Bombardier (Sweden)

In order to fulfil standards governing the development of safety-critical systems, requirements are often shown to be satisfied by means of traditional techniques such as system analysis and testing activities. While these techniques have been used for many years, issues can still arise due to weak tests, not fully covering all requirement scenarios; and due to misinterpretation of requirements, leading to futile test activities. Having simpler techniques to show that requirements are properly fulfilled and that depend less on thoroughness of the tester is beneficial. To tackle these issues, we present an analysis method together with an accompanying toolset, VrFy, implementing a novel technique to automate the detection of violations of require-ments. Monitors are generated automatically, and the risk due to misinterpretation of requirements is reduced by using a formal notation (LTL3). Compared to related work, the proposed technique is programming language agnostic and can identify the exact time when requirements are violated, supporting the end user to quickly spot the root cause. By means of a real-world use case in the railway domain, we show how the tool can be used to augment traditional verification techniques.

In this paper several discontinuous pulse width modulation methods (DPWM) are compared with space-vector pulse width modulation (SV-PWM) method. The comparisons are done based on measurements of motor magnetic noise and total drive losses for inverter switching frequencies from 500Hz to 4000Hz. It is concluded that using SV-PWM it is possible to reach lower magnetic noise on the traction motor without increasing the total losses significantly.

This paper considers the up-to-date railway RAMS (Reliability, Availability, Maintainability, and Safety) standards, i.e. EN 5012X series and FprEN 50657, and provides an overview of different definitions and requirements upon non-safety-related software in the context of those standards.

Safety requirements describe risk mitigations against failures that may cause catastrophic consequences on human life, environment and facilities. To be able to implement the correct risk mitigations, it is fundamental that safety requirements are defined based on the results issued from the safety analysis. In this paper, we introduce a heuristic approach to elicit safety requirements based on the knowledge about hazard's causes, hazard's sources and hazard's consequences (i.e. hazard's components) acquired during the safety analysis. The proposed approach is based on a Hazard Ontology that is used to structure the knowledge about the hazards identified during the safety analysis in order to make it available and accessible for requirements elicitation. We describe how this information can be used to elicit safety requirements, and provide a guidance to derive the safety requirements which are appropriate to deal with the hazards they mitigate.

ABSTRACTPareto optimisation of bogie suspension components is considered for a 50 degrees of freedom railway vehicle model to reduce wheel/rail contact wear and improve passenger ride comfort. Several operational scenarios including tracks with different curve radii ranging from very small radii up to straight tracks are considered for the analysis. In each case, the maximum admissible speed is applied to the vehicle. Design parameters are categorised into two levels and the wear/comfort Pareto optimisation is accordingly accomplished in a multistep manner to improve the computational efficiency. The genetic algorithm (GA) is employed to perform the multi-objective optimisation. Two suspension system configurations are considered, a symmetric and an asymmetric in which the primary or secondary suspension elements on the right- and left-hand sides of the vehicle are not the same. It is shown that the vehicle performance on curves can be significantly improved using the asymmetric suspension configuration. The Pareto-optimised values of the design parameters achieved here guarantee wear reduction and comfort improvement for railway vehicles and can also be utilised in developing the reference vehicle models for design of bogie active suspension systems.

The Silicon Carbide (SiC) MOSFET is considered to be the leading candidate for future 1.7 kV and 3.3 kV switches in 2-level voltage source converters (VSC) up to 2 MW. For those converters, short circuit (SC) in the dc-link loop can occur due to a number of reasons, e.g. faulty semiconductor modules, faulty gate drivers (GDs), or electro-magnetic interference (EMI). Termination of such SCs is important in order to protect components and reduce the damage in the converter box. This paper presents a new short circuit protection scheme based on a universal current-source GD principle without dedicated hardware components. The performance of the design is evaluated for SC in the dc-link loop under load conditions, called type II and type III. Moreover, measurement results are presented using the proposed GD connected to a 1700 V 300 A SiC MOSFET tested during SC type II and III at two different dc-link stray inductances, 30 nH and 100 nH, and at two different temperatures, 25 °C and 125 °C. The conclusions are that the proposed scheme is able to terminate both SC type II and III with fast reaction time, with low energy dissipation, with a margin of about 15 times below the destructive level for dc-link voltages and load currents up to 1050 V and 300 A respectively.

Track geometry quality has an important influence on the dynamic behaviour of the vehicles. Control of track geometry during the maintenance process and for the vehicle assessment (homologation) is necessary. Within the project, DYNOTRAIN methods for describing and assessing track geometry have been studied. Data from a comprehensive test campaign have been used to measure the effectiveness of different track geometry assessment methods. The vehicle behaviour has been studied by a multiple regression model with varying track geometry description methods. It had been shown that it is essential to include track geometry in the vehicle assessment process in a proper way. Depending on the assessment quantity and the vehicle type, the mostly used method in Europe (standard deviation in wavelength range 3–25 m) allows in combination with speed, cant deficiency and curvature the explanation of 20–80% of the total variation of the vehicle reaction. Other methods and ‘new’ alternative methods intended to model a typical vehicle behaviour mostly give no or only a small improvement.