A Multi Scalable Model Based On A Connexity Graph Representation
Free (open access)
L. Gely, G. Dessagne, P. Pesneau, F. Vanderbeck
Train operations will be greatly enhanced with the development of new decision support systems. However, when considering problems such as online rescheduling of trains, experience show a pitfall laying in the communication between the different elements that compose them, namely simulation software (in charge of projection, conflict detection, validation) and optimization tools (in charge of scheduling and decision making). The main problem is the inadequacy of the infrastructure’s monolithic description and the inability to manage together different description levels. Simulation uses a very precise description, while optimization mathematical problem usually does not. Indeed, an exhaustive description of the whole network is usually counterproductive in optimization problems; the description must be accurate but should rely on a less precise representation. Unfortunately, the usual model representing the railway system does not garantee compatibility beetwen two different description levels; a representation usually corresponds to a given (unique) description level, designed in most case with a specific application in mind, like platforming. Moreover, further modifications that could improve performances or precision are usually impossible. We propose therefore a model with a new description of the infrastructure that permits to scrool between different description levels. These operations can be automated via dynamic aggregation and disaggregation methods. They allow to manage heterogeneous descriptions and cooperation between various tools using different description levels. This model is based on the connexity graph representation of the infrastructure ressources. We will present how to generate corresponding mathematical models based on ressource occupancy and will show how aggregation of ressources leads to aggregation of properties (e.g. capacity) that can be translated into mathematical constraints in the optimization problem.
modeling optimization railway operations traffic management infrastructure representation