Plugins in rospec

Plugin Fundamentals

In ROS, plugins:

• Are dynamically loaded libraries that extend component functionality
• Allow for modular design and flexible configuration
• Are widely used in navigation, perception, and control systems
• Often have their own configuration parameters and requirements
• Can introduce misconfigurations if not properly documented and verified

Specifying Plugins in rospec

rospec provides a specific syntax for defining plugin types:

plugin type right_arm_type {
  param tip_name: string;
  param root_name: string;
  optional param robot_description: string = "robot_description";
  optional param tf_safety_timeout: Second = 0.0;
}

Similar to node types, plugin types can include:

• Required and optional parameters with types and constraints
• Connections to topics and services
• TF frame broadcasts and listeners
• Parameter dependencies

Plugin Usage in Nodes

Nodes can use plugins by declaring parameters of type Plugin:

node type arm_kinematics_constraint_aware_type {
  param group: Plugin;
}

Instantiating Plugins

When configuring a system, you create plugin instances and assign them to nodes:

system {
  plugin instance right_arm: right_arm_type {
    param tip_name = "right_gripper";
    param root_name = "base_link";
  }
  
  node instance arm_kinematics: arm_kinematics_constraint_aware_type {
    param group = right_arm;  // Assigns the plugin to the node
  }
}