Dual-motor tailsitters

that tune looks great! I think that is the best tune I’ve seen yet for a non-vectored tailsitter.

I notice that you still had some FF on pitch and yaw, which isn’t covered by the ZN method. Did you try adjusting that at all? I notice your flight had 0.2, which is the default, but I’m more curious about whether you found a way to incorporate the FF into the ZN approach.
Cheers, Tridge

Nice work palm369 !
Your plane has really huge elevons.

Would be interesting to know how it will perform in windy conditions.

Thanks James. Just trying to share my experience as I learn more about these tailsitters. Once I get comfortable I plan on putting together a series that shows how to get into the air.

Thank you, Tridge. I’m going to dive in this weekend and will report back.

Hi Tridge,
Now I learned how to profit of the information of this LOG.
Before I did not know, where the oscilations came from.
In the meantime I fount another critical Param during FBWA Flight.

Here the result of the modifications.
Rig-Test


Real Test
https://drive.google.com/file/d/0Bxldq38bfbqHYlJEbHBab2EzaW8/view?usp=sharing
https://drive.google.com/file/d/0Bxldq38bfbqHaDhYallzeURlbU0/view?usp=sharing

There are still some oscilations in the section after FBWA.

As to see in the video, 10 kph Wind are difficult
Can I increase Q_ANGLE_MAX to get more Thrust forward in Copter Mode?

Did you already modify the Backtransition as promised?

Regards
Otto

Thanks man.

Actually I had no specific reason to put the FF 0.2 there. However the P_crit was determined without FF. Only remember that FF is better for flight via control surfaces instead of rotors, so I left it for yaw and pitch.

Still without Ziegler–Nichols method, but decreased pitch P and a pinch of pitch I (instead of 0) it looks better:

Thanks all for the explanation about PIDs and PIQx logs

Rolf

2 Likes

yes, looks like D oscillation in pitch for FBWA. As usual, halve the parameter when you see oscillation.

yes, but to really improve flight a lot in wind we’ll need to move to the control strategy that Paul is developing. For now increasing Q_ANGLE_MAX makes sense, but I’d like to get Pauls controller into a release soon.

I have started working on it. I have already discovered that both the forward and back transition code needs work. The forward transition is not doing what it is supposed to do as well. It works, but it should be much smoother.
I’ll post when I have something to test.
Cheers, Tridge

@palm369

thanks for making the Ziegler-Nichols-Method known here.

How do you calculate the values exactly ?

I think, that P is simply 60% of P-Value under stable oscillation frequency ?

But how do you calculate I and D from the oscillation period ?

Q_A_RAT_PIT_I = oscillation period [Unit second]/2 ?
Q_A_RAT_PIT_D = oscillation period [Unit second]/8 ?

Regards Rolf

Exactly.

actually I used:

P = 0.6 * P_crit
I = (2 * P) / T
D = (P * T) / 8

because there are different approaches for that when you google it. Didn’t know before…
Now I will test both of them.

Have been flying today and crashed a lot

  1. Crash: Been flying in FBWA and wanted to backtransition. switched to Qloiter an nothing happened. Tried three times and then wanted to land in FBWA. Was to low and crashed into a tree. Actually ALL of my SD-Log stopped very early this day for no reason, so I only have the tlog.
    https://www.dropbox.com/s/nv01miyd2ii8wjl/2017-09-23%2012-07-11.tlog?dl=0

  2. Crash: Switched to FBWA in 4m and plane got too low while transitioning.

FYI: Are the results from that implemented in Arduplane?
http://www.springer.com/cda/content/document/cda_downloaddocument/9783319515311-c2.pdf?SGWID=0-0-45-1612588-p180523070

https://www.inf.ethz.ch/personal/pomarc/pubs/BapstIROS15.pdf

Thank you for the reply.
Of course I will wait. I asked in order not to miss the release.:wink:
Kind regards Otto

Probably 10 times to high. My wing 900 gr Wing shakes due to the reaction of the motion of Tilt and/or Elevons already without running the mots.
0.003 ist the upper limit.

did the SD log stop near the time when you switched to QLOITER?
Can you upload the SD logs as well?

Ok, shame on me: Backtransition was not working because of me being absolutely stupid, switching into normal Loiter and not QLoiter. :persevere:

ahh! I’m glad you let me know. I was just starting to analyse the tlog.

Sure, here they are:

@Tridge,

In the meantime, I feel safer in FBWA.
Therefore here a closer look at the described backtransition.
May help for the new one.


The log: https://drive.google.com/open?id=0Bxldq38bfbqHYXFBb3dQcVZaYkU
Regards, Otto

@tridge

When flying a tailsitter, do these parameters actually do something?

Q_TRAN_PIT_MAX
Q_TRANSITION_MS
Q_ASSIST_SPEED
Q_ASSIST_ANGLE
Q_WVANE_

@Tridge,
As recommeded I increased Pitch I > 0.
This produce a critical Lift off with tilt over
During the slow or cautious start Phase the integrator is running high, and comes down according his value.
To show what I mean, the short video and the following Graphs.
The transitions are similar special control cases.
May a reduction of Q_PIT_IMAX help, or do you know a better solution?