T-Rex 450 Test flight -- Loiter / Guided / RTL and Alt Hold

APM 2.0   firmware 2.7.3

MediaTek MT3329  and barometer

 

After replacing the hidden Torque Tube Bearing in my T-Rex 450 the shifts in attitude are gone.

Everything changed to the best.

 

I found a great new flying field, so I went to test Loiter, Guided and RTL, Alt Hold worked always great.  I planned a mission too, but the wind became too strong after a while so I will try this another day.

 

As you can see in the video (thanks to my lovely wife) everything worked very well.

 

This are the PID  I used.  The Nav speed is low 2m/sec which is relaxing to watch and you have no overshoots.

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Thanks a lot DIY Team.

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Comments

  • Yes you right, soo 3 high fives to the heli guys!!

  • Developer

    Randy and all the Heli dev guys are truly heroes!

    I'm just wondering how proud you are now.
    This is so beautiful to see.

  • Hi Christoph

    Yes I tried that high values of yours and it behaved too erratic.

    Be carefull with the I term and the I max. As you can see I reduced that very much.

    The I force ramps up very fast to I max if the heli can’t reach the target in a certain time, because of a wind pushing it out and then you get that overshoot or oscillation.  

    The D force gives an initial push and then ramps down fast, like you kick a ball into the target; this is much more calming but introduces a bit noise. The P force is just proportional to the distance to the target.

    With lower values it might get pushed a bit further of target but it comes much softer back and the system calms down quickly.  And yes the same applies to ALT Hold. As you can see in the video my Alt Hold is calm when flying a bit erratic, it raises a bit and softly cams down again.

    My advice, get I max an I down use a medium P and quite a bit of D.

  • In addition poor alt_hold has direct influence on loiter, as another observation. Having strong reactions on alt_hold can make really bad oscillations in loiter, because the loiter corrective movement gets in worst case leveraged by an alt_hold reaction of the heli.

  • What I also observed is, I think due to the high loiter rate P of 5 I am using, in case of some gusts the reaction of the heli is really harsh to compensate, leading to oscillations. As I reported before that is also in issue when the heli changes from a nav command to loiter command. Then there is a quite high loiter error, which in combination with the high loiter rate P leads to very agressive reactions. On your video I see much smaller reactions. But with a low loiter rate P I could not really get a stable loiter in windy conditions.

  • Cristoph

    That you get a drift at lower P suggests to me, you might have sometimes small unnoticed leans.

    A higher P counteracts the leans more, but also causes oscillations.

    As you see I also have a higher D term, this calms oscillations.

    D is the counter part of I.

    Have a try if your heli hovers in stab mode without interaction for quite some time, then you set for a good loiter.

  • And I realize from your settings that you use much lower I terms in general. As well much lower loiter rate p term. When I tried to lower the p term I got to much drift and oscillations. But maybe I will play with lower I terms as well.
  • Hi Cristoph

    It’s the latest flybarless upgrade on my 450.

     

    Since I replaced the Torque Tube Bearing everything changed.

    The leans are gone at the head speed of about 2800rpm.

    So the bad Loiter is mainly caused by “bad frequency of vibrations“, this I always mentioned.

    I realized that at the beginning of every flight where the head speed is a little higher (battery voltage higher)  the heli tents for tiny leans and in this time loiter tents to circle, but after a minute or so the head speed settles to a lower speed and everything is just fine.

    This is all I found out.

  • Very nice loiter and RTL.

    I did several loiter flights now and tried to tune the PIDs, but found out that not every loiter is as stable as the one on your video. I had similar good ones, but also often overshooting ones.

  • Is your 450 flybarless?

This reply was deleted.