{"comment":{"created_at":"2011-10-08T17:54:42Z","body":"Paul,\r\nwhat's the status on this?","updated_at":"2011-10-08T17:54:42Z","url":"https://api.github.com/repos/paparazzi/paparazzi/issues/comments/2333053","id":2333053,"user":{"avatar_url":"https://secure.gravatar.com/avatar/17a8aaf6d782b30b3d6011c2e173215b?d=https://a248.e.akamai.net/assets.github.com%2Fimages%2Fgravatars%2Fgravatar-140.png","url":"https://api.github.com/users/flixr","id":104257,"login":"flixr"}},"action":"created","issue":{"number":17,"created_at":"2010-11-20T20:15:40Z","pull_request":{"diff_url":null,"patch_url":null,"html_url":null},"body":"The current estimator and analog IR sensor code do not take into account inadequate IR contrast. The request is to add a detection of low IR contrast (using some sort of low pass filtering and hysteresis of course) to set off a \"low-IR failsafe\" mode. The intent here is that if an aircraft climbs into a cloud, that the low IR contrast would be detected, the control surfaces zeroed or neutraled out, throttle reduced or cut, and the aircraft's natural stability would be depended upon to keep the aircraft horizontal until it descended from the could layer at which point normal operation could resume (where home mode could be activated by user or flightplan for example).\n\nThe current behavior is not acceptable for some users as the aircraft attitude estimation and control surfaces go wild when the IR contrast craters on cloud entry. When the aircraft exits near a horizontal attitude proper operation resumes. But when the aircraft exits the clouds near a vertical attitude the vertical IR sensors (top/bot) are both looking at or near the horizon and the aircraft will continue its vertical trajectory with erroneous attitude estimates. This usually continues until high-velocity impact with the ground.\n\nThe current FBW failsafe mode is used to detect when the autopilot component of the airborne code goes unresponsive. We can't reuse that directly but instead we can reuse the basic idea. The proposal is to add IR threshold detection and add mode capability to the estimator (something we will need soon anyways). Proposed estimator modes or states might be:\n- ATT_GOOD    No sources of detectable attitude estimation error present\n- IR_LOW   IR unusable contrast detection\n- IR_FAIL   Detect sensor full-scale or zero readings (intermittent/permanent?)\n- KALMAN_BAD  estimation not ready, covariance unacceptable, etc\n- IMU_BAD  Communication lost, etc\n\nThe first two are the only ones currently requested under this specific issue. Users paulcox and SilaS are ready to volunteer to test attempts to resolve this issue.","comments":2,"title":"Low IR contrast detect and failsafe mode","updated_at":"2011-10-08T17:54:42Z","url":"https://api.github.com/repos/paparazzi/paparazzi/issues/17","id":430414,"assignee":null,"milestone":null,"closed_at":null,"user":{"avatar_url":"https://secure.gravatar.com/avatar/8423ae0702d5ebbacdb42ca4f9d9a33d?d=https://a248.e.akamai.net/assets.github.com%2Fimages%2Fgravatars%2Fgravatar-140.png","url":"https://api.github.com/users/paulcox","id":275697,"login":"paulcox"},"html_url":"https://github.com/paparazzi/paparazzi/issues/17","labels":[{"name":"Airborne","url":"https://api.github.com/repos/paparazzi/paparazzi/labels/Airborne","color":"37b6d6"},{"name":"Feature Request","url":"https://api.github.com/repos/paparazzi/paparazzi/labels/Feature+Request","color":"178700"}],"state":"open"},"legacy":{"issue_id":430414,"comment_id":2333053}}