Mysterious Moving Gain Range

[Cheshirecat]

I have my WKM Gains on a pot on my Futaba T14SG TX.
0 - 200% on the pot with 100% at the centre.
All been fine and Dandy.

I recently added Telemetry to my HerkulesIII and swapped out the WKM IMU V1 with a V2 at the same time (as i had the soldering iron out) and on the following test flights i see oscillation in the hover, it is quite gentle but an oscillation for sure.
This pronounced without the camera and gimbal payload.
So i am thinking that the FC is over correcting at the point where the sweet spot used to be on the pot at around the 150% mark.
Horizontal and vertical performance is stable and fine but when back in the hover it is good for around 30-45 Seconds then gets the wobbles, i can dial it out and now find the sweet spot seems to be at around 80% on the dial.

Nothing has changed in the TX settings as far as i can see and i am mainly flying in ATTI mode, although it also happens in GPS. I have not changed the WKM firmware at all and can't see why the HerkulessIII telemetry will have had this effect although it did require me to re program all of the motor locations, so i might be accusing a completely innocent component.

So my question is:
is the V2 IMU more sensitive than the V1 causing the FC to over correct.
I could just go with the new gain position but i would like to understand why this has changed.

Has anybody else seen increased sensitivity going from V1 to V2


many thanks...........

 

[Cheshirecat]

Well i tried out an increased pitch lower set of props today.
15X5 upstairs nad 15X6 on the bottom motors, early days and only around 30 Mins on the new setup but looking more stable in Horizontal movement (albeit in just 5Mph wind)
Still got this puzzling oscillation in the hover especially with a payload on, looks very much like over set gains but where i normally sweet spot these at around 120-130% i am backing off to around 50% to get stability just can't get my head around it.
Only change is V1 to V2 IMU and new Herkules Firmware for telmetry.
I guess the easy comparison is to put the V1 back on and see what effect that has.

I will trawl through the IOSD and Herkules Telemetry logs to see if anything stands out... Hmmm!

 

[Cheshirecat]

Finally found out this is likely to be a Faulty IMU V2, It got so bad that it was down right dangerous, all over the place, i couldn't even get back on the deck without it tipping over 4 times out of 5.
Changed back to the V1 IMU and reset the gains to where they were and presto, flying solid again.

That's the first and last time i buy any used MR part, only shrink wrapped originals from now on.

 

[gtranquilla]

When you say it tipped over during the landing process..... are you landing level first then finding that some of the motors speed up after landing or are you saying that it is tipping immediately as it contacts the ground?

 

[Cheshirecat]

My landing approach is to bring it in to around 3 feet and let it stabilize in its prop wash. The back off the throttle and let it sink nice and slow and at around 6-8 Inches, check there is no horizontal drift.
If there is i hold it at around 6 inches wait for it to settle again and then drop the throttle and the MR plants itself.
With the IMU V2 there was a lot of drift and oscillation (i had to have the basic gains right down to around 40% just to stop oscillation in GPS or Atti) so at the last 6 inch part of the landing (just about every) time i was happy it was not drifting and dropped the throttle and just as it was about to touch down it would suddenly drift horizontally, the skids would dig in and over she would go.
By the time i can react it is already past 45 Degrees and gunning the throttle at that point will guarantee broken props and shock loaded motors, so i just let it tip over (didn't try to fight it)

IMU V1 back on and the basic gains are back at 80-90% for most flying in Atti and GPS. no more oscillation in the hover and the landings are solid and no longer very embarrassing in front of the 3D heli pilots at the local RC field.
I can only put it down to a bad V2 IMU, maybe it was crashed and the Gyro is damaged, who knows. At some point i may trawl through the IOSD data to see if i can spot any clues but i doubt if i will fly that IMU again.