Distance sensor has a hardcoded "fcu" frame

[AlexisTM]

Problem:

The distance sensor frames are hardcoded. to fcu while we changed them all to base_link in PR #791

mavros/mavros_extras/src/plugins/distance_sensor.cpp

Lines 255 to 256 in 0273f99

	transform.header = m_uas->synchronized_header("fcu", dist_sen.time_boot_ms);
	transform.child_frame_id = sensor->frame_id;

Solutions:

Adding a parameter fcu_frame_id to distance_sensor, yet, it interferes into the yaml parsing.

distance_sensor:
  fcu_frame_id: "base_link"
  hrlv_ez4_pub:
    id: 0
    frame_id: "hrlv_ez4_sonar"
    orientation: ROLL_180 # RPY:{180.0, 0.0, 0.0}
    field_of_view:  !degrees 3
    send_tf: true
    sensor_position: {x:  0.0, y:  0.0, z:  -0.1}

Or we can add a frame_id and child_frame_id parameters for every sensor. But it interferes with the current config of users if they just update to the new version.

distance_sensor:
  fcu_frame_id: "base_link"
  hrlv_ez4_pub:
    id: 0
    orientation: ROLL_180 # RPY:{180.0, 0.0, 0.0}
    field_of_view: !degrees 3
    send_tf: true
    sensor_position: {x:  0.0, y:  0.0, z:  -0.1}
    frame_id: "base_link"                            # UAV frame_id
    child_frame_id: "hrlv_ez4_sonar" # Distance sensor frame

Adding the hardcoded base_link is less versatile for custom setups.

[AlexisTM]

A last solution can be to split parameters for TF:

distance_sensor:
  fcu_frame_id: "base_link"
  hrlv_ez4_pub:
    id: 0
    orientation: ROLL_180 # RPY:{180.0, 0.0, 0.0}
    field_of_view: !degrees 3
    sensor_position: {x:  0.0, y:  0.0, z:  -0.1}
    frame_id: "hrlv_ez4_sonar" # Distance sensor frame
    tf:
       send: true                  # send TF?
       frame_id: "base_link"  # fcu frame_id

[vooon]

I added base_frame_id as a base for all distance sensor parent frame_id.
But imho better do not use send_tf: preconfigure TF in URDF and set orientation (to check consistence between FCU and URDF).
That way you will use static tf, that save a lot of bandwidth.

[AlexisTM]

It is indeed a better solution.