Mechatronic guidance of rail vehicles through switches and crossings to enable vehicle-based switching
thesisposted on 12.02.2019 by Nabilah Farhat
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
The research presented in this thesis demonstrates the theory that a mechatronic rail vehicle could be used on conventional switches and crossings (S\&Cs) to reduce wear. Railway track switches withstand high vertical and lateral forces leading to wear and damage. This necessitates a disproportionately high level of maintenance of over 10 \% of total maintenance costs, despite accounting for less than 0.1 \% of the network length. Mechatronically-guided rail vehicles are of paramount importance in addressing the increasing interest in reducing wheel-rail wear across the network and improving guidance and steering. Conventional passively-guided rail vehicles are limited by the mechanical constraints of the suspension elements. Currently, a typical rail vehicle suspension needs to be sufficiently stiff to stabilize the wheelsets while being complaint enough to negotiate curved track profiles. The suspension is therefore a compromise for the contradictory requirements of curving and stability. In mechatronic vehicles, actuators are used with the conventional suspension components to provide pseudo stiffness or damping forces needed to optimise a vehicle for a wide variety of scenarios, which can be positive or negative. This means that the vehicle is not reliant on a sub-optimal combination of passive components. Previous research in the area of mechatronic rail vehicles has shown the performance improvement in different straight or curved track profiles compared to a conventional vehicle. In this thesis, three vehicle configurations discussed previously in the literature, are evaluated on several different track profiles. These are the secondary yaw control (SYC), actuated solid-axle wheelset (ASW) and driven independently-rotating wheelsets (DIRW) steering mechanisms. The vehicle models are implemented in a multi-body simulation software Simpack to obtain high fidelity simulations that are comparable to a real rail vehicle. The DIRW vehicle showed the best performance in terms of reduced wear and minimal flange contact and was therefore chosen for studying its performance on a conventional S\&C. The DIRW vehicle was simulated on a C switch which is the most common on the UK mainline and on a high speed H switch. The results show that the DIRW vehicle gives a significant reduction in wear and reduces flange contact on the through and diverging routes of both S\&Cs. This proves the theory that active vehicles could be used to reduce impact forces at conventional S\&Cs. This could be an intermediate step towards a longer term vision of having a track switch without any moving parts where the switching is vehicle-based instead of track-based. Ultimately, if active elements on the vehicle could fully control the route while the track switch was completely passive i.e. had no moving parts, the reliability of the railways as a transport system would increase significantly. The technology could be combined with electronically-coupled vehicles which could form longer trains on busier routes and decouple to serve intermediary routes.
- Mechanical, Electrical and Manufacturing Engineering