Add gimbal device

[StefanoColli]

Feature

Gimbal device to be controlled in SITL environment when using gazebo simulator (gz-garden). The device can act as a Mavlink gimbal (following Mavlink gimbal protocol v2) or as a non-Mavlink gimbal (responding to gimbal_controls messages) depending on MNT_MODE_OUT PX4 parameter.
It supports both angle and angular rate commands, it doesn't support yet the gimbal device flags (WIP).
It is meant to work with the gz_x500_gimbal model (PX4/PX4-gazebo-models#47).

Test coverage

Tested with QGC

WIP

The submodule Tools/simulation/gz is temporarily pointing to https://github.com/StefanoColli/PX4-gazebo-models waiting for
PX4/PX4-gazebo-models#47 to be merged into main.

Context

gimbalQGCm.mp4

[lierdakil]

What's the status on this? I.e. why is it drafted? I kinda want a SITL gimbal real bad, hence asking whether this (mostly) works or if it's not ready at all.

[Jaeyoung-Lim]

@lierdakil You can already try out the current status?

[StefanoColli]

@lierdakil It is drafted because you would need to use my PX4-gazebo-models fork instead of the PX4 default one. But most of the functionalities are there except from the gimbal device flags as stated in the PR message

[lierdakil]

@StefanoColli thank you very much for the reply, that sounds great! I'll be trying this branch out shortly, then.

[lierdakil]

So this works great, but apparently the gimbal in the model is installed with the neutral position pointing backwards. I've rotated it 180⁰ in the model, and everything is fine, but was this intended?

[0uterspaceguy]

Cant make it work with qgc. Can you share parameters settings?

[lierdakil]

Sorry, I didn't use qgc, I'm interfacing with it from software via mavlink.

But qgc v 4.4 has added some gimbal controls, which kind of work.

For one, there are some buttons at the top (click the joystick-looking thing to the right of the battery indicator)

If you've also enabled video in qgc, then "on Screen Camera Control", or at least "click to point" will work when you switch to the video feed.

(whether you actually have some video there is irrelevant)

That said, it seems pitch is inverted between qgc and px4, the camera very stubbornly pitches upwards instead of downwards (this may be my modifications to blame though). Also, the yaw indicator on the map is messed up, apparently the yaw angle shown is the sum of the frame's yaw and camera's yaw relative to the frame. So things are rough around the edges.

[Jaeyoung-Lim]

@StefanoColli Any updates regarding this PR?

[StefanoColli]

So this works great, but apparently the gimbal in the model is installed with the neutral position pointing backwards. I've rotated it 180⁰ in the model, and everything is fine, but was this intended?

@lierdakil Are you sure about that? because in QGC I see that the gimbal in neutral position is correctly pointing forward...

[lierdakil]

Are you sure about that?

Well, the actual video feed from the simulated camera (captured with ROS) does not point in the direction the drone flies in when the pitch stick is tilted forward. Also, the model visibly points backwards in Gazebo. When SITL first starts up, you're not looking at the front of the drone, you're looking at its butt 😅

P.S. Disclaimer: I didn't actually check the version that got eventually merged, but this was the case at the time I wrote the original comment. So take this with a grain of salt.

[hamishwillee]

When this is ready can we please have some docs. Specifically and addition to https://docs.px4.io/main/en/sim_gazebo_gz/vehicles.html and to the list here: https://docs.px4.io/main/en/sim_gazebo_gz/#running-the-simulation

Also in https://docs.px4.io/main/en/sim_gazebo_gz/ a new section "Simulating a Gimbal" that explains how you set up gazebo/PX4 to use this, and how it can be tested.

What we need is enough information so that someone can run a turnkey set of instructions and then send MAVLink commands to a gimbal-protocol v2 compliant gimbal manager and drive the simulation. QGC has that implementation, at least in part, so should be a good first test point. MAVSDK too.