Closer running - railway capacity analysis and timetable improvement

Sufficient railway capacity can deliver enhanced reliability, customer experience and better revenue outcomes. Through qualitative and quantitative analysis, the result shows that it is not appropriate to try to improve capacity by changing train speed and braking rate as they are both limited by physics. Also, train length has a minor negative impact on the line capacity, even though passenger capacity can be increased significantly by coupling more carriages. So, optimising operational strategy is the reasonable and achievable approach to capacity improvement. While running at different speeds is an organisational problem without any upside, the research on an effective stopping pattern strategy is underdeveloped with potential benefits. Therefore, a stopping pattern algorithm and a novel timetabling method are proposed in this thesis. These tools provide an approach to timetable improvement and future dynamic (re-)scheduling to handle unexpected delays and failures rapidly in a heavily trafficked area. Meanwhile, combining relative braking distance approach and moving block system, an advanced signalling system concept is introduced, namely, the Optimised Headway Distance Moving Block. The simulation shows that reducing the technical headway in line with the principles of it could increase capacity by nearly 60% compared to the traditional moving block system

The application of active control in railway pantographs

Pantographs are essential elements of modern electric trains, coupling the train to the overhead electric lines in order to deliver a continuous supply of electrical energy to the vehicle. Undesired contact can cause excessive wear and poor train operation performance. In the worst case, this can eventually lead to dewirement incidents that can damage both the train and the overhead lines. Pantographs in operation today, are essentially passive devices. However, active pantograph design has the potential to significantly improve the robustness of the pantograph–catenary interaction, in order to deliver a continuous power transmission for electric trains. However, it is found that the model-based controllers of current active pantograph research are not properly validated, whereas those that are tested in the laboratory are not designed based on the model. This thesis proposes a new and complete design and test approach for active pantographs following the typical model-based control design process. A validated pantograph–catenary model and simulation framework are first developed, based on which a new (real-time-capable) disturbance-observer-based catenary model is proposed to improve the accuracy of active pantograph validation in simulation. It is advised that the proposed model should replace the classic time-varying lumped-mass catenary model in active pantograph validation. A variety of control laws, ranging from the classic control methods to the state-of-the-art sliding mode control, are applied to the active pantograph design. The goal of designing a closed-loop pantograph system is to control the contact force by providing the measured contact force (i.e., output feedback), so as to make the contact force closer to the desired magnitude and thus reduce fluctuations. The active pantographs designed based on the linearised pantograph–catenary model have been demonstrated to be effective in reducing contact force fluctuation when validating with accurate catenary models. Through the model-based active pantograph design approach, a novel frame-actuated active pantograph prototype (controlled by pneumatic pressure) is designed and tested with a hardware-in-the-loop experiment. The designed active pantograph in the laboratory can reduce the contact force fluctuation as expected at the design and simulation stages. It is recommended that more refined modelling approaches would be beneficial in delivering better control performance in the active pantograph

Disturbance Observer-Based Sliding Mode Controller for Regulating Pantograph–Catenary Contact Force

For most electrified railways, pantographs play a vital role in transmitting energy from overhead line to vehicles, and therefore a stable and continuous contact behavior is required. This paper proposes a disturbance observer-based sliding mode controller (DO-SMC) for the problem of pantograph–catenary contact force regulation. The simulation results show that the DO-SMC with a chattering alleviation approach can effectively reduce contact force fluctuation through a reasonable control input. <br/

Genetic Mapping of a Candidate Gene <i>ClIS</i> Controlling Intermittent Stripe Rind in Watermelon

Rind pattern is one of the most important appearance qualities of watermelon, and the mining of different genes controlling rind pattern can enrich the variety of consumer choices. In this study, a unique intermittent rind stripe was identified in the inbred watermelon line WT20. The WT20 was crossed with a green stripe inbred line, WCZ, to construct F2 and BC1 segregating populations and to analyze the genetic characterization of watermelon stripe. Genetic analysis showed that the intermittent stripe was a qualitative trait and controlled by a single dominant gene, ClIS. Fine mapping based on linkage analysis showed that the ClIS gene was located on the 160 Kb regions between 25.92 Mb and 26.08 Mb on watermelon chromosome 6. Furthermore, another inbred watermelon line with intermittent stripe, FG, was re-sequenced and aligned on the region of 160 Kb. Interestingly, only two SNP variants (T/C, A/T) were present in both WT20 and FG inbred lines at the same time. The two SNPs are located in 25,961,768 bp (T/C) and 25,961,773 bp (A/T) of watermelon chromosome 6, which is located in the promoter region of Cla019202. We speculate that Cla019202 is the candidate gene of ClIS which controls the intermittent stripe in watermelon. In a previous study, the candidate gene ClGS was proved to control dark green stripe in watermelon. According to the verification of the two genes ClIS and ClGS in 75 watermelon germplasm resources, we further speculate that the ClGS gene may regulate the color of watermelon stripe, while the ClIS gene regulates the continuity of watermelon stripe. The study provides a good entry point for studying the formation of watermelon rind patterns, as well as providing foundation insights into the breeding of special appearance quality in watermelon