Design of Hybrid Dynamic Balancer and Vibration Absorber

[[abstract]]This study proposed a novel hybrid dynamic balancer and vibration absorber that is cheaper than active dampers and more effective than passive dampers. The proposed damping system does not need to be altered structurally to deal with different damping targets. Rather, the proposed vibration absorber is capable of self-adjustment to the optimal damping location in order to achieve balance and, thereby, optimize damping effects. The proposed device includes a groove under the damping target with inertial mass hung from a coil spring beneath. This allows the device to bounce vertically or rotate in order to reduce vibrations in the main body. The coil spring vibration absorber can also slide along the groove in order to adjust its location continuously until the vibrations in the system are minimized and the main body is balanced. Experiments verify the efficacy of the proposed device in improving damping performance beyond what has been achieved using conventional devices. We also provide an explanation of the theoretical underpinnings of the design as well as the implications of these findings with regard to future developments.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SCI[[cooperationtype]]國外[[ispeerreviewed]]Y[[booktype]]電子版[[countrycodes]]NL

Characteristics and capacities of the NASA Lewis Research Center high precision 6.7- by 6.7-m planar near-field scanner

A very precise 6.7- by 6.7-m planar near-field scanner has recently become operational at the NASA Lewis Research Center. The scanner acquires amplitude and phase data at discrete points over a vertical rectangular grid. During the design phase for this scanner, special emphasis was given to the dimensional stability of the structures and the ease of adjustment of the rails that determine the accuracy of the scan plane. A laser measurement system is used for rail alignment and probe positioning. This has resulted in very repeatable horizontal and vertical motion of the probe cart and hence precise positioning in the plane described by the probe tip. The resulting accuracy will support near-field measurements at 60 GHz without corrections. Subsystem design including laser, electronic and mechanical and their performance is described. Summary data are presented on the scan plane flatness and environmental temperature stability. Representative near-field data and calculated far-field test results are presented. Prospective scanner improvements to increase test capability are also discussed

減振器位置對於雙層振動平板減振效能之研究

[[sponsorship]]中華民國航空太空學會; 交通大學機械工程系; 交通大學前瞻火箭研究中心; 國家科學委員會工程技術發展處工程科技推展中心[[conferencetype]]兩岸[[conferencedate]]20121215~20121215[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]新竹, 臺

Index to nasa tech briefs, issue number 2

Annotated bibliography on technological innovations in NASA space program

An Assessment of Modern Methods for Rotor Track and Balance

One routine maintenance item facing the helicopter industry today is the issue of rotor track and balance (RT&B). While the task of reducing vibrations is often overlooked as simply an unimportant maintenance concern, what should not be overlooked is the extensive amount of time and money committed by maintenance to smoothing an aircraft. If there were a way to make the process of rotor track and balance more efficient it would be a huge boost to the helicopter industry in both time and money. The first steps towards research into new and improved methods is to evaluate what is currently used in the field, determine if there is room for improvement and if so what can be improved. While each company may use a slightly different approach to correct the problem, each method has essentially the same objective--to reduce vibrations in the helicopter structure due to main and tail rotor rotation. This document reflects the findings of a study done to gather information and evaluate the different RT&B methods that currently exist, pinpointing the existing weaknesses in the process. In most all cases, a qualitative approach was used in determining problems and comparing current systems as the actual proprietary algorithms used by RT&B companies were unavailable

Energy efficient engine: Flight propulsion system preliminary analysis and design

The characteristics of an advanced flight propulsion system (FPS), suitable for introduction in the late 1980's to early 1990's, was more fully defined. It was determined that all goals for efficiency, environmental considerations, and economics could be met or exceeded with the possible exception of NOx emission. In evaluating the FPS, all aspects were considered including component design, performance, weight, initial cost, maintenance cost, engine system integration (including nacelle), and aircraft integration considerations. The current FPS installed specific fuel consumption was reduced 14.2% from that of the CF6-50C reference engine. When integrated into an advanced, subsonic, study transport, the FPS produced a fuel burn savings of 15 to 23% and a direct operating cost reduction of 5 to 12% depending on the mission and study aircraft characteristics relative to the reference engine

Shape Memory Polymer Resonators as Highly Sensitive Uncooled Infrared Detectors

Uncooled InfraRed (IR) detectors have enabled the rapid growth of thermal imaging applications. These detectors are predominantly bolometers, where the heating of pixel from incoming IR radiation is read out as a resistance change. Another uncooled sensing method is to transduce the IR radiation into the frequency shift of a mechanical resonator. We present here a highly sensitive, simple to fabricate resonant IR sensor, based on thermo-responsive Shape Memory Polymers (SMPs). By exploiting the phase-change polymer as the transduction mechanism, our approach provides 2 orders of magnitude improvement of the temperature coefficient of frequency (TCF). The SMP has very good absorption in IR wavelengths, obviating the need for an absorber layer. A Noise Equivalent Temperature Difference (NETD) of 22 mK in vacuum and 112 mK in air are obtained using f/2 optics. Such high performance in air eliminates the need for vacuum packaging, paving a path towards flexible IR sensors

Air vehicle diagnostic system rotor head load and global fault evaluation as installed on the SH-60F helicopter

This study covers SH-60F rotor head load estimation, track and balance fault detection, and degraded component diagnostics of the Air Vehicle Diagnostic SystemAdvanced Technology Demonstration. The purpose of this study was to acquire load data from selected,SH-60F main rotor components; provide proof of concept for the use of neural networks in load estimation; acquire SH-60F main rotor track and balance and vibration data in nominal (no known defect) condition and with intentionally induced known out of track and balance conditions in the main rotor; and acquire SH-60F main rotor track and balance and vibration data in nominal condition and with degraded rotor head components at varying flight conditions. The method of data collection was a survey recorder which houses a memory unit, a neural network and the maneuver recognition algorithms. The memory unit was used to record the load estimation,maneuver recognition algorithms, track and balance, and main rotor degraded component detection system results. Data signals are received directly from the aircraft 1553 databus, existing aircraft systems, and special sensors designed for each task. Strain gauges placed at four different rotor head locations to provide truth data for comparison with the neural network data. The instrumentation monitors 37 parameters for three testing phases totaling over 50 flight hours. Results indicate that the neural network estimation are within 10 percent of the actual strain gauge loads and that the main rotor track and balance capability of the system was able to quickly and accurately track the rotor system and lower vibrations to acceptable levels. The main rotor head fault detection data provided further support for the use of neural networks in vibration analysis