AC3.2.1 APM 2.5 Throttle pulsates in Loiter

Hi.

I have a problem after updating AC to 3.2.1 from 3.1.5.

When in Loiter, the the speed of the motors rev up and down/pulsate quite rapidly. This was working fine when I was using previous versions of arducopter.

I have downloaded the logs, and have looked into accX, accY and accZ. These seems to be inside the range specified in the wiki at arducopter. (Log_vibrations.bin)

Please have a look at the Log.bin, and note the difference between ThrIn and ThrOut when I'm in Loiter mode.

 

Anyone having any idea what the problem may be?

Log.bin

Log_Vibration.bin

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                • Thanks "Henny V"!

                  I forgot to mention it in my previous posts - so much to remember...

                  From my "tuning log" (sorry for formatting and Norwegian) I changed this earlier:

                  "DIYdrones - Autotune-tråden, side 64, omtalar mulige endringar:

                                                         Original    Ny 270315.    (Lefébvre)
                  ATC_ACCEL_RP_MAX     0          72000             54000
                  ATC_ACCEL_Y_MAX        0          36000            36000
                  ATC_RATE_FF_ENAB      0          1                     1
                  Standard...
                  ATC_RATE_RP_MAX      18000   18000             72000
                  ATC_RATE_Y_MAX         9000     9000              18000
                  ATC_RATE_SLEW_YAW 1000    1000               1000
                  Dette fungerte ikke. (..did not help)"

                  I tried... :-)

                  I shall keep it in mind when I reinstall 3.2.1 - maybe increase ATC_ACCEL_RP_MAX  even more.

                  -Jan

      • Try to set thr_mid to ~430/450

        • sry to 620 bad graph.

          • Hehe, I noticed - thanks for your suggestion anyway! From the log you may see that the thr_mid already was set to 640 (recommended, same as ThrOut). Before your latest message I set it back to standard 520 and made a test - as we can see, same jumping throttle in Loiter... In this test I used a lighter battery so the thr_out was about 520.

            I also made a video from flying the tricopter, uploading to YouTube now. I think it performs very well in Stabilize, but looks like there is something wrong in all autonomous modes. Perhaps it is lack of tuning (but have performed AutoTune and adjusted/reduced PID a little after that), perhaps because of the frame construction (scratch build), or something wrong with the controller.

            Here is the YouTube link: http://youtu.be/kYiwiqPYlvY

            3702837793?profile=original

  • Hi guys,

    We can only help if we have good data logs to look at. So far only Rolf has posted logs.  I had a look at them, and can't see much. His vibration levels do seem fine.  For the short segments he's in Loiter, the motors are clearly pulsing.  There is a negative correlation between climb rate and throttle output, but impossible to say if this is cause or effect. The logging resolution is not high enough to see which happens first.

    I do notice that his Alt Hold PIDS are exactly the default settings.  These might need to be tuned.

    The talk of "bugs" is a bit premature.  Keep in mind, we have over 10,000 users, and there are only a handful of people complaining of a problem.

    Is this only happening on APM-class hardware?  Or Pixhawk as well?

    • Hi Rob,

      Thanks for posting.  I will try to post a log after 2 weeks, going away and using my quads.  I think I can help a bit as I got both APM and Pixhawk class FC.  Here is what happened to me.

      I have a V550 (TBS Discovery Clone), using HK Pilot32 (Pixhawk clone).  When I bought a HK APM micro set I decided to replace the pilot32, as pilot32 was big and the APM micro will enable me to put the battery inside the frame.  V550 with HK Pilot32 runs very well from 3.1.4 -> 3.2

      After replacement of APM micro with 3.2.1 on the V550, I found the alt hold and motors where hunting down a lot.  I thought it was due to barometer not being covered properly.  I tried 4 different materials/ways to cover the baro and I was able to make it better, but not good.  I decided to lower the throttle acceleration, which made the quad sluggish.  However this did not cure it, even after several attempts of manual tune.  I decided to put the Pilot32 back, upgraded to 3.2.1 and the V550 is back to it's very stable and crazy fast response nature.

      Here is a post when I was attempting to use the APM on the V550, before I decided to put the Pilot32 back.  There is some data flash logs link on that post.

      http://diydrones.com/forum/topics/help-tune-my-apm-so-it-flies-clos...

      I then built a new frame H600 (QAV 550 clone) and used the APM micro on it.  With AUW 1.3kg which means I am at 50% power for hover.  It ran really very very well.  So I just thought, maybe my V550 is not as stable.  The H600, has a top deck that is floated by rubber balls.  The APM also sits on a thick double sided foam tape.  

      240fps proof with APM 3.2.1 the H600 is very stable alt hold

      https://youtu.be/feeoLK1L7eY

      After being happy with the bare frame I decided to add payload on it (gimbal, fpv, etc.).  This moved the AUW from 1.3kg to about 1.6kg.  To my surprise the issue I saw on the V550 manifested on the H600 as well.  The altitude hold was very sketchy, the motors started to pulsate as well.  I had a few very hard landings, only way to keep in holding altitude is to use stabilise mode which also makes the motor smooth.  This is the only time I looked at the dataflash logs, which is a cool feature of the APM.  Actually its only the time I downloaded the Pilot32 as well, and showed me some interesting stuff.  Anyway I can't see much in terms of the barometer, aside from the fact it kinda over compensates for things.  I even tried to put the hover to 65% which is closer what is needed for the heavier AUW, this made it worse.

      I saw this post, then decided to downgrade to 3.1.5 and the H600 flew well and stable.  The battery life was a bit shorter than I expected, but it was stable.  I had to abort my H600 build and get my trusty F450 with Naza back online, as I was going away and would want to have some good video footage.

      In summary it doesn't seem to affect Pixhawk class hardware, only APM in my case.  Also it only manifested when I moved the AUW beyond the 50% hover on 3.2.1, and instantly fixed by downgrade to 3.1.5.  After I come back I will rebuild the H600 and get some logs and see what the vibration is like for both 3.1.5 and 3.2.1.

      Again thanks.

      • Jun, so I see that your Throttle PIDS are *not* the default, at least some of them aren't.  So it looks like you have attempted to tune it which is good.

        However, I do see some divergence between the Baro altitude, and the Inav altitude estimate, which makes me suspect you have a vibration problem.  There is no vibration data in that log.  Also, how is the barometer covered on the board you used?

        • I just got back from my break, last week.  Yesterday I reassembled the H quad, so I can start testing 3.1.5 and 3.2.1 again.  It was pretty good, and I was testing if the new quad can handle high winds... it did.  Unfortunately towards the end of testing a big gusts pushed the quad in an angle that was not recoverable and I had a crash.

          The logs on the post was still when I was experimenting on different ways to cover the barometer.  Also it was installed on a different frame.  This thread has run so fast now.  I will read it.  If I can I will rebuild the H quad that has the APM and give you logs from different firmware 3.1.5 and 3.2.1 which hopefully can help.

      • Yes, strangely I noticed the problem wildly accentuated by increasing AUW on my h-quad, doesn't correlate to 50% power with mine though as this model is very over-powered.

         

    • Hardly going to be a handful of people Rob, I have 3 APM's doing this with vibration isolation platforms. A 330mm quad, a 525mm quad (just retired this frame and now in a H- quad, same problem) and a 680mm hex. None of these had issues with old firmwares. I have a time issue at present to spend looking into tuning and pids, it may be simply fixed, will definately post details when I've the chance to look further on.

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