Active vibration control of support sting in wind tunnel by using adaptive method

The low-frequency and large-amplitude coupled vibration of the support sting in wind tunnel affects the accuracy of the wind tunnel test’s data. An active vibration control system of support sting in wind tunnel is demonstrated using adaptive control method in this paper. Following the establishment of the finite element model, and the extraction of parameter matrix, the original model is reduced to lower-mode model which contains first two pitching modes based on DC gain ranking method. The active control model is proposed based on model reference adaptive control method (RACM) to control the low-frequency vibration of supporting sting in wind tunnel. Research results have justified the effectiveness of the controlled system and provided insight into the practical application of the proposed method

Analysis of wind tunnel model support system vibration

A number of wind tunnel test facilities are experiencing undesirable vibrations of the model support system. These vibrations lead to a number of problems. For example, when the model vibrates, the test conditions are no longer realistic. The dynamics of the model and sting cause the flow to become unsteady. The data collected from unsteady flow differs from that collected when the flow is steady state. Another major concern is that the vibrations could cause the model to come apart and damage components inside the wind tunnel, such as compressors or blades, which could be costly to repair. Therefore, limitations are placed on the conditions at which the tunnel can be operated. In order to reduce the vibrations in the wind tunnel, the vibration must first be measured, which will be the primary topic of this paper. The purpose of this thesis was to design a generic model support system that closely represents a typical wind tunnel model support system (sting, balance, and a generic model), measure the vibration in the model support system, perform modal analysis, and compare the results with finite element modeling. Passive damping techniques were also explored experimentally. Several experimental methods were considered as options to measure deflection of a vibrating beam. This study utilizes a cylindrical beam as a simplification of the sting problem. Three experiments were conducted, and finite element analysis was performed on the model. Experimental results showed that the model behaved similar to a typical wind tunnel model. They also showed that the insertion of a sleeve around the sting could be an effective way to attenuate the frequency, once improved. Finite element solutions obtained were generally in good agreement with the results from the experiments

Fourth NASA Workshop on Computational Control of Flexible Aerospace Systems, part 2

A collection of papers presented at the Fourth NASA Workshop on Computational Control of Flexible Aerospace Systems is given. The papers address modeling, systems identification, and control of flexible aircraft, spacecraft and robotic systems

CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999

The proceedings of a workshop sponsored by the Confederation of European Aerospace Societies (CEAS), the American Institute of Aeronautics and Astronautics (AIAA), the National Aeronautics and Space Administration (NASA), Washington, D.C., and the Institute for Computer Applications in Science and Engineering (ICASE), Hampton, Virginia, and held in Williamsburg, Virginia June 22-25, 1999 represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft

CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999

These proceedings represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft

Aeronautical engineering: A continuing bibliography with indexes (supplement 255)

This bibliography lists 529 reports, articles, and other documents introduced into the NASA scientific and technical information system in June 1990. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Distributed Sensing and System Identification of Cantilever Beams and Plates in the Presence of Weak Nonlinearities

While the mathematical foundation for modal analysis of continuous systems has long been established, flexible structures have become increasingly widespread and developing tools for understanding their mechanics has become increasingly important. Cantilever beams and plates, in particular, have been extensively studied due to their practical importance as approximations of more complex structures. The focus of this thesis is on understanding the dynamics of vibrating cantilever beams and plates through analytical and experimental investigation. Various models for the mechanics of these structures, of varying physical fidelity, are described and compared. A fiber optic sensing system is utilized to experimentally acquire distributed strain measurements, which are used to estimate the mode shapes and natural frequencies for the cantilever structures. These experimental estimates are compared with analytical and numerical solutions corresponding to the models previously introduced. Next, a detailed case study is described which demonstrates the nonlinear response in a cantilever beam\u27s first mode and implements an empirical procedure for estimating a variable parameter model which accounts for its varying system parameters. By implementing the described identification methods, parameter variations due to a system\u27s nonlinear response are included in a modified linear model and significantly reduce the errors in predicted response. Based on this research, methods to experimentally estimate and validate the mode shapes and system parameters can be implemented for other beam- and plate-like structures

Aeronautical engineering: A continuing bibliography with indexes (supplement 276)

This bibliography lists 705 reports, articles, and other documents introduced into the NASA scientific and technical information system in Feb. 1992. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

First International Symposium on Strain Gauge Balances

The first International Symposium on Strain Gauge Balances was sponsored and held at NASA Langley Research Center during October 22-25, 1996. The symposium provided an open international forum for presentation, discussion, and exchange of technical information among wind tunnel test technique specialists and strain gauge balance designers. The Symposium also served to initiate organized professional activities among the participating and relevant international technical communities. Over 130 delegates from 15 countries were in attendance. The program opened with a panel discussion, followed by technical paper sessions, and guided tours of the National Transonic Facility (NTF) wind tunnel, a local commercial balance fabrication facility, and the LaRC balance calibration laboratory. The opening panel discussion addressed "Future Trends in Balance Development and Applications." Forty-six technical papers were presented in 11 technical sessions covering the following areas: calibration, automatic calibration, data reduction, facility reports, design, accuracy and uncertainty analysis, strain gauges, instrumentation, balance design, thermal effects, finite element analysis, applications, and special balances. At the conclusion of the Symposium, a steering committee representing most of the nations and several U.S. organizations attending the Symposium was established to initiate planning for a second international balance symposium, to be held in 1999 in the UK

Aeronautical engineering: A continuing bibliography with indexes (supplement 267)

This bibliography lists 661 reports, articles, and other documents introduced into the NASA scientific and technical information system in June, 1991. Subject coverage includes design, construction and testing of aircraft and aircraft engines; aircraft components, equipment and systems; ground support systems; theoretical and applied aspects of aerodynamics and general fluid dynamics; electrical engineering; aircraft control; remote sensing; computer sciences; nuclear physics; and social sciences