Shock Workflows¶

fdscore provides dedicated transient shock workflows built on a recursive IIR SDOF backend. These workflows are intentionally separate from the generic FFT-domain ERS path.

SRS and PVSS¶

Use compute_srs_time(...) for shock response spectra and compute_pvss_time(...) for pseudo-velocity shock spectra.

from fdscore import SDOFParams, compute_srs_time, compute_pvss_time

sdof_srs = SDOFParams(q=10.0, metric="acc", fmin=5.0, fmax=2000.0, df=5.0)
sdof_pvss = SDOFParams(q=10.0, metric="pv", fmin=5.0, fmax=2000.0, df=5.0)

srs = compute_srs_time(x, fs, sdof=sdof_srs, detrend="median", peak_mode="abs")
pvss = compute_pvss_time(x, fs, sdof=sdof_pvss, detrend="median", peak_mode="both")

Important constraints:

compute_srs_time(...) requires sdof.metric="acc".
compute_pvss_time(...) requires sdof.metric="pv".
both support peak_mode="abs", "pos", "neg", or "both".
peak_mode="both" returns ShockSpectrumPair.

For short extracted shock windows, detrend="median" is often a practical starting point.

Event Detection¶

Detected-event workflows are useful when one long signal contains multiple transient shocks.

from fdscore import detect_shock_events

events = detect_shock_events(
    x,
    fs,
    detrend="median",
    threshold_reference="rms",
    threshold_multiplier=5.0,
    min_separation_s=0.050,
    window_s=0.040,
)

The returned ShockEventSet stores the selected windows and the detector settings used to produce them.

Rolling SRS and PVSS¶

Once events are detected, each event window can be evaluated independently.

from fdscore import compute_rolling_srs_time, compute_rolling_pvss_time

rolling_srs = compute_rolling_srs_time(
    x,
    fs,
    sdof=sdof_srs,
    events=events,
    detrend="none",
    peak_mode="abs",
)

rolling_pvss = compute_rolling_pvss_time(
    x,
    fs,
    sdof=sdof_pvss,
    events=events,
    detrend="none",
    peak_mode="abs",
)

The returned RollingERSResult.response matrix has shape (n_events, n_freq).

Shock Envelope Helpers¶

Mission-style shock composition is handled explicitly through sided envelope helpers.

from fdscore import envelope_srs, envelope_pvss

srs_env = envelope_srs([srs_run_1, srs_run_2, srs_run_3])
pvss_env = envelope_pvss([pvss_run_1, pvss_run_2, pvss_run_3])

For peak_mode="both", these helpers envelope the negative and positive sides separately and return another ShockSpectrumPair.

Half-Sine Reduction¶

PVSS can be reduced to an equivalent half-sine pulse for requirement simplification or bench setup studies.

from fdscore import fit_half_sine_to_pvss, synthesize_half_sine_pulse

pulse = fit_half_sine_to_pvss(pvss_abs)
x_half_sine = synthesize_half_sine_pulse(
    pulse,
    fs=20000.0,
    total_duration_s=0.100,
    t_start_s=0.010,
)

This fit is an enveloping approximation derived from the PVSS. It is not intended to reconstruct the original measured pulse exactly.