Question about 'controller_node' line 230

[zshayann]

Hi,

Thank you for providing this repository. I am having trouble understanding the logic behind the matrix defined on line 230. I am trying to design a controller for my own drone with different parameters. Could you please explain how you derived the throttles_to_normalized_torques_and_thrust_ matrix?

Here is the link to the specific line of code:

px4_offboard_lowlevel/src/controller_node.cpp

Line 230 in 82f4a24

throttles_to_normalized_torques_and_thrust_ <<

Additionally, I am curious about how you calculated the omega-to-PWM coefficient.

px4_offboard_lowlevel/config/uav_parameters/x500_param.yaml

Line 15 in 82f4a24

omega_to_pwm_coefficient:

I really appreciate any help you can provide.

[321thijs123]

@ayhamalharbat could explain the matrix?

To get the omega_to_pwm_coefficient we mounted the motor on a thrust stand from tyto robotics equipped with an tachometer. Using this setup we measured the velocity of the motor with propeller for different PWM inputs. We then fit a polynonominal to these values, you can find how we did that in this script:
https://github.com/SaxionMechatronics/px4_offboard_lowlevel/blob/82f4a24ffda4e8169e6e5bc1dd54238c77302807/scripts/identification.py#L110C1-L115C32