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Fig. 15. Planet Gear Vibration Separation Schematic
The number of cycles available is Nextract which depends on the amount of data. For example, a typical run under the current study collects data for 40 seconds. A transmission input of 6,060 RPM produces a carrier cycle of 5.79 Hz., resulting in Nextract = 232 complete cycles captured. Since the hunting tooth ratio is Np, The .rst Np cycles correspond to alignment of a different planet tooth with the accelerome-ter and constitute a set. Likewise, each additional set of Np columns creates another set. There are .oor( Nextract ) sets
Np
available in the current Assembly Family, and, for the ex-ample provided, give 210 carrier cycles. Since, for each set, all columns represent the same tooth orientation, and the data was interpolated to correspond to the same angular po-sition; they can be averaged into a single set of Np columns and termed a time synchronously averaged set. The num-ber of columns required in a TSA set is Nset , where, for the current case, Nset = Np.
Figure 16, shows a detailed view of the TSA set, where each column of TSA set is now mapped to a row in the il-lustration. Recall the extraction index, Ni j . only need to be determined once for each Pi/Aj pair, and data is extracted about this region for all subsequent cycles. The extracted data is placed at its corresponding position along the Vibra-tion Separation Vector given by the mapping index, Ni j .. , which is governed by the planet’s tooth mesh schedule. If Mv > 1, overlapping of data will occur and the amount of overlap is governed by the number of points extracted,缸E . In addition, special windowing is required to merge over-lapping data without introducing distortion. (Refs. 26, 27)
Determining the Mapping Index, Ni j ..: PGVS
As a planet meshes with each ring tooth, it advances one ring gear pitch. For a full carrier cycle, it will have rotated Nr ring gear pitches. For a planet containing Np teeth, the next tooth to be in mesh one cycle later is determined from:
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本文链接地址：Sun Gear Fault Detection on an OH-58C Helicopter Transmission(17)
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