFD based methods. Remaining chapters summarize certification issues including regulation requirements, a description of possible certification approaches and several examples of aircraft certification from the aerospace practice. Finally, a database of relevant books and reports is provided. - Provides complex information of turboprop aircraft whirl flutter phenomenon - Presents both theoretical and practical (certification related) issues - Presents experimental research as well as analytical models (basic and advanced) of matter - Includes both early-performed works and recent developments - Contains a listing of relevant books and reports
Download or read book 13th International Conference on Adaptive Structures and Technologies 2002 written by Elmar J. Breitbach and published by CRC Press. This book was released on 2003-08-27 with total page 686 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book will be a valuable step toward the common goal of an "adaptive" scientific community: improving everyone's quality of life in a sustainable and safe way.
Download or read book Vertica written by and published by . This book was released on 1990 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt:
