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
Ultrafuge,
Item 2 above is somewhere amongst the 240+ to-do items for Copter.
Hi Leonard!
I am currently in the process of making a new tricopter, it will have a front mounted gimbal in the 600mm class. I hope to finish it in a week or 2, so i will definitely report back here with 3.3 testing.
One of the issues right of the bat is that motors are limited to max 80% of the max throttle.
Hi Johnex,
Can you tell me where you see that?
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?
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.
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.
RCE 3.0 inspired build.
2216 800kv
1155 CF props
4s 5000mah lipo
20a Afro slim ESCs
2-Axis brushless gimbal with tarot t2d controller
AUW ~1.5kg
Flight time 17-20min depending on how it is flown and elevation.
No tailwag on 3.2.1 even with Yaw stab at 2.8
very noticabale tailwag on 3.3rc9 stock PIDs and generally poorly controlled yaw. Much better after settig imax value to 200 and increasinf P/I as Randy suggested, but still much worse overall yaw controll than on 3.2.1
Autotune on RC9 gave for some reason sluggish PIDs on the he contrary to 3.2.1 autitune being overshoot.
I have the log from rc9 autotune and several other in the folder link I PMed you.
P.S. this tricopter is a tud nose heavy.
Here are some pics of the frame, it is an "all terrain vehicle" meaning it gets bumped into stuff almost every lipo.. still going strong since June 2015 (second set of arms, replaced 2 motors one yaw servo and a LOT of props) :)
IMG_20150821_165018.jpg
IMG_20150821_165056.jpg
IMG_20150822_103950.jpg
-
4
-
5
-
6
-
7
-
8
of 8 Next