Fix Ackermann world topic name, change Ambulance to AmbulanceSlotcar, use robot spawning for test_ackman map

[luca-della-vedova]

Bug fix

Fixed bug

Depends on rmf_simulation #49, change the topic name for the ackermann test world to follow the RMF standard, as well as add a bit of documentation for users to launch it.

[ddengster]

Thanks for the changes!

[Yadunund]

I find the name AmbulanceSlotcar to be a bit strange since other robot models in rmf_demos_assets also include the slotcar plugin but are simply called TinyRobot, DeliveryRobot etc. Also, it seems that the top level folder was renamed to AmbulanceSlotcar but the model name in model.sdf and mode.config is ambulance which is a bit confusing.

I understand the need to rename the model as fuel may contain other Ambulance models which don't have the plugin included. My recommendation would be to rename to EmergencyVehicle or HospitalVan.

[Yadunund]

@luca-della-vedova what makes this only available in ign?

[aaronchongth]

Looks like it is related to the plugin, running the simulation in rmf_demos_gz shows that it fails to find the necessary joints,

[gzserver-14] [INFO] [1631084275.040217309] [slotcar_ambulance23]: Initialising slotcar for ambulance23
[gzserver-14] [ERROR] [1631084275.040260706] [slotcar_ambulance23]: Could not find tire for [joint_tire_left]
[gzserver-14] [ERROR] [1631084275.040271843] [slotcar_ambulance23]: Could not find tire for [joint_tire_right]

[luca-della-vedova]

Good question, in the original implementation of slotcar there was a lot of code specific to the simulator, I believe this might be fixed with the latest rmf_simulation refactor, however Gazebo is hanging on startup on my side so not sure what is happening there.

Edit: Saw @aaronchongth reply below, I believe that is one of the reasons the specific demo wouldn't work in Gazebo, however if the model happened to have wheels instead of being a big box that should be fixed, that might require some work though, especially for this narrow use case demo scenario.

[aaronchongth]

Thanks for updating!

The names of the model AmbulanceSlotcar in model.sdf and model.config are not matching, as well as the names of the .obj and .mtl file, which causes a clean build to fail.

[ign-14] [GUI] [Err] [SystemPaths.cc:377] Unable to find file with URI [model://Ambulance/meshes/ambulance.obj]
[ign-14] [GUI] [Err] [SystemPaths.cc:467] Could not resolve file [model://Ambulance/meshes/ambulance.obj]
[ign-14] [GUI] [Err] [MeshManager.cc:172] Unable to find file[model://Ambulance/meshes/ambulance.obj]
[ign-14] [GUI] [Err] [MeshDescriptor.cc:56] Mesh manager can't find mesh named [model://Ambulance/meshes/ambulance.obj]

There is currently an issue regarding model downloading that is being tracked, open-rmf/rmf_traffic_editor#386. In the meantime, could you try a clean build, cleaning up ~/.gazebo/models such that there is only sun and ground_plane left, and deleting everything in ~/.ignition/fuel/fuel.ignitionrobotics.org/openrobotics?

[aaronchongth]

Looks like it is related to the plugin, running the simulation in rmf_demos_gz shows that it fails to find the necessary joints,

[gzserver-14] [INFO] [1631084275.040217309] [slotcar_ambulance23]: Initialising slotcar for ambulance23
[gzserver-14] [ERROR] [1631084275.040260706] [slotcar_ambulance23]: Could not find tire for [joint_tire_left]
[gzserver-14] [ERROR] [1631084275.040271843] [slotcar_ambulance23]: Could not find tire for [joint_tire_right]

[Yadunund]

Also just noticed within the test_ackman.launch.xml, the <arg name="use_tpe" value="$(var use_tpe)"/> is included within the common.launch.xml include. I think it should be under <include file="$(find-pkg-share rmf_demos_ign)/simulation.launch.xml">.

Also in my personal opinion, it seems like a lot of the work to support ackermann vehicles is not fully there yet. I think it would be best to remove the test_ackman map and Ambulance model from main. We can work on this in a separate branch. Then when everything is finalized (including a proper map for demonstrating ackermann steer vehicles and updated Ambulance model with wheels), we can merge these components into main and release as a patch.

[luca-della-vedova]

Also in my personal opinion, it seems like a lot of the work to support ackermann vehicles is not fully there yet. I think it would be best to remove the test_ackman map and Ambulance model from main. We can work on this in a separate branch. Then when everything is finalized (including a proper map for demonstrating ackermann steer vehicles and updated Ambulance model with wheels), we can merge these components into main and release as a patch.

Closing in favor of #88 removing the test world.