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P3 118.7 133.7 170.7 339.7 350.7
P4 210.1 225.2 262.2 71.2 82.2
Table 2. Separation Index Schedule (θij sep): OH-58C (de-
grees)
The extraction index, Ni j. , is interpreted as the point for which the center of the planet tooth is aligned with the ac-celerometer. Although it serves as a convenient means to conceptualize the process, most likely this is not physically correct. The accelerometer locations are approximate to within about 1 the ring gear pitch; thus, the exact location
4
within the mesh cannot be determined. All that can be said is that each collection of NTP points in the Vibration Sep-aration Vector represents a full mesh time period between a planet and a ring gear. If the partial dynamics associated with one tooth are captured in one extraction, the remainder is extracted in a subsequent extraction.
Choosing the Extraction Length,缸E
One way to ensure that a tooth’s full TMP is extracted from a single carrier cycle is to use additional data points corresponding to multiple TMPs. Setting Mv to an odd in-teger representing the number of TMPs of data desired, the corresponding number of points extracted is given by:
缸E = Mv(NT P . 1)+ 1 (14)
The constraint that Mv is an odd integer simpli.es anal-ysis in that it centers the waveform associated with N.
ij. The location of the .rst point extracted is given by:
N.= Ni. , j . .oor(缸E ), (15)2
resulting in a range of points given by:
RANGE : {N.,N.+ 1,..., N.+缸E . 1} (16)
With four planets and .ve accelerometers, there are 20 extraction locations within each carrier cycle.
Assembly Families
The extraction process is illustrated in Figure 14. In this example, accelerometer A1 is the signal under study. There are three cycles shown representing the .rst three columns of the Interpolation Matrix. Each of the four boxes in each cycle represent the extraction region, centered on Ni j, for a given accelerometer/planet pair. The ones shown are the ones associated with accelerometer A1. The width of the box represents the length of data extracted,缸E .
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