order op• データ種: signal → table
• 呼び出し: import acoustics; acoustics.angular_resample(x, rate, rpm, samples_per_rev=64) (または opsacoustics.get("angular_resample"))
時間波形を軸回転角の軸へ再標本化する(計算次数比分析)。
> 以下の詳細説明は原文のままです —— 要約と見出しは訳出済み。
Under a changing shaft speed, a component locked to the shaft has a moving
frequency and smears across the spectrum, while a structural resonance stays
put. Resample the record so the samples are equally spaced in shaft angle
instead of in time and the situation reverses exactly: the order becomes a
single line and the resonance smears.
`rpm` is either a single number (constant speed — the transform is then a
pure rescaling) or a per-sample array on the same clock as the signal. The
cumulative revolution count is the trapezoidal integral of `rpm/60`, and
the signal is linearly interpolated onto a uniform grid in it.
Returns a dict — an angle-domain record is not put into circulation as a
plain signal, deliberately. Its samples are indexed by angle, not time, so
handing it to any op that takes a `rate` would produce frequencies in Hz
from an axis measured in revolutions: no exception, no NaN, just wrong
numbers. (Same judgement, and the same reason, as `motionmag.motion_magnify`
not exposing a bare video adapter.) The dict carries `signal`,
`angle_rev, samples_per_rev, revolutions` (total),
`whole_revolutions, rate` (the original time-domain one, for
provenance), `mean_rpm, max_order`.
`max_order is samples_per_rev / 2` — the Nyquist of the *angle* axis.
Measured: a pure order-3.5 component on a 600 -> 1800 rpm ramp, resampled at
64 samples/rev over 78 whole revolutions, reads amplitude 0.999371 in a
single bin of the order spectrum; the same component in the ordinary
spectrum peaks at 0.070203 and is 66.5 Hz wide.
Raises `ValueError: everything :func:_as_signal` refuses, a
non-positive or wrong-length `rpm, samples_per_rev` outside
`[2, 65536], an output over :data:MAX_ANGULAR_SAMPLES`, fewer than one
complete revolution in the record, and — the aliasing refusal — a
`samples_per_rev` whose implied Nyquist order needs content above the
time-domain Nyquist. Asking for 64 samples/rev on a shaft turning at 30 Hz
means representing 960 Hz, which a 100 Hz recording does not contain; the
resampler would happily manufacture it from the interpolation.
• 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
table を入力に取れる)order)*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.