bearing op• データ種: なし → table(引数だけで決まる op —— 画像やデータの入力を取らない)
• 呼び出し: import acoustics; acoustics.bearing_defect_frequencies(rpm=1800.0, n_elements=9, element_diameter=8.0, pitch_diameter=40.0, contact_angle_deg=0.0) (または opsacoustics.get("bearing_defect_frequencies"))
The four characteristic rates of a rolling-element bearing, from geometry.
Derived, not tabulated. Under pure rolling the cage advances at half the sum
of the race surface speeds, which with `r = d/D cos(alpha)` gives, per
shaft revolution rate `f_r = rpm/60`:
• `FTF (cage / fundamental train) = f_r (1 - r) / 2`
• `BPFO (ball pass, outer race) = N f_r (1 - r) / 2 = N * FTF`
• `BPFI (ball pass, inner race) = N f_r (1 + r) / 2`
• `BSF (ball spin) = f_r (1 - r^2) D / (2 d)`
Two exact identities fall out and are asserted in the tests, because they
catch a transposed `d and D immediately: BPFO + BPFI = N f_r`
exactly, and `BPFO = N * FTF` exactly. Measured for the defaults
(1800 rpm, 9 elements, d = 8, D = 40, alpha = 0): `ratio = 0.200000`,
`f_r = 30.000000, FTF = 12.000000, BPFO = 108.000000`,
`BPFI = 162.000000, BSF = 72.000000` Hz, with
`BPFO + BPFI - 9 f_r = 0.000e+00 and BPFO - 9 FTF = 0.000e+00` —
exactly zero in float64, not merely small.
Returns a dict with `shaft_hz, ftf_hz, bpfo_hz, bpfi_hz`,
`bsf_hz, ratio (d/D cos alpha`), and the inputs echoed back.
Also `bsf_hz_2x`: a rolling element normally strikes *both* races per
spin, so a spall on the element itself is usually seen at `2 * BSF`, and
reporting only `BSF` is the classic way to miss it.
These are the no-slip kinematic rates. Real bearings slip by roughly a
percent, so an observed line within about 1 % of one of these is a match and
an exact match is a coincidence; that tolerance is the caller's to apply.
Raises `ValueError: non-real / string / bool scalars, rpm <= 0`,
`n_elements` not an int >= 2, non-positive diameters, an
`element_diameter >= pitch_diameter` (geometrically impossible — the
rolling elements would not fit inside the pitch circle, and the usual cause
is the two arguments being swapped, which otherwise returns a negative FTF
and a plausible-looking BPFI), and `|contact_angle_deg| >= 90`.
• acoustic_condition_monitoring ファミリ ガイド
• サンプルデータ カタログ(DL URL / ライセンス) — 2-D は skimage.data(BSD/public)+ 合成、3-D は実データ源(Stanford/PDS 等)の DL URL。
• 演算子の来歴・参考文献 — この op 族の元になった研究/手法の出典。
• アルゴリズムの正典(著者・年)と用途は上記ファミリ使い方ガイドに記載。
• acoustic_condition_monitoring — py -3.11 examples/acoustic_condition_monitoring.py
• poc_bearing_diagnosis — py -3.11 examples/poc_bearing_diagnosis.py
table を入力に取れる)bearing)envelope_spectrum · spectral_kurtosis · cepstrum
*Provenance: acoustics.py — ACOUSTICS operator registry. この per-op ノートは tools/opdocs.py md が自動生成(手編集しない)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.