Transport

Railway transport system modelling approach for robustness analysis

Łukasz Wolniewicz — Tue, 31 Dec 2024 00:00:00 +0200

The article presents an approach to train traffic modelling that allows for the analysis of how railway networks respond to various disturbances, including increased traffic and disturbance events. It discusses different methods of reconfiguration actions in key points of the railway network, which helps reduce delay propagation in the transport system. The 1st part covers building simulation models, which include defining infrastructure, setting train routes, configuring rolling stock, and disturbance scenarios, enabling the analysis of various disruptive events. The simulations allow for testing disturbance scenarios with minimal downtime risk without interfering with the real-world environment. The study results identified key system parameters generating the largest delays, such as platform availability, signaling, and the number of block sections. Probability density distributions for event intervals and durations were analyzed. The Kolmogorov–Smirnov test was used to confirm the fit of empirical distributions with theoretical ones, which were then implemented in the model of railway line No 271, running from Wrocław to Żmigród (Poland). As part of the reconfiguration of this railway line, new platforms were added, the time required for route setting was reduced, and the number of block sections was increased. These actions significantly reduced average delays, improved line capacity, and enhanced the robustness of the railway transport system against disturbances. The reconfiguration effectively reduced delays in areas causing significant time exceedances above 359 s, which was recognized in the Polish railway network as critical.

First published online 3 January 2025

Computer-aided simulation of unmanned aerial vehicle composite structure dynamics

Tue, 31 Dec 2024 00:00:00 +0200

The dynamic response of an aerial vehicle structure is a key parameter that must be determined before further aeroelastic phenomena can be analysed in the aerospace sector. Natural frequencies, mode shapes, and damping can be measured or predicted through experimental, operational, or computational studies. To reduce the costs and complexity of experimental investigations, there is a demand for numerical models that accurately represent the structure′s dynamic behaviour. This article focuses on modelling composite structures, which are increasingly utilised in the aerospace industry and whose dynamic properties are heavily influenced by fibre directionality. ANSYS software and the ACP module were employed to develop a numerical model of a wet Epoxy Carbon UD (230 GPa) composite commonly used in Unmanned Aerial Vehicle (UAV) components. Ten layers of 0.1 mm thick carbon fibre were incorporated into the model to create a 1 mm thick composite plate, with fibres oriented at 0°, 30°, 45°, and 90° relative to the horizontal direction of the plate. The simulations demonstrated that careful consideration and modelling of the material significantly impact the values of natural frequencies and, more importantly, the mode shapes.

First published online 28 January 2025

A multi-objective fuzzy optimization model for multi-type aircraft flight scheduling problem

Ming Wei, Shangwen Yang, Wei Wu, Bo Sun — Tue, 31 Dec 2024 00:00:00 +0200

This study proposes a multi-objective optimization model for an Aircraft Flight Scheduling Problem (AFSP) for assigning a set of aircraft located at different airports to conduct all flight trips. The proposed model features each flight trip with its own special aircraft type and fuzzy flight time. Moreover, a flight trip with a small aircraft being covered by a larger one is fully accounted for in the model. The model can effectively reduce the number of aircraft and achieve the minimum total idle time for adjacent flight trips covered by an aircraft. A novel heuristic algorithm based on the Non-dominated Sorting Genetic Algorithm (NSGA-II) is further designed to yield meta-optimal solutions efficiently for such a Non-deterministic Polynomial (NP) problem. Finally, a real airline scheduling example in China is conducted using CPLEX and the proposed heuristic algorithm to evaluate the difference between the proposed and traditional models. The results show that the given scheduling problem effectively enhances the operational efficiency of the aircraft fleet.

First published online 28 January 2025