Dual-motor tailsitters

Yes, I’m modifying the control surfaces. Will let you know after testing. Did your airframe be able to recover itself from control lost ?

unfortunately that log is completely empty. No msgs at all.
Do you have a tlog from a ground station for this flight?

that log actually shows some quite severe control problems, plus quite bad vibration. It oscillated over about 20 degrees in pitch while in LOITER mode, plus the vibration was enough that the DCM attitude estimate differed from the EKF estimate by about 30 degrees at times.
I’d suggest adding more vibration isolation (and mass) to the flight board, and then doing an AUTOTUNE of the fixed wing tuning parameters.
I suspect the bad flight is just a worse example of the same sort of issues.
Cheers, Tridge

I had my android phone connected via QGC, but there is no file I can find on it.

Yeah on the beginning of the flight I had bad ozzilations in pitch. Then I adjusted the pids a bit (higher d) and the were not visible anymore from gnd.
The PIDs I used are results from Autotune though. Seems not to work well on my plane, because it its aerodynamically unstable. (CG is very far back)
In FBWA its flying Ok.

Just noticed that this log is faulty also, I was flying 17 min, but log stoped more early.

[quote=“tridge, post:806, topic:15302”]
plus the vibration was enough that the DCM attitude estimate differed from the EKF estimate by about 30 degrees at times
[/quote] Whats DCM? Which params do you compare here?

Might be. I will repeat this test.
Did you check AUTO in SITL?

Also it would be awesome if we find a way to restore my PIDs for hover. Before your patch they were perfect.

I think I calculated them at full throttle (100%). So now my hover thr is at about 0.7 (70%)
100/70= 0.7
So I calculate my PIDs: “New = old * 0.7”, right?
Are all (P + I + D) scaled like this? Whats with FF?

@Rolf,

I enjoy watching your videos as I lurk on this thread. Two questions: 1) what is the incremental weight (in grams, or % of AUW) of the tilt hardware relative to a non-VTOL, fixed motor version of the same wing? 2) I can tell on landing, but do the motors tilt skyward as the wing flops to belly? Or do you simply cut the motors as soon as you have wingtips on the deck, and belly slightly inclined toward resting position.

Sorry if the answers to these questions are obvious to those following this interesting thread more closely.

Kelly

Did this for PIDs for all axis. Looking better now.

Sir,

This is my updated reply for you and readers.

I just understand how CG is very important specifically for non vectored tailsitter through some successful and non successful test flight on YouTube.

Normally CG of flying wing is aprox 20% but this non vectored tailsitter require large CG, I think require close to Natural point.

Low CG increase weight in bottom side, therefore airframe tilt in hower and sleep in air and loss of control.

I tried yesterday with large control surface, but results was uncontrollab, CG was only 13%.

My 4ft wingspan frame which is made from my crashed 6ft wingspan flying wing. So built is not so perfect.

Sir I am waiting for your test result soon. . . . . Please.

Hey Tridge and everyone else. Thanks for starting this thread and posting the information. I’ve just started building a dual motor tail sitter, so I’ve found the information in this thread valuable. I started my first fixed wing VTOL 3 or so years ago, a wing/tricopter mashup, only to discover that there was very little support for transitioning, so I was really excited to see how far things have progressed. Cheers! -David

Hi Kelly ( @wkf94025 )

The weight of a small digital 180 ° servo with cables and some wood (we did not measure)

Yes, they do

Regards Rolf

Thanks Rolf. Are there any photos or a build log of your aircraft, or a similar build? I am curious about the build details of the tilt mechanisms. With 800+ posts in this thread, serial search is somewhat daunting.

Kelly

hi
i have q
… how to make airspeed senser off in qgraoundcontrol as a pixhawk tailsitter mode

Best you ask @Walter , who has designed and built the mechanism

Regards Rolf

Like this


And here the manual.
Manual Tilt motor carrier.pdf (571.6 KB)

The servo weight 12.5 gr.
Regards, Otto

https://youtu.be/WpwU4eh7mdc FYI looks interesting, need more info on this

in case anyone here missed it, here is the result of the great work @lorbass has been doing creating a TVBS model in RealFlight8:


it is so much nicer working on the code with a model that looks realistic!
Using this model I’ve already fixed two small tailsitter bugs today

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Awesome! Great work!

Now I have to buy RealFlight 8 and convince my wife it’s a tool, ya right, oh ya, a better computer too… honey…wish me luck…thanks Otto+Tridge

Hi,

I have tested the modified airframe. The result seems to be good. More stable in hover especially after moving CG back towards neutral point (in fixed-wing perspective). I will do more tests in a wider area for transition.

In additional to control surface modification, I also use a new firmware Arduplane 3.8.3. I realized that some default values of certain parameters have also been changed. So, I’m not sure if it because of larger control surfaces or PID value that help to achieve more stable hover.

But after looking at you picture. I think your control surfaces seem to be small. Not sure which prop diameters of your plane. A bigger prop will also help incraese control surface area that is exposed to slipstream effect of propeller, resulting in more control surface effectiveness.

Cheers,
RW

2 Likes

Hey folks

Been flying yesterday.
Havnt retested auto, cuz too windy.
Tuned the forward flight PIDs of Pitch via Nichols Ziegler method and much better results now, though I have not set the exact correct PIDs due to lack of accuracy of me analyzing the video for the ozzilation frequency.

Results for Pitch: P_critical = 0.30 , freq_ozzi= 0.5s.

Was quite exiting cuz the plane ozzilated very hard, as you can see in the video.

Here second short flight with FPV chase:

Logs: https://www.dropbox.com/sh/fj5qi9gbm0vdrnt/AAAF6jhFalfi3_1FDAjgzFU5a?dl=0
(for some reason I only got non, or empty log files all flights before. But MP was not saying bad logging or any other fault. Dunno why)

Is there any way to get differential thrust mixed to the turns? I found that its flying much better if I put some yaw in the turn, but it does not do this automatically while in loiter for example.

Cheers, David

FYI working on a production model … got new pixhawk, cheap version, lots of vibration in stabilize mode, servos hunting just sitting nose up, ok in hover and manual mode,… tried to read sd card …not readable, defective,but no indication til I removed it to download, replaced it, also thinking firmware may also be corrupt, not tuneable, zero out everything I could think of but still hunting, reloading with latest and will test again…
Rick

Hello Sir,

Thanks for your reply, I updated my previous reply to you. I updated info on CG according to your guideline, I updated that CG good at Natural point.

Flight test of copter mode with updated control surface and CG with firmware Arduplane 3.8.3 is here . I found lot of improvement in copter modes.

I used 6 inch prop, 2300kv motor. Wingspan - 4 ft, total weight - 720gm

I used small size prop, there was two reasons, those motor and prop was available towards me, another reason was, I thinks in the view of forward flight 6 inch prop are good in the view of large tip speed requirement (2.5 * stall speed).

I need more test, and if I found need of large prop than I will update same.

Sir best of luck for your forward flight test, I will also test soon.

Well I found some difficulty , and need help on following points from all members.

  1. Climb Sensitivity - Normally in ArduCopter the climb sensitivity can be set by THR_ACCEL_P and THR_ACCEL_I , but I couldn’t found similar parameter to set climb sensitivity of copter mode in Arduplane tailsitter.

  2. Maximum Spin Control of motor for Copter modes - I couldn’t not found any output spin change in motor by set Q_M_SPIN_MAX . Please guide how we can control on spin at Arduplane tailsitter

Thanks