Moment coefficient Only for CW Rotors

PX4 Autopilot
1

Hello,

I was looking into making a costume airframe in PX4 and noticed only Clockwise rotors are set with a default value. The value is -0.05 in all the airframes I checked.

Here is an example of a Quadcopter X:
param set-default CA_ROTOR_COUNT 4
param set-default CA_ROTOR0_PX 0.15
param set-default CA_ROTOR0_PY 0.15

param set-default CA_ROTOR1_PX -0.15
param set-default CA_ROTOR1_PY -0.15

param set-default CA_ROTOR2_PX 0.15
param set-default CA_ROTOR2_PY -0.15
param set-default CA_ROTOR2_KM -0.05

param set-default CA_ROTOR3_PX -0.15
param set-default CA_ROTOR3_PY 0.15
param set-default CA_ROTOR3_KM -0.05

Can anyone share with me the reasoning behind it ?
Why not set an equal and opposite moment for CW and CCW rotors?
Why is it such a small moment value as a default?

2

Hi @CPGHtz .
The default value for CA_ROTOR{i}_KM is defined here PX4-Autopilot/module.yaml at 9b7a8d45685ead479abeed76f8faff61f5832ac4 · beniaminopozzan/PX4-Autopilot · GitHub and is equal to 0.05. That’s why you only need to modify it for CW rotors. And as you can see in the end you have equal and opposite values for CW and CCW.

3

thank you for the replay. It all makes a lot more sense now.

Now only need to get it to show in QGC and Ill be in business.