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VBAR log meaning ?

Posted by cdric 
VBAR log meaning ?
January 18, 2020 10:31AM
Hello everybody,

On my VBar when I read a flight log, I see many messages...

During a flight with a kraken, I have a log saying:
- IMU Sensor Z Axis released
- IMU Sensor Z Axis hangs (here there is a danger flag). What does it means exactly?

Is there somewhere a documentation about the log? and their meaning?

Many thanks thanks
RV
Re: VBAR log meaning ?
January 18, 2020 01:07PM
Quote:
this is a issue based on some helicopters (especially TDR2 with a very stiff frame) and thier microvibrations. They can't be monitored - and can't be dampened in a known way.

We have tested this effect extensively on a TDR2 - and it was nothing that could be solved permanantely (i talk about 200 flights in each variation, i have a local buddy here who did all the extensive testing on this heli) when using another NEO, dampening or mounting position. It resists with the heli and its mechanical things like gear, bearings, motor, stiffnes of the frame, tail drive, dampenings etc.

So - unfortunately we can't do anything to solve the initial trigger effect, just watch the sensor and if it hangs - give a message. The 15g z-axis sensor is driven to its end due those microvibs and stucks there. It could possibly also release again in next flight or ground handling as it is mechanical.

So - what we do - and why we can (and others not):

We have 9 sensors inside the NEO - 3 rate sensors as for all VBars already for flight control, then 3 accelerometers with 15g range, then 3 accelerometers with 200g range.

The 15g accelerometers have a factory calibration and are used during power up to calibrate the 200g ones which have no factory calibration. Both sets are used in flight to align the "virtual rescue model" together with the rate sensors (they are mainly used but have always a bit drift) from time to time when flying will permit this.

Now - knowing that a heli has some vibrations in flight - we measured them and found that even a Logo with plastic frame has 13g, a 600 nitro has 43g, a gasser up to 85g vibrations. So we have the 200g sensors in use in flight and fade over to them when the heli starts as the 15g were at the end of their measuring range.

So - if the high range sensors are once calibrated during power up - the rescue is safe.

And here we started to work. We added a "standard initialization" to the rescue panel which gives us the possibility to decide on power up based on a hanging 15g z-Axis sensor. If it hangs - we calculate the z-Value out of x and y (which is very close to a measured result, no noticeable difference in flight when using rescue) - and calibrate the 200g with this result. The swash will bump 3 times then as info for the pilot. If it does not hang - it will do the usual init and bumps 1 time as known.

The only disadvantage now is - you can't turn on the heli more than 45 deg (!!!) off from its "skids down" levelled position - but this won't care 99,999999% of all pilots as we think.

So - using this initilization all is working and no reason for warranty claim or repair - it would possibly shift, but not solve the initial problem.

regards (EN) / Gruss (DE)

Rainer Vetter

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