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MAVLink to ROS gateway with proxy for Ground Control Station
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Controlling px4 with joystick using setpoint_velocity/cmd_vel #623

Closed L4ncelot closed 7 years ago

L4ncelot commented 7 years ago

Hi,

I've been playing with px4 firmware which I connected with ROS and Gazebo. What I want to achieve right now is controlling my copter with joystick for which I use teleop.launch from mavros_extras package. I'm able to control my copter by sending geometry_msgs/TwistStamped to mavros/setpoint_velocity/cmd_vel topic.

The problem is that it seems like this message is related not to current body frame of my copter rather than to the world coordinates. Which means that when I want to fly forward in e.g. north direction, I have to send positive values of pitch. But when I want to fly forward in south direction, I have to send negative values of pitch to do so (I'm not sure where the north is right now, it's just an example of what's going on).

So my question is if there's a way to send velocity messages in respect of body_frame rather than world_frame and if so then how do I use it. Perhaps I've been using the wrong topic for this?

Thank you for any advice.

Jaeyoung-Lim commented 7 years ago

The standard ROS frame is based on ENU frame and the cmd_vel topics are based on the inertial frame

You can use the setpoint attitude topics to directly control the attitude

L4ncelot commented 7 years ago

Oh, thanks, that's what I wanted.

vinhk commented 6 years ago

@Jaeyoung-Lim would you able to share your complete code for attitude control?

L4ncelot commented 6 years ago

@vinhk if you want you can write it yourself, it's not that hard. Make some PID control loop with e.g. desired position. Read values about local position of your copter and give errors to your PID controller. Don't forget to use OFFBOARD mode. Here is the link on OFFBOARD tutorial.

L4ncelot commented 6 years ago

Also don't forget when changing to OFFBOARD mode you need to actually publish some messages to setpoint_attitude topic. Otherwise the switch will be denied.

vinhk commented 6 years ago

Do you have a code for publishing setpoint_attitude topic?

On Fri, Oct 20, 2017 at 5:20 AM, L4ncelot notifications@github.com wrote:

Also don't forget when changing to OFFBOARD mode you need to actually publish some messages to setpoint_attitude topic. Otherwise the switch will be denied.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/mavlink/mavros/issues/623#issuecomment-338153657, or mute the thread https://github.com/notifications/unsubscribe-auth/AQacPymGulJVaazPnH4YWRVrx7IS3A4Dks5suGXfgaJpZM4KmLD_ .

L4ncelot commented 6 years ago

Hi,

here's my very old code for simple attitude control. mavros_tools is just some library I've written which takes care of publishing and subscribing to some mavros topics. I don't know if the code works or not, but it should give you a hint how to write your own controller. Hope it helps.

Have a nice day.

2017-10-20 17:00 GMT+02:00 Vinh K notifications@github.com:

Do you have a code for publishing setpoint_attitude topic?

On Fri, Oct 20, 2017 at 5:20 AM, L4ncelot notifications@github.com wrote:

Also don't forget when changing to OFFBOARD mode you need to actually publish some messages to setpoint_attitude topic. Otherwise the switch will be denied.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/mavlink/mavros/issues/623#issuecomment-338153657, or mute the thread https://github.com/notifications/unsubscribe-auth/ AQacPymGulJVaazPnH4YWRVrx7IS3A4Dks5suGXfgaJpZM4KmLD_ .

— You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub https://github.com/mavlink/mavros/issues/623#issuecomment-338231917, or mute the thread https://github.com/notifications/unsubscribe-auth/AV-D3rX-MojPo0fWYp5tYC4-Lj6US8odks5suLWIgaJpZM4KmLD_ .