[SOLVED] Quad losing control after a while

Andy7 · Post by **Andy7** » Fri Jun 13, 2014 9:46 pm

I've been experiencing some odd behaviour from my Quad.
I've only just got it working properly, so there might be a few things for me to get right. However I've been at it a while and have been through all the usual MultiWii 101 stuff.

It'll take off nicely and hover really nicely with just the odd stick nudge to keep it in the same place.
But after 30 seconds or so it'll begin to drift backwards and eventually even almost full forwards pitch control won't bring it straight.

This is flying in stable mode on a completely still day with no wind whatsoever.

One thing that I seem to find is that if I let it start up on a VERY level surface I get a much better stability from the beginning than if I start up on a slightly uneven surface.... but maybe I'm just imagining it?

Anyone got any clues as to what's happening to make it lose control. :?:

waltr · Post by **waltr** » Mon Jun 16, 2014 3:50 am

Is it absolutely still after you apply power and when the FC cals the Gryo (blue LED flashing)?

Are there any vibrations? This can cause sensor errors to build up so it'll be fine for a short time.
What if you land, disarm, then re-arm and take off. Is it ok for a while?

Are you in ANGLE or ACRO mode? or another mode?

How is the NanoWii mounted?

Andy7 · Post by **Andy7** » Mon Jun 16, 2014 9:16 am

Hi waltr,
Yes, I keep it totally still during startup. (Flyduino nanowii, fwiw) I've been making sure it's on a good level surface such as a bench when I apply power and let it go through all the calibrations. I get the usual arduino glow-glow-glow then some flickering and then a few seconds of flashing at about 3hz... is that last part normal?
I'll then carry it over to the grass and start up. Could this moving from one place to another before starting cause a problem? My garden has a bit of a slope - incidentally, the slope (only slight) is in the direction of drift.

When it's misbehaving I land it (keep motors idling) then try to take off and it immediately pulls away in the drift direction.
If I disarm (not power down), put it back in my take-off spot and take off then it's okay for a bit.

Angle mode is responsive though I'm not too good at flying in that mode yet so I can't really analyse flight in that mode meaningfully yet. In level mode, as described it does a GREAT job initially.

There's a LITTLE bit of 'P wobble' so I might take that down a little. From what I understand D will help a bit with drift but yes, I'm fairly certain it's vibrations.
My FC is on shock mounts (picked up some nice blue hard-drive shocks from Maplin) and my props/motors are (were) balanced.

However, I'm not too happy with the plastic adapter ring that come with the props. They fit nice and snug but I'm worried about eccentricity there. I swapped my two CCW props (it was drifting back and left) and that made a big difference. So I'm rather suspicious of that.

Kind of tempted to buy or make on my lathe some aluminium conical washers that COULD help to auto-centre the props.

waltr · Post by **waltr** » Mon Jun 16, 2014 2:55 pm

Ok, disarming and re-arming seems to re-set the issue.
LED blinking seem correct and once booted moving it around will not cause an issue. I typically pick up my quad and launch from my hand.

ANGLE mode is the Auto-level mode in MW. This is the recommended beginner mode. Ensure this is enabled (use the MW config gui, ANGLE should be Green).
The other mode is ACRO which is gryo only and is enabled when none of the mode in the gui are green. This is also called Rate mode.

In ANGLE mode you will need to do some ACC TRIM to get the copter to hold level well.

Andy7 · Post by **Andy7** » Mon Jun 16, 2014 3:50 pm

Argh: I always get the modes mixed up... I should have said: "ACRO mode is responsive though..."

So, yes, I fly in ANGLE (auto-level) mode.
I've trimmed Angle mode (land, disarm, throttle 100%, push pitch / roll to click the trim), that gives me the nice initial level flight - it's actually REALLY stable while it's behaving with just a little drift caused by the breeze.

Andy7 · Post by **Andy7** » Sat Jun 21, 2014 6:03 pm

Today, I LASER balanced my motors then my props, took my bird out in the garden in the sunshine for a spin and it's PERFECT!!!
Got a lot of the vibration out of the system and it's SUPER stable now. I was able to loiter about in ~roughly~ the same place (my skills aren't honed yet) until I'd had enough.

THEN: After a SLIGHTLY hard bump (nothing really much to do any damage) it started AGAIN pulling back and left and wouldn't take off.

I finally checked my props carefully and found that the back-left prop mount wasn't tightening properly, allowing the prop to slip - and THAT was what was causing the weird random drift.

Took the prop mount apart, cleaned it up and so far 100% reliable.

Mission to the end of the garden to the office and back successful !

waltr · Post by **waltr** » Sun Jun 22, 2014 2:17 am

Ok, success is always good to hear about.
Now go fly.

MultiWii