Improving the workflow for supporting new Robots

[Sharwin24]

The current workflow requires modifying the core pfield_manager source code for every new robot, which violates the Open/Closed Principle.

Recommendation: Convert MotionPlugin and IKSolver into ROS 2 Plugins using pluginlib.

Benefits:

• Zero changes to pfield_manager: It loads classes dynamically at runtime based on a string parameter.
• No Clutter: You can create a separate package (e.g., my_robot_pfield_plugin) for your specific robot files. You don't need to touch the core potential_fields repo at all.

Proposed Changes

1. Refactor ABCs for Pluginlib:
   pluginlib requires a default constructor (0 arguments). You should add an initialize method to pass parameters after instantiation.

   // In MotionPlugin
   virtual void initialize(const std::string& name, rclcpp::Node::SharedPtr node) {
       this->name = name;
       // Use node to declare/get parameters like "franka_hostname"
   }

2. Update pfield_manager.hpp:
   Replace the hardcoded includes with a ClassLoader.

   #include <pluginlib/class_loader.hpp>
   // ...
   pluginlib::ClassLoader<MotionPlugin> motion_plugin_loader_;

3. Update pfield_manager.cpp:
   Replace the if/else block with dynamic loading:

   // In Constructor
   motion_plugin_loader_("potential_fields", "MotionPlugin"); // Package and Base Class
   
   try {
       this->motionPlugin = motion_plugin_loader_.createUniqueInstance(this->motionPluginType);
       this->motionPlugin->initialize(this->motionPluginType, shared_from_this());
   } catch(pluginlib::PluginlibException& ex) {
       // Handle error
   }

4. For the User (New Workflow):
   The user now creates a separate package and adds a simple XML registration file.

   • my_robot_plugins.xml:

     <library path="my_robot_lib">
       <class name="my_robot" type="my_pkg::MyRobotPlugin" base_class_type="MotionPlugin">
         <description>Plugin for My Robot</description>
       </class>
     </library>

   • CMakeLists.txt: No need to edit the core repo. Just export the plugin in the user's package.