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Efficient COLREGs-Compliant Collision Avoidance using Turning Circle-based Control Barrier Function

Changyu Lee, Jinwook Park, Jinwhan Kim

TL;DR

The paper tackles COLREGs-compliant collision avoidance for autonomous ships by introducing turning circle-based control barrier functions (TC-CBFs). It derives two CBFs, LTC-CBF and RTC-CBF, from left and right turning circles to explicitly encode turning capabilities and avoidance direction, and integrates them into a TC-CBF-QP safety filter that minimally alters a nominal controller. The encounter decision-making module uses CPA/DCPA/TCPA to determine which CBF constraints to apply, enabling direction-aware, rule-compliant maneuvers for single and multi-ship scenarios. Simulation results show that the TC-CBF-QP framework achieves collision avoidance performance comparable to MPC-based methods while substantially reducing computational effort, making it suitable for real-time maritime operations in complex environments.

Abstract

This paper proposes a computationally efficient collision avoidance algorithm using turning circle-based control barrier functions (CBFs) that comply with international regulations for preventing collisions at sea (COLREGs). Conventional CBFs often lack explicit consideration of turning capabilities and avoidance direction, which are key elements in developing a COLREGs-compliant collision avoidance algorithm. To overcome these limitations, we introduce two CBFs derived from left and right turning circles. These functions establish safety conditions based on the proximity between the traffic ships and the centers of the turning circles, effectively determining both avoidance directions and turning capabilities. The proposed method formulates a quadratic programming problem with the CBFs as constraints, ensuring safe navigation without relying on computationally intensive trajectory optimization. This approach significantly reduces computational effort while maintaining performance comparable to model predictive control-based methods. Simulation results validate the effectiveness of the proposed algorithm in enabling COLREGs-compliant, safe navigation, demonstrating its potential for reliable and efficient operation in complex maritime environments.

Efficient COLREGs-Compliant Collision Avoidance using Turning Circle-based Control Barrier Function

TL;DR

The paper tackles COLREGs-compliant collision avoidance for autonomous ships by introducing turning circle-based control barrier functions (TC-CBFs). It derives two CBFs, LTC-CBF and RTC-CBF, from left and right turning circles to explicitly encode turning capabilities and avoidance direction, and integrates them into a TC-CBF-QP safety filter that minimally alters a nominal controller. The encounter decision-making module uses CPA/DCPA/TCPA to determine which CBF constraints to apply, enabling direction-aware, rule-compliant maneuvers for single and multi-ship scenarios. Simulation results show that the TC-CBF-QP framework achieves collision avoidance performance comparable to MPC-based methods while substantially reducing computational effort, making it suitable for real-time maritime operations in complex environments.

Abstract

This paper proposes a computationally efficient collision avoidance algorithm using turning circle-based control barrier functions (CBFs) that comply with international regulations for preventing collisions at sea (COLREGs). Conventional CBFs often lack explicit consideration of turning capabilities and avoidance direction, which are key elements in developing a COLREGs-compliant collision avoidance algorithm. To overcome these limitations, we introduce two CBFs derived from left and right turning circles. These functions establish safety conditions based on the proximity between the traffic ships and the centers of the turning circles, effectively determining both avoidance directions and turning capabilities. The proposed method formulates a quadratic programming problem with the CBFs as constraints, ensuring safe navigation without relying on computationally intensive trajectory optimization. This approach significantly reduces computational effort while maintaining performance comparable to model predictive control-based methods. Simulation results validate the effectiveness of the proposed algorithm in enabling COLREGs-compliant, safe navigation, demonstrating its potential for reliable and efficient operation in complex maritime environments.
Paper Structure (16 sections, 25 equations, 19 figures, 2 tables)

This paper contains 16 sections, 25 equations, 19 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Preliminaries
  3. International Regulations for Preventing Collisions at Sea (COLREGs)
  4. Control Barrier Functions
  5. CBF-based Safety Filters using Quadratic Programming
  6. Encounter Situation Decision Making
  7. COLREGs-Compliant Collision Avoidance using Control Barrier Function
  8. Guidance and Control Algorithms for Waypoint Following
  9. Turning circle-based CBF design
  10. TC-CBF-QP Safety Filter
  11. Simulation Results
  12. One-to-one encounter simulation
  13. Multi-traffic ships encounter simulation
  14. Complex traffic environment simulations
  15. Conclusion
  16. ...and 1 more sections

Figures (19)

  • Figure 1: COLREGs-compliant evasive maneuvers. Blue ships take an evasive maneuver (give-way), while red ships maintain their course and speed (stand-on) in accordance with COLREGs.
  • Figure 2: Architecture of the CBF-QP safety filter.
  • Figure 3: Illustration of the DCPA and TCPA.
  • Figure 4: Coordinate systems used for encounter classification.
  • Figure 5: Illustration of COLREGs encounter types.
  • ...and 14 more figures