Auto level not so level! and I don't know why! It is sooo fustrating!

[bunnygirl80]

Hiya,

I';ve been trying everything to get my quad flying on level. I';ve balanced the props, calibrated the ESCs, calibrated the MultiWii (TX, ACC, MAG, GYRO) and it';s auto levelling to an angle of about 10'; degrees which is causing it to drift terribly! Flying in ACRO with all features disabled is okay, quite nice! But as soon as I enable any of the features like LEVEL, POS HOLD, etc, everything goes belly up and all over the place. HEEEELLLLPPPP! Please! 

Thx, Stef

[teslahed]

Do you understand how to ';trim'; the auto-level mode? That';s separate from trimming / calibrating the gyros and accelerometers when you turn the thing on.

What you need to do is to get everything trimmed as well as possible in acro mode and sit the quadcopter hovering in front of you.

Flip stable mode on and remember which way the quadcopter wants to drift (i.e backwards towards you).

Now land and disarm.

Once disarmed stick the left throttle stick up to maximum and you can now trim auto-level with the stick on the right. If you push the stick forward you will trim one forward ';blip'; and if you push the stick right you';ll trim the auto-level mode to the right. The light on the flight controller should blink with every ';blip'; and you can hold the stick forward or sideways and count the flashes to work out how much trim you are entering. The longer you hold the more the light blinks and the more trim you';ve inputted - you';ll need to input at least 4 blips or so to see much change as the individual blips are quite small.

Now take off, try auto-level again, land and re-trim if necessary.

Here is post on the multiwii forums that goes into a bit more detail;

http://www.multiwii.com/forum/viewtopic.php?f=17&t=188

I';ve always thought it a bit odd the way you have to trim auto-level mode in multiwii. None of the other flight controllers seem quite so fussy when it comes to that side of things.

[bunnygirl80]

Hi teslahed, 

Oh! Thanks for the info. I';m sure I';ve tried that before, but I will try again tomorrow weather permitting of course.

After reading the information you sent http://www.multiwii.com/wiki/index.php?title=Flightmodes , I am a little concerned that I';ve been testing something I haven';t got. I';m also worried that I';m expecting too much of the multiwii 2.1 software with crius multiwii se v2.0 board. I';ve been trying to get position hold to work, but from reading your link, it seems that i need an optical flow sensor for this and i don';t think the crius se has one built in?

I really thought the position hold would have used the GPS info to stay within a 2-4 meter window. I didn';t realised i needed another sensor!

So, if I understand this correctly, with the standard Crius SE board, all i can use from the multiwii features is gyro (also knows as acro), autolevel (also knows as angle and stable), headfree and altitude hold ( but not good as the sensor is crap on the se board - hence the reason i ordered a AIOP ). 

So, I need a optical flow sensor for the position hold! What is this?

Thanks, Steffie

[QuadBod]

Hi Stef,

An optical flow sensor is based on the same sensor used in an optical mouse, but fitted with a lens more suited to detecting movement of a multi-rotor relative to the ground. The sensor sends relative position information for two axes. It complements the accelerometer.

Matt.

[teslahed]

That diagram is odd - and wrong i think. You don';t need an optical flow sensor for position hold. You need gyros / accelerometers (obviously), a decent barometer and a magnetometer, and GPS. A 2 to 4 meter box should be doable once everything is properly tuned.

On my multiwii quadcopter i have a 3 way switch setup so that the middle position turns on the barometer, magnetometer, autolevel and GPS position hold, and the bottom position all of the above only GPS return to home instead of position hold. Seems to work for me.

I';ve not seen any flight controllers with a working optical flow sensors. It might be a cool feature once it';s working properly - another thing like sonar (which works well on the rabbit flight controllers) - but I';ve not seen it done yet.

[bunnygirl80]

Hi,

Ah! that explains things a little. I';m okay with the software side of things, but pants when it comes to the hardware side!  I will program my AUX switches like yours tomorrow. I naturally thought that position hold would have turned on the GYRO, LEVEL etc by itself.

I';ve also got a HC-SR04 Sonar in a box, it came for free with my arduino development board. So what is the difference between the sonar and the optical flow sensor? is one better than the other? how easy is it to connect and changes to the software. i did have a quick look and the multiwii does not support the HC-SR04 sonar! Please don';t mention the horrid soldering iron word! LOL. It might be worth trying to get this working once i have everything else working.

Thx, Stef

[bunnygirl80]

Does this look okay? Thanks.

[teslahed]

That looks fine to me, except you might want to turn off the magnetometer when you aren';t using GPS (middle setting). That';s because if you are flying around with the magnetometer on and bank too much it can get confused and crash your quadcopter (or so I';ve heard). The magnetometer has no beneficial effect when you aren';t using the GPS that I';ve noticed so you may as well leave it off.

You';ve got your switch the other way around to mine (i.e. high values everything off, low values on) but that shouldn';t make any difference at all. When you come to setup failsafes this might be important though - if you set your radio failsafe defaults to GPS return to home mode, there is a chance that might save you on radio signal loss. 

I naturally thought that position hold would have turned on the GYRO, LEVEL etc by itself.

I thought that too before i tried it. There doesn';t seem to be any point in turning GPS on without turning the magnetometer on as well, but you can if you want for some reason.

I';ve also got a HC-SR04 Sonar in a box, it came for free with my arduino development board. So what is the difference between the sonar and the optical flow sensor? is one better than the other? how easy is it to connect and changes to the software. i did have a quick look and the multiwii does not support the HC-SR04 sonar! Please don';t mention the horrid soldering iron word! LOL. It might be worth trying to get this working once i have everything else working.

Multiwii doesn';t (yet) support the sonar, it';s still in testing, so i wouldn';t bother with it if I were you. Maybe they';ll add it to 2.2 when that';s out

[bunnygirl80]

 ::) Okay guys, I';m getting somewhere. Whippee! Yes, I';m up bright and early and flying in the garden!  Cheesy Grin! I did everything in the instructions provided. I activated the PH Position Hold and it did hover around, I left it to it';s own devices for a few seconds and it hovered in a circle until eventually landing in a bush. Whippe! The fact it did two sort of circles looks quite good. LOL. After disarming, I tried again, but all the levels seemed different and messed up. It was drifting to the right again! Mmm!

So, what do I have to calibrate setup at each arm/disarm and power on? It';s used most of my battery to get the calibration setup above. So, I';m hoping I don';t have to do this all the time!!! 

Thanks again! xxx

[teslahed]

Autolevel is more affected by vibrations from badly balanced props / motors than gyros only  (acro mode).

If your quadcopter is suffering from some vibration issues (a common problem) this could be affecting autolevel and not acro mode.

I believe there are apps you can get for smart phones that measure vibrations - you clamp your phone to one of your quadcopter arms whilst running the right app and only spin up one motor at a time (unplug the others) you can then chart the vibrations from each motor / prop combination independently to get them as well balanced as possible. I need to look in to this myself now i have my very own smartphone (it';s new).

http://www.androidblip.com/android-apps/max-vibrometer-304570.html

But i do agree that autolevel on the multiwii boards isn';t the best - the fact it drifts a bit at times is a pain. Once you have everything properly configured you shouldn';t need to do it before every flight but getting to that point is not easy compared to the DJI naza or even the cheaper KK2.

[bunnygirl80]

Hi,

I have balanced the props old fashioned style with a prop balancing rig, but haven';t done it with any phone app. I also am interested in this! ;o)

So, at the moment, what would you expect me to have to do before each flight? Just the calibration of the auto level??? or gyro and acc also?

Do, you take a board with a spirit level with you each time you go flying to ensure you take off from a level surface?

Thanks,

Steffie

[Gaza07]

I set my acc / auto level up with a small bubble level the circular type with a circle in the middle I do this on the initial setup my level is normally spot on or very close and just needs a little trimming in the way Chris (Teslahed) explained earlier, I find that some times probably due to temperature drift it can change a little and takes trimming to get it right but I never re-calibrate 
Its always a good idea to let your copter stand a while when making rapid temperature changes as it can affect the sensors a lot 

[Biffa]

Its always a good idea to let your copter stand a while when making rapid temperature changes as it can affect the sensors a lot 

+1 This is something you quickly get in the habit of doing flying helicopters, or expensive fun ensues 

[bunnygirl80]

Bloomin Eck! I know I';m blonde... but this is silly... lol... You mention...

I find that some times probably due to temperature drift it can change a little and takes trimming to get it right but I never re-calibrate

What do you mean you never recalibrate? So, I will make a board with a bubble level on it and i can use this to take off from all the time? is this a good idea? then i can go up to 2 meters and adjust for auto level quickly before my battery goes flat!!! LOL.

[Gaza07]

Hi Stef I don';t fly with a bubble level on the copter, I sit the copter on the bench with the bubble level on and level the copter then click the calibrate button in the GUI, I then fly it and normally it sits level but if it is out its normally only a small amount I then land and use the trimming method described by Chris,
Using the bubble level just means I know its sat level on the bench rather than just assuming its level 

[bunnygirl80]

OK. Gotcha! Thanks. 

I';ll do that next time. I';m sooo used to flying planes and just taking them down the field and flying.

I haven';t got much room in my little car! so, I will get my leprechaun friend to make me a little platform with a bubble! ;o)

So are all flight controllers like this? Even the expensive NAZA?

Thx.

[mickyt]

I';ve got the Naza Stef and I';ve never used a spirit level or any other for of bubble, if I';m correct so long as I input the correct measurements into dji assistant with regards the GPS antenna position and I do the simple compass calibration it should stay put and level in GPS mode and sit level in attitude mode.

[bunnygirl80]

Hi Mick,

Thanks for that. Have you actually tried it in Position Hold and Level mode. Tell you why... mine flies beautifully when position hold and level is off, but was sooo erratic when it was turned on. Now it seems sorted though, I';m keen to give it another try in a larger field and not land in the bushes in the back garden again! LOL.

Stef

[guest325]

I';m keen to give it another try in a larger field and not land in the bushes in the back garden again! LOL.
Stef

Haha been there done that one with mine except it was a bit of topiary on the neighbours front garden..........as he vanishes pdq and denies any possible responsibility     

[mickyt]

Hi Stef yeah I fly in GPS mode most of the time, if you thinks thing are going a bit pete tong come of the stick it settles into a hover untill you regain your composure lol it';s great for fpv I';ve tried manual mode and its does have this butt clench effect lol attitude mode is also very good if you want to take a cam shot or film something as it sits level and steady