Using /mavros/vision_speed/speed_twist in PX4

han-so1omon · October 20, 2017, 4:05pm

Which uORB topic should I subscribe to in order to use speed_twist?

{vx,vy,vz},{rollspeed,pitchspeed,yawspeed} do not show up in vehicle_vision_position and vehicle_vision_attitude respectively.

Side note: can’t use listener vehicle_vision_position command. Is this because we can only use listener commands on raw uORB msg types and not uORB topics?

AlexisTM · October 24, 2017, 1:13pm

Aren’t you mixing MAVLink, Mavros and uORB?

han-so1omon · October 24, 2017, 1:29pm

Yes, but how? Speed twist does not seem to be included by default.

AlexisTM · October 24, 2017, 1:49pm

Mavros handles the MAVLink connection which is handled in the PX4 to convert it to a uORB message.

The command listener vehicle_vision_position is to be run on the NuttX system.

I don’t see where the vision velocity messages might be used.

github.com

PX4/Firmware/blob/master/src/modules/mavlink/mavlink_receiver.cpp#L1152-L1239




	/* Dcm rotation matrix from body frame to local NED frame */
	matrix::Dcmf Rbl;


	odometry.timestamp = _mavlink_timesync.sync_stamp(odom.time_usec);
	/* The position is in the local NED frame */
	odometry.x = odom.x;
	odometry.y = odom.y;
	odometry.z = odom.z;
	/* The quaternion of the ODOMETRY msg represents a rotation from NED
	 * earth/local frame to XYZ body frame */
	matrix::Quatf q(odom.q);
	q.copyTo(odometry.q);


	// TODO:
	// - add a MAV_FRAME_*_OTHER to the Mavlink MAV_FRAME enum IOT define
	// a frame of reference which is not aligned with NED or ENU
	// - add usage on the estimator side
	odometry.local_frame = odometry.LOCAL_FRAME_NED;

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han-so1omon · October 24, 2017, 2:54pm

The velocity twist could be mixed into the position/attitude messages, but it isn’t.

AlexisTM · October 24, 2017, 4:20pm

Then you have to send at least the position and the velocity if available

han-so1omon · October 24, 2017, 4:36pm

It is being sent thru MAVROS in the /mavros/vision_speed/speed_twist topic.

Is this a new px4 feature to include velocity vision in vision position/attitude uorb topics? My firmware is a month or so old.