Azeey/marsupial

[nkoenig]

This is a copy of the contents in #396 with the addition of drone platform model.

The following is from #396.

This adds a command line argument marsupial#:=<parentRobotName>:<childRobotName> where parentRobotName and childRobotName are names of robots specified using robotName#. The variable MARSUPIAL_VALID_PARENT_ROBOT_TYPES is used to store valid parent robot types, which is currently just the X1 . Similarly, MARSUPIAL_VALID_CHILD_ROBOT_TYPES is used to store valid child robot types, which is currently just the X3.

It works by adding the DetachableJoint system to the parent robot. This is done by parsing the XML string generated by the spawn functions and injecting the <plugin> tag for the DetachableJoint.

This PR adds a new topic, /detach`, which is used for detaching the child robot.

Example

ign launch -v 4 cave_circuit.ign  robotName1:=Xa robotConfig1:=X1_SENSOR_CONFIG_1 robotName2:=Xb robotConfig2:=X3_SENSOR_CONFIG_1 robotName3:=Xc robotConfig3:=X1_SENSOR_CONFIG_1 robotName4:=Xd robotConfig4:=X3_SENSOR_CONFIG_1 marsupial1:=Xa:Xb marsupial2:=Xc:Xd

To detach Xb, run:

rostopic pub /Xb/detach std_msgs/Empty "{}"

Known Issues

There is currently a bug that seems to disable collisions between detached robots and the rest of the environment See ign-physics PR 31

[azeey]

I ran

ign launch -v 4 cave_circuit.ign  robotName1:=Xa robotConfig1:=X1_SENSOR_CONFIG_1 robotName2:=Xb robotConfig2:=X3_SENSOR_CONFIG_1 robotName3:=Xc robotConfig3:=X1_SENSOR_CONFIG_1 robotName4:=Xd robotConfig4:=X3_SENSOR_CONFIG_1 robotName5:=Xe robotConfig5:=X1_SENSOR_CONFIG_2 robotName6:=Xf robotConfig6:=X3_SENSOR_CONFIG_2 marsupial1:=Xa:Xb  marsupial2:=Xc:Xd marsupial3:=Xe:Xf

and it looks like the position of the UAVs on the platform is not constant.

while for one of the vehicles, the gap between the platform and the UAV is much smaller.

Looking closer, I think the platform itself is lower in some of the robots.

[nkoenig]

Can you try again with: 4889d0f, and also get the latest version of: https://app.ignitionrobotics.org/OpenRobotics/fuel/models/DronePlatformX1

[azeey]

Same issue. The problem is that the X1 falls a small amount as soon as it's spawned. This is the exaggerated version. Not sure what we can do about it though

[nkoenig]

I see. I'll have to create new models for each of the X1 models.

[nkoenig]

I've update this PR to spawn all vehicles at once. This now depends on:

1. Multi enitty gazebosim/gz-msgs#58
2. Support multi entity spawn gazebosim/gz-sim#146
3. Multi spawn gazebosim/gz-launch#30