Dear DiyDroners, APM experts,

First of all, I would like to thank you. Do made something great and unbeatable.

Im creating this topic, because I have some sort of a configuration issue. After trying several things suggested across these forums, I still wasnt able to solve it.

My configuration:

ZMR 250 frame, APM mini 3.1 (please forgive me, im using cheap parts from china), with GPS, external compass, etc.., MT1806 motors, vibration dampening, 5x4.5 props, 3s 2200mah lipo. PCB-PDB with LC filter, step down regulators, minimosd

Issue:

Copter does not perform well in AltHold, Loiter, etc. There seems to be some throttle problem. The copter jumps up/down. This also leads to the copter almost falls back when levels out of a 10km/h speed.

What I've tried:

Balanced motors, balanced props, added vibration dampening, made sure there is a foam covering the baro.

The copter files well in stab or acro, no oscillation. The pids are not perfect, but easily flyable and seems to be ok.

My vibration levels are +-1 on accx, accy around 0. Accz is a bit higher +-2 around 9.8.

I'm feeling a bit hopeless now, if you have any idea, please let me know.

Also if you think its because the parts i have (eg. i should use pixhawk instead), please also let me know.

I'm not new to the field, but I'm still a noob, I'm building this drone for more than a year now. I had a long time frame when it was holding altitude well, but a lot of things changed since than. New props, new PDB, new firmware, new camera, a small servo moving the camera (powered from 5v step down regulator, not from APM), so I dont knwo what the issue is. I have another 500 sized copter having the same issue with about the same electronics and same firmware.

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// +some more photos, including the acc x,y,z chart and another photo of the build.

Also I like to add, some of my motors seems to be loose. Its moving a bit...(less than a millimeter, but i can still feel it). Sadly, I'm not sure I can repair these small 1806 motors, I have no tools for them.

Also on the charts, the accz is waaay higher than the others.

For the first sight, you may say this is clear, replace/repair your motors, but... There is simply no difference before and after adding dampening. The values got better (from +-4 to +-1 on x,y; z to about 50%), still cant hold altitude well.

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Tested with 3.1.5, and the problem does not seem to exists for the first try indoors.

My only problem using 3.1.5 is the scary release notes between 3.2.1 and 3.1.5. It does have some great news in there which i would miss i guess. What do you think?

I need you to set logging higher and then do a test flight.  APM has issues with small frames and over powered copters.

http://ardupilot.org/copter/docs/parameters.html#log-bitmask-log-bi...

set it to NearlyAll for the test and then set it back as it causes performance issues for APM.

Hi, Thanks for relying. What logs would you like to see?

All+FullIMU

is this ok? Wont be too mutch? Can you please tell some params of a flight to help the most?

Currently I can fly indoors, there is high wind out there. :(

Are you fine with a 15-30 sec flight, ~1m alt? In alth-hold and stab as well? I have only one battery left to do the test now. the others are on the charger :)

I'm currently experimenting with 3.1.5, there this issue just does not exist, although since the downgrade, I cannot access dataflash logs. Think I had to clear the eeprom before update.

Hi,

Finally managed to update it back to 3.2.1, enabled all the logging.

Switched to althold and the issue got reproduced.

Thanks

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I can see in the log where the Throttle out bounces up and down but don't know the cause.

Thanks for the replies so far!

I still have no hope to fix this other than buying a Pixhawk harware, which I have to avoid at the moment.

As a workaround, I can fall back to 3.1.5, but there I miss the sonar meters/volt parameter and some others as well (no, i haven't use sonar when created reports, just wanted to try out).

Beside of reverting and forget about sonar and 3.2.1, do you see anything I can do to move this forward?

I can create more and more logs, videos, tests, but I'm not sure if that would help. Also I have the intention and maybe the skills to look at the code and changes since 3.1.5, but I can hardly imagine to find anything without having experience and domain knowledge in Ardupilot development.

So do you have any idea or hint how to proceed?

I'm already thankful of your work, not expecting any customer-service kinda support. Also its a shame I use some cheap clones. I'm regretting it, because now I'm here asking for help without supporting the team by buying the official HW.

Therefore I would be fine with a "leave us alone with those old legacy clones, go buy a Pixhawk". That's already something, I can deal with. But... would this issue be solved on a Pixhawk? I guess there is no guarantee for that.

Maybe you should opt for the Pixracer as it has the same features as the Pixhawk but in a smaller package and there is two flight stacks to choose from with one doing some work with racing.

:) thanks, i think i will do so. Will take some time :( Then I will have an extra APM mini, still deserves to fly. Maybe I'll put them on a foam plane.

Although this may solve the issue for my 250, but there is a HJ-H4 reptile frame with APM 2.6 and having the same problem. Wondering if I have it on 2 (all) of my quads, how isn't it a issue for about everyone else. At least my small quad's setup is very common.

Do you think if i should open a ticket on Ardupilot's GitHub?

If the issue is with 3.2.1, no. The current official release is 3.3.3 and 3.4 is starting beta testing in the next days.

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