How to add X and Y control in custom airframe/mixer

PX4 Autopilot
13

Hi Riccardo, well done on setting up your custom mixer. I still don’t understand how to implement a custom mixer for a multicopter following the guidance on the px4 website. Could you please point me to an example of a mixer (preferably one with a servo) which I can use as a working example? Thank you.

EDIT:
So after a nice long chat with @RicardoM17, I have some idea of how mixing works. This is to confirm that I understood correctly and for any one in the future who stumbles on this post like I did.

So let’s take an example with the quadrotor in + configuration, where the numbering starts from the top (motor 1) then to the right (motor 2), and then the bottom (motor 3) and finally ends at the left (motor 4).

quad_conf
quad_conf326×521 38.6 KB

The mixer file can contain something like the following:
Motor 1

M: 3
S: 0 1 10000 10000 0 -10000 10000
S: 0 2 -10000 -10000 0 -10000 10000
S: 0 3 10000 10000 0 -10000 10000

  • here, the first line M:3 means, the motor takes in 3 inputs.
    -The next line S: simply declares a mixer. The next no. 0 implies actuator control group #0 - flight control (see Mixing and Actuators · PX4 Developer Guide).
    -the next no 1. signifies the ‘pitch’ channel,
    -the next two nos., each 10000 represent scaled values of the input (-1…1). In this case motor 1 will increase speed in order to ‘pitch up’.
    -For the last three numbers, the first is a 0, which is just an offset, the next two specify min and max output values typically -1 to +1 represented as scaled values of -10000 and 10000.

  • The second and third lines have similar values as described already. the difference is the numbers ‘2’ and ‘3’ after the actuator control group #0 specification. This stands for ‘yaw’ and ‘thrust’ respectively as also given here Mixing and Actuators · PX4 Developer Guide

It follows similar idea for the remainder of the motors.

Motor 2
M: 3
S: 0 0 -10000 -10000 0 -10000 10000
S: 0 2 10000 10000 0 -10000 10000
S: 0 3 10000 10000 0 -10000 10000

Motor 3

M: 3
S: 0 1 -10000 -10000 0 -10000 10000
S: 0 2 -10000 -10000 0 -10000 10000
S: 0 3 10000 10000 0 -10000 10000

Motor 4

M: 3
S: 0 0 10000 10000 0 -10000 10000
S: 0 2 10000 10000 0 -10000 10000
S: 0 3 10000 10000 0 -10000 10000

Hope that helps, and if anything is off, for those who are more experienced in this, kindly correct me. Thank you.