Table 1 Frequency-domain feature extraction.
From: A novel simultaneous monitoring method for surface roughness and tool wear in milling process
No. | Signal feature | Expression |
|---|---|---|
1 | Frequency center (fc) | \(\frac{\int _{0}^{+\infty } f P(f) df}{\int _{0}^{+\infty } P(f) df}\) |
2 | Mean square frequency (msf) | \(\frac{\int _{0}^{+\infty } f^{2} P(f) df}{\int _{0}^{+\infty } P(f) df}\) |
3 | Root mean square frequency (rmsf) | \(\sqrt{\frac{\int _{0}^{+\infty } f^{2} P(f) df}{\int _{0}^{+\infty } P(f) df}}\) |
4 | Frequency variance (fv) | \(\frac{\int _{0}^{+\infty } (f-fc)^{2} P(f) df}{\int _{0}^{+\infty } P(f) df}\) |
5 | Frequency standard deviation (fsd) | \(\sqrt{\frac{\int _{0}^{+\infty } (f-fc)^{2} P(f) df}{\int _{0}^{+\infty } P(f) df}}\) |
