chapulina
commented
3 years ago an example of how to package a custom systems plugin for ignition
There are a few examples here:
https://github.com/ignitionrobotics/ign-gazebo/tree/master/examples/plugin
This tutorial should also be helpful:
https://ignitionrobotics.org/api/gazebo/3.3/createsystemplugins.html
The recommendation is to write pure CMake packages for all functionality that isn't ROS-specific and use the ros-ign bridge to connect to ROS. This is meant to make the code more reusable. For example, on Gazebo-classic, we have a pure-cmake gazebo::DiffDrivePlugin, and also the ROS-enabled gazebo_plugins::GazeboRosDiffDrive - which has always been a pain to maintain.
I'd like to prototype an ackermann steering model, but want to avoid having to rebuild the entire ign-gazebo code base until the plugin is working
With the separation of concerns above in mind, I'd recommend you write a ROS package that contains:
- An Ackermann drive
ign-gazebosystem that's a pure CMake project and links againstign-gazebo, but not against ROS - A launch file that spawns a model with the plugin above, and also starts the
ros_ign_bridgefor thecmd_veltwist message
Perhaps a simple ignition plugin to control the tail_joint of dolly, that could be controlled via topic to active waggle, passively dampen, or hold still/break. It would also provide as a reference template for the cmake and ament exports necessary for ignition to find and load the externally compiled plugin.
I agree that this would be a valuable example, I'll look into adding one
As of yet, the current Ignition Robotics plugin and systems docs do not specify how to write your own, external from the upstream binaries.
I think we could do a better job linking to the resources I pointed out above: the example plugins and the tutorials.
cocodmdr
It would be nice to have an example of how to package a custom systems plugin for ignition. For example, the classic gazebo version of dolly uses the
libgazebo_ros_diff_driveplugin for mapping command velocities to the joint control for a respective wheelbase of the robot:https://github.com/chapulina/dolly/blob/349c35288b3a78a66249a1eef66bd507a0fed750/dolly_gazebo/models/dolly/model.sdf#L330
The ignition gazebo version of dolly uses the
libignition-gazebo-diff-drive-systeminstead:https://github.com/chapulina/dolly/blob/349c35288b3a78a66249a1eef66bd507a0fed750/dolly_ignition/models/dolly_ignition/model.sdf#L330-L332
For instances where an existing plugin bundled in ignition may not suffice or not exist, it would be helpful to have a packaged example of something like the
diff_driveplugin as a local package here.https://github.com/ignitionrobotics/ign-gazebo/tree/5b21ec87306c35b3494adc25694fac8b8d1bb7de/src/systems/diff_drive
Perhaps a simple ignition plugin to control the
tail_jointof dolly, that could be controlled via topic to active waggle, passively dampen, or hold still/break. It would also provide as a reference template for the cmake and ament exports necessary for ignition to find and load the externally compiled plugin.https://github.com/chapulina/dolly/blob/349c35288b3a78a66249a1eef66bd507a0fed750/dolly_ignition/models/dolly_ignition/model.sdf#L296
Personally, I'd like to prototype an ackermann steering model, but want to avoid having to rebuild the entire
ign-gazebocode base until the plugin is working and ready to upstream, keeping my development confined to a minimal dolly like colcon workspace/repo. As of yet, the current Ignition Robotics plugin and systems docs do not specify how to write your own, external from the upstream binaries.