Download or read book Application of Higher Harmonic Blade Feathering for Helicopter Vibration Reduction written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-22 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Higher harmonic blade feathering for helicopter vibration reduction is considered. Recent wind tunnel tests confirmed the effectiveness of higher harmonic control in reducing articulated rotor vibratory hub loads. Several predictive analyses developed in support of the NASA program were shown to be capable of calculating single harmonic control inputs required to minimize a single 4P hub response. In addition, a multiple-input, multiple-output harmonic control predictive analysis was developed. All techniques developed thus far obtain a solution by extracting empirical transfer functions from sampled data. Algorithm data sampling and processing requirements are minimal to encourage adaptive control system application of such techniques in a flight environment. Powers, R. W. Unspecified Center NASA-CR-158985 NAS1-14552...

Download or read book Application of Higher Harmonic Blade Feathering for Helicopter Vibration Reduction written by Richard W. Powers and published by . This book was released on 1978 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of Higher Harmonic Blade Feathering on the OH 6A Helicopter for Vibration Reduction written by F. K. Straub and published by . This book was released on 1986 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Survey of Research in Helicopter Higher Harmonic Control with Plans for Nearterm Naval Postgraduate School Tests written by and published by . This book was released on 1995 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: A survey of research in the area of helicopter vibration reduction through the use of higher harmonic bade pitch control is presented. Higher Harmonic Control (HHC) is an active vibration suppression system for helicopters. Vibration is reduced through feathering of helicopter rotor blades at (b-1)omega, bomega, and (b+1)omega harmonic relationships to reduce airframe vibrations at the blade passage frequency bomega where b is the number of blades and omega is the main rotor rotational speed. Research has been in the areas of blade stresses, vibrations, control systems HHC algorithms, and methods of actuation. HHC has also been reported to affect helicopter performance and main rotor noise. Also presented are preliminary plans for performance testing testing of a Higher Harmonic Control system by the Naval Postgraduate School on the U.S. Naval Academy whirl tower at Annapolis.

Download or read book On the Use of Active Higher Harmonic Blade Pitch Control for Helicopter Vibration Reduction written by Charles E. Hammond and published by . This book was released on 1980 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vibration levels have been a problem in helicopters since their inception. The reason for this lies in the method whereby the helicopter generates its lift, namely, the rotor system. As the rotor blades rotate they encounter a continuously changing aerodynamic environment which results in a continuously changing environment which results in a continuously changing aerodynamic loading on the blades. This changing environment is repeated on each revolution of the rotor. Hence, the rotor develops aerodynamic loads which are oscillatory in nature. These oscillatory loads are transferred directly to the helicopter airframe through the mechanical connection of the rotor to the airframe, i.e., the rotor-shaft/transmission attachment. Oscillatory loads are also transmitted to the airframe by impingement of the rotor wake on the upper portion of the airframe, but the mechanically transferred loads are in most cases much more significant than the aerodynamically transferred loads. (Author).

Download or read book A Survey of Research in Helicopter Higher Harmonic Control with Plans for Nearterm Naval Postgraduate School Test written by Jeffrey H. Carlsen and published by . This book was released on 1995 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: A survey of research in the area of helicopter vibration reduction through the use of higher harmonic bade pitch control is presented. Higher Harmonic Control (HHC) is an active vibration suppression system for helicopters. Vibration is reduced through feathering of helicopter rotor blades at (b-1)omega, bomega, and (b+1)omega harmonic relationships to reduce airframe vibrations at the blade passage frequency bomega where b is the number of blades and omega is the main rotor rotational speed. Research has been in the areas of blade stresses, vibrations, control systems HHC algorithms, and methods of actuation. HHC has also been reported to affect helicopter performance and main rotor noise. Also presented are preliminary plans for performance testing testing of a Higher Harmonic Control system by the Naval Postgraduate School on the U.S. Naval Academy whirl tower at Annapolis.

Download or read book Higher Harmonic Blade Pitch Control for Helicopter Vibration Reduction a Feasibility Study written by John Shaw (Jr) and published by . This book was released on 1968 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: The concept of eliminating most helicopter vibration by changing certain rotor harmonic airloads and blade motions with harmonic pitch control is discussed in detail. A simple method of obtaining the required pitch harmonics by periodic tilting of the swashplate is presented. Attention is given to the origin and characteristics of four problems expected in applying the pitch control concept: shed wake reduction of harmonic pitch effectiveness, high blade bending moments, high blade bending moments, high loads in the pitch control linkages, and the need for adjustment of the pitch control as flight condition changes. Numerical results are given to show the effect of third harmonic pitch on the cockpit vibration caused by a three-bladed articulated rotor at moderate forward speed. Several examples are given to illustrate the strong influence of shed wake on the effectiveness of harmonic pitch variations. Finally, the smooth single-minimum character of vibration dependence on pitch harmonic magnitude and phase suggests that inflight adjustment by steepest-descent type search is feasible. (Author).

Download or read book Higher Harmonic Blade Pitch Control written by John Shaw and published by . This book was released on 1980 with total page 1010 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 NASA Technical Paper written by and published by . This book was released on 1982 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Feasibility Study of Helicopter Vibration Reduction by Self optimizing Higher Harmonic Blade Pitch Control written by John Shaw (Jr) and published by . This book was released on 1967 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Feasibility Study of Helicopter Vibration Reduction by Self optimising Higher Harmonic Blade Pitch Control written by John Shaw and published by . This book was released on 1967 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1987 with total page 1126 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Download or read book Application of Chaos Methods to Helicopter Vibration Reduction Using Higher Harmonic Control written by Martinus M. Sarigul-Klijn and published by . This book was released on 1990 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chaos is a discipline used in understanding complex nonlinear dynamics. The geometric and topological methods of Chaos theory are applied, for the first time, to the study of flight test data. Data analyzed is from the McDonnell Douglas OH-6A Higher Harmonic Control (HHC) test aircraft. HHC is an active control system used to suppress helicopter vibrations. Some of the first practical applications of Chaos methods are demonstrated with the HHC data. Although helicopter vibrations are mostly periodic, evidence of chaos was found. The presenc3e of a strange attractor was shown by computing a positive Lyapunov exponent and computing a non-integer fractal correlation dimension. Also, a broad band Fourier spectrum and a well defined attractor in pseudo phase space are observed. A limit exists to HHC vibration reduction due to the presence of chaos. A new technique based on a relationship between the Chaos methods (the Poincare section and Van der Pol plane) and the vibration amplitude and phase was discovered. This newly introduced technique results in the following: 1) it gives the limits of HHC vibration reduction, 2) it allows rapid determination of best phase for a HHC controller, 3) it determines the minimum HHC controller requirement for any helicopter from a few minutes duration of flight test data (for the OH-6A, a scheduled gain controller for HHC appears to be adequate for steady level flight), 4) it shows that the HHC controller transfer matrix is linear and repeatable when the vibrations are defined in the?Rotor Time Domain? and that the matrix is nonlinear and nonrepeatable when the vibrations are defined in the?Clock Time Domain.? This technique will reduce future HHC flight test requirements. Further, the technique does not require the helicopter to be equipped with HHC. These methods may be applicable to other vibration control and flight testing problems.

Download or read book Morphing Wing Technologies written by Sergio Ricci and published by Butterworth-Heinemann. This book was released on 2017-10-27 with total page 970 pages. Available in PDF, EPUB and Kindle. Book excerpt: Morphing Wings Technologies: Large Commercial Aircraft and Civil Helicopters offers a fresh look at current research on morphing aircraft, including industry design, real manufactured prototypes and certification. This is an invaluable reference for students in the aeronautics and aerospace fields who need an introduction to the morphing discipline, as well as senior professionals seeking exposure to morphing potentialities. Practical applications of morphing devices are presented—from the challenge of conceptual design incorporating both structural and aerodynamic studies, to the most promising and potentially flyable solutions aimed at improving the performance of commercial aircraft and UAVs. Morphing aircraft are multi-role aircraft that change their external shape substantially to adapt to a changing mission environment during flight. The book consists of eight sections as well as an appendix which contains both updates on main systems evolution (skin, structure, actuator, sensor, and control systems) and a survey on the most significant achievements of integrated systems for large commercial aircraft. Provides current worldwide status of morphing technologies, the industrial development expectations, and what is already available in terms of flying systems Offers new perspectives on wing structure design and a new approach to general structural design Discusses hot topics such as multifunctional materials and auxetic materials Presents practical applications of morphing devices

Download or read book Adaptive Inverse Control for Rotorcraft Vibration Reduction written by Stephen A. Jacklin and published by . This book was released on 1985 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Historical Overview of Aeroelasticity Branch and Transonic Dynamics Tunnel Contributions to Rotorcraft Technology and Development written by and published by DIANE Publishing. This book was released on 2001 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: