Loiter and RTL not reacting as expected

I've recently changed to the APM 2.5 with uBlox GPS.

The stabilize mode is brilliant, but the loiter, and rtl are of no use. 

Loiter will hold position for around 5-8 seconds, but then it starts to drift, and when it starts, it carries on, and the stick inputs seems very sluggish and cant bring the craft back, so I have to switch back to Stabilize mode and fly that way. 

RTL, when triggered will climb the craft, and then shoot off away from the "home" position, and carry on, again with me having to go to stabilize to avoid losing the craft somewhere.

It is an F450 quad, with simonk flashed ESC's and 2826 Motors.

I am awaiting the power module to arrive, so as yet, its powered from the BEC in one of the ESC's. The other three have their +ve pins removed. 

The GPS is locked before I arm, and from what i can see, never looses lock during flight.

Please, help!

Thank you.

Ben

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Replies

  • Ben, for the time being I would remove your FPV gear from the quad, if you already haven't.  Try a smaller LiPo, 4400mah is a touch on the heavy side for this setup.  I have used a 3 cell 4000mah LiPo on this frame with MT2216 750kV motors turning 9X4.5" props and had excellent Loiters, RTLs' and waypoint navigation flights. Check out the youtube link provided below.  Compassmot with this setup was 62%, well into the grey area.  I have since reduced that value by reconfiguring my hardware.  This is why I think it is more of a hardware issue.  

    https://www.youtube.com/watch?v=ky_rkyMuDxM

  • Hello to all in this thread.  I had a similar problem yesterday.  Flew auto mission 3 times.  First two times quad lost altitude till landing between wp1 and wp2. I then edited the mission to just waypoints with no loiter. Third attempt the last wp was ignored and the quad went to rtl.  Lastly i did some controlled flight in stabilized mode, switched to loiter, moved around a bit, then went to rtl.  This is where the problem arose.  Quad executed rtl as usual, elevate, hover, lower alt, BUT then rolls to right and moves out loosing altitude until impact. I should have been quick enough to return to stabilize mode to recover but oh well.  SPecs below and tlog attatched.  Can Any of you help me diagnose the failure...multiple compassmot 37 to 42

    550 quad

    2822 1200kv motors

    9047sf props

    20a esc

    3s 440mah lipo

    arducopter3.0.1

    crius ublox gps

    915mhz telemetry

    3dr power module

    apm is mounted approximately 2.25 inches above pdb

    2013-07-26 07-01-26.tlog

  • Developer

    It'll be interference on the compass from the Power Distribution board I'll bet.  With the symptoms you describe 90% of the time, that's what it is.  Without logs it's hard to be 100% sure but I'd recommend you try moving your APM up a few cm from the power wires and when your power module arrives do the compassmot as described on this new advanced compass set-up wiki page.

  • Ben, can you give us a little more info on your setup?  Battery used, props, payload (if any).  I have a F450 that is rock solid.  As Marco said electromagnetic interference, vibration and PIDs' are often times problems for the newbie as well the seasoned flyer.  Hardware can also be an issue.  You will see variations in flight characteristics just switching between a three and four cell pack.  Adverse flight characteristics can also be noticed when using the wrong props.  Its all in the details.  :-)

  • Developer

    Hi Ben, you must check better your hardware setup and all the parameters of your APM.
    The problems you have are related to something wrong, certainly not to the APM Copter V3 code, which works perfectly "at the moment", as I have blatantly shown.
    Excessive vibration, magnetism induced by the motors, check everything well.

    Bests, Marco

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