A Study to Improve the Dragging Anchor of Surface Ship Performing Rescue Missions

A modified path-following control system using the vector field method for an underactuated autonomous surface ship model is proposed in the presence of static obstacles. With this integrated system, autonomous ships are capable of following the predefined path, while avoiding the obstacles automatically. It is different from the methods in most published papers, which usually study path-following and obstacle collision avoidance, separately. This paper considers the coupled path following and collision avoidance task as a whole. Meanwhile, the paper also shows the heading control design method in the presence of static obstacles. To obtain a strong stability property, a nonlinear autopilot is designed based on the manoeuvring tests of the free-running ship model. The equilibrium point of the controller is globally exponentially stable. For the guidance system, a novel vector field method was proposed, and the proof shows the coupled guidance and control system is uniform semi-global exponentially stable (USGES). To prevent the obstacles near the predefined path, the proposed guidance law is augmented by integrating the repelling field of obstacles so that it can control the ship travel toward the predefined path through the obstacles safely. The repelling field function is given considering the obstacle shape and collision risk using the velocity obstacle (VO) algorithm. The simulations and ship model test were performed to validate the integrated system of autonomous ships.

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Towards a Framework of Operational-Risk Assessment for a Maritime Autonomous Surface Ship

Energies ◽

10.3390/en14133879 ◽

2021 ◽

Vol 14 (13) ◽

pp. 3879

Author(s):

Cunlong Fan ◽

Jakub Montewka ◽

Di Zhang

Keyword(s):

Expert Knowledge ◽

Safety Evaluation ◽

Manual Control ◽

Operational Mode ◽

Surface Ship ◽

Open Questions ◽

Study Results ◽

Operational Modes ◽

Mass Case

Global research interest in the domain of maritime autonomous surface ships (MASS) is dramatically increasing. With new prototypes planned to be set to the seas where various operational modes (OMs) are claimed, the issue of the safety evaluation of an MASS, and criteria for selecting the appropriate OM for given conditions remain open questions. This paper proposes a four-step risk-informed framework to assess risk in a scenario for an MASS operating at one of three OMs: manual control (MC), remote control (RC), and autonomous control (AC). To this end, the concept of risk priority numbers (RPNs), adopted from failure mode and effects analysis (FMEA), is utilized. The required parameters to defined RPNs are obtained in the course of analyzing a model MASS accident with expert knowledge. The applicability of the proposed framework is demonstrated via a model MASS case study. Results reveal that, in the same scenario, the risk of MASS varied across the analyzed OMs. On the basis of the aggregated results for each operational mode, suggestions for OM switching are put forward.

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A Variable-Geometry Power Turbine for Marine Gas Turbines

Volume 2: Aircraft Engine; Marine; Microturbines and Small Turbomachinery ◽

10.1115/89-gt-282 ◽

1989 ◽

Author(s):

Karl W. Karstensen ◽

Jesse O. Wiggins

Keyword(s):

Fuel Consumption ◽

Gas Turbines ◽

Part Load ◽

Surface Ship ◽

Marine Propulsion ◽

Medium Speed ◽

Power Turbine ◽

Wide Range ◽

Electrical Generator ◽

Variable Power

Gas turbines have been accepted in naval surface ship applications, and considerable effort has been made to improve their fuel consumption, particularly at part-load operation. This is an important parameter for shipboard engines because both propulsion and electrical-generator engines spend most of their lives operating at off-design power. An effective way to improve part-load efficiency of recuperated gas turbines is by using a variable power turbine nozzle. This paper discusses the successful use of variable power turbine nozzles in several applications in a family of engines developed for vehicular, industrial, and marine use. These engines incorporate a variable power turbine nozzle and primary surface recuperator to yield specific fuel consumption that rivals that of medium speed diesels. The paper concentrates on the experience with the variable nozzle, tracing its derivation from an existing fixed vane nozzle and its use across a wide range of engine sizes and applications. Emphasis is placed on its potential in marine propulsion and auxiliary gas turbines.

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A Target Selection Algorithm of Seeker Based on the Prior Information and SVM

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.734-737.3071 ◽

2013 ◽

Vol 734-737 ◽

pp. 3071-3074

Author(s):

Guo Dong Zhang ◽

Zhong Liu

Keyword(s):

Prior Information ◽

Simulation Experiment ◽

Target Selection ◽

Support Vector ◽

Selection Algorithm ◽

Distribution Law ◽

Surface Ship ◽

False Target ◽

Target Characteristics ◽

Selection Of

Aiming at the phenomenon that the chaff and corner reflector released by surface ship can influence the selection of missile seeker, this paper proposed a multi-target selection method based on the prior information of false targets distribution and Support Vector Machine (SVM). By analyzing the false targets distribution law we obtain two classification principles, which are used to train the SVM studies the true and false target characteristics. The trained SVM is applied to the seeker in the target selection. This method has advantages of simple programming and high classification accuracy, and the simulation experiment in this paper confirms the correctness and effectiveness of this method.

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