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The article presents a system for determining dynamic under keel clearance. In order to build a DRWPS system, a mixed model was created based on the analysis of math models. The system includes advisory software for defining the conditions for the entering of large LNG vessels in the context of under keel clearance and software was built to support the decision-making of operators who are responsible for introducing these vessels to the Port of Swinoujscie.

The paper presents new results on the inherent properties of ship linear dynamics. The focus is made on the second-order formulation for the uncoupled equations of sway and yaw, and on their unique, unknown performance within the zigzag test. From the standpoint of application to full-mission model tuning, a very important loop in the drift-yaw domain of the zigzag behaviour, as governed by the rudder rate dependent time constants (of T3-type), is brought to the light. This and some other dependent effects, like overshoot angle performance, are likely to be lost, if the well-known, rather ambiguous, first-order approximations are deployed.

This paper is devoted to expand the very promising research undertaken in the author's previous work, basically done on simplified modelling the escort push operation. Now, the other two modes of a tug's employment, as stated in the title, are covered. The special focus is again set on the indirect towing in that the towline force is much higher than the thruster force. The ratio of these two forces, referred to as the relative towing force (or amplification ratio) is evaluated together with the hull drift angle and the thruster(-s) angle for a given escort speed. This mutual relationship is known as the tug performance diagram. Although rather generic (container-type) formulas are derived, they are supplied for exemplification purposes with simple, analytically given hull hydrodynamic forces. The aim is also here to provide a basis for further sensitivity analysis of the model and possible improvement/optimisation to the tug design. The obtained charts also could serve as rough and clear guidance for towmasters while escorting.

The overall objective of the study presented in this paper was to evaluate the selectivity properties of three innovative codends in Baltic cod fishing: (1) an ultracross codend of 120 mm square mesh, (2) an ultracross codend with additional devices reducing the speed of water flow—one tarpaulin diffuser and one net confusor of 120 mm mesh, and (3) an ultracross codend with two tarpaulin diffusers and two net confusors of 120 mm mesh. These codends were firstly tested at sea by single trawls and compared to T90 and herring codend trawls, allowing assessment of caught fish mass and dimensions. Additionally, a special divided small-mesh coat for the innovative codends enabled determination of the amount as well as the length and mass of cod escaping from the codend both while the trawling gear was towed and while it was hauled. Further validation of codend selectivity was carried out by a double (twin) bottom trawl set deployed from one cutter in various variants of innovative codends compared to standard ones. The results of the study indicate that the use of an innovative ultracross codend and innovative devices reducing the water flow speed (tarpaulin diffusers and 120 mm net confusors) significantly reduces the number of undersized cod (

One of the components necessary to determine the width of a safe maneuvering area on two-way fairways is a safe passing distance. Existing methods do not consider modern model studies of interactions between passing vessels, additionally, they ignore the influence of the vessel’s position accuracy and navigators’ qualifications. This paper presents a method to determine the passing distance, which is free of the drawbacks of the methods used so far. The proposed method is based on simulation research carried out using an FMBS-type (Full Mission Bridge) simulator. The tests were carried out for three loaded vessels (bulk carrier, tanker, and sea ferry), on four sections of the fairway with different parameters and aids-to-navigation available. The results obtained allowed the modification of the authors’ previous, but still widely used, deterministic–probabilistic MTE (Marine Traffic Engineering) method for determining the width of a safe maneuvering area.

The purpose of this article is to present a methodical approach to increasing the efficiency of a tug with an azimuth stern drive (ASD). The difficulties in the bow-to-bow (as a reverse tractor) operations of an azimuth stern-drive tug, while pulling at the assisted (towed) ship’s bow, are investigated through a parametric study. The authors’ original generic analytical model of a tug in a steady state is utilised. Various design and operation options are also compared, which cover the escort speed, hawser angle, and relative location of the towing point, among others. The latter also means a shift to stern-to-bow operation. The thruster power required and the remaining surplus for executing new alignment (steering) orders are assessed. The study is, thus, aimed at energy savings for the whole operation and, consequently, at long-term harbour-tug-fleet energy effectiveness. The basic output of the present research is the comparison of the behavioural and control patterns of various tug arrangements at a ship’s bow. The results of the study show a slight advantage for a midship winch tug working through her stern for bow operation (stern-to-bow) over the reverse tractor acting bow-to-bow. Comparing various tug designs or operation options is difficult due to complicated tug dynamics and statics patterns under the hawser action. Both relative and absolute towing forces have to be considered (a high relative force may result in a low absolute force, much less than ordered by the pilot), with some geometrical and safety constraints additionally. The practical implementation of the conducted research should cover the guidance and training rendered to tug masters in the scope of the operational limitations of a particular tug and towards the design or acquisition of the tug that is best-suited for a particular harbour operation.

This paper looks at a typical problem encountered in the process of designing an automatic ship’s course stabilisation system with the use of a relatively new methodology referred to as the Active Disturbance Rejection Control (ADRC). The main advantage of this approach over classic autopilots based on PID algorithms, still in the majority, is that it eliminates the tuning problem and, thus, ensures a much better average performance of the ship in various speed, loading, nautical and weather conditions during a voyage. All of these factors call for different and often dynamically variable autopilot parameters, which are difficult to assess, especially by the ship’s crew or owner. The original result of this article is that the required controller parameters are approximated based on some canonical model structure and analysis of the hydrodynamic properties of a wide class of ships. Another novelty is the use of a fully verified, realistic numerical hydrodynamic model of the ship as a simulation model as well as a basis for deriving a simplified model structure suitable for controller design. The preliminary results obtained indicate good performance of the proposed ADRC autopilot and provide prospects for its successful implementation on a real ship.

The International Maritime Organization adopted a strategy to reduce the total annual GHG emissions from international shipping by at least 50% by 2050, compared to 2008 levels. The European Union proposed an even farther reaching transformation: the European Commission adopted a set of proposals to make the EU’s transport policies fit for reducing net greenhouse gas emissions by at least 55% by 2030, compared to 1990 levels. Therefore, all industrial actions in line and consistent with these strategies are essential. One of such activities may be a gradual transition from the most common independent controls of transport ships’ thrusters, propellers, and rudders to an integrated, power optimized, 3 degrees of freedom joystick control. In this paper, the full mission bridge simulator (FMBS) research on potential energy savings and, consequently, a GHG emission reduction, while steering a RoPax twin-screw ferry equipped with bow thrusters by a joystick control, is presented. The task of navigators engaged in the research was to steer the vessel either via classic engine, rudder, and thruster levers or via a joystick while (1) following the predefined straight track, (2) rotating at the turning area, and (3), finally, crabbing (moving sideways) until stopping at the quay fenders. The conclusions are that energy savings of approximately 10% can be expected for berthing manoeuvres controlled by a joystick, compared to independent actuators’ controls. These conclusions have been drawn from a statistical analysis of the ship’s energy consumption during typical manoeuvring phases of 18 berthing operations performed in FMBS.