MicroArduCopter, 3" props, Omnibus Nano, Success!

@andyp1per (or anyone), have you done much more fine tuning of loiter? At some point I had non default settings for my PID’s related to position hold, but earlier this spring I reset everything and started from scratch again.
Now that everything else is working so well, I’d like to get it to hold its position more steadily… W/ the default settings it’s on now it rocks back and forth a lot in GPS position hold modes. I don’t think it’s just chasing a bad GPS signal either… It’s like every movement causes it to rock back and forth a bit.
In stabilize it’s completely solid…

If you’ve fine tuned that could you give me any advice or post a parameter file?

I never use loiter - usually - but today was trying the autotune in loiter feature. Didn’t work great from an autotune perspective (maybe too much wind?) but loiter was very steady. I usually use PosHold as my goto EKF mode. Rocking back and forth sounds like toilet bowl? maybe too much compass interference?

I think it is oscillating… I can see it in the logs. Basically the desired position is a straight line, and the actual position is a sine wave over it. I spent a day tuning the PSC settings in my first iteration of ‘microcopter’, but those settings aren’t working well for this new setup. I’ll just have to jump in and start tuning again…
It’s not going around in a circle at all… But if I move forward and stop, it rocks back and forth. If it sits still w/ a good GPS signal it’s fine. If it repositions itself, it rocks back and forth again. It’s subtle and not anything you could see flying line of sight… But in FPV, it’s obvious.
I’ll get it sorted next time I have some tuning time.

Nice question @wicked1,

on controller tuning with oscillations @Leonardthall once said this:

By the way, I was reading this that is somewhat related:

and

EK2_ABIAS_P_NSE
This noise controls the growth of the vertical accelerometer delta velocity bias state error estimate. Increasing it makes accelerometer bias estimation faster and noisier.

so making accelerometer bias estimation slower solves this problem? What values have you tried?

Thanks for the reply. I hadn’t seen Leo’s post about it.

For EK2_ABIAS_P_NSE, I’m currently on the default setting of .0005 (I may have an extra zero in there, I don’t have the parameters in front of me). The leaning issue is a little complex. If EKF is not using the GPS due to bad reception, at .0005, the copter leans to the left based on the amount of throttle I give it. Once it gets a good GPS signal, it levels itself and is fine as long as it has GPS, even in non GPS modes. I lowered it to .0001, and it no longer leaned even when it has no GPS reception, but my flight time decreased. So, I am putting up w/ the leaning in order to get the longest flight time possible.
The issue is somehow related to the IMU’s or noisy power in the cheap omnibus boards… Different Omnibus Nano’s do it differently. One was so bad it wasn’t flyable. Another leaned back rather than left, etc… It seems like a hardware issue to me.

I have a problem with my micro copter (3" props, kakute f7). I put it on the ground, arm in stabilize mode, put a little throttle (but not takeoff). After inspecting the log, I found when motors start to spin, AccZ decreased enough to make copter feel there is a velocity downward. This do not happened on my 250 frame.


1 1980-1-1 上午 08-00-00.bin (300 KB)

this is my 250 frame

@maroquio Compliments for the design of your microcopter. I think that the parts under the motors that holds the legs are 3D printed. Is it possible to have the STL file of that part?

This is one of those tuning threads that might benefit from the tuning instructions I wrote on the wiki:
http://ardupilot.org/copter/docs/tuning-process-instructions.html

Please give feedback and suggestions here:

1 Like

Hello, Andrea.
Actually, that part is made of CNC machined nylon, but you can 3D print as well. It will not be so strong as solid nylon, but can work. I’m sending the file as an attachment. Btw, the new version does not use this part anymore. I use a M2.5 nylon 8mm standoff with a 2mm carbon fiber rod. You can see in the assembly 3D animation in the video below:

Anyway, the STL of that old landing gear base is attached.

Best regards!

Sub250 Landing Gear Support.stl (221.3 KB)

3 Likes

Thanks Ricardo
I really enjoyed the 3D rendered video, super detailed and super useful!

1 Like

Thanks, bro. I hope it can help people to build their own… :slight_smile:

2 Likes

Hi Maroquio, could you post your param file for your sub 250 ? Thx

Of course, Hugues.
Regards.

Sub250A.Maroquio.FC-KakuteF7AIO.GPS-Matek.LiDAR-TFMini.OF-ThoneFlow.RX-R9MMwithFrSkyTelemetryPassthrough.NanoPiOnRx1Tx1.param (19.5 KB)

1 Like

Thank you. What firmware version does it correspond to ? and in 2S voltage, right ?
Do you get a flyable ship (external flights, slight winds) and poshold modes working right with these parameters ?

Yes… it is working nice. I’m using firmware 3.7 from June 15 and 2S battery. PosHold and Loiter working with and without GPS.

I can post my latest param file later, too… I fly it daily. Heavy winds (Wind doesn’t seem to bother it as much as a larger copter), all modes, auto missions, etc. Everything works great. 135mm frame. 3" props. 2s.
6 min flights with my 950mah lipo and fast flying. 18 minute hover w/ 3000mah 18650’s.

Have you tried althold based on baro only (no lidar, no optical flow) ? I can’t seem to have any alt hold working on mine : Kakute F7 with its integrated baro (with or without covering foam), 2S, firmware 3.7

nice performance. Would be great to check your params too. This would compile into a useful database for people building 3" arduships. Good flying time too with 18min. Your total weight without battery= ?

Yes… It was working with baro in AltHold, but always with vertical step up/step down variation (around 40cm). I think that it can be configured (parameters) to discard very subtle measures, but I did not try.

Total Weight w/out battery now is 123 grams… It has gotten heavier over the past year… I was right around 100g when I first built it… (Now using diversity RX, different GPS, glue and various repairs, etc).
That 18 minute time is literally just hovering and the flight ended when the ESC cut out… I have flown for about 12 minutes and landed before the battery died. I’m not super comfortable w/ the 18650’s yet, because the voltage sags a lot, and I don’t really know the limits. I know I was flying around at about 5.7v when I decided to land.

I agree about compiling all the info we can… These small copters take considerable tuning… More than just PID’s. I think Andy has a well performing 3" copter, too, so maybe he’ll share his config file if he sees this.

My baro only alt hold performance is good… If I’m above all the ground disturbances it seems to hold its position quite well. I’ve not measured it, but I’d say 40cm at worst. Maybe even more like 20cm vertical drift. Basically, nothing bad enough to notice or worry about for what I’m doing. I did tune those parameters… There’s a filter in I think the PSC settings that needs adjustment, and the related PID’s. I don’t remember the names… I’ll get a parameter file uploaded after work. My first flights were not successful! I basically destroyed my copter the first time I tried alt_hold! It flew up and hit my ceiling hard. It took me a couple days of tuning to get alt_hold working well.