Ingemar Persson

Co-simulation of a mechatronic system using Gensys and Simulink

The design of mechatronic systems for rail vehicles requires the implementation of modern software tools. Nowadays, it is common to use co-simulation for the creation of mechatronic models. This approach is usually based on the combination of two types of software – multi-body simulation packages for mechanical models and tools for simulation of electric, control systems, etc. The existing commercial codes (SIMPACK, VI-RAIL, VAMPIRE, UM) provide different approaches for co-simulation; however, they have a lot in common. The one thing that makes them very similar is the use of Simulink for co-simulation. In this paper, we propose a description of the client interface in Simulink for co-simulation with Gensys. The evolution of the proposed approach has been performed by means of a simulation of a simplified traction control system for a hauling locomotive running on straight track conditions.

Assessing track geometry quality based on wavelength spectra and track–vehicle dynamic interaction

This paper presents a study of assessing track geometry quality (longitudinal level and alignment) by the use of dynamic track–vehicle simulations and wavelength spectra analysis. Two simulation models are developed: one is based on the software package GENSYS, which provides realistic simulations of the nonlinear dynamic behaviour of a vehicle running on real track, and the other one is based on a newly developed linear track–vehicle model, which is suitable for effectively calculating wheel–rail forces for very long track sections. The linear model, first proposed in 1 2 to assess vertical track geometry quality (longitudinal level), is extended in the present paper to simulate lateral track–vehicle dynamic interaction and, thus, to assess lateral track geometry quality (alignment) as well. Numerical results are presented to compare the simulation results with online measurement and to demonstrate the possibilities of enhancing track quality assessment and maintenance by simulations of track–vehicle interaction.

Development of a real-time bogie test rig model based on railway specialised multibody software

The design of mechatronic systems of rail vehicles requires performing verification and validation in the real-time mode. One useful validation instrument is the application of software-in-the-loop, hardware-in-the-loop or processor-in-the-loop simulation approaches. All of these approaches require development of a real-time model of the physical system. In this paper, the investigation of the usage of the model of the locomotives bogie test rig created in Gensys multibody software has been performed and the calculation time for each time step has been analysed. The verification of the possibility of the usage of such an approach for real-time simulation has been made by means of a simple data transferring process between Gensys and Simulink through the TCP/IP interface. The limitations and further development issues for the proposed approach have been discussed in this paper.

Use of a genetic algorithm to improve the rail profile on Stockholm underground

In this paper, a genetic algorithm optimisation method has been used to develop an improved rail profile for Stockholm underground. An inverted penalty index based on a number of key performance parameters was generated as a fitness function and vehicle dynamics simulations were carried out with the multibody simulation package Gensys. The effectiveness of each profile produced by the genetic algorithm was assessed using the roulette wheel method. The method has been applied to the rail profile on the Stockholm underground, where problems with rolling contact fatigue on wheels and rails are currently managed by grinding. From a starting point of the original BV50 and the UIC60 rail profiles, an optimised rail profile with some shoulder relief has been produced. The optimised profile seems similar to measured rail profiles on the Stockholm underground network and although initial grinding is required, maintenance of the profile will probably not require further grinding.

New simulation model for freight wagons with UIC link suspension

The previous freight wagon model developed at KTH is able to explain many of the phenomena observed in tests. In some cases, however, simulated and measured running behaviour differ. Therefore, in this paper, a new simulation model is presented and validated with on-track test results. The performance of standard two-axle freight wagons is investigated. The most important parameters for the running behaviour of the vehicle are the suspension characteristics. The variation in characteristics between different wagons is large due to geometrical tolerances of the components, wear, corrosion, moisture or other lubrication. The influence of the variation in suspension characteristics and other parameters on the behaviour of the wagon on tangent track and in curves is discussed. Finally, suggestions for improvements of the system are made.

Using simulations for approval of railway vehicles: a comparison between measured and simulated track forces

Traditionally, the acceptance of railway vehicles with respect to vehicle dynamics such as safety of running has relied on the use of practical tests rather than on simulations. The track sections used in the tests are long, and the evaluation is based on statistical processing of the test data. Simulations, on the other hand, have more often been used for detailed analysis in specific shorter track segments in connection with, e.g., the vehicle design process. With new efficient track recording cars, new less time-consuming methods of handling measured track data and the development of faster computers new possibilities to use simulations also for statistical analysis arise. In this work, a comparison between track force measurements from tests with a Swedish Rc-locomotive and simulations on the same track using the statistical approach according to UIC 518 is done. In the example presented, there is a notable agreement between measurements and simulations.

On the use of second-order derivatives of track irregularity for assessing vertical track geometry quality

This paper studies the use of second-order derivatives of track irregularities (longitudinal level, LL) for assessing vertical track geometry quality. Both a single-degree-of-freedom and a three-DOF vehicle–track model are investigated in order to explain theoretically why from the aspect of vehicle–track dynamic interaction it is relevant to consider not only the amplitudes of LL but also their second-order derivatives (LL2). Simulation results are then presented to demonstrate that dynamic vertical track forces are more correlated with the second-order derivatives (LL2) than to the amplitudes (LL) themselves. A comparison of the power spectral density (PSD) spectra for typical track reveals that it is more convenient to use the PSD spectra for the second-order derivatives than for the amplitudes, as the curves for the second-order derivatives are flat within the short wavelength range. Finally, the practical use of derivatives within the maintenance management system in order to achieve improved assessment of track geometry quality is also discussed.

Implementation of a Wheel-Rail Temperature Model for Locomotive Traction Studies

ABSTRACT Calculation of the temperature in the contact zone at the wheel–rail interface is a very complex and important issue for multidisciplinary railway studies. The knowledge of temperature in the contact interface between two bodies, and with the possible presence of a third body interfacial layer, allows making informed judgments on processes in areas such as lubricant choice, wear estimation, life cycle prediction, etc. This paper focuses on development of a temperature modelling methodology in Gensys, and also presents its implementation for the study of temperatures at different contact points (top of rail, gauge corner, and gauge face contacts). In operational practice, all these mentioned contacts have different coefficients of friction which should be characterized as velocity and slip-dependent variables. To demonstrate the workability of the developed methodology, numerical experiments for a heavy haul locomotive equipped with a simplified bogie traction control system have been performed on curved track, where a locomotive has been operated under maximum traction forces and with longitudinal and lateral coupler forces attached in order to take into account train dynamics. Both new and worn rail profiles have been used. Limitations of the proposed methodology as well as proposed future work and further improvements are discussed.

Estimation of wheel–rail friction for vehicle certification

In certification of new rail vehicles with respect to running characteristics, a wide variety of operating conditions needs to be considered. However, in associated test runs the wheel–rail friction condition is difficult to handle because the friction coefficient needs to be fairly high and the friction is also generally hard to assess. This is an issue that has been studied in the European project DynoTRAIN and part of the results is presented in this paper. More specifically, an algorithm for estimating the wheel–rail friction coefficient at vehicle certification tests is proposed. Owing to lack of some measurement results, the algorithm here is evaluated in a simulation environment which is also an important step towards practical implementation. A quality measure of the friction estimate is suggested in terms of estimated wheel–rail spin and total creep. It is concluded that, tentatively, the total creep should exceed 0.006 and the spin should be less than 1.0 m−1 for the algorithm to give a good friction estimate. Sensitivity analysis is carried out to imitate measurement errors, but should be expanded in further work.

BODY STRUCTURE AND VEHICLE DYNAMICS

SUMMARY This paper is a presentation of aspects on car body design for mass transit vehicles and methods which has been evolved for the analysis of non-linear flexible railway vehicles by use of normal modes. In the end of the paper results from an experimental modal analysis are shown.