Automatic Berthing System Research Articles

Collision-free automatic berthing of maritime autonomous surface ships via safety-certified active disturbance rejection control

This paper addresses the automatic berthing of a maritime autonomous surface ship operating in a confined water environment subject to static obstacles, dynamic obstacles, thruster constraints, and space constraints due to shorelines. A safety-certified active disturbance rejection control (ADRC) method is proposed for achieving the automatic berthing task of an MASS in the presence of model uncertainties and ocean disturbances. An extended state observer (ESO) based on a second-order robust exact differentiator (RED) is employed to estimate an extended state vector consisting of internal model uncertainties and external ocean disturbances. With the aid of the RED-based ESO, a nominal ADRC law is designed to achieve the position and heading stabilization. To avoid collisions with static obstacles, dynamic obstacles, and shorelines, input-to-state safe high-order control barrier functions are used to guarantee safety. Optimized control signals are obtained based on a constrained quadratic programming (QP) problem within safety constraints. In order to translate the control signals into the individual thruster command, a constrained QP problem is further used to search for optimized commands in real time. It is proven that the closed-loop automatic berthing system is input-to-state stable. By using the proposed method, the MASS is able to reach the desired position and heading with collision avoidance. Simulation results verify the effectiveness of the proposed safety-certified ADRC method for automatic berthing.

Application of Reinforcement Learning to Generate Non-linear Optimal Feedback Controller for Ship's Automatic Berthing System

In this paper, we present an application of reinforcement learning for automatic ship's berthing system. In the proposed method, the model-based reinforcement learning is used to generate non-linear feedback controller. The proposed system is composed of an Actor-Critic algorithm suitable for continuous state and a function approximator by Radial Basis Function networks. To evaluate the performance of the proposed system, extensive computer simulations and actual sea tests are carried out using small training ship Shioji-Maru III under various conditions. As a result, we can see that the proposed non-linear optimal feedback controller by reinforcement learning is useful for designing automatic berthing system for the ship.

Study of 3D measurement of ships using dense stereo vision: towards application in automatic berthing systems

Autonomous navigation of ships is actively discussed nowadays. It is essential to recognize the surrounding conditions using radars and acquire position information using GPS. However, each of these existing sensors has its own problems. In order to achieve safer autonomous navigation in scenes such as automatic berthing, passing in a narrow line and closing to other ships, an imaging system that integrates various information is essential. Therefore, the authors propose a 3D position measurement method for ships using a stereo camera. In the case of the automatic berthing system, detailed information such as the position of various parts of the hull, heading, roll angle, etc. is necessary. This paper describes a system that measures 3D locations of many parts of ship’s hull with a dense stereo algorithm applied to stereo-pair images captured by cameras set up on land. An experiment to measure an actual ship as a target was conducted. The result indicated that the more disparity data, which meant depth of the ship from the cameras, were obtained by semi-global matching (SGM) even from the featureless images like ship’s hull and the measurement error was within 1 m.

Path following algorithm application to automatic berthing control

This paper aims to verify a new automatic berthing system using a path following algorithm. Berthing operation is one of the most burdensome tasks for crews among several ship operations. The maneuverability of a ship at low speed during berthing operation deteriorates and becomes more vulnerable to disturbances such as wind. Therefore, it is necessary to support and automate operations that require advanced skills such as berthing operation. Previous studies on automatic berthing have investigated various methods to handle the nonlinearity of ship maneuvering motion and determine the optimal control variable. There is a trade-off between accuracy and real-time performance of berthing control from these studies. The algorithms must have sufficiently real-time performance while maintaining the accuracy of control. For these purposes, we propose the automatic berthing system applied a path following algorithm for a ship with one propeller and one rudder in this paper. We show the mathematical model for numerical simulation of berthing control and carried out system identification of the subject ship. In full-scale experiments, the proposed system performed automatic berthing control in both calm wind conditions around 2 m/s and strong wind conditions around 6 m/s.

Research on a Support System for Automatic Ship Navigation in Fairway

In previous investigations, controllers for the track-keeping of ships were designed with the assumption of constant ship speed. However, when navigating in a fairway area, the ship’s speed is usually decreased to prepare for berthing. The existing track-keeping systems, which are applied when the ship navigates in the open sea with a constant ship speed, cannot be used to navigate the ship in the fairway. In this article, a support system is proposed for ship navigation in the fairway. This system performs three tasks. First, the ship is automatically controlled by regulating the rudder to follow planned tracks. Second, the ship’s speed is reduced step by step to approach the berth area at a low speed. Finally, at low speed, when the ship’s rudder is not effective enough to control the ship’s heading to a desired angle, the ship’s heading is adjusted appropriately by the bow thruster before changing the control mode into the automatic berthing system. By the proposed system, the automatic systems can be combined to obtain a fully automatic system for ship control. To validate the effectiveness of this proposed system for automatic ship navigation in the fairway, numerical simulations were conducted with a training ship model.

Implementation and Evaluation of Non-linear Optimal Feedback Control for Ship’s Automatic Berthing by Recurrent Neural Network

In this paper, we present an automatic ship’s berthing system by non-linear optimal feedback controller. In the proposed method, the recurrent neural network is used for non-linear optimal feedback controller for the realistic operational conditions such as different berthing distances and different disturbances. To obtain the feasible non-linear controller, the recurrent neural network is trained using pre-computed non-linear optimal solutions for various conditions. In order to evaluate the performance of the proposed system, extensive computer simulations and actual sea tests are carried out using small training ship Shioji-Maru under various conditions. As a result, we can see that the proposed non-linear optimal feedback controller by recurrent neural network is useful for automatic berthing system for the ship.

Study on ship automatic berthing system with mooring lines

This study describes an automatic berthing system with mooring lines. It is designed to be berthed by using mooring device on the upper deck of a ship. It is to berth once maintaining parallel with the quay by controlling both forward and aft breast lines. Berthing method is used through length adjustment of mooring lines connected between ship and quay by controlling the angular velocity and the torque of hydraulic motor in mooring device. The study is conducted under three changing conditions of draft, such as even-keel, rise of the gravity center and trim to stern. Variables affecting berthing stability are determined based on the control performance of each condition. Bond graphs method is used to model the system. Controller is designed as PID control method of reference-model algorithm. The control program is composed of synchronous control system based on the equations derived with the numerical analysis. The tank test is conducted to verify the usefulness of the control program.

海翔丸の自動着桟システムの開発とその性能評価

The Kanmon Kaikyo Traffic Route is important as an international route, and main route to connect main economic blocks of Japan. In the Kanmon Kaikyo, there is a problem that a route is being buried by sand and clay because of extremely strong tidal current. Therefore, the continuous dredging is needed to keep the route navigable. Kaisho Maru that is an oil recovery ship and a dredger is also dredging the Kanmon Kaikyo with the round-the-clock-system. Then an automatic mooring system was installed on the berth for Kaisho Maru. The automatic mooring system has two movable suckers and fenders to catch the bow and stern side. A hull of Kaisho Maru is absorbed with these suckers, and moored firmly. In order to use this system effectively, Kaisho Maru has to be guided to the positions of suckers correctly. Thus, automatic control system for Kaisho Maru has been developed. Kaisho Maru is controlled by the automatic berthing system with specified point guidance control method. The system guides a reference point on the ship to the specified point on the planned route. In this study, actual berthing data of Kaisho Maru was analyzed and effectiveness of automatic berthing system was evaluated.

Some recent developments of next generation's marine traffic systems

Some recent developments of next generation's marine traffic systems from Marine ITS project in Japan are roughly introduced. One is marine traffic simulation utilizing automatic collision avoidance system. It can simulate marine traffic simulation for any interested area based on a given OD tables etc. The safety assessment in congested area and utilization for planning of on-land AIS stations are shown as examples of its applications. The other is automatic berthing system utilizing artificial neural network. A proposal of automatic teaching data creation is introduced. A result of a model ship experiments is shown.

A GPS-based system for precise shipping guidance and control

This paper discusses the general concept of an automatic berthing system. The research considered the automatic berthing of a large merchant ship. A global positioning system (GPS)-based system, which provides the necessary information on position, velocity, attitude (roll, pitch, and heading), angular velocity, and time, was the principal sensor used. Field tests were conducted on board a hydrographic sounding ship to assess the quality of information obtained from a GPS-based system. The data were processed using the software with which the algorithms developed in this research were implemented. This paper also discusses various aspects concerning a real-time GPS-based system in relation to an automatic berthing system, such as integration of sensors, mathematical models, port infrastructure, and training of crews.

A Fully Automatic Berthing Test Using the Training Ship Shioji Maru

In this paper, the authors discuss a fully automatic berthing system and actual tests using a small training ship, Shioji Maru. The ship is about 440 gross tonnage and furnished with a controllable pitch propeller, a bow thruster and a stern thruster to which a computer can easily be linked. The system developed is composed of an electro-optical position measuring system and the computer software necessary for manoeuvring the ship.The electro-optical position measuring system can measure a distance between the ship and a target on a berth within 4 cm accuracy and cover an area out to about 100 m range. The manoeuvring is divided into two stages. The first one is from a start line to a transition point off the final berth. At this point, the ship must be stopped in an alongside attitude to the berth. In the second stage, the ship is pushed by the thrusters in an athwartships direction towards the berth and the final speed at the berth must be limited to within 0.5 ms. The computer software generates an appropriate strategy following an approach line which has been determined in advance.According to the actual tests under slightly rough sea conditions, the system could manoeuvre the ship along the approach line by a direct path and maintain her final speed within the predetermined limit.

汐路丸による自動離着桟実験について

In order to operate the berthing maneuver automatically, a control system was developed. This system is composed of a ranging system and a controller. A control logic based on a prediction of a motion was adopted and a feed back control was used subsidiarily to improve the performance of the system. Actual trial using this automatic berthing system was executed. And following results were obtained. (1) The smooth course was obtained during the trial. (2) The final position error and the berthing velocity seem to be acceptable. (3) A control logic based on a prediction of the motion did not operate successfully but a feed back control recovered this well.