mad oscillation

[powerlord]

Firstly, thanks to all your work on here - I wouldn';t have got this far without the manuals, etc you guys have been good enough to put together.

I made a multiwii last year around the AIO but it was always rubbish - really unstable compared to my DJI so I left it in a cupboard.

However, I thought I';d give it a refresh, with new ESCs (hobbyking 20a with simonk), new 2213 emax motors and a new DJI450 style frame (old aluminium thing before).

I flashed the AIO over the megapirateng, followed the guides, etc and it all works.

sort of.

except it takes off up to a foot really oscillating, then throttle seems to have a mind of its own - only cutting throttle and letting it crash stops it going on a journey.

This is in stabilise mode.

Now I have triple checked all motors correct way around, connected properlly, rotation correct, but the wierd thing is that when the elevation is set correctly (push forward increases output (min is 980), pushing on the elevator seems to result in it going backwards, like it is reversed. Now, I can swap it on the tx but then it shows as reversed on APM... and that doesn';t seem right to me.

So I';m wondering if I';ve screwed up somewhere and that the massive oscillations are caused by the elevator being reversed internally somehow (i.e. controller wants to to go forward - increased elevator and it goes back - leading to oscillations).

if i hold it in my hand and move it about it feels wrong too - it';s not fighting the movement the same way the DJI does.

It';s a regular X quad - and I have 2,3,5,6 connected as per diagrams (these are definitely correct I assume ?)


So I have:

2 : 10 o';clock CW
5: 2 oclock CCW
6: 8 oclock CCW
3: 4 oclock CW

I';m running 4s.

I';ve tried lowering PIDs, but it';s more than that - its not a PID wobble - it';s a this thing is totally out of control wobble.

I';ve also recalibated the ESCs.

Any ideas ?

[Gaza07]

Hi Powerlord and welcome to the forum I have always had to reverse the elevator on my tx to get it working right to so I don';t think you have any problem there,
The main cause of wobbles in megapirateNG is normally the Rate P being to high although this is the acro setting it still has a huge affect on sable mode to, try lowering the Rate P
It might help to if you could post some pictures of your copter and a short video showing the problem 

[powerlord]

OK, it might get my point about the reverse across too.

I';ve already lowered the P down to 2 and its just the same.

I';ll post a video and my settings and see what you think.

First flight yesterday I made the mistake of glying in alti mode - I didn';t have a failsafe set yet, and the thing just went mental - shot 100 foot up into the air and shot off sideways. the throttle was unresponsive.

crashed somewhere - and only reason I managed to find it was throttling up a bit and listening for motors - amazingly it had got stuck in some bushes 200m away with one of props free to rotate so I could hear it after much running around. arg.

anway - failsafe set now to cut motors, plus testing in stabilise mode (so cutting throttle works).

hopefully we can get it controllable :-(

stu

[Gaza07]

The throttle doesn';t work to well when altitude hold is engaged, just to make sure we are talking about the same setting I have have put circles around the section with Rate P which is the bit that should be reduced,
sorry if this is the ones you have adjusted but i thought i would just make sure 
What version of megapirateNG have you got on the board ?

[powerlord]

did you mean to attach a screenshot there ?

anyhoo - good news !! Just before I shot the video, I made one more change to angular rate control. I changed it from the default to 0.110.

and shot the video - only to find - it was a damn site more stable!!

Reduced it to 0.09 and even more stable - maybe can go even lower!

I assume it';s maybe that the simonk firware makes the esc so quick that they are acting like more powerful motors would ??

I took the stablise P back up from 1.5 to 2 and that seems to give me quite stable, but quick control.

Next thing is throttle response:

- in stablise mode its up and down like a yoyo - the defaul throttle rate was 0.3... and tried going as high as 5 and it seemed to make no difference - basically almost impossible to keep it at a stable alto - up down up down up down.

I tried flipping in into loiter mode, and it acts very weirdly - shooting up into the sky (and this is with working sonar!).

Once setup I intend to fly it almost always in loiter mode (simple on for by sight and off for FPV), so that';s the important one to get working.

A google shows some others finding weird alti mode rocketry.... any ideas ?

I';ve got my sponge over the bario, but still - it should be taking sonar when it';s only at around 5 feet surely ???

Instead, it seems to work okish at about 2 feet off the ground, but give it a bit more height and it jsut goes mental - shooting up into the sky and ignores reductions in throttle after that - I have to flick it back to stablise and bring it back down manually.

stu

[Gaza07]

Hi stu have you tried checking the function of the sonar in the CLI to see what its reading ?

[otis888]

Gaza with regards to the sonar what should it read in the CLI - mine reads 0 cm for 50lines or so then changes to 555cm.  Is this a sign that it';s working or not??
Thanks

[Gaza07]

I think that is showing a error as you lift the copter you should see the CM climb slowly and fall as you drop it I think it displays 555cm when it has an error or is to close to the ground, I stopped using sonars because they are delicate and dont work very well in the cold 

[powerlord]

yeh sonar is working fine on command line, but yes if you tap the top of it, it also shows 555.

So it is generally working.

I did try flying with it disconnected to see if made any difference.. which I think might have identified the problem... since I then had a look
on APM again... and ';alt'; is showing as 0.

I tried tests->altitude

and it just says ';press return to finish'; and does nothing.

So.. I';m thinking that somehow the alti isn';t working ??

I';ve double checked the settings, and I have definately selected the right board for the AIO. I even tried the other and rebooted just in case.

Does the tests->altitude display alti for others ok ?

If so, I suppose I';ll have to assume for some weird reason the alti sensor on my board is knackered :-(

stu

[powerlord]

can someone do me a favour please and tell me if :

test>altitude works and shows altitude ?

or if they see altitude properly on artificial horizon ?

cheers

stu

[Gaza07]

Sorry I cant I currently have Multi Wii 2.2 on my AIOP at the moment, Anyone with megapirate on a AIOP do the test   

[powerlord]

In case anyone else had the same problem - I got my alti working in the end.

It turned out it was not working when compiled with 1.0.4

even though it compiled and everything else was fine, the alti was 0.

recompiling with 1.0.1 and suddenly I have a working alto.

Saying that - in loiter/alti hold mode it is now far far too slow at keeping alti - if activated at say 30 feet, it shoots up a bit, then slowly falls... till nearly at ground then powers up again to 20/30 feet and repeats.

my P is at 5 for throttle and alti so I';m not sure what to try next to sort it tbh.