Replies to This Discussion

Permalink Reply by Veikko Vierola on March 19, 2012 at 2:44pm

Has this bug been long time or only in the latest code versions 2.28-2.30?

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Permalink Reply by Andke on March 19, 2012 at 2:46pm

I don't know before 2.30

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DeveloperPermalink Reply by Michael Oborne on March 21, 2012 at 4:12am

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?

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Permalink Reply by Andke on March 21, 2012 at 5:05am

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_MAX,16

ARSPD_FBW_MIN=6  //this is near stall speed (not tuned perfectly yet)

THR_MAX,75
THR_MIN,0

ENRGY2THR_D,0
ENRGY2THR_I,0

ENRGY2THR_IMAX,20
ENRGY2THR_P,0.5

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 ?

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Permalink Reply by Veikko Vierola on March 21, 2012 at 1:21pm

What is target speed? And how to set it up? 

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Permalink Reply by Andke on March 21, 2012 at 1:31pm

TRIM_ARSPD_CM   set it using planner, then in m/s

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Permalink Reply by Veikko Vierola on March 22, 2012 at 1:02pm

Ok, thanks

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Permalink Reply by Marcos Souza on August 4, 2012 at 9:45pm

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.

Regards

Marcos Souza

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3D RoboticsPermalink Reply by Chris Anderson on August 4, 2012 at 9:58pm

Are you using an airspeed sensor? If so, try disabling it. 

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Permalink Reply by Marcos Souza on August 5, 2012 at 4:41pm

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?

Regards

Marcos Souza

 

 

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