RTL comes home at right altitude. FBW-A flies nice. so PID's ire not too bad.
When in AUTO, AP applies negative pitch, and would hit terrain.
WP altitude is 100 -"Verify Altitude" not checked in planner.
I see in the log that targetalt = 103 and targetaltd100=1,0285 (what is this value??)
Actual altitude is 73, and AP is still descending at -7 degree when going for first WP. - any idea of why ?
Has this bug been long time or only in the latest code versions 2.28-2.30?
I don't know before 2.30
Andke, looking at your log, you have your airspeed set to 12 m/s but your plane only ever does 8-10 in auto, hence the drop.
i would try 2 things.
increase your throttle cruise, and lower your target airspeed.
your plane also makes no attempt to throttle up. is your throttle configured correctly?
The throttle is configured "connectly" in terms of min/max PWM are correct max 1930, min 1123 trim=1129 (small difference between trim and min, but should be ok ?) - this works fine with RTL, Stabilize, FBW-A. with or without airspeed sensor - but not with AUTO+airspeed.
ARSPD_FBW_MAX=16 // the plane may travel faster, and airframe will certainly handle much higher speed - but this number being "too low" should not cause problem, because the speed does not exceed 16m/s during the "problem" - and if it did - to avoid overspeed, lowering nose would not be correct.
Please: I see in the source that FBW_MAX is used for other than FBW too, could you please update the tooltip with more information on how/when it is used ? I could just set it to 30m/s ?
ARSPD_FBW_MIN=6 //this is near stall speed (not tuned perfectly yet)
TRIM_ARSPD_CM,1200 //a sane target
TRIM_THROTTLE,50 //also - a decent value.
Please: Regarding Min airspeed, I did not find any code for it - but could you confirm if/what anti-stall measures will be performed ? - will it lower/level nose and/or increase throttle ? (tooltip would be nice.)
I see throttle % on OSD, the plane does not seem to increase throttle at all when this problem is observed. AUTO without airspeed flies very fine. - and uses throttle actively.
I guess you've seen log at http://code.google.com/p/ardupilot-mega/issues/detail?id=569
Back to your suggestions:
Increasing cruise throttle above 50% should not help, as AUTO turns motor *off* when airspeed sensor is enabled.
Lowering my target airspeed, - that too, will not make AUTO use motor ? - am right ?
What is target speed? And how to set it up?
TRIM_ARSPD_CM set it using planner, then in m/s
My airplane is a glider with AMP 1.0 and I'm facing the same problem. I did update the firmware version from 2.33 to 2.34 and from that moment I began to observe this behavior. Last weekend I updated the firmware to 2.5 but the behavior remained. Only today I figure out the relation of my problem with the Airspeed.
As described by Andre KJ, my plane also going decreasing altitude constantly, but doesn't stop the throttle. I observed this behavior only at those flight modes which uses navigation. e.g.: "Return to Launch" and "Auto". I had same experience once at "Loiter" mode too.
Until now I was trying to set every related PIDs I could find, but with no effect.
In the ground, when I set flight mode to AUTO, I became curious of why elevator was set "down" when the logical thing is to set it "up" once the plane need to persecute the defined altitude at each waypoint.
I'll appreciate any help.
Are you using an airspeed sensor? If so, try disabling it.
Thank you for your advice Chris.
Today I flew a lot in AUTO mode, but I had to DISABLE the parameter USE AIRSPEED ( recently introduced at version 2.5). Thus I could keep seeing the airspeed information at PLANNER but it doesn't affected my flight.
What I understood about it:
If you are using airspeed sensor at previous firmware version is presumed that you wish to give to APM the task of manage this parameter, otherwise (or in those case where you don't have the airspeed hardware) you MUST DISABLE HARDWARE at setup page on PLANNER. Now at version 2.5 you have the option to HAVE THE HARDWARE BUT DON'T USE ITS MEASURES FOR NAVIGATION.
The algorith in code seems to use airspeed to monitor the CRUISE SPEED you set at PIDs PARAMETERS LIST on PLANNER. So, once your airplane was having trouble to reach this CRUISE SPEED the NAVIGATION routine says "Hey, I'll pitch down this airplane to increase speed", what I agree, but if your AIRSPEED SENSOR fail somehow and deliver a wrong reading, the NAVIGATION routine will keep pitching down until hit the ground.
Is that it?