MultiWii

Hi All
Ok bit of a newby with multiwii butjust setting up my multiwii SE V2 in a quad.
Got the GPS and ic2 board all working (I get 7 sats inside near a window)
So got it working pretty good in angle mode nice response but also steady hover so thought i would try gps hold.
I setup gps hold with angle mode.
So I have pos 1 as angle mode and pos 2 as angle and gps hold - nothing else
Made sure I have sat lock but when switching from angle to angle/gps hold it kind of trys to hold pos but it seems like one or two of the motors start pulsing very quick and sudden.
It isnt a fast oscilation more like i had quickly pushed and released the roll or pitch stick very quickly every few seconds.

I'm sure this is something simple but cant find any other post with these symptoms
Any ideas?

Second quicker question
Once gps hold is activated I appreciate it should try and hold that position.
So while in gps hold if i say roll to the right 10 metres or so then centre the sticks what should happen next
1. The quad stays in the new pos under gps hold.
2. The quad trys to resume the original position where gps hold was originally activated.
Stu

To answer your second question, GPS Hold will maintain the new position. See the following lines from the config.h file (MW v2.3):



When moving the sticks outside of the deadspan, GPS Hold is temporarily disabled. When the sticks are released, GPS Hold is re-engaged with the new position as the hold point.

The jerking problem you mention is PID tuning of NavR and PosR. These PIDs control the attitude adjustments made to the craft to navigate (back) to, and hold in the hold position.

I found the default settings made regular pulses on the motors on my large quad and have re tuned the PIDs by starting with P very low and gradually increasing it while I and D are 0. By doing this you will gradually see the effect of the proportional control. The further the quad is pushed from the hold location, the more it will correct towards the hold location. The last lot of tuning I did was in quite strong wind and it shows the effects up quite clearly.

The pulsing is likely to be caused by the PosR/NavR D being set too high. If it drifts away from the hold position you'll need to increase P.

NavR is used when you are further away from the hold position, PosR is the fine tuning of position hold so should naturally be tuned a bit less aggressively than NavR.

I hope that helps...