Crius V2 board comp with gps stability problem

[Johnc]

Hi Guys,
This is all new to me. I have built a Hexacopter complete with Crius V2 board and have got it flying very smoothly in hover and quick to respond when moving around. Goes up fast & smooth but very twitchy & seems unstable when coming down.
Also when in gps or altitude mode seems to bounce around a lot.
Any ideas?
thank you,
John

[Hands0n]

I don';t know the Crius V2 that well, but in respect to the twitchy coming down, that will be perfectly normal if you are descending vertically within the propwash (column of air under the propellers).   The air there is very unstable and turbulent which is why the multi-rotor will wobble on its way down.  You can reduce that by descending slower, but that may not suit.  In any event, the Crius V2';s stabilisation (if enabled) should help handle it.

The GPS and Alt modes bouncing sounds like the PID need adjusting - or you may have too much vibration making its way to the flight controller.  Balanced props are a good first place to start vibration elimination.

[Oakie]

Hi, your now in the realms of the PID';s, well done on getting to this stage. There are good guides and bad.

http://www.multi-rotor.co.uk/index.php?topic=411.0 start with this one.

let us now how you get on

Paul

[Johnc]

Thank you for the info so far.
I balanced the props prior to fitting but will try another set to see if any difference, only using basic plastics to start in case of mishaps, then will try carbon ones to see if better.
Do you balance motors or leave them as stock?
Re PID';s should they be increased or decreased?
The Hex seems to be almost hands free in hover & stable in stable flight mode, using mission planner to set up, it';s only when I select GPS hold or loiter that it seems to bounce around?
Or is that normal?
thank you.
John

[barneyg]

Thank you for the info so far.
I balanced the props prior to fitting but will try another set to see if any difference, only using basic plastics to start in case of mishaps, then will try carbon ones to see if better.
Do you balance motors or leave them as stock?
Re PID';s should they be increased or decreased?
The Hex seems to be almost hands free in hover & stable in stable flight mode, using mission planner to set up, it';s only when I select GPS hold or loiter that it seems to bounce around?
Or is that normal?
thank you.
John

There are separate PID';s for GPS and Alt hold - for that matter you do have level, baro and Mag also enabled in Loiter ?

[Hands0n]

The Hex seems to be almost hands free in hover & stable in stable flight mode, using mission planner to set up, it';s only when I select GPS hold or loiter that it seems to bounce around?
Or is that normal?
thank you.
John

It shouldn';t be bouncy.  Can you grab a short video of it happening?

[BadgerG]

JohnC,

I added one of these to my Hex and my alt hold and loiter are now rock solid:


http://www.uavobjects.com/product/rctimer-avdome-protection-antivibration-dome/

This little jewel is worth the $30.

[Oakie]

Have you covered the barometer with something to defuse direct wind wash across the top.

If you are using the mission planner with ';ng then do take a moment to look over the arducopter site, the PID instructions are comprehensive enough. http://copter.ardupilot.com/wiki/tuning/


hope that helps.....

[Johnc]

Just had a fiddle with PID in loiter mode, it';s a bit windy here at present but will try it to see if different, will check motor vibration levels, also put foam over baro to see if that helps.
There is a lot more to this than you think.
Thank you for the link to PID instructions/arducopter they are very informative.
Regards,
John

[Oakie]

As i keep forgetting, its not only the covering of the baro but stopping light getting into it as well.....

[Johnc]

The Hexacopter seems to be a bit better since I have adjusted some of the settings.
Just a quick question. RTL, how do you set it to work or does it re-set itself when you power up, or do you have to do some thing at power up to let it know were it';s new launch point is?
I have set RTL on a switch on transmitter, but have not tested it yet.
Thank you,
John

[pheasant_plucker]

The location you arm at is the rtl point. Disarm and rearm to change it.
The only time it should change is if you don';t have a lock when you arm. The rtl point will be whatever position the gps aquires a lock at.

Gerry

[Johnc]

Thank you Gerry,
John

[Johnc]

New problem, recently had a fly away, just testing in back garden at about 4 to 5 foot height then the copter decided to jump up to about 30 foot, powered off to get it back, but controls seemed unresponsive, then came back under some control but buzzing around as if someone else was in control at times.
Then up to 100 foot by itself and started to rotate, turned it back powered off to get it to drop down but it just powered into forward flight and away it went no control at all.
Found it some 400 yards away, luckily hit a tree which stopped its forward flight.
No major damage done so once sorted took it to my local park surrounded by trees to re test. All seemed O.K. then off by itself. Seems to have a mind of it';s own.  Tried again today after re setting failsafe plus tranny fail safe but same thing flys great for a few minutes then off it goes & cannot get it to respond to transmitter.
This within 10 yards of transmitter.
Any ideas. Get good GPS lock etc. 

[Johnc]

Problem seems solved.
It appears that in re programming/adjusting at some point the Hex X now thinks it';s a Hex + or at least the front was approx 30 gegrees off set, also motors would go intermittent when flying, hence feels like someone else is controlling.e.g. forward is diagonal, reverse/back is bias to left or right, left or right would be back or forward diagonal. So if it got caught in a gust or as you moved off very hard to stop/regain control.
I thought I was going mad untill I spotted the tilt to right when going into slow forward flight.
Finally managed using Peters video to erase the board of all info, re flashed using flash tool & then re set basic params, just tried in back garden even though gusty able to control.
At least I can start a re-tune but will be more cautious just changing one param at a time and then re testing.
What is the best programme to flash onto the board, crius pro v2?

[Hands0n]

Glad you got it solved. That was a sneaky fault to develop!

Several on here swear by the MPNG Add Ons version of the software. It has had the sonar code removed to ease up the load on the processor.  It may be a bit behind MPNG itself by a few months.

Otherwise you';re then into the MultiWii software for that particular FC afaik. 

[Johnc]

With flash tool I had the option of 3.0.1-R4 which I used or 3.1.5-R2 Beta!!! but could not get that one to load.
Just wondering if the last one would have been O.K./better or to go for an earlier issue.
Just tried Hex again and it is staying as x config & stable so at least I can fly it.
I must admit with what it was doing I was going to give up as it was uncontrollable & I started doubting myself thinking it was me at fault. Just lucky that I noticed the 30 degree offset when inputting a control.
Good job there is this site/forum which helped me through the process of sorting it out.
Cheers,
John

[Hands0n]

My advice would be to stay away from the Release Candidates (usually suffixed RC) and Beta unless you know exactly what you are doing and why. Generally, that means you';re intending to be a tester of the new code - and accept that code may very well be very buggy, with all of the risks that carries, such as fly aways

I';d say to stick with 3.0.1-R4 which is the latest "stable" release of the code (from what I read): http://www.megapirateng.com/2014/02/megapirateng-3-0-1-r4-released/

More mature, and arguably stable, is the 2013 version of MPNG Add Ons dated to 2013. https://code.google.com/p/megapirateng-add-ons/

[Johnc]

Thank you for that,I will stay with the version now on the board. 3.0.1.R4.
I now have to start tuning PID';s etc.
Getting there, also going to have a go at balancing the motors to see if it helps.
I am new to this so all assistance is great.
Cheers,
John

[Hands0n]

If you';ve not already done so - take some time out to balance your props. They';ll be more likely to be the "big culprits" in terms of unbalanced rotating parts.  Some motors come balanced out of the factory.  Propeller hubs can be a problem also, but it is all a matter of diminishing returns. If you can get the vibrations down to sufficient levels for the FC just by balancing the prop blades then thats probably good enough and nothing much to be gained by doing much more.

I';m glad you';re getting good use out of the forum    

Piccies and videos when you';re ready are always appreciated by the folk here  ::)   

[Johnc]

Just finished checking motors, they were as you said all O.K.
Balance /Re-balanced the props, just a gentle sand on a couple to bring back to level. Then tried it again in garden, seemed a little quieter but nothing really different in flight characteristics.
Will know more when I take it to the park to test.
Thank you,
John
After my fly away I have put a clear disc in the top of the cover so that I can see what the boards status lights are doing.
Might just be able to see it in photo.

[Johnc]

Went to the local park today, nobody about so set up the Hex, waited for GPS lock, then armed it and took off into a very stable hover. ( 15 to 20 mph  slow wind gusts ). Moved it around a bit, noticed it was twitchy, i.e. trying to counteract the wind giving it a bit of a wobble.
Went up to about 20 feet and then activated altitude hold, again a bit wobbly but in control, then into GPS/loiter mode and it only moved about 4 foot around and up & down about 2 foot, still with the wobble.
Feeling confident let it go to a fair distance away and low then activated RTL. Up it went vertically to pre set height, then it paused for a few moments as if confirming it';s GPS position, then to my relief it started on it';s journey back to me, when overhead, paused and then came down with final height adjustments as it got to within 5 foot of the ground. Getting blown around a bit by the wind but touched down a bit hard but nice and level.
That was my first RTL and it was so good I sent it off for at least two more plus some awesome vertical climb outs to over 100 foot & then some fast drops back to 10 foot before stopping the drop with some hard throttle bursts.
Will ease off the PID values to see if that helps control the wobbles.
Feeling great after three good flights. Even flew it in and through and around a couple of trees with camera on front, next time I will check that I have actually turned the record function on.
Starting to enjoy the Hex now.
John
Any body got a brief set of PID values that work on a hex for me to look at?

[Hands0n]

The wobble suggests that your Rate Roll/Pitch P value may be a bit too high.

If you';ve got a spare channel (usually Ch6) available on your TX and can assign a rotary knob to it then you may get some good mileage adjusting the P I and D using that - setting Mission Planner to use Ch6.   

The process is explained in the Ardupilot wiki: http://copter.ardupilot.com/wiki/tuning/#In-flight_tuning

Do the Rate Roll/Pitch first - http://copter.ardupilot.com/wiki/ac_rollpitchtuning/

Then do the Stabilise Roll/Pitch - http://copter.ardupilot.com/wiki/stabilize-mode/#Tuning_Parameters

Hope this helps.

[Johnc]

Just had a play in the back garden with the channel  6 control over PID settings, I put the range a bit too high to start with, flip that makes exciting take off and very hard to control, bouncing around like a copter on steroids.
Got it down a bit hard but flat, turned the dial down and eventually tuned to a stable hover.
Turned out to be just a bit lower than my initial settings.
Will go to the park to test and check loiter, altitude hold, etc.

Thank you for the links,
John

[Hands0n]

Excellent     It often doesn';t take much of a tweak.  From what you described I thought they';d be a bit higher than necessary 

[Johnc]

Just got back in after a quick walk around car park with the Hex at my local Engineering Society, in the dark.
LED lights were a lot better than I expected.
It was a bit blustery with the wind so kept it below 10 foot for safety reasons.
Photo';s attached of it on the ground, also can see the spy hole in the cover letting me see the led board indicators.
Seems a lot more stable but give it a good test in daylight.

[robshaw]

Awesome! Great thread. Only just spotted it. Sorry I didn';t contribute. Good to see the MPNG still in the race. I cut my teeth on that with a V2. I';ll second what';s already been said, reducing vibes is key to a stable loiter. Mount the v2 on foam. Cover the baro in foam. Shield it from light. Make sure any cables aren';t transmitting vibes too. Then follow that with work on the compass calibration.  There is a mod for v2 (like apm 2.5) external compass. This makes a massive difference. I would recommend it.