Thrust - stabilizer.thrust and height relationship

Firmware/software/electronics/mechanics
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Xellon
Beginner
Posts: 1
Joined: Mon Jul 22, 2019 12:57 pm

Thrust - stabilizer.thrust and height relationship

Post by Xellon » Tue Jul 23, 2019 11:23 am

Hello,

Using CrazyFlie 2.0 I am trying to find a relationship between the input thrust (that I type from the keyboard in python) and the output thrust, that the drone sees.
As for now I can't find any conclusive data as for an input thrust of let's say 40000, I get a stabilizer.thrust of 16384. However, when I input a thrust of 30000, I get an output of 24576 ( so it is bigger than the previous although the input thrust was smaller).
Even more surprising is when I input a thrust of 20000 and I get the same output thrust of 16384(that was for 40000) and also for an input thrust of 15000 I get 24576 as an output (the same as for 30000).

Why do I try to figure this out?
Basically I want to find a relationship between the thrust that I introduce from the computer(in python) and a certain height. However, my final purpose would be finding a function of thrust based on height, so that the input thrust would change depending on the changes of height. ( I don't use any joysticks, just python).

I know about the Kalman, however my thrust function is something like this:
thrust = thrust_offset + Kalman_feedback

To be more precise, that "thrust_offset" is the unknown variable for me. How should I choose that based on the height

Do you have any suggestions on what I should do?



tobias
Bitcraze
Posts: 1891
Joined: Mon Jan 28, 2013 7:17 pm
Location: Sweden

Re: Thrust - stabilizer.thrust and height relationship

Post by tobias » Fri Aug 09, 2019 1:39 pm

Unfortunately, this is not possible, as thrust will output a force. Then force will result in acceleration, or hovering if the upward force equals gravity. So to change height the drone will have to first accelerate -> move -> decelerate -> hover.

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