Back and forth oscillation, pitching forward PLEASE HELP

[ucscSeniorDesign]

My team has run into a bit of a roadblock, trying to tune PID's and get stable flight for the last week or so.

So while tuning the PID' s while the quad is suspended horizontally by two strings, the quad seems to start rocking back and forth when increasing throttle, and once it starts swinging it will over correct more and more on each swing. This will either happen immediately if throttle is high enough or it will slowly build up when throttle is lower.

Here is a video ( http://youtu.be/LSx20gIY3no ), the last 15-20 seconds show what I'm talking about.

I've tried re-calibrating all sensors, balancing motors, reprogramming the board and and re-adjusting the PID for days. I've watched so many videos on tuning PID's including this one ( https://www.youtube.com/watch?v=YNzqTGEl2xQ )
the only real improvement we've noticed is by essentially turning 'off' PID by setting Pitch/Roll values to 1:0:0. In that case, the problem still exists, but it isn't as bad and the problem presents itself at higher throttles. We certainly don't want to solve the problem by removing the effect of the PID though.

We though perhaps the movement of the string was contributing to the back and forth swing, so instead we suspended the quad from a sting attached to the ceiling, we also anchored it to a weight on the ground to stop any crazy moves in one direction. Sometimes the back and forth swing could be seen,but the main issue was that it would just pitch forward.

You can see this in the video here ( https://www.youtube.com/watch?v=oie4atEjImo#t=45s ) Sorry about the long video

We tried unplugging the board and rebooting it on a stable, flat surface, as well as re-calibrating the accelerometer, and using stick commands to trim the accelerometer in-flight. Still no matter it drifts forward.

We feel like we've exhausted every method to try and fix this, is there something we're not seeing?

[Noctaro]

Wich mode are you using?
You need to test it in acromode. Trim acromode on your transmitter trims, not via stickcommands.
Once acro is stable, take the next step to levelmode.

Greetz Noc

[waltr]

In the first video, the throttle is not high enough. The quad needs to lift the string which then has the props up to a speed where the FC can control the quad's pitch/roll. Also what Noctaro said, must be in ACRO mode to tune PIDs.

Another thing I saw is the huge weight far below the Quad. This causes a pendulum effect which quad controllers tend not to like.

[ucscSeniorDesign]

Wich mode are you using?
You need to test it in acromode. Trim acromode on your transmitter trims, not via stickcommands.
Once acro is stable, take the next step to levelmode.

Greetz Noc

As far as what mode I'm in, I assume you mean flight mode? We tried tuning in Horizon mode but didn't really notice any difference, so we've been doing most tuning while not actually set in a specific mode.
You mention acro mode, but the GUI only lists ANGLE, HORIZON, BARO, MAG, HEADFREE, and HEADADJ. I am familiar with ACRO mode, I've seen it mentioned on the forum, but perhaps ACRO mode isn't in my current MultiWii version (2.3)
How exactly would I enter ACRO mode if its not in the GUI?

In the first video, the throttle is not high enough. The quad needs to lift the string which then has the props up to a speed where the FC can control the quad's pitch/roll. Also what Noctaro said, must be in ACRO mode to tune PIDs.

Another thing I saw is the huge weight far below the Quad. This causes a pendulum effect which quad controllers tend not to like.

The weight below the quad is no longer there, we have rebuilt the quad so that isn't there anymore.

[ucscSeniorDesign]

Wich mode are you using?
You need to test it in acromode. Trim acromode on your transmitter trims, not via stickcommands.
Once acro is stable, take the next step to levelmode.

Greetz Noc

Also I'm not quite sure what you mean by transmitter trims, I used the clicking buttons below and to the side of the sticks to make sure the midpoint of all sticks was at 1500, and I've been calling those transmitter trims. I'm not sure how that helps with with stable flight though.

[scrat]

Wich mode are you using?
You need to test it in acromode. Trim acromode on your transmitter trims, not via stickcommands.
Once acro is stable, take the next step to levelmode.

Greetz Noc

Also I'm not quite sure what you mean by transmitter trims, I used the clicking buttons below and to the side of the sticks to make sure the midpoint of all sticks was at 1500, and I've been calling those transmitter trims. I'm not sure how that helps with with stable flight though.

First you must set center sticks to 1500 and use subtrims for that. Then fly in acro mode and use clicking buttons for trim acro mode. Then when acro mode is perfect, turn on ANGLE and trim angle with stick command - quad must be UNARMED - the set full throotle and use AIL and ELE sticks to trim ANGLE mode.

I hope you have flashed your turnigy to er9x or openTx firmware and you're not using original firmware.

[waltr]

ACRO mode is when no other flight mode is enabled, all are NOT GREEN in MW Config program.
ACRO is also know as GRYO only mode and MW must be in this mode to adjust PIDs for Pitch and Roll.
Once these are good then in ANGLE (auto0level) mode you can adjust the LEVEL PIDs.

The buttons below and to the side of the sticks are the 'trim tabs'. In other RC Transmitters these are analog sliders.

[ucscSeniorDesign]

Well in that case we are tuning in ACRO mode already.

Scrat when you say "Then fly in acro mode and use clicking buttons for trim acro mode." Where can I find more details about that? Am I just clicking them in the direction I need to compensate? Do I use the buttons on the left stick or right stick?

As far as the Transmitter, we are using original firmware. What's wrong with it?

[scrat]

For triming quad in acro mode this is fine. And use buttons on that side where you have stick for pitch and roll. But if you want then trim ANGLE mode...use my previous post.

Change the transmitter FW, because only then you'll see the light Trust me.

http://code.google.com/p/er9x/ - er9x
http://www.open-tx.org/ - openTx