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/__76263__Hobbyking_8482_Ti...

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=...

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.

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Nope, not confusing. Yaw stab value.

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"

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Thanks for the idea :) 

Hi Artem,

I suspect that might be because of the filtering setting. Can you try changing Rate_Yaw_Filt to 20?

Will try on Sunday tomorrow is going to be really busy for me. It is always packed in my car, so whenever I have time to FPV I do :) 

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Hi Leonard!

The limiter is present here:

https://github.com/diydrones/ardupilot/blob/master/libraries/AP_Mot...

Randy said it was put in place because more complex stabilization code was never implemented, that quads have.

Hi Johnex,

I will remove that for the next release and implement a stability patch for tri's.

Thanks!!

Wow, so does that mean all tricopters have had their throttle limited to 80% and have no stability patch?

Yes the throttle is limited to 80% on all tri's, but there is some stability, but not as complex as the quadcopters have from what i understand.

Hi Graham,

Yep.

It shouldn't be too much trouble to get it done. I want to add an angle for the rear motor so I can directly calculate the additional thrust needed on the rear motor.

Hi,

two front rotating booms instead of tail servo: Avatar-tricopter

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