基于動態分階勢場法的船舶自動避碰系統

羅賢程 尹建川 李宏賓

摘要：為使船舶在多船避讓環境下適應航行環境的變化并自動復航，提出基于動態分階勢場法的船舶自動避碰系統。該系統基于動態勢場避障規劃算法，利用模糊綜合評價法量化船舶碰撞危險度;依據《國際海上避碰規則》確定本船在不同會遇局面下的避讓行動，并據此對斥力勢函數進行調整。該系統將本船的避碰過程劃分為航跡保持、避讓和復航3個階段，根據不同階段的要求構建動態分階勢場;利用動態分階勢場法對船舶的航行環境進行建模，進而生成恰當的航向指令;利用自動舵產生舵角指令控制船舶完成避讓、復航和航跡保持。仿真結果表明：該自動避碰系統可以引導船舶完成既定的避讓行動，并能使船舶在安全會遇距離上駛過;該系統可以適應航行環境的變化，且具備航跡保持能力。

關鍵詞： 動態分階勢場法; 船舶碰撞危險度; 船舶自動避碰; 航跡保持

中圖分類號： U675.96 ? ?文獻標志碼： A

Abstract： To make a ship adapt to the change of navigation environment and go back to the channel automatically under the multi-ship avoidance environment， an automatic collision avoidance system of ships is proposed based on the dynamic hierarchical potential field method. The system is based on the dynamic potential field obstacle avoidance planning method， and the fuzzy comprehensive evaluation method is adopted to quantify ship collision risk; the avoidance actions of an own ship under different encounter situations are determined according to the International Regulations for Preventing Collisions at Sea， and the repulsive potential function is adjusted accordingly. The collision avoidance process of the own ship is divided into three stages： track keeping， avoidance， and track restoration， and the dynamic hierarchical potential field is built according to the requirements for different stages; the dynamic hierarchical potential field method is used to model the ship navigation environment so as to generate the appropriate heading command; the autopilot is used to generate the rudder angle commands to control the ship to complete the avoidance， track restoration， and track keeping. The simulation results demonstrates that： the automatic collision avoidance system can guide the ship to complete the determined avoidance action， and make the ship pass with keeping a safe distance of approach; it also has the adaptability to the changing navigation environment， and has track keeping ability.

Key words： dynamic hierarchical potential field method; ship collision risk index; automatic collision avoidance of ship; track keeping

0 引 言

船舶航行的首要任務是確保安全、避免事故的發生。據統計，在造成傷亡的海上事故中，有60%的事故是由船舶碰撞引起的[1]，而超過80%的船舶碰撞事故都與人的因素有關[2]，因此提高船舶避碰的自動化水平并降低避碰過程中人的因素的影響成為保障船舶航行安全的重要課題之一。

勢場法最早由KHATIB[3]提出，其基本思想是：將智能體所處的環境抽象為一個虛擬勢場，智能體所期望到達的目標點對智能體產生引力勢場，智能體所處環境中的障礙物對智能體產生斥力勢場，將引力勢場與斥力勢場疊加后得到全局勢場，智能體沿著全局勢場負梯度方向完成避障路徑規劃并最終到達目標點。……