colav-automaton

Overview

colav-automaton is a maritime collision avoidance hybrid automaton, built on the hybrid-automaton framework. It steers an autonomous surface vehicle (USV) toward a goal waypoint while avoiding a dynamically-updatable unsafe region (a risk envelope), generating temporary "virtual" avoidance waypoints on the fly rather than requiring a pre-planned path.

This is not a full COLREGs rule-engine (it doesn't encode give-way/stand-on role logic for head-on, crossing, or overtaking encounters) - it's a general risk-envelope-avoidance automaton. Feed it any polygon as an unsafe region (a static hazard, a buffered obstacle, a COLREGs-derived exclusion zone computed upstream, etc.) and it will route around it.

Framework Status: v1.0.1 - Stable API, tested against real hybrid-automaton>=1.0.1, ready for simulation use and ROS2 integration testing on hardware.

If you have ideas for improvement or want to contribute, please reach out and become a collaborator!

Table of Contents

• colav-automaton
  • Overview
  • Table of Contents
  • How It Works
  • Installation
  • Usage
  • Practical Use Cases
  • Collaborators
  • License

How It Works

The automaton has 4 discrete states, driven by the agent's continuous state [x, y, theta, velocity, yaw_rate]:

stateDiagram-v2
    direction LR
    [*] --> Cruise
    Cruise --> Transition_to_LOS: e1 heading off / e2 LOS blocked
    Transition_to_LOS --> Cruise: e5 heading corrected
    Transition_to_LOS --> Fallback: e6 unsafe conditions
    Fallback --> Cruise: e8 conditions safe again
    Cruise --> Waypoint_Reached: e4 waypoint reached
    Waypoint_Reached --> Cruise: e7 pop virtual waypoint

• Cruise - holds heading/speed toward the current waypoint.
• Transition_to_LOS - actively corrects heading using line-of-sight (LOS) guidance. Entered either because the heading has drifted out of tolerance, or because los_clear_to_waypoint_guard found the direct path to the waypoint blocked by the unsafe region - in that case a virtual waypoint is generated (an offset around the nearest visible edge of the unsafe region) and pushed onto the waypoint stack ahead of the real goal.
• Fallback - entered if the agent's safety-radius circle starts intersecting the unsafe region while turning. Holds current heading/velocity (no active re-planning while too close to danger) until the safety circle clears, then returns to Cruise.
• Waypoint_Reached - a terminal-ish state hit whenever any waypoint (virtual or goal) is reached within an acceptance radius. If virtual waypoints remain queued, the most recent one is popped and the agent resumes toward the next; otherwise the run ends.

Every guard has a corresponding flowchart and input/output truth table under docs/guards/, and the shared ctx: RuntimeContext data contract used by every guard/reset/invariant/dynamics function is documented in docs/architecture/shared_context_data_table.md.

Installation

pip install colav-automaton

Usage

import asyncio
import numpy as np

from colav_automaton import ColavAutomaton
from hybrid_automaton import Automaton, RunResult, ContinuousState, AuxiliaryState

ha: Automaton = ColavAutomaton(
    heading_tolerance=0.2,
    constant_velocity=2.0,
    safety_radius=30.0,
    acceptance_radius=5,
)

async def run():
    results: RunResult = await ha.activate(
        initial_continuous_state=ContinuousState(
            name="agent_state",
            x0=np.array([0.0, 0.0, 0.0, 0.0, 0.0]),
            x_labels=["x", "y", "theta", "velocity", "yaw_rate"],
        ),
        initial_auxiliary_states=[
            AuxiliaryState(name="waypoints", aux0=[180.0, 140.0], aux_buffer_len=10),
            AuxiliaryState(
                name="unsafe_region",
                aux0=[[40.0, 20.0], [80.0, 20.0], [80.0, 60.0], [40.0, 60.0]],
                aux_buffer_len=10,
            ),
        ],
        delta_time=0.1,
        enable_real_time_mode=False,
        enable_self_integration=True,
        should_write_logs=True,
        output_dir="./colav-automaton-logs",
    )
    print(results)

asyncio.run(run())

A runnable version of this (with a few example scenarios) is in scripts/run_demo_scenario.py.

Practical Use Cases

Is this ready for real-world use? As of v1.0.0 it's ready for simulation and ROS2 integration/hardware-in-the-loop testing - it hasn't yet been validated on a physical vessel.

Key Applications

• 🚢 USV Navigation - the original motivating use case: risk-envelope-aware waypoint following for unmanned surface vehicles.
• 🛰️ ROS2 Integration - built on hybrid-automaton's ROS2-ready design; unsafe regions and waypoints are just AuxiliaryState updates, so they can be wired to a live perception/mapping stack.
• 🎓 Research & Education - hybrid systems / marine autonomy coursework, COLREGs-adjacent research (see Roadmap for planned rule-category work).

What's Deliberately Out of Scope (for now)

See ROADMAP.md for the full list - notably, this package does not (yet) implement COLREGs give-way/stand-on rule logic, only generic unsafe-region avoidance.

Collaborators

This project was created by:

• Ryan McKee

Contributing

Please open an issue or pull request on GitHub.

Citation

Please cite this package as described below if used in research:

@misc{colav_automaton_2026,
  author       = {Ryan McKee},
  title        = {colav-automaton v1.0.1},
  howpublished = {GitHub repository},
  year         = {2026},
  note         = {Accessed: Aug. 10, 2026},
  url          = {https://github.com/rymc-dev/colav-automaton}
}

License

colav-automaton is distributed under the terms of the MIT license.