Dan O Posted at 2018-6-19 05:57
Ok, I seen it now, so one of the speeds, the one hardly decelrating is false, might be the gps one as the drone had issues understanding it's own position, no?

My instincts tell me that your GPS data is perfectly fine, but the data from the accelerometer isn't as reliable.

KlooGee Posted at 2018-6-19 06:01
My instincts tell me that your GPS data is perfectly fine, but the data from the accelerometer isn't as reliable.

Which is consistent with IMU h/w issue :-)
GPS signal for this flight was fine.

Mirek6 Posted at 2018-6-19 08:38
Which is consistent with IMU h/w issue :-)
GPS signal for this flight was fine.

So,

In order to reproduce the defect or at least effect I did fly indoor with very poor light. I must say that indeed the speed the spak will do in atti is even higher than in sport and the inertia is as expected. I do believe now I had full control of the craft.

In other order DJI has responded my ticket asking to send the drone on my own expenses in Holland, well DJI Officials please be aware that I find this unacceptable and I will claim to the officials.

Dan O Posted at 2018-6-19 11:00
So,

In order to reproduce the defect or at least effect I did fly indoor with very poor light. I must say that indeed the speed the spak will do in atti is even higher than in sport and the inertia is as expected. I do believe now I had full control of the craft.

One more experiment would be interesting. To go outside and see if picture still "sways" and "swims" if you fly from side do side. I wonder if my theory of one gyroscope (part of IMU) controlling Spark's gimbal motor is correct. If your Spark flies fine now and picture no longer swims, this would, most likely, confirm my theory. If picture swims and Spark flies fine than you may have both gimbal issue and IMU h/w issue where something got stuck and unstuck.  

It would be interesting and could warn users of potential gyroscope and IMU problems if they see abnormal "sway" and "swim" of their gimbal movements.

Just speculating. But we are on a journey of discovery here.

Fingers crossed for your dealings with DJI.

Dan O Posted at 2018-6-19 05:30
All the info's and the flight record was posted already. On top I did send it in the case No above. Would be nice if you will starting giving me answers instead of questions I have already answered before.

DJI Wanda told me in this post that the data's are already sent for analyze, should I understand she was giving me false information?

Sorry for the confusion. We do not support to analyze the data from the third party software or website, so it is suggested to export the original flight records and the flight logs in the aircraft when the issue appeared, so that we can forward all info to our engineers for analysis.
Please kindly upload all data to Google Drive or Dropbox, and share the link here, thanks for your cooperation.

Dan O Posted at 2018-6-19 05:42
Mirek,

Please help me understand the following:

Necro an old yet still relevant thread.. that seems DJI has yet to fully address and continues to show its ugly head..

there are several misconceptions here and perhaps a lot of ignorance .. perhaps on both sides as to the gravity of the issue..

keeping a quad in the air... is a monkey standing on the head of a pin balancing on a ball bearing.. IE its not simple..

people think that the flight control boards and MEMS packaged 'gyro' boards are just plug and go... that they produce acceleration compensated position and attitude reverence and that is inaccurate ...

nothing there could be further from reality.

one of my favorite quotes from 'The Right Stuff' ..

you know what makes these birds go up...?

hell the science alone would take so long to explain....  

and that perfectly surmises MEMS attitude and positional systems

The integrated MEMS gyros used in just about anything are raw sensor boards.. IE they don't have the processing algorithms built in to take raw measurements and filter and process them for angular and accelerated motion to calculate AHARS...

to try and dumb it down into layman's terms..

when a MEMS package is at rest.. a 5 year old could process the data coming from the on package gyro, accelerometer and compass ... its easy math

now add into the mix movement and acceleration in all axis and now you need a combination of kaman and complimentary filtering (advanced mathematical calculations) in order to keep a horizon level..

gravity aint gravity when something is moving or spinning...

ie.. without these mathematical equations.. if you held a package level with the horizon and started spinning around in a circle, say in a barbers chair,  the horizon would tilt due the the centripetal forces.. i.e. .. the artificial gravity.. the filters have take the inputs from the accelerometers and compass .. sense its spinning and take those rates to null the gyro to show the horizon as level.. as it still is.. not where the centripetal (gravity) is pointing

This 'MATH' is generally applied 'off package' ... i.e. the MEMS board provides raw data and its up to the engineer to code 'flight software' to make the magic happen. in the FC package

in an attempt to find a paper that further highlights this...

http://journals.sagepub.com/doi/full/10.1155/2014/214726

enjoy.

When DJI release a new firmware, we don't know what 'tweaking' they are doing to this mathematical soup.

keeping further in mind that there is no redundancy in the spark.. any gross change or incoherent (incorrect) data coming from a sensor can cause catastrophic issues if not filtered properly (i.e. mathematical BS flag ) and in some cases CANT fully be correct for. (oh **** now what response)

without seeing the raw sensor data, and the algorithms that process it.. its IMPOSSIBLE to say for certain what is occurring. ..or how DJI are processing the data stream and handling 'exceptions'

what is definitive I believe here is this..

the compass is a very weak link in MEMS AHARS solutions.. and there are MANY MANY videos out there showing DJI or any drone product really, where the compass heading is moving all over the place, when the drone is not turning ..

GPS can't produce or even estimate aircraft heading since quads can hover and fly in any direction.. GPS can only calculate heading made good (course) but has no idea where the aircraft is pointing

there are only 2 sensors on the aircraft that relate to aircraft heading.. the compass and the accelerometer in the yaw axis.. if the rotation of the aircraft compass and the yaw angles felt by the accelerometer don't match up.. the software has to HANDLE THE EXCEPTION ..

similarly .. if GPS data begins to deviate from MEMS calculations of motion, an algorithm has to try and deal with that..

depending on the calculations being used in the complimentary filters to handle the euler angle and Quaternions .. if not dealt with properly can effectively hit mathematical gimbal lock (deadman) where the math falls apart...

add to this filters and tables to deal with vibration, drift, precession, thermal instability of MEMS, MEMS package degradation, etc..

its not simple...

I 'believe' that the failure mode that we witness where the events seem to appear in a distinct order where  the drop to atti  starts with yaw errors, then compass warnings, then the GPS working error message.. followed by a period of apparent 'unusual behavior and sometime lack of input control' is in fact the system RESETTING itself  it reached a level of mathematical confusion to the point where the engineers coded a reset.. i.e. it gives up and restarts.

if the GPS is degraded to the point where navigation is not capable.. it will stay in ATTI.. until it regains enough sats...

now factor in that some have made the observation that these issues are more prevalent in 'REFURB' products and perhaps with latter produced sparks..  a different manufacturer.. different tolerances, installed improperly? more/less vibration due to tightness of mounting hardware... etc..

there are literally hundreds or possible reasons that could cause additional issues

also keep in mind that its 'easy' for the engineers to hide these warnings from us.. just adjust the thresholds that trigger the warning.. it doesn't mean they are not happening ... etc

there is a lot of secret sauce that goes on here and it doesn't take much to screw up the recipe...

this is the principle reason that real aircraft still RARELY rely on MEMS based AHARS for anything except battery powered backup systems like a standby attitude indicator..

I noticed with my 2 sparks that were calibrated identically, at the same time, on the same engineers plate, at the same temperature etc... had 2 very different flight characteristics..

one would sense lateral motion caused by wind blowing off course and correctly tilting into the crosswind while the other didn't


one would point as much as 45 degrees off during RTH while the other was maybe 10

one spark would rotate the video (in camera yaw correction) while at rest while the other rarely did..

ie.. the IMUs where behaving markedly different ...

the spark that had greater errors had more flight time on it.. neither had experience a crash or hard landing

any who.. food for thought...

DeuceDriv3r Posted at 2018-10-27 06:23
Necro an old yet still relevant thread.. that seems DJI has yet to fully address and continues to show its ugly head..

there are several misconceptions here and perhaps a lot of ignorance .. perhaps on both sides as to the gravity of the issue..

Now that is a very complete analyze with more technical information than most of the users over here would be able to understand.

One on top of another I did sold my Spark after this event as I did found myself doing only short flying and nerve wrecking activities. For me the aerial filming was always an hobby relaxing activity but after the episode I had just could not enjoy it anymore.

Spark was the perfect fit for my needs but as sad as it is I needed to separate from it.

Hopefully future products small and light as Spark would have more robustness on this chapter. I do understand that problems may occur but Spark was a fly away champion on DJI product list.