Timetable stability depends on the regularity of trains. Any deviation from the planned timetable leads to its instability. Railway network characteristics determine the capacities of the transport ...service. Depending on the capacity calculation method, time components are added to the minimum headway to ensure timetable stability. The UIC 405 method is simple and can be used on all railways. The disadvantage is that the calculations are based on average data. According to the method, the minimum headway consists of the time of the average headway interval, additional time and the buffer time. The additional time is precisely defined by the number of APB sections, while the buffer time is in the average value. When creating the timetable, the goal is optimal utilisation of the infrastructure. If the headway is too long, the capacity is not used, and if it is too short, timetable instability will ensue. Instead of averaging, this work calculates a buffer time that depends on the ratio of the travel time of the previous and the following trains. In this way, the headway is optimised and the calculation of the UIC 405 method is improved.
The problem of maritime traffic in Singapore Strait is traffic density, also the probability of collision,
which is increased beside the existing Vessel Traffic System (VTS). The paper discusses the ...synthesis early warning system, or
automatic crossing supervisor for Singapore Strait by using the Timed Petri Nets (TPN). Authors proposes dividing the strait
in zones, so called crossings, where routes are crossing and in which the number of ships must be limited. The maximum number
of vessels in period of time of the highest traffic density through the crossings are determined. Derived constraints are used
for synthesis of crossing supervisor. The authors uses Petri nets to make model Singapore Strait, and use P-invariant method
to syntheses crossing supervisor, which limits the number of ships in all critical crossings. Finally, the author verified
derived supervisor by using Visual Object Net ++ programme for computer simulation. With the aid of Transas nautical simulator,
the traffic in the strait is analysed.
The paper deals with collision prevention problem in maritime transport in the area of the narrow canals with predefined routes. The Dover incident, which is analysed and described in the paper, has ...shown that the control of the passage of ships through the critical areas must be upgraded with an automatic supervising system, which warns the human operator of incorrect ship motion and help the operator to make the right and timely decision. The general idea is to improve the safety of navigation by introduction of automatic collision prevention based on automated supervisor helping to human operator in Vessel Traffic System (VTS) control centre. The VTS supervisor automatically monitors marine traffic by using data from Automatic Radar Plotting Aid (ARPA) radar and others sensors. Such supervisor detects real time and Course Over Ground (COG) of the vessel entering a particular sector, and then estimates the required time for vessel’s passage into another sector. VTS supervisor compares the real time and estimated time of passage of the specific ship through particular sector as a part of surveillance area. In addition, it compares and monitors the deviation of the course during transition of zones (sectors). If significant difference for both values are occurred VTS supervisor triggers a time alarm or a course alarm respectively. In the paper authors have modelled and simulated collision prevention with performed by the alarm actions of VTS supervisor improved with algorithm module based on hybrid Petri net formalism and Visual Object Net ++ tool.
A maritime collision avoidance system built on a database is being developed. Different information important for navigation, like electronic charts, bathymetric data, sea current and forecast ...weather conditions, etc., as well as knowledge about weather and load-dependent maneuvering capabilities of the involved vessels, are entered into the database tables. When using the system in real-time, the targeted data must be found very quickly in the database. In parallel, for the prediction of ship courses and for the calculation of evasive courses, the system must be capable of solving very many calculations in the shortest possible time, and these calculations often use database tables. Fast communication for updating database tables with the latest data is equally important in such a system. This article briefly presents the hardware developed for the project. We designed such data models for the efficient application of the Postgres database, capable of real-time calculation.
The purpose of this study is to show how coloured Petri nets can be used to select the crossing rules guaranteeing that two ships avoid collisions at sea in accordance with the international ...regulations on this matter. This paper is exclusively focused on the solution to this small sub-problem within the overall “Collision Avoidance System” that the authors of the present study are currently developing. For easier understanding, the overall system is also briefly presented. How the Petri net in the CPN Tools software is fed with “Real Time Real World” data is presented. These data are generated outside the Petri net from the function block to predict a possible collision and from the current meteorological data. We also demonstrate how the rule selections made by the Petri net are transferred from the CPN Tools software into the “Real Time Real World”. This transferred information is used outside the Petri net in the function block to calculate avoidance routes. The definition of the colour sets that are used and the individual operations applied to these colour sets in the coloured Petri net are presented.
U nastojanju da se poduzmu učinkovite mjere protiv piratskih napada pokazala se potreba za izradom modela koji će pridonijeti povećanju zaštite od piratskih napada na brodove u područjima gdje ...postoji visok rizik od te opasnosti. Zato je korištenjem hibridnih vremenskih Petrijevih mreža izrađenasimulacija vremenske dinamike piratskog napada na brod u plovidbi. U simulaciji vremenske dinamike događanja tijekom piratskog napada – studija slučaja (CaseStudy) – korištenjem Petrijevih mreža razvijeni su, prikazani i analizirani najnepovoljniji piratski napadi na brod u plovidbi uz dodatnu zaštitu ratnog broda s helikopterom. Izrađena su i analizirana tri scenarija napada pirata na brod s jednim, dva i tri piratska broda. Ovakavje sustav u svojojprirodi vrlo složen. Sastoji se od kontinuiranog dijela (Continous Systems), tj. gibanja napadnutog broda, gibanja piratskog broda i gibanja vojnog broda/helikoptera (promjena brzine, udaljenosti), i diskretnog dijela (Discrete Event Systems), tj. početak napada, slanje distressa. Analizirani su čimbenici koji utječu na sigurnost plovidbe broda kroz područje povećanog rizika od mogućih piratskih napada. Navedeni su karakteristični pokazatelji i istraženi načini poboljšanja sigurnosti kako bi se na kraju pokazalo darazvijena primjena vremenske dinamike piratskog napada vodi k optimalnom rješenju planiranja plovidbe broda kroz piratska područja.
The paper deals with the traffic control and job optimization in the marine canal system. The moving of vessels can be described as a set of discrete events and states. Some of these states can be ...undesirable such as conflicts and deadlocks. It is necessary to apply adequate control policy to avoid deadlocks and blocks the vessels’ moving only in the case of dangerous situation. This paper addresses the use of Petri net as modelling and scheduling tool in this context. To find better solutions the authors propose the integration of Petri net with a genetic algorithm. Also, a matrix based formal method is proposed for analyzing discrete event dynamic system (DEDS). The algorithm is developed to deal with multi-project, multi-constrained scheduling problem with shared resources. It is verified by a computer simulation using MATLAB environment.
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