CODE¶

static int estimate_damping(const float *corr, int n_pts, float fs,
                             float freq, float *damping)
{
    // Find positive peaks in IFFT time-domain signal
    int n_peaks = 0, peak_indices[50];
    for (int i = 2; i < n_pts - 1 && n_peaks < 50; i++)
        if (corr[i] > corr[i-1] && corr[i] >= corr[i+1] && corr[i] > 0)
            peak_indices[n_peaks++] = i;
    if (n_peaks < 3) { *damping = 0.0f; return -2; }

    // Select peaks with > 0.3× period spacing
    float min_sep = (1.0f / freq) * fs * 0.3f;

    // Adjacent peak log ratio → ζ
    for (int i = 0; i < n_selected - 1; i++) {
        float ratio = peaks[i] / peaks[i + 1];
        if (ratio > 1.001f) {
            double zeta = log((double)ratio) / (2.0 * M_PI);
            if (zeta > 0.0 && zeta < 0.2) sum_damping += zeta;
        }
    }
    *damping = (float)(sum_damping / n_pairs);
}

int tiny_sysid_efdd(...) {
    // 1. FDD: CPSD → SVD → SV1 spectrum → peaks → freqs/shapes
    // 2. Per mode: IFFT SV1[peak±3] → SDOF autocorrelation → estimate_damping()
    // 3. Dedup by MAC
}