Calibrating table

The Editor · Mar 28, 2016

Dobmatt said:
Of course I'm not talking about calibration in proximity, this must be performed in the park nearby. I'm talking about taking off and landing near my metal shed. Is it too risky and better not to wake up devilish spirits in it, or not to worry having the bird calibrated somewhere else?

It will be fine if calibrated elsewhere.

Dobmatt · Mar 28, 2016

The Editor said:
It will be fine if calibrated elsewhere.

Thank you very much, you've been very patient and polite with all this expert advice ...

Baron1964 · Mar 28, 2016

Phatzo said:
i share The Editors opinion. but nice work. at the end we'll be selling to DJI for the thing we invent for us with their stuff to finally work well... lol

edit: with the new calibration method with the nose to the side you should make an add on to place the AC on the side...

Sent from my iPhone using Tapatalk

I missed something.

New calibration method ? Please provide a link.

Edit: Found :

new compass calibration method , perhaps an algorithm change requirement. This found in diagram of GOApp 2.7.1 / FW 1.7.0.90 compass calibration diagram part 2. It shows part 2 with a inspire on Side ( not down ).

The Editor · Mar 29, 2016

Baron1964 said:
I missed something.

New calibration method ? Please provide a link.

Edit: Found :

new compass calibration method , perhaps an algorithm change requirement. This found in diagram of GOApp 2.7.1 / FW 1.7.0.90 compass calibration diagram part 2. It shows part 2 with a inspire on Side ( not down ).

Either method will work.

Terry G · Apr 2, 2016

Dobmatt said:
F...k, I was suspecting that this is an overkill. Interestingly, the official DJI instructions still loudly and clearly recommends compass calibration at every new place. Gee, what a messy environment I've stumbled in ...

I will continue to do the dance until DJI firmware updates wont let me.

Phatzo · Apr 2, 2016

on other systems you do everything once, kind of and only re-calibrate the gyros for a good height telemetry info. meaning that befor you take off you kind of "reset" the height of the AC so the spot where you are is "NULL" meters. that is the only thing you do more than once. about compass calibration The Editor is right. go out into a field where there is not metal in ground or around you and do the dance. make sure the mod value is around 1500 and the other are also good. (can´t remember the values but should be something about 0.1 or something) - really close to "ZERO".
from then on make sure you check the mod value before taking off. when way out of bounce find a spot and re-due it. but also have a check once airborne and away from possible interference.

my2c - please correct me if I stated something not correctly.
cheers

The Editor · Apr 2, 2016

Terry G said:
I will continue to do the dance until DJI firmware updates wont let me.

Then you will greatly increase your chance of introducing a skewed calibration unwittingly.
Your Inspire though, if you want to play a game of roulette, your choice.

Norman Quinn · Apr 3, 2016

Dobmatt said:
That's the part of my amphibious drone mod, had nothing to do with the calibration table ...

Did you make the amphibious mods or purchase them somewhere. If purchased do you mind sharing where you got them?

David Baxter · Apr 3, 2016

Dobmatt said:
Embarrassing as it is, I'm getting dizzy during ritual compass calibrating dance. It comes with age, trust me. Add less-than-perfect, off level dancing floor (rocks, roots, tall grass etc.) and you'll fall helplessly, trying to protect $5K bird. Ouch ... Long story short, I've build MFCT (Multipurpose Field Calibrating Table) ...

View attachment 7508
View attachment 7509

It's equipped with 3-point adjustable feet and spirit level, rotates smoothly like a bar stool (in better bars, however) and - of course - it's of non-ferrous construction. I'm not sure I'll drag this thing everywhere I go, but when flying in remote places it may prove to be very useful. Any comments - critical or not - will be appreciated ...

Very nice project. Looks great. How about selling a few?

Dobmatt · Apr 3, 2016

Norman Quinn said:
Did you make the amphibious mods or purchase them somewhere. If purchased do you mind sharing where you got them?

This device is made entirely in my hobby shop. As far as I know there's no commercially available and reliably working mod of this type anywhere. Mine is still to be tested thoroughly with all DJI drones ...

Dobmatt · Apr 3, 2016

Davud Baxter said:
Very nice project. Looks great. How about selling a few?

Thank you for kind tap on my back ... This is one-off hobby project, making a few clones will be just too complex and labor costly, rendering over-the-top price tag ...

STClassic01 · Apr 6, 2016

and this is why I troll!
Thank you Dobmatt and Editor for refreshing my Memory. it seems as though I will comprehend something and have it slip my mind.

Bruce Cuz · May 29, 2016

As a keen fell walker - living in the UK - I would add that it's not just obvious magnetic/ferrous sources that can affect a compass. Some rocks also affect compass settings. For instance: Cullins of Skye; Hecla on South Uist; Ben More on Mull the Torridon area and Ore Gap in the Lake District are known upland areas of the UK with magnetic anomalies. Given other parts of the world have similar issues adds further weight to the point of calibrating your compass in a KNOWN safe location...

ace1 · May 29, 2016

timax said:
I need to read over the forum about this also as I do a calibration for each location and like you get dizzy doing it. Today when in an industrial estate it took some time to calibrate. I think that turntable on a plastic camp table would be great in the back of my car.

"Do not calibrate the compass near large metal objects"

The_Learning_Curve · Oct 20, 2016

Hey dudes, was lurking around looking for IMU calibrating techniques and this thread brought up a question that has somewhat been answered.

Assuming a successful compass calibration is done, how much can a metal object affect flight charastics as you get into it's proximity? Wether it's natural rocks high in metals or or buildings?

My main question I've been looking for is how would you suggest calibrating the IMU using a level?

Also, how would you go about checking and adjusting the alignment of the rotors?

I'm thinking once it's level using a pitch gauge to read the angles.. maybe use the motor hubs to rest a level on to find absolute 0

I'm experiencing a sudden drift forward and right as soon as atti is engaged. So it's either an IMU calibration issue or motor alignments

Dobmatt · Oct 21, 2016

1. Here is my "field calibrating table", made of kitchen cutting board with 3 wood screws. To set it level I used tablet with Surface Bubble Level free app from Handy Tools. That's all it takes.
2. Compass calibration is also very simple: do it once in confirmed iron free environment and forget it, unless you move few hundreds miles away. Make sure there's no buried old Sherman tank beneath LOL.
3. Don't dance with the devil and avoid flying in close (few meters) proximity to a huge steel mass, i.e. ships, bridges, buildings, towers etc. I doubt the deposits in rocks will affect compass reading, unless you're flying inside iron ore mining hole LOL.
4. I assume you're talking about Inspire. Motors (actually booms) alignment is a tricky issue, usually performed at factory with special jig. I'll not recommend messing with this, unless you clearly see visible misalignment. Point the ends of props pairs toward each other as close as possible (front L & R, back L & R) and see if they're at different levels. Take a photo at eye level and post it here if unsure. If so, than perhaps the strut clams jumped a notch or two on shoulder just behind T-joint on the boom, usually a result of very rough or crash landing side way. Fixable, although challenging for unskilled mechanic. Motors itself doesn't provide any alignment.
5. Is this sudden drift in Atti Mode persistent or it goes away when you compensate? Is it perhaps related to wind conditions? As soon as you undo GPS leash the craft will go wherever Mother Nature dictates with even the most gentle breeze.

Cheers.

IrishSights · Oct 21, 2016

Dobmatt said:
View attachment 10357 View attachment 10358
1. Here is my "field calibrating table", made of kitchen cutting board with 3 wood screws. To set it level I used tablet with Surface Bubble Level free app from Handy Tools. That's all it takes...

Cheers.

Out of curiosity why would you want to calibrate the IMU in the field? In years of flying I have never had a need to calibrate the IMU in the field. Usually only after firmware updates on the bench. Just interested to know.

PFAW Holder
BNUC-S Qualified

Dobmatt · Oct 21, 2016

IrishSights said:
Out of curiosity why would you want to calibrate the IMU in the field? In years of flying I have never had a need to calibrate the IMU in the field. Usually only after firmware updates on the bench. Just interested to know.

PFAW Holder
BNUC-S Qualified

This was an emergency IMU calibration during my summer vacations this year. The bird took a dip belly up in the lake, fully disassembled for drying and assembled back. I felt the IMU calibration is needed, just for the peace of mind. Was it successful, you are going to ask for sure? Yes, it was! The miracle happen, thankfully the water was glacier clear and sunny breeze vaporized the moisture after a day or two.

Cheers.

The_Learning_Curve · Oct 21, 2016

I appreciate your answer. I'm basically looking for the most accurate possible method of calibrating the IMU and measuring the angles of each pair of motors. The surface may be perfectly level, but that doesn't mean the aircraft and IMU is sitting perfectly level. Basically I'm getting OCD about it.

I have a good idea of how I can achieve what I'm trying to do, I'm just throwing it out there to see if anyone has a method of their own.

The drift I'm getting after I switch to atti is a calibration or motor alignment problem and is not caused by environmental factors. It will literally pitch to the same direction regardless of orientation. I think it's safe to say it's an IMU calibration issue, but I don't want to rule out the motor angle possibility. I want to check alignment anyway just so I know it's as mechanically perfect as possible.

The_Learning_Curve · Oct 22, 2016

So I made a bunch of measurements trying to find discrepancies with motor alignments. It checked out pretty well for what little reference points I found to work with.

I got a perfect IMU calibration by simply setting a level on top of the prop hubs and then using business cards to shimmy the legs as needed. Pretty straight forward obviously, I don't know why I never thought to do this in the first place. It needed a few cards in one corner and unique amounts on 2 other corners to get it OCD perfect.

Now when I flip to atti, she doesn't move a bit!

This inspire has had a couple of crashes, both pilot error by poor setup or dumb thumbs. Couple of weeks ago return home kicked in after losing signal and flew through some trees at a decent rate since I didn't have rth altitude high enough. Also had a mishap around 13 ft high where it landed upside down from a free fall. Both times I expected airframe damage and component damage. Only the camera and prop/ prop guards were damaged both times. DJI may build some really delicate gimbals, but the inspire itself is a friggin TANK lol