{"action":"created","issue":{"url":"https://api.github.com/repos/TauLabs/TauLabs/issues/1969","labels_url":"https://api.github.com/repos/TauLabs/TauLabs/issues/1969/labels{/name}","comments_url":"https://api.github.com/repos/TauLabs/TauLabs/issues/1969/comments","events_url":"https://api.github.com/repos/TauLabs/TauLabs/issues/1969/events","html_url":"https://github.com/TauLabs/TauLabs/issues/1969","id":108423206,"number":1969,"title":"Discussion around Chebyshev type-II filtering for both D-term and gyro cutoff vs. Butterworth, current implementation","user":{"login":"fujin","id":6873,"avatar_url":"https://avatars.githubusercontent.com/u/6873?v=3","gravatar_id":"","url":"https://api.github.com/users/fujin","html_url":"https://github.com/fujin","followers_url":"https://api.github.com/users/fujin/followers","following_url":"https://api.github.com/users/fujin/following{/other_user}","gists_url":"https://api.github.com/users/fujin/gists{/gist_id}","starred_url":"https://api.github.com/users/fujin/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/fujin/subscriptions","organizations_url":"https://api.github.com/users/fujin/orgs","repos_url":"https://api.github.com/users/fujin/repos","events_url":"https://api.github.com/users/fujin/events{/privacy}","received_events_url":"https://api.github.com/users/fujin/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/TauLabs/TauLabs/labels/discussion","name":"discussion","color":"bfdadc"},{"url":"https://api.github.com/repos/TauLabs/TauLabs/labels/firmware","name":"firmware","color":"02e10c"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":5,"created_at":"2015-09-25T23:26:45Z","updated_at":"2015-09-26T03:30:01Z","closed_at":null,"body":"http://eelinux.ee.usm.maine.edu/courses/ele486/docs/Chebyshev%20II.pdf\r\nhttps://github.com/hrrr/ChibiFlight/blob/master/source/filter.c\r\n\r\nfrom @mlyle on IRC regarding chibiflight butterworth:\r\n> 22:33 <icee> just higher order\r\n> 22:33 <icee> it rolls off faster\r\n> 22:34 <icee> i dunno, even under the best of circumstances it doesn't feel like D does that much, so a better/stronger D isn't worth it\r\n\r\nfrom @Trex4Git on IRC:\r\n> 22:43 <trex_> From the naming he uses a second order Butterworth lpf. If we want also go in that direction I think a second order chebyshev type 2 might be better\r\n> 22:45 <trex_> Disadvantage of both: tuning /setting the filter in the flight controller would not be so easy, so externally calculating the filter coefficients and maybe having some selectable presets might work\r\n> 22:46 <trex_> For the gyro filtering a higher order chebyshev filter could also reduce the delay\r\n\r\nopen questions:\r\n- how do we make D-term / D-term filtering feel like it is more effective? why doesn't it feel effective presently? (@mlyle)\r\n- how can we conclusively analyze 2nd order butterworth vs. chebyshev type-II?\r\n- in the case of chebyshev type-II, what research is required in order to gather selectable presets for filter coefficients? presumably based on filter delay/response/passband?\r\n- in the case of gyro filtering, does any similar filter coefficient discovery work need to take place?"},"comment":{"url":"https://api.github.com/repos/TauLabs/TauLabs/issues/comments/143394429","html_url":"https://github.com/TauLabs/TauLabs/issues/1969#issuecomment-143394429","issue_url":"https://api.github.com/repos/TauLabs/TauLabs/issues/1969","id":143394429,"user":{"login":"mlyle","id":90903,"avatar_url":"https://avatars.githubusercontent.com/u/90903?v=3","gravatar_id":"","url":"https://api.github.com/users/mlyle","html_url":"https://github.com/mlyle","followers_url":"https://api.github.com/users/mlyle/followers","following_url":"https://api.github.com/users/mlyle/following{/other_user}","gists_url":"https://api.github.com/users/mlyle/gists{/gist_id}","starred_url":"https://api.github.com/users/mlyle/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/mlyle/subscriptions","organizations_url":"https://api.github.com/users/mlyle/orgs","repos_url":"https://api.github.com/users/mlyle/repos","events_url":"https://api.github.com/users/mlyle/events{/privacy}","received_events_url":"https://api.github.com/users/mlyle/received_events","type":"User","site_admin":false},"created_at":"2015-09-26T03:30:01Z","updated_at":"2015-09-26T03:30:01Z","body":"@tracernz Do you mean the same filter as us (first order IIR?)"}}