Hello,
I am trying to make an octo-H mixer model in ROMFS/px4mu_common/mixers according to https://docs.px4.io/master/en/concept/mixing.html
There seems to be no Multirotor mixer for the octo-H, and I failed to make one using the Summing mixers. Is there any way to make a new mixer model with different geometric configuration?
(picture of the drone crash due to wrong motor mixing btw)
Thank you, Kangmin Lee
Hello @kangmin7
Have you tried creating a new mixer geometry: https://github.com/PX4/PX4-Autopilot/tree/master/src/lib/mixer/MultirotorMixer/geometries
It should be fairly simple. You can call it octa_h with the key “8h”
If you have any issues let me know, I can support you with it.
@RicardoM17 Thank you very much for your help!
I have made the new octo-H geometry like this
[info]
key = “8H”
description = “Generic Octacopter in H configuration”
[rotor_default]
axis = [0.0, 0.0, -1.0]
Ct = 1.0
Cm = 0.05
[[rotors]]
name = “front_right”
position = [1.08, 0.543, 0.0]
direction = “CW”
[[rotors]]
name = “rear_left”
position = [-1.08, -0.543, 0.0]
direction = “CW”
[[rotors]]
name = “mid_front_right”
position = [0.36, 0.543, 0.0]
direction = “CCW”
[[rotors]]
name = “rear_right”
position = [-1.08, 0.543, 0.0]
direction = “CCW”
[[rotors]]
name = “front_left”
position = [1.08, -0.543, 0.0]
direction = “CCW”
[[rotors]]
name = “mid_rear_left”
position = [-0.36, -0.543, 0.0]
direction = “CCW”
[[rotors]]
name = “mid_front_left”
position = [0.36, -0.543, 0.0]
direction = “CW”
[[rotors]]
name = “mid_rear_right”
position = [-0.36, 0.543, 0.0]
direction = “CW”
The only confusing part was that I had to invert the y position of the rotors in this file order to match the rotor geometry in the sdf file.
I wrote
R: 8H
in the mixer file and
. ${R}etc/init.d/rc.mc_defaults
set MAV_TYPE 14
set MIXER octo_H
in the configuration file.
I added the file names of configuration, mixer, and mixer geometry (the one you told me) to the CMakeLists.txt, but I still got the following error:
ERROR [mixer_module] mixer load failed with -1
ERROR [mixer] failed to load mixers from etc/mixers/octo_H.main.mix
ERROR [mixer] failed to load mixer
ERROR [init] Failed loading mixer: etc/mixers/octo_H.main.mix
Is there something more to do in order to use the “8H” key?
does the mixer have the right name?
octo_H.main.mix
And you added both the mixer file and the new geometry to the respective CMakeLists?
geometry here:
and the mixer here:
You said you did but just making sure.
Because if not it looks all good:
EDIT: nevermind I believe your mixer needs to be like
R: 8H 10000 10000 10000 0
Also I would change all so it’s “8h” as per PX4 standards, but it should work like that.
@RicardoM17 Changing “8H” to “8h” made the error to disappear!
Now I have to just change the control gains for the octocopter
Thank you!
no problem @kangmin7 ! Glad I could help.
Please select the comment with the solution so that this post can be closed.
Hi @kangmin7 and @RicardoM17,
I am facing a similar issue. I am able to compile and launch the new custom airframe and mixer when I run without ROS. But when I run Px4 from ROS this gives the following issue:
With ROS
INFO [px4] Creating symlink /home/user/catkin_ws/src/PX4-Autopilot/build/px4_sitl_default/etc -> /home/user/.ros/etc
...
Info: found model autostart file as SYS_AUTOSTART=6013
INFO [param] selected parameter default file eeprom/parameters_6013
[param] Loaded: eeprom/parameters_6013
INFO [dataman] Unknown restart, data manager file './dataman' size is 11798680 bytes
INFO [simulator] Waiting for simulator to accept connection on TCP port 4560
INFO [simulator] Simulator connected on TCP port 4560.
INFO [commander] LED: open /dev/led0 failed (22)
ERROR [mixer_module] mixer load failed with -1
ERROR [mixer] failed to load mixers from etc/mixers/dodeca_octo.main.mix
ERROR [mixer] failed to load mixer
ERROR [init] Failed loading mixer: etc/mixers/dodeca_octo.main.mix
Without ROS
INFO [px4] Creating symlink /home/user/catkin_ws/src/PX4-Autopilot/build/px4_sitl_default/etc -> /home/user/catkin_ws/src/PX4-Autopilot/build/px4_sitl_default/tmp/rootfs/etc
...
Info: found model autostart file as SYS_AUTOSTART=6013
INFO [param] selected parameter default file eeprom/parameters_6013
[param] Loaded: eeprom/parameters_6013
INFO [dataman] Unknown restart, data manager file './dataman' size is 11798680 bytes
INFO [simulator] Waiting for simulator to accept connection on TCP port 4560
INFO [simulator] Simulator connected on TCP port 4560.
INFO [commander] LED: open /dev/led0 failed (22)
INFO [init] Mixer: etc/mixers/dodeca_octo.main.mix on /dev/pwm_output0
I checked if the mixer file is missing in the symlink path but it is there.
This is how I am launching px4 node
<node name="sitl_$(arg ID)" pkg="px4" type="px4" output="screen" args="$(find px4)/build/px4_sitl_default/etc -s etc/init.d-posix/rcS -i $(arg ID) $(arg px4_command_arg1)">
</node>
Any thoughts on what I might be missing?
I am also having the same issue with the rotor ordering. You said you had to mirror the rotors position in the Y-axis right ?
SOLUTION: I forgot to catkin build px4 ! ups