I am using a pc running linix with lyx 1.1.5fix2. When I put in a file like the one I've enclosed and try to save it as post-script, all of the reference numbers turn to question marks. Could you try this on your system to see if it also happens with you? I've never had this happen before, and I have no idea what I have changed to make it that way. Any ideas would be greatly appreciated...as my coworker wants to switch to Microsoft Word to write our paper!! Yikes! Anna Pryor
#LyX 1.1 created this file. For more info see http://www.lyx.org/ \lyxformat 2.16 \textclass article \begin_preamble \usepackage{pslatex} \end_preamble \language default \inputencoding latin1 \fontscheme default \graphics default \paperfontsize default \spacing single \papersize Default \paperpackage a4 \use_geometry 0 \use_amsmath 0 \paperorientation portrait \secnumdepth 3 \tocdepth 3 \paragraph_separation indent \defskip medskip \quotes_language english \quotes_times 2 \papercolumns 1 \papersides 1 \paperpagestyle default \layout Title \series bold The Application of Time-Frequency Methods to HUMS \layout Standard \added_space_top 0.3cm \added_space_bottom 0.3cm \align center \LyXTable multicol5 6 2 0 0 -1 -1 -1 -1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 0 0 "" "" 8 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" 0 8 1 0 0 0 0 "" "" \series bold Anna H. Pryor \series default \newline \series bold Marianne Mosher \series default \newline NASA Ames Research Center \newline NASA Ames Research Center \newline Moffett Field, Ca 94035 \newline Moffett Field, CA 94035 \newline M.S. 269-3 \newline M.S. 269-3 \newline [EMAIL PROTECTED] \newline [EMAIL PROTECTED] \newline \newline \layout Subsubsection* Background \layout Standard Metrics based on frequency analysis are currently used on vibration data to detect faults from gearboxes \begin_inset LatexCommand \cite{8} \end_inset . These methods have been shown to find faults \begin_inset LatexCommand \cite{12} \end_inset . Frequency methods give global information about the signal. In Health and Usage Monitoring Systems (HUMS), it is critical to determine as soon as possible when a fault has occurred so that corrective actions can be taken. In standard Fourier analysis, a signal is decomposed into individual frequencie s. Unfortunately, there is no way to determine at what point in time each of those frequencies has occurred. However, there are signal processing methods which give local information about both time and frequency. These methods localize faults in time and therefore may be more sensitive to early changes in the signal due to impending faults. Some of these methods have been studied by other researchers \begin_inset LatexCommand \cite{1,10,11} \end_inset . \layout Subsubsection* Paper Focus \layout Standard In this paper, five methods of time-frequency (TF) analysis will be discussed: the Short Time Fourier Transform (STFT) \begin_inset LatexCommand \cite{2} \end_inset , the Choi-Williamson method \begin_inset LatexCommand \cite{1,9} \end_inset , Instantaneous frequency \begin_inset LatexCommand \cite{5} \end_inset , the Nelson method of cross-spectral analysis \begin_inset LatexCommand \cite{6,7} \end_inset , and the Wavelet transform \begin_inset LatexCommand \cite{2} \end_inset . In comparing these methods, the following will be included: the assumptions, resources, resolution, speed of calculation, resulting information, invertibili ty and a ranking of importance. \layout Standard There are two important data sets that have been obtained and which will be used to compare the methods. The first data set was obtained from an OH-58A transmission on a test-rig \begin_inset LatexCommand \cite{3} \end_inset . It consists of 146 records where torque, bending force and lifting force are varied in a controlled experiment. No teeth were notched in the gear. This data serves as a baseline and shall be referred to as the phase1a data.The second is a set of 449 records of vibration data from a gear with 19 teeth in which 9 teeth were innitially notched. The experiment was run until all 9 teeth broke. This shall be referred to as the historical data. Before this paper is completed, a third set of data from the same group as in \begin_inset LatexCommand \cite{3} \end_inset will be taken. An OH-58A test-rig with a single notched tooth will be tested until rupture. These data will be useful in obtaining information about the study of HUMS. \layout Standard \added_space_top 0.3cm \added_space_bottom 0.3cm \align center \begin_inset Figure size 283 283 file RMS.eps width 1 10.00 height 1 10.00 flags 9 \end_inset \layout Subsubsection* Example \layout Standard The figure below is included to show some of the information that can be obtained with one of these methods. Using the historical data, each set of records was transformed using the Daubechies Wavelet transform into 1024 time units by 512 time scales. Then for each transformed time history, the inner product was taken along each row, and finally the composition of all inner products was placed into a single plot. From this composition it is easy to see that at the 44th, 127th and 210th records, there is a distinct change in the data when the torque was increased at each of those points. In addition, there are other records in which there is a dramatic change in the data which may occur because of tooth anomalies or other problems with the gear. Obviously, for practical use, this plot must be condensed into something simpler for implementing on-line use. This will also be presented in the final paper. \layout Standard \added_space_top 0.3cm \added_space_bottom 0.3cm \align center \begin_inset Info \end_inset \layout Bibliography \bibitem {1} Cohen, Leon: Time-Frequency Distributions-A Review, Proceedings of the IEEE, Vol. 77, No. 7, July 1989. \layout Bibliography \bibitem {2} Kaiser, Gerald; A Friendly Guide to Wavelets, Birkhauser, 1994. \layout Bibliography \bibitem {3} Huff et. al.; Experimental Analysis of Mast Lifting and Bending Forces on Vibration Patterns Before and After Pinion Reinstallation in an OH-58 Transmission Test Rig, Proceedings of American Helicopter Society 56th Annual Forum, May 2-4, 2000. \layout Bibliography \bibitem {4} Lewicki, David G.; Coy, John J.; Vibration Characteristics of OH-58A Helicopter Main Rotor Transmission, NASA Technical Paper 2705, 1987. \layout Bibliography \bibitem {5} Nachtsheim, Philip R.: Analysis of the Effects of Tooth Fracture on the Vibration Characteristics of a Helicopter Main Rotor Transmission, NASA TM 112232, 1998. \layout Bibliography \bibitem {6} Nelson, Douglas J., Wysocki, Wayne; Cross-Spectral Metnods with an Application to Speech Processing, Proceedings of Advanced Signal Processing Conference of SPIE, 1999. \layout Bibliography \bibitem {7} Nelson, Douglas J.; Cross-Spectral Methods for Processing Speech, submitted to JASA, downloaded April 26, 2000. \layout Bibliography \bibitem {8} Samuel, Paul D., Pines, Darryll J., Lewicki, David G.; A Comparison of Stationary and Non-Stationary Metrics for Detecting Faults in Helicopter Gearboxes, Journal of the American Helicopter Society, 1998. \layout Bibliography \bibitem {9} Staszewski, W.J.; Worden, K.; Tomlinson, G.R.; Time-Frequency Analysis in Gearbox Fault Detection Using the Wigner-Ville Distribution and Pattern Recognition, Mechanical Systems and Signal Processing, Vol 11, No. 5, pages 673-692, 1997. \layout Bibliography \bibitem {10} Wang, W.J.; McFadden, P.D.; Early Detection of Gear Failure by Vibration Analysis--I. Calculation of the Time-Frequency Distribution, Mechanical Systems and Signal Processing, Vol 7, No. 3, pages 193-203, 1993. \layout Bibliography \bibitem {11} Wang, W.J.; McFadden, P.D.; Early Detection of Gear Failure by Vibration Analysis--I I. Interpretation of the Time-Frequency Distribution Using Image Processing Techniques, Vol 7, No. 3, pages 205-215, 1993.2 \layout Bibliography \bibitem {12} Zakrajsek, James J.; Handschuh, Robert F.; Lewicki, David G.; Decker, Harry J.: Detecting Gear Tooth Fracture in a High Contact Ratio Face Gear Mesh, NASA Technical Memorandum 106822, 1995. \the_end
