Please Help!!! Working with some kids - won't take off

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Joined: Sun Jan 13, 2019 8:48 pm

Please Help!!! Working with some kids - won't take off

Post by sdalgleish »

I am a Destination Imagination team manager ( ... anager.pdf) and I'm working with a group of 8th grade kids. They built a drone for an upcoming competition and we can't get it to fly. They put a huge amount of work into this and I don't want to see them fail. They asked me to get them some "expert help".

They used the plans for an arduino MultiWii drone from YouTube.

It is an Arduino quadcopter drone using MultiWii and a gyro+accelerometer chip.

They made lots of mistakes building it - but as far as I can tell - they have addressed all of them. I am a non-practicing electrical engineer and I've dabbled with electric RC planes and I'm a pretty good technical troubleshooter - but I'm now stuck too.

The problem they are having now is just getting it to take-off. They previously could get it to get off the ground - but then if flipped over. (We found that the gyro board was 180 degrees in the wrong orientation - and fixed that). Then it would spin when it took off - and they fixed that props that were not correct for counter-rotation.

Now, when they power-up the drone, the motors oscillate when the throttle stick is not touched. If they let it sit, one or two of the props will stop turning completely.
This happens when no mode is selected (all mode boxes are blank) and when the Angle mode (3 angle boxes checked) under Aux1.

When the drone is set on the floor at an angle, the two lower props spin (as expected) when the drone is powered-up - but then one of the lower props stops spinning - which seems really strange. What seems even stranger is that the kids noticed that this behavior is mimicked in the software (MultiWiiConf). With the USB cable attached to the Arduino and the MultiWiiConf software running, when the turn-up they throttle and then don't touch it - they see 2 of the motors slowly dropping in speed (in the software). That seems really strange and makes me think that this is a code configuration problem of some sort. They put some extreme values in the PID settings and found a way to make the "motor dropping in speed" problem go away - but the I and D values were so high (maxed out) that I doubt they would work.

They have been using the PID settings that are shown in the video. But, this does not seem like a PID tuning issue since the oscillations during attempted-take-off are so bad that the done won't get off the ground.

We had battery issues - and killed a few expensive LiPos. They then learned a lot about LiPo batteries. We have new batteries with LEDs on them and we are taking care of these batteries. So I don't think that is the issue now.

It seems like we are missing something that takes experience to understand.

PLEASE HELP. They have a meeting on Sunday 2/17 - and this is nearly the last chance to get it going.

Out of desperation, I'm going to post this in a few different categories in the forum. I hope someone sees this that has experience and insight.

Thank you in-advance for your help.

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