search

bryanwweber / UConnRCMPy

Data processing code for the RCM at UConn
BSD 3-Clause "New" or "Revised" License
4 stars 3 forks source link

Automatically determine filter cutoff frequency #6

Closed bryanwweber closed 7 years ago

bryanwweber commented 8 years ago

http://nbviewer.jupyter.org/github/demotu/BMC/blob/master/notebooks/ResidualAnalysis.ipynb

bryanwweber commented 7 years ago

Still need to figure out if smoothing is necessary (probably not) and test against a few first-stage cases.

bryanwweber commented 7 years ago

It seems like the second-order Butterworth filter will be enough, no need for smoothing (which is essentially another low-pass filter). However, the optimal frequency determination is not always good enough, so need to add a way to specify the filter frequency and reprocess the data.

bryanwweber commented 7 years ago

As an example of the previous comment, this is the result for a condition with a relatively short ignition delay. We can see the unphysical extreme drop just prior to ignition. This can be removed by increasing the filter frequency from the optimum of near 900 Hz to 5 kHz. For this case, the selection of the second frequency for the linear fit had to be adjusted as well. download

bryanwweber commented 7 years ago

Also need to make sure to record the actual filter frequency used. Also need to check the initial pressure - the portion near the beginning may need smoothing if pathological problems with V(0) are there.