Optimization on Planning of Trajectory and Control of Autonomous Berthing and Unberthing for the Realistic Port Geometry

Abstract

To realize autonomous shipping, autonomous berthing and unberthing are some of the technical challenges. In the past, numerous research have been done on the optimization of trajectory planning of berthing problems. However, these studies assumed only a simple berth and did not consider obstacles. Optimization of trajectory planning on berthing and unberthing in actual ports must consider the spatial constraints and maintain sufficient distance to obstacles. The main contributions of this study are as follows: (i) a collision avoidance algorithm based on the ship domain which has variable size by the ship speed is proposed, to include the spatial constraints to optimization; (ii) the effect of wind disturbance is taken into account to the trajectory planning to make a feasible trajectory based on the capacity limit of actuators; (iii) showing that the optimization method for berthing is also eligible for the unberthing, which has been almost neglected; (iv) waypoints are included to the optimization process, to make optimization easier on practical applications. The authors tested the proposed method on two existing ports. The proposed method performed well on both the berthing and the unberthing problem and optimized the control input and the trajectory while avoiding collision with the complex obstacles.

Warm-started Semionline Trajectory Planner for Ship's Automatic Docking (Berthing)

“…Research on trajectory planner for docking operation sees various efforts to balance three things: low computational cost (Bitar et al, 2020;Martinsen et al, 2020), applicability to underactuated conventional vessel (Maki et al, 2021(Maki et al, , 2020Mizuno et al, 2015), and feasibility with respect to the surrounding dynamic (Han et al, 2021;Mizuno et al, 2015) and geometric information (Bitar et al, 2020;Liao et al, 2019;Martinsen et al, 2019;Miyauchi et al, 2021b). This is relevant, because in practice a shipmaster will try to replan a new trajectory for docking operation if it is considered not feasible anymore.…”

“…This article limits the discussion within the scope of OCP-based trajectory planner that was pioneered by Shouji et al (1992). The trajectory planner introduced in Maki et al (2021) and Miyauchi et al (2021b) can produce an almostglobal, feasible, and safe trajectory for a conventional vessel, but requires long computational time. The one introduced in Mizuno et al (2015) is relatively fast and also applicable to conventional vessel, but there are no spatial constraints that can guarantee safe trajectory.…”