Example ROS bridge for electro-hydraulic PTO

[chapulina]

Here's an example launch file that loads the electro-hydraulic PTO world and exposes all the Gazebo topics to ROS.

Try it out

Launch the world:

ros2 launch buoy_gazebo electrohydraulic_pto.launch.py

Check that topics are available with ROS:

$ ros2 topic list
/battcurr_HydraulicRam
/deltaP_HydraulicRam
/loadcurr_HydraulicRam
/model/Hydraulics_Test/joint/HydraulicRam/BiasCurrent
/model/Hydraulics_Test/joint/HydraulicRam/RetractFactor
/model/Hydraulics_Test/joint/HydraulicRam/ScaleFactor
/model/Hydraulics_Test/joint/HydraulicRam/UserCommandedCurr
/parameter_events
/pistonvel_HydraulicRam
/retractfactor_HydraulicRam
/rosout
/rpm_HydraulicRam
/scalefactor_HydraulicRam
/targwindcurr_HydraulicRam
/windcurr_HydraulicRam

Listen to a topic with ROS, for example:

$ ros2 topic echo /loadcurr_HydraulicRam                                              
data: 2.2142660968671457e-15                                                                                                                
---                                                                                                                                         
data: -4.370744217940814e-15                                                                                                                
---                                                                                                                                         
data: 8.880699994828767e-16                                                                                                                 
---                                                                                                                                         
data: 2.0216033708164716e-15                                                                                                                
---                                                                                                                                         
data: 4.3921030007387785e-16

Publish to a topic with ROS, for example:

$ ros2 topic pub --once /model/Hydraulics_Test/joint/HydraulicRam/UserCommandedCurr std_msgs/msg/Float64 "{data: 3}"
publisher: beginning loop
publishing #1: std_msgs.msg.Float64(data=3.0)

[parameter_bridge-2] [INFO] [1650325732.031830191] [ros_ign_bridge]: Passing message from ROS std_msgs/msg/Float64 to Ignition ignition.msgs.Double (showing msg only once per type)
[ign gazebo-1] ## Adjusting UserCommanded Current 3

Open question

I'm not sure if we're planning to expose the same topics for all worlds, or different worlds will expose different topics. Some things we may want to do:

• compose a launch file of smaller ones - for example, we could have:
  • Launch file to bridge the electro-hydraulic PTO
  • Launch file to bridge the pneumatic spring
  • Other launch files for other components
  • A top-level launch file that includes the others based on parameters
• make the model and joint names configurable as launch parameters

[andermi]

I could see loading plugins a la carte for a general use, configurable product of which MBARI's is a specific implementation. It would be nice to easily launch individual plugins for testing in isolation (or superposition) when modeling.

[andermi]

👍

[chapulina]

It would be nice to easily launch individual plugins for testing in isolation (or superposition) when modeling.

I'll open a separate PR breaking this apart 👍🏽

[chapulina]

It would be nice to easily launch individual plugins for testing in isolation (or superposition) when modeling.

• See Add spring bridge and split launch files #28