17 September, 2019 at 18:17 #63681zophonParticipant
This is my first drone build, I have never flown anything before that. Yeah, I know, I read the warnings by @david (he tricopter is not designed as a beginner platform, etc…) but decided, what the heck, his build video are so clear, nothing can go wrong 🙂 The knowledge presented in the videos is awesome btw. And I’ll get myself a simulator, I’ll learn 🙂
Also, I know my way around soldering, electronics design, part machining, programming, so I sould be able to understand if something goes wrong.
Therefore I’d like to stress out that this no expert opinion on how to do things. These are only Rc/drone noob thoughts, problems and how I went around them.
I’m open to any comment on my material and component choices, how to upgrade or what were bad choices etc…
– frame : Tricopter LR – Kit
– the recommended : Tricopter LR Electronics kit.
– RC Transmitter : FRsky Taranis XD9+
– RC receiver : FrSky R-XSR Ultra Mini Redundancy Receiver (but will be testing a 900 mHz also).
– Camera : Foxeer Falkor 1200TVL FPV
– For Video tx, I went the 5.8 Ghz route : TBS Unify Pro Race 5G8 HV Race V2.
– Antennas : Aomway 5.8GHz 4-Leaf Clover Antenna.
Building the frame
I followed the build video here:
First remark, contrary to the previous videos, there is no mention of filing the edges of the carbon fiber frame. Is this no more needed?
A small remark on tightening the screws of the arms : I’ve already had the arms folding a little bit backwards after a few rough landings, so it is better to tighten them really good, just so that you can still barely move them by hand.
Nothing else to say, I followed everything to the letter, and it worked.
Great instructions and infos about soldering to prevent common mistakes, thumbs up!
Dronin setup video
Then switching to the dronin setup video here:
First remark, the link in the description goes to here. But this mentions only the build from 2019-01-13, which is not the newest one! But this thread is worth a read, loads of infos in there! I checked again the forum and found this thread (quite obvious if you go to the forums first, but not if come you directly from the youtube video) which has the newest build from the 2019-06-05 (apart from a more recent experimental build, more on that in the GPS section).
I had a few problems with the betaflight install to flash the dronin firmware, but I should have listened to David and directly watched this video. Joshua Bardwell explains everything very clearly and thoroughly, it’s great! After that I was able to flash the dronin firmware on my kakute.
At the 1:17 mark, I have to disagree, I could select the receiver type (I chose SBus for my FrSky receiver), probably only the more recent build have that.
At 1:30, I didn’t know which ESC protocol I should use for the ESC included in the tricopter LR kit. So I think I selected Dshot600 but I am not sure. I don’t see in Dronin where I could find this info again. What should be the best choice?
At 6:16, it should be said that the servo output should be reversed (button with two arrows on the right of the servo output line, otherwise you will have a furiously spinning tricopter on the first take-off (is this only the case for the tricopter LR?).
At 9:48, the servo speed is measured. If, like me, you don’t really know if you prepared the tilt mechanism well, do this a few times. The measured speed should be consistent (not varying to much) at around 190°/s. More on that in the “Tilt mechanism and friction” section of this post.
I had a lot of problem with random disconnects in Dronin, after 5 sec, the board was not recognised any more. Go to tools -> erase all settings from board. That solved almost all problems (still having them from time to time…).
On a calm day, I had no trouble completing the autotune, everything went fine. I did several because I crashed and I tried different batteries and so on… The last autotune I did delivered following results. This could be used to compare with other setup, but it is by no means a reference point or values to put directly in your copter.
Roll P 15 I 55 D 27
Pitch P 25 I 91 D 54
Yaw P 56 I 349 D 10
Roll and pitch values are directly from the autotune, but I modified a bit the yaw values:
I think I halved the yaw P term after the advice in post 62240 (thanks @Vantasstic) and 62271 (thanks @billyd) and lowered a bit the yaw I term (it was over 400 or 500 with the autotune).
I followed the advice on zeroing the yaw D term, but then I tried a first incrementation at a value of 10. Seems allright, probably not perfect, but fine.
Well let’s call it ServoCal since it is the new name. It went without problem to get a value different from 13.8, but it was a bit harder to get a good value. More on that in the next section.
With the newest build, the beep pattern for successful calibration after landing is 2 beeps pause 2 beeps etc… if I am correct.
Tilt mechanism and friction
A thing that I did not quite catch on my attempt is characterising the right fricton to have in the tilt mechanism. David said to “file it in order to have not too much friction, but you don’t want it too loose”.
On my first attempts to tune the copter (autotune and servocal), I ended up with a nice tune in roll and pitch and what I thought to be correct tune for yaw. I got a bit of tail movement, and if I hit the throttle hard there was a significant amount of tail wag. The HoverThrottle was at about 0.40 something. But the MotorThrustFactor was worrying me as it was over 40!
Reading further in the forum, I saw one or two reports of MotorThrustFactor being 8, 9 or 10-ish values (post 62431 for example)… So after a crash that had broken the zip-ties of the tilt mechanism I went back to the workbench and tried to have less friction on the tilt mechanism. And already at the servo speed tune step I saw some changes : the speed measurement were much more consistent : 190°/s + or – 3°/s. Before I had done this three times with a max 217°/s and a low 180°/s (I think), I kept the max value, because well, the more the better…
After an autotune and a servocal, here it is : MotorThrustFactor at 10.5! And even less tail wag when I punch the throttle (It’s visible that the servo is doing its thing, but the tail doesn’t go crazy). I am not sure that this corrects avery vibration problem, but the tail behaves nicely (noob point of view 😀 ).
So here might be an indication that the friction is too much in the tilt mechanism:
– Your MotorThrustFactor is too high (could some confirm that a 10 ish value is good, and that 20 to 40 is way too high?).
– Check for a consistant speed at servo setup.
In the Hardware pane, I selected the MAX7456 OSD for the OSDPort. Every info showed one my osd screen, out of the box.
I connected the smart Audio line from my VTX to Tx4 on the kakute. Selected “VTX config TBS SmartAudio” for UART4 in the hardware panel. Seels to work as I can select the power configuration in the dronin OSD menu. But I have yet to confirm that.
Thanks to this post 62655 in this thread. I bought this
and connected it like this: rx to tx and tx to rx, and SDA to SDA and SCL to SCL, on UART6.
I selected GPS for UART6 in the Hardware pane and selected HMC5983 for ExtMag.
I enabled the GPS module in the Module pane, selected “UBX” and “57600” in the GPS tab.
Even though I put the GPS board with the arrow pointing forward, the orientation of the copter was wrong on the dronin flight data map. I had to change ExtMag Orientation to “Bottom90degCW” on the harware panel. And now it works 🙂
I did the 6 point mag calibration.
Then I redid the accelerometer calibration alone, with the “Start and zero vertical”. This is seamingly needed for “Altitude hold” and “RTH” mode.
To enable that, post 62439 by @billyd was helpful.
You have to activate the modules “Path Planner” and “VTOL Path Planner”
Then go to the filters tab of the attitude settings to select the proper filters (“INSOutdoor” for Attitude algorithm and “INS” for Navigation algorithm).
But on the filters I had strange behavior selecting INSOutdoor. It took time to stabilise (30sec after boot) and somehow showed a few degrees difference with a previous calibration.
Reading on the dronin documentation, I chose the “complementary” filter for Attitude algorithm instead. This seems a better choice.
With the 2019-06-05 build, I can confirm that there is an inconsistancy in the arrow movement (looks like a bad atan/atan2 computation or something like that, a quadrant error maybe). but with the latest @jihlein build (experimental) here in post 63251, i think it is fixed!
The movement of the arrow is consistent with the tricopter rotation around itself, always pointing the home location.
I’ve read about setting this up and I will try that in the future. The dronin documentation should be helpful. They say : first set up the altitude hold mode, then try to get the position hold mode to work, and then try the RTH feature.
I would love to know the setup that that led to an hour estimation of hover time. Again I am not here to throw stones, I only have a genuine interest in how to optimise and approach that number.
I already know that my setup isn’t the lightest build. I added the GPS, added self-vulcanising tape on the arms to prevent moisture to get in, I am flying with a lipo inside a fireproof bag (remember I am a noob 🙂 and I don’t want to puncture my Lipo in case of a crash, and oh god loose everything in the fires of hell 😀 ).
This setup amounts to 398g, with a 5200 mAh Lipo and its bag it amounts to roughly 798g. This, according to the osd needs a current of around 10 Amps to hover (between 9.5 and 10.5).
This seems realistic, I read someone report a 9 Amps current with other props. This would give around 32 minutes of flight. But during flight, conditions vary a lot and depending on the wind to counter etc, it might be more or less.
Advertised is : “Flight time hovering: ~40 minutes (3s 5200mAh)”, with no wind and a bit of weight shaved off, would I hit the 40 min mark?
Second question : what would it take to get the “with the right battery and a light build, makes it possible to achieve over an hour of hovering flight time!”
What is there to optimise, or what other non ideal conditions have I overlooked?
Ok, I rewatched the build video and David says 10 Amp 10C battery and a light build. Even more with 18650 Lithium Ion batteries. Somebody tried that?17 September, 2019 at 18:18 #63682zophonParticipant
Some pictures of the build 🙂
Attachments:18 September, 2019 at 03:53 #63692yumemi5kParticipant
My build with GPS is 350 g without battery, so yours might be a bit heavy. The bag also add quite a bit of weight. If you are worried about fire, I recommend adding a thin plastic shield or some foam to cushion the impact. If your battery does catch fire, the bag won’t be of much help in saving your drone.
Reducing weight help with flight time in many ways: Reduced weight shaves off mechanical power required at least linearly. Props also become more efficient at lower thrust. Voltage sags less means you can use a tiny bit even lower current. I’d say if you can hover for 32 mins in this build, 40 mins with an optimized build shouldn’t be impossible.
I haven’t seen anyone flying for 1 hour though. I can try it later with a 3S 6000mAh 18650 pack weighing 316 grams. Don’t expect 1 hour though.14 July, 2020 at 05:30 #65681Brom72Participant
I would recommend going to 18650 (or 2170) and dropping LiPo. Samsung, LG, and Sanyo/Panasonic sell 3.5 Ah at 3C. They weigh about 50g.
In the example of @zophon, he had 800g hovering at 10A, 3S. Thus the TR (thrust ratio, g/W) is:
TR = 800 / (3.7 x 3 x 10) = 7.2 g/W
HT (hover time) = 60 * 5.2 / 10 = 31 minutes
Note, this assumes the 10A drain was not on a fully charged LiPo, but a 50% charged LiPo. Thus it is possible that the actual TR and HT are lower.
Now assume a 3S3P 18650 3500 mAh. Gross weight is 400 + 9 * 50 = 850g.
Hover power = 850 / 7.2 = 118W.
Current = 118 / (3.7 x 3) = 10.63A
HT = 60 * 3.5 * 3 / 10.63 = 59 minutes
And more without the unnecessary battery wrapping and arm tape.2 August, 2020 at 18:31 #65747slavasavParticipant
What is the most efficient power setup for a tricopter? 3s looks not so efficient, right? I am testing 4s now, but looking for more insight as this is my first tri for long range.3 August, 2020 at 00:43 #65748Brom72Participant
@slavasav — The higher the S number the better. Depends on your ESC and motor max voltage. Try going to 6S or 7S. I am doing 14S (60V). At 7S, your ESC and motor should be rated for 7 * 4.2 = 30 V. And don’t use LIPO. Use 18650.4 August, 2020 at 10:56 #65749slavasavParticipant
ok, thanks. currently flying 4s li-ion, will try 6s too
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