Hi all,
I have finally put a Tri-Copter together in an attempt to get Tri's up to the same level of performance as the more common quad, Y6, X8, Hex and Octo. This is what I have put together:
based on these Hobbyking parts:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=66417
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14458
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=65156
The tricopter has tuned up reasonably well using autotune and I feel happy with the performance so far. I didn't find the initial setup much more complicated compared to normal quad. I did find the first flight much more nerve racking because of the poor yaw performance during take off. I am interested to see if my confidence in the yaw performance improves now I have a reasonable yaw tune.
I am looking for feedback on what issues Tri-Copter pilots are having with Arducopter. Some of the issues I see are:
1. Dynamics of having the rear motor and propeller CG above the pivot point causes the opposite rotation to the thrust.
2. Roll, pitch, yaw and lift coupling potentially causing issues with auto-tune.
3. The frame type needs a stability patch to prioritize motor output.
4. There is no thrust adjustment on the rear motor based on angle.
5. Yaw auto-tune could be made more efficient by removing any D term or filter frequency tuning and going directly to Rate P tuning.
6. There may be improved motor mixing that does a better job at isolating the 4 control axis.
So let me know what you think I should be looking at that is particularly relevant to Tri-Copters.
Replies
Nice frame. I once had my battery tray mounted hanging on bobbins like that, but I switched over to wire suspension since bobbins sheer off quite easily. I like the the idea of using a 2D gimbal and extra top plate. I can't quite see how you attached the gimbal to the battery tray though, as I was thinking of doing the same thing.
those bobbins last me over a year now :) I cannot buy the replacements now.. since the seller doesn't have anymore of those and I cannot find 15mm m3 ones.. 8mm m3 are really fragile.
I am now using blackout red bobbins+shim on the back and the original 15mm 3m soft bobbins on the back.
here is the picture of the ESC installation, but you can sort of see how the gimbal is mounted- simply two screws through the thick 2mm CF battery plate.
pardon the dust everywhere on the frame the photo was taken right after a flight with some "touch-n-goes"
IMG_20150822_171232-2.jpg
Thanks for the idea :)
Hi Artem,
Yeh, I got that pm but I haven't had time to search through the folder for the autotune log. It would be great if you could point me to the correct file.
Thanks
Sorry, maybe I forgot to mention it is one of the 3logs from 22nd of August. I cannot pinpoint one.myself as I am not sure which messages to look for. If you'll advise me What to look for I will go through all 3 and try to pinpoint the correct one.
Thanks Leonard. I'll follow along and test specific builds if that is helpful.
One high-level thing I'd suggest looking at is yaw wag, which I personally have not been able to tune away. Meaning, following a yaw maneuver (and especially when applying only yaw when other wise stationary), yaw will 'ring out' and bounce back and forth for a bit before settling out. It's subtle, but definitely discernible.
Anything else specific I can do to help, I am happy to do so. My tri is 400mm-or-so, so relatively common size.
Hi Patrick,
It would be great if you could add a couple of pictures of your Tri. I suspect that some of this ringing may be unavoidable if the CG of the rear motor and prop is above the pivot point. So I am interested to get photos or accurate descriptions of Tri's along with the problems people are seeing.
Thanks!!
The rear definitely is high; it would be interesting to pull it down via an adapter bracket to see what that does.
Thanks Patrick!
What do you think of the tough tilt?
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