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IMU calibration with/without propellers
3870 24 2017-3-8
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M_str
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Belgium
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Hello, A bit strange for the IMU calibration : why do they ask to "dismount propellers first" meanwhile the pictures the app shows are with the propellers ??

Do you know if this is necessary to dismount propellers ?  
And how often would you do such calibration ?
Thanks !
2017-3-8
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AACY
Second Officer
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As a rule of thumb anytime you are going to do anything with your device that doesn't imply imminent take off, always remove the propellers.

The lack of propellers will not influence on the calibration process since, if you compare the CG (center of gravity) of your device with the propellers on and extended against your drone without them, it will remain almost the same.

Regarding the frequency on which you should calibrate the IMU. I am no expert, but I do recommend to do it after a long trip, long storage time (more than a month) or after 20 flights. But also you can always check the amount of resolution and noise your sensors are having on the diagnostics page before entering the IMU calibration option in DJI GO4 APP.
2017-3-8
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DroneFlying
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In the comments for the video DJI Support mentions that it's fine to leave the propellers on.
2017-3-8
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M_str
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  what should we do then ?!  Easier to let them (but less safe ?)
And you would do it only when the app tells you to do so ?
2017-3-8
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hallmark007
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AACY Posted at 2017-3-8 02:14
As a rule of thumb anytime you are going to do anything with your device that doesn't imply imminent take off, always remove the propellers.

The lack of propellers will not influence on the calibration process since, if you compare the CG (center of gravity) of your device with the propellers on and extended against your drone without them, it will remain almost the same.


It clearly says in the manual to only preform IMU if the app tells you continually preforming IMU when AC doesn't need it , you run the risk of getting a bad IMU, travelling a distance will not do anything to your AC that will require IMU calibration, also not using your AC for a month will have no influence on the IMU . If your IMU is working after 20 flights why the need to calibrate it..
2017-3-8
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hallmark007
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M_str Posted at 2017-3-8 04:59
what should we do then ?!  Easier to let them (but less safe ?)
And you would do it only when the app tells you to do so ?

Yes only when the app tells you to do it, you can also check in the app the current status of your IMU , if when you are going for a flight to check everything is ok .

First raise your aircraft approx 8 feet let it hover for 30 sec fly it forward 3 feet backward 3 feet left right 3feet and up down 3feet yaw right yaw left, if your AC does everything you command and always reaches a good horizontal, you will then know you have a good IMU a good compass and good gps, it takes two minutes and you can go flying and be reasonably happy..
2017-3-8
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AACY
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hallmark007 Posted at 2017-3-8 05:03
It clearly says in the manual to only preform IMU if the app tells you continually preforming IMU when AC doesn't need it , you run the risk of getting a bad IMU, travelling a distance will not do anything to your AC that will require IMU calibration, also not using your AC for a month will have no influence on the IMU . If your IMU is working after 20 flights why the need to calibrate it..

Thank you for the clarification!

I was using some of my RC background to answer that part, that's why I stated that I am no expert. And yep with model aircraft, you should calibrate with certain frequency because the flight computer tends to get a bit frisky in time, but this is also due to the fact that most of the DIY devices are quite susceptible to the conditions stated and also because of the lower quality of their sensor and shielding.
2017-3-8
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hallmark007
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AACY Posted at 2017-3-8 06:16
Thank you for the clarification!

I was using some of my RC background to answer that part, that's why I stated that I am no expert. And yep with model aircraft, you should calibrate with certain frequency because the flight computer tends to get a bit frisky in time, but this is also due to the fact that most of the DIY devices are quite susceptible to the conditions stated and also because of the lower quality of their sensor and shielding.

I do know where your coming from, although know very little about building model aircraft I am aware of the need to calibrate home builds,
I think the need to put the note in the manual about IMU Cal was a lot to do with those incorrectly doing IMU , it's a bit like which is the better of two evils. Lol..

Good luck..
2017-3-8
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AACY
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hallmark007 Posted at 2017-3-8 06:42
I do know where your coming from, although know very little about building model aircraft I am aware of the need to calibrate home builds,
I think the need to put the note in the manual about IMU Cal was a lot to do with those incorrectly doing IMU , it's a bit like which is the better of two evils. Lol..

Totally agree with you...hehehe!

Cheers!
2017-3-8
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DRONE-flies-YOU
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I've done it both ways & it makes no difference.  Well, I've gotten my 2 best IMU calibrations with the props installed.
2017-3-8
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M_str
lvl.2
Belgium
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Thanks for your answers !
I believe I'll do it only when asked by the app (or if I feel it's not flying "right") and keeping on the propellers (a bit lazyyyyy - and I would be afraid of breaking a propeller dismounting them too often ).
2017-3-8
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MikeQView
Second Officer
United Kingdom
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A clear case of "Left hand" "Right hand" not knowing !   why is it so hard for DJI to NOT put out the EXACT sequence required to do this properly,  there is NO case that doing calibrations will damage or upset your machine if done correctly each and every time,  hard jolts and bumps can indeed upset calibrations of many fine instruments and most modern drones are examples of this.   IMU calibrations is "No black art"     DJI should release an exact sequence for all Calibrations and set ups,  putting out information that is not correct or conflicting procedures is not acceptable by the worlds leading drone manufacturer,  there should be just ONE way of doing it right !    its NOT Microsoft Windows,  ( Windows was developed in a strange way to make some engineers look clever by being able to do the same thing in different ways,  Pah,  )  why confuse the market you are selling too ! ?   
2017-3-8
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hallmark007
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MikeQView Posted at 2017-3-8 08:41
A clear case of "Left hand" "Right hand" not knowing !   why is it so hard for DJI to NOT put out the EXACT sequence required to do this properly,  there is NO case that doing calibrations will damage or upset your machine if done correctly each and every time,  hard jolts and bumps can indeed upset calibrations of many fine instruments and most modern drones are examples of this.   IMU calibrations is "No black art"     DJI should release an exact sequence for all Calibrations and set ups,  putting out information that is not correct or conflicting procedures is not acceptable by the worlds leading drone manufacturer,  there should be just ONE way of doing it right !    its NOT Microsoft Windows,  ( Windows was developed in a strange way to make some engineers look clever by being able to do the same thing in different ways,  Pah,  )  why confuse the market you are selling too ! ?

There is very little confusion about calibration, there are redundancies in the dji aircraft that can tell you when to calibrate, why is it so difficult to understand this , your AC  is also covered by warranty, to have proper warranty cover you should operate your AC as per the guidance of the manufacturer, telling people to go against the best advice of the manufacturer is wrong and helps no one.

Calibration of IMU with or without props will make no difference.
2017-3-8
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DJI Mindy
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Hi, here is the video tutorial for your reference.
It's fine to do the IMU calibration with or without the propellers.
2017-3-9
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MikeQView
Second Officer
United Kingdom
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Thank you Mindy, that has cleared that up for everyone!  
2017-3-9
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MikeQView
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hallmark007 Posted at 2017-3-8 09:28
There is very little confusion about calibration, there are redundancies in the dji aircraft that can tell you when to calibrate, why is it so difficult to understand this , your AC  is also covered by warranty, to have proper warranty cover you should operate your AC as per the guidance of the manufacturer, telling people to go against the best advice of the manufacturer is wrong and helps no one.

Calibration of IMU with or without props will make no difference.

Ok i follow your thought process on when to calibrate,  (though i do have my own preference on this). But i dont get the warranty bit,  when i fly, i try to ensure BEFORE flight that everything works correctly and reliably,  i hate aircraft crashes,  and would not want to endanger anyone i fly with or near,  so to that effect i do not include warranty as a safety measure,  warranty is about as much use as a chocolate teapot,  if you were to crash into someone and then end up in court.  Also redundancy systems do not tell you when to calibrate, that is controlled by a different system.  
2017-3-9
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hallmark007
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MikeQView Posted at 2017-3-9 02:40
Ok i follow your thought process on when to calibrate,  (though i do have my own preference on this). But i dont get the warranty bit,  when i fly, i try to ensure BEFORE flight that everything works correctly and reliably,  i hate aircraft crashes,  and would not want to endanger anyone i fly with or near,  so to that effect i do not include warranty as a safety measure,  warranty is about as much use as a chocolate teapot,  if you were to crash into someone and then end up in court.  Also redundancy systems do not tell you when to calibrate, that is controlled by a different system.


Ok so I said redundancy, warnings so, your right about that, as you will see in post #6, this is how I prepare for flying, and to check everything is working as good as it should be,
Your point about warranty, there is a certain amount of safety in preparing your AC under manufacturer recommended practices, if you choose to ignore these, and get your set up wrong, you also fly with the same risks you pointed out.
2017-3-9
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MikeQView
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hallmark007 Posted at 2017-3-9 02:52
Ok so I said redundancy, warnings so, your right about that, as you will see in post #6, this is how I prepare for flying, and to check everything is working as good as it should be,
Your point about warranty, there is a certain amount of safety in preparing your AC under manufacturer recommended practices, if you choose to ignore these, and get your set up wrong, you also fly with the same risks you pointed out.

Agreed.   good advice to ensure following manufacturers recommendations
2017-3-9
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M_str
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DJI Mindy Posted at 2017-3-9 00:12
Hi, here is the video tutorial for your reference.
It's fine to do the IMU calibration with or without the propellers.
https://www.youtube.com/watch?v=guD8qFRRv-c&index=14&list=PL8-vxWY64sBNLusG0MvxD4Dm-tX4cnvzX

Thank you !
2017-3-9
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DJI Mindy
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No problem. :-)
2017-3-10
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travelrikk
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What I find weird is DJI telling us to always switch on the mavic unfolded and then you have fold the mavic to calibrate the IMU. Since the arms have a fold limit, isn't this reducing the lifetime of the drone?
2017-3-10
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DroneFlying
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travelrikk Posted at 2017-3-10 04:03
What I find weird is DJI telling us to always switch on the mavic unfolded and then you have fold the mavic to calibrate the IMU. Since the arms have a fold limit, isn't this reducing the lifetime of the drone?

"The folding mechanism has been tested to last at least 5000 folds. It is unlikely that it will wear out during the Mavic’s lifetime."

Folding and unfolding the arms a handful of times (at most) over its lifetime won't have a noticeable effect on your Mavic's longevity. You shouldn't need to perform an IMU calibration very often and if you do need to for some reason then the number of folding / unfolding cycles you can perform isn't likely to be your biggest problem.
2017-3-10
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travelrikk
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DroneFlying Posted at 2017-3-10 05:22
"The folding mechanism has been tested to last at least 5000 folds. It is unlikely that it will wear out during the Mavic’s lifetime."

Folding and unfolding the arms a handful of times (at most) over its lifetime won't have a noticeable effect on your Mavic's longevity. You shouldn't need to perform an IMU calibration very often and if you do need to for some reason then the number of folding / unfolding cycles you can perform isn't likely to be your biggest problem.

Thanks for clearing it out. Didn't read the second part of the first line.
2017-3-10
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Jdwyier
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My issue with performing an IMU calibration with the props on is that unless you position the folded props carefully the step where you lay the Mavic on it's back may not result in the drone laying flat. I don't know that this is an actual problem. If it is using this position for calibration in relation to the other positions it recorded during calibration process I would imagine it would tweak the results a little. However DJI says it's fine, so I reckon it is.

The only thing I can state with certainty is that my IMU calibrations with the props off result in the drone being very stable when in ATTI mode with no tendency to drift in any one given direction. I assume since DJI says it can be done with the props on that the results would be the same. I stick with what I know works, largely becuase I beleive in the motto "If it ain't broke don't fix it" and the props off method has always worked for me. ;)



2017-3-10
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M_str
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Belgium
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Jdwyier Posted at 2017-3-10 06:15
My issue with performing an IMU calibration with the props on is that unless you position the folded props carefully the step where you lay the Mavic on it's back may not result in the drone laying flat. I don't know that this is an actual problem. If it is using this position for calibration in relation to the other positions it recorded during calibration process I would imagine it would tweak the results a little. However DJI says it's fine, so I reckon it is.

The only thing I can state with certainty is that my IMU calibrations with the props off result in the drone being very stable when in ATTI mode with no tendency to drift in any one given direction. I assume since DJI says it can be done with the props on that the results would be the same. I stick with what I know works, largely becuase I beleive in the motto "If it ain't broke don't fix it" and the props off method has always worked for me. ;)

if you decide to try it with props on, don't forget to share the results
2017-3-10
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