By name: create-state-machine description: Create state machine implementation with states, transitions, events, and lifecycle management for robotics behavior. Use when implementing robot behavior control, finite state machines, state transitions, python-statemachine, or ROS 2 lifecycle integration.
Create State Machine
Generate state machine implementation with states, transitions, events, and lifecycle management following robotics behavior patterns.
When to Use This Skill
- Implementing robot behavior control
- Creating finite state machines for system modes
- Need structured state transitions with guards and actions
- Building hierarchical state machines or reactive control systems
Prerequisites
- Understand required states and their behavior
- Know valid transitions between states
- Identified events that trigger transitions
- Package exists or will be created
Inputs
- Machine Name: e.g.,
robot_behavior,motion_control - States: Comma-separated (e.g.,
idle,walking,turning,stopped) - Initial State: Must be in states list
- Language:
cpporpython(default: python) - Transitions, Events: Optional, generate common ones
- ROS 2 Integration: yes/no for lifecycle node wrapper
Workflow
Step 1: Validate Inputs
At least 2 states. State names: valid identifiers (lowercase, underscores). Initial state in list.
Step 2: Determine Package and Location
Python: <package>/<package>/<machine_name>_sm.py. C++: src/<machine_name>_sm.cpp, include/<package>/<machine_name>_sm.hpp.
Step 3: Design Transition Table
Generate default transitions. Document: states, transitions, events.
Step 4: Python (python-statemachine)
Use statemachine library. Define State (initial=True for initial), to() for transitions. on_enter_<state>, on_exit_<state>, before_<transition>, on_<transition>. process_event() maps events to transitions. Reference: packages/runtime/drqp_brain/.
Step 5: C++
Header: enum State, enum Event, to_string() helpers, StateMachine class with process_event(), callbacks. Implementation: setup_transitions(), execute_transition(), entry/exit callbacks.
Step 6: ROS 2 Integration (Optional)
Node wrapper: publishers for state, subscribers for events, timer for state publishing. Topics: /<machine_name>/state, /<machine_name>/event.
Step 7: Test File
Test initial state, valid transition, invalid transition, state sequence, entry/exit callbacks.
Step 8: State Diagram
Add Mermaid diagram to README: stateDiagram-v2, states, transitions.
Step 9: Update Build
Include new files in CMakeLists.txt or setup.py.
Edge Cases
- Circular transitions: Allow state to self
- Multiple transitions: Same state to multiple targets by event
- Invalid events: Handle gracefully
- Guard failures: Log when guard blocks
Related Resources
- python-statemachine
- Example:
packages/runtime/drqp_brain/ - create-ros2-package, add-test-file