| commit | ad9197ca6ae4370f4004c9e7d254341370cb26a6 | |
| author | ctzsnooze <chris.thompson@sydney.edu.au> | |
| Sat, 21 Jul 2018 12:53:07 +0000 (21 22:53 +1000) | ||
| committer | ctzsnooze <chris.thompson@sydney.edu.au> | |
| Sat, 21 Jul 2018 12:55:41 +0000 (21 22:55 +1000) | ||
| tree | 82c8310982623f13ff7fa55a527b2f1daaa95952 | treesnapshot (tar.gz zip) |
| parent | 039c74c8961136beb88502103f0025a526f29e61 | commitdiff |
Dynamic Notch Filter Update
Improves performance of the dynamic notch filter, increasing peak accuracy over a wider band of frequencies, and generally using a narrower, higher notch.
Details:
- FFT now operates on gyro data *after* gyro notches and lowpasses
- FFT bandpass Q changed from 0.707 to 0.05, to 'open up' the FFT to a greater range of incoming frequencies
- FFT centre output now ranges from about 130 to 666Hz.
- ignore the lowest couple of FFT bins going into centre frequency calculation
- analyse FFT bins from low to high, keep ignoring bins until a bin is found that exceeds its previous bin by a factor of 2; then start examining bins from the bin before that (stops the FFT from being biased low, or going to the lowest value if there is no notch at all).
- if no bin exceeds previous by more than 2 times, ie no obvious peak, smoothly go to maximum allowed notch frequency to avoid delay (might be better to bypass filter altogether?)
- dominant bin emphasised by cubing bin height before calculating mean
- maximum cutoff frequency is half the highest allowable centre frequency
- default notch width is +/-25% of centre, narrower than before most of the time
- code tidied up
- thanks to rav, Flint, UAV Tech, icr4sh, diehertz and everyone else who helped with this.
Improves performance of the dynamic notch filter, increasing peak accuracy over a wider band of frequencies, and generally using a narrower, higher notch.
Details:
- FFT now operates on gyro data *after* gyro notches and lowpasses
- FFT bandpass Q changed from 0.707 to 0.05, to 'open up' the FFT to a greater range of incoming frequencies
- FFT centre output now ranges from about 130 to 666Hz.
- ignore the lowest couple of FFT bins going into centre frequency calculation
- analyse FFT bins from low to high, keep ignoring bins until a bin is found that exceeds its previous bin by a factor of 2; then start examining bins from the bin before that (stops the FFT from being biased low, or going to the lowest value if there is no notch at all).
- if no bin exceeds previous by more than 2 times, ie no obvious peak, smoothly go to maximum allowed notch frequency to avoid delay (might be better to bypass filter altogether?)
- dominant bin emphasised by cubing bin height before calculating mean
- maximum cutoff frequency is half the highest allowable centre frequency
- default notch width is +/-25% of centre, narrower than before most of the time
- code tidied up
- thanks to rav, Flint, UAV Tech, icr4sh, diehertz and everyone else who helped with this.