Reading this whole discussion well, even if it is very long, might inspire you… 
1 Like
I have a question about RC Transmitter Based Tuning:
" You can tune multiple parameters in one flight by setting TUNE_PARAM to one of the “tuning set” parameters. For example, if you set TUNE_PARAM to 101 then you will have 4 different stages to your tune:
Roll: Rate DRoll: Rate P and Rate IPitch: Rate DPitch: Rate P and Rate I
notice that Roll: Rate P and Rate I is actually two parameters in one, controlling both the P gain and the I gain for roll. This follows the normal advice for MultiCopters that you should keep the P and I values equal when doing a manual tune."
is this applicable for a Dual Motor Tailsitter?*
P & I at the same time? maybe it would work for a Tailsitter Copter but one DMT does not have multi type motors*
Maybe this method is better?
"manual method is to start with a low D value then increase P until oscillations, reduce P by 30%, then increase D until oscillations, reduce D by 30 %, increase P again as much as possible."
You can also tune them individually.
Yes, but I was referring to the sequence of P_I_D and the sequence of axes
I read in this DMT forum that transitions are from QHOVER <> FBWA.
But, why not QHOVER <> CRUISE / FBWB?
Hello, I have asked in the Arduplane 4.0 forum but I post it here because it is one DM tailsitter:
“PreArm: DCM Roll/Pitch inconsistent by xx deg”
https://discuss.ardupilot.org/t/prearm-dcm-roll-pitch-inconsistent-by-xx-deg/65181
EDIT: SOLVED
The problem was something intrinsic to the Tailsitter. I had read it one thousand times here:
But by not observing EKF errors and the compass was working properly, I thought there was another problem.
For months when I was documenting about Tailsitter, I asked if it would not be better to turn the compass 45º towards the sky when the tailsitter is sitting. In this way we are not obliged to place it horizontally for a few seconds.
COMPASS_ORIENT = 100
COMPASS_CUS_PIT = -45 or 315
I think I will opt for this compass position.
I have been struggling with the Loiter tuning (tuning in general) on one of my TVBS (this was an early vid…its tuned in roll a lot better now…pitch is the problem https://youtu.be/0Pw0UojYRfo)…it flies okay in QSTAB…and loiters in place fairly well, but anything other than slow VTOL speeds are very squirelly and AUTO mode VTOL operation is a disaster…I can VTOL takeoff, and transition into FW fine, but auto transitions back to VTOL and landing are all over the map…
It seems that pitch is not tuned well, and I have no idea what is up with VTOL loiter position tuning…
I have been trying to get a good pitch tune and good loiter vtol position changes for several months…
we really need a good TVBS tuning guide for the wiki, unfortunately, I have not succeed in getting competent enough to write it up…tuning a normal quadplane is pretty straightforward, but getting the tilt rotor setup tuned properly is escaping me…
here are a couple of logs with QSTAB, QLOIT and vtol AUTO segements…the roll attitude control seems acceptable…the pitch is not…and loiter is horrible…suggestions from anyone that has been successfully through the TVBS tuning process would be most welcomed…
its funny, my larger C1 Chaser TVBS was a pussycat without much tuning required…and performs much differently…https://youtu.be/LixSx6wSnH4
logs:
I still have a TVBS flying, the one you can see post 1034 but I never really tested Q_loiter or Auto VTOL or transition to Q_loiter with it.
There is a lot information in your post. From your experience, what would be a step by step objective ? I also observed that Q_loiter is less stable than Q_stabilize and max lean angle cannot exceed 45° whatever requested speed.
Did you read post 2079 from @marco3dr ?
Thanks…interesting regarding braking in Loiter…I also think that the Loiter movement stability and pitch stability issues maybe related to the lever arm from CG to tilt point…on the C1 Chaser that lever is much longer than on the S800…ie a longer pendulum…maybe that has an impact?
The most disconcerting thing about the Loiter movements is when its pitch greatly exceeds the demanded pitch…and almost flies off on its back…
I suppose that the pitching moment produced by tilt motors is proportional to sin(tilt angle)*length (tilt axle-CG position). With a swept wing this distance depends on motor distance from wing root and on the length/design of the motor mount. It means you can expect a better pitching authority with motors closer to wing root and longer motor mount.
Is it true according to your experience ?
Only experience is with those two (actually another but its much like the S800)…the s800 is closer to the root, but a little closer to CG than the C1 chaser so cant really tell which has the bigger moment…the C1 chaser definitely has a longer suspended arm from motor to CG…
The key thing about the tilts from far from the GC is you get the same pitch moment with much less angle. This means your servos have to move less far so effectively become ‘faster’. Any vectoring at all gives you so much more authority than control surfaces the maximum possible pitching moment is not so important.
This is the reason this works so well, because its not a flying wing the tilts are a huge distance in front of the CG.
Sooo, as it turns out, master is kinda “broken” for vectored tailsitters due to a tilt rotor gain scaling error…your PR that corrects that did the trick and got the behavior usable again…thanks!..I have to retune everything, but pitch defaults allowed the TVBS to actually execute a VTOL->FW->VTOL Land mission without control ever being an issue…since it was okay in Stable, the C1 Chaser flew well since it was using that, but for the last couple of months I had been using master on the S-800 with the incorrect gain scaling for tilt…was going insane
1 Like
Hello! I am designing a non-vector engine tailsiter for survey use, I am going to reuse two engines from a dji s800 crashed with 6s batteries, I estimate that the wing span will be close to 1.5m, with a gondola capable of storing electronics and a camera Do you have any recommendations regarding the location of the engines? distance to each other or distance to the leading edge?
Greetings from Argentina!
From post 1453 you can see construction details and videos of my non vectored tailsitter. I cant say much more.
Hope to see your plane soon.
For several days I have been testing and tuning Q_loiter and auto transition to VTOL with my blue wing TVBS. I use plane 4.0.7
I am now very happy with Q_loiter and transition from fbwa to Q_loiter are always very good. I made plenty of them and they are always OK, this is how they look.
Auto transition do not behave the same, Sometime they are OK but sometime they produce scary maneuver and the wing does not crash because the vectoring thrust is very efficient to recover. During the auto transition it seems that sometime the wing want to lean on its back. Looking at the log the desired pitch looks bad.
Probably worth jumping on master (4.1.dev) quite a few improvements to transitions and logging.
With master 4.1, which of the gains is advisable? I will try to test Disk Gain when the weather improves. I don’t know if it will be the best option. I will need your advice before switching to FBWA 
Thanks for the suggestion,
I have uploaded ‘latest’ 4.1.0 firmware_version_type_dev
Q_tailsit_thscmx parameter is gone.
I have instead the q_tailsit_gscmsk parameter which default value is =2 (disk loading) but q_tailsit_dskld parameter description tell us the mask value should be set to 4. Could you check ?
I would like to start with my former parameters setup so I suppose I have to set q_tailsit_gscmsk=0 and q_tailsit_gscmax = q_tailsit_gscmin = 1 (I had q_tailsit_thscmx=1)
Is that true ?
The wing is now blowing with gale force on the Biscay bay and is expected to blow several days… It is time for windsurfing 
Q_TAILSIT_THSCMX is now Q_TAILSIT_GSCMAX
Q_TAILSIT_GSCMSK should default to only throttle (1). Although with GSCMAX and GSCMIN = 1 your not actually doing any scaling at all.