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How does the Tello remain so still

Joined
Mar 21, 2018
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theskyview.net
#1
I have been trying research this question for ages the information is so difficult to find I know it uses optical flow senses and a barometer but I can't find out how this is used on the Tello.
I would very much appreciate if anyone can direct me to articles that explain how the Tello could remain so solid and still on a patterned floor..
I know most drones uses this technology but again articles on exactly how it's implemented is difficult to find I would very much appreciate any help and finding exclamations so I can understand how it works. Any videos would be awsome.
Thanks
John
 

Ansia

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#4
Thanks Ansia.
But it is so hard to find stuff directly on the Tello systems, infact on any drones systems.
So any help would be appreciated, I'll post on other pilots sites.
Basically it's a dumb down system from what it's used in obstacle avoidance in the phantoms, Typhoons, Evo, etc. The big fishbowl like lenses underneath the Tello send a light that determines the current height of the Tello and calculates this from take off point. Not to be confused with the barometer which holds the height of the Tello. Like with the Phantoms, the Tello can take off from X height and fly over a small canyon, but it will continue reading the height from take off point. I've never tried it above the 30m height limit, but read somewhere that the Tello get's a bit confused when it cannot do a reading of the floor.

There is a smaller little camera that takes photos of the floor (I believe every 2 seconds or so) to determine the exact position of the drone. What you can do is do a little experiment. Cover the fish bowl lenses and leave the camera exposed and see how it reacts. Then do the opposite. It may give you a better understanding on how they work.
 
Joined
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#5
Obviously, since:

vx=Tzx−Txf/Z − (ωyf+ωzy) + ωxxy/f−ωyx2/f(4)
vy=Tzy−Tyf/Z − (ωxf+ωzx) − ωyxy/f+ωxy2/f(5)
where (Tx,Ty,T/z) and (ωx,ωy,ωz)are the translational component and angular velocity of the relative motion of the scene point Pin the camera coordinate system, respectively.
 

Ansia

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#6
Obviously, since:

vx=Tzx−Txf/Z − (ωyf+ωzy) + ωxxy/f−ωyx2/f(4)
vy=Tzy−Tyf/Z − (ωxf+ωzx) − ωyxy/f+ωxy2/f(5)
where (Tx,Ty,T/z) and (ωx,ωy,ωz)are the translational component and angular velocity of the relative motion of the scene point Pin the camera coordinate system, respectively.
I believe no one has every made me feel as dumb as you made me feel right now...:LOL::ROFLMAO:
 
Likes: Mrmund

volate!lo

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#7
Obviously, since:

vx=Tzx−Txf/Z − (ωyf+ωzy) + ωxxy/f−ωyx^2/f(4)
vy=Tzy−Tyf/Z − (ωxf+ωzx) − ωyxy/f+ωxy^2/f(5)
where (Tx,Ty,T/z) and (ωx,ωy,ωz)are the translational component and angular velocity of the relative motion of the scene point Pin the camera coordinate system, respectively.
fixed it for you.

The problem for Tello: How do you get a correct value of Z?
 

umanbean

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#11
A neat experiment I did one time was to take a gameboard and launch the tello above it. I then slid the board around and the tello moved to maintain the position above the same section of the board.

mikeg
I've done that too, pretty neat... the bottom-facing camera senses patterns in 'real time' and the Flight Controller responds accordingly. Even in low light, flying over something with a high contrast pattern works well
 
Joined
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#12
Thanks guys very helpful. Great links volate!lo, I am planning to do the first video on the Visual Position System. Its called Optical Flow System and works just like an Optical Mouse works, like taking zillions of images of the ground for stabilization. Which is why drones get confused over a plain surface such as water or sand.
Appreciate all the help I can get.
 

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