A Constructive Framework for the Preventive Signalling Maintenance Crew Scheduling Problem in the Danish Railway system

In this paper we consider the problem of planning preventive maintenance of railway signals in Denmark. This case is particularly interesting, as the entire railway signalling system is currently being upgraded to the new European Railway Traffic Management System (ERTMS) standard. This upgrade has significant implications for signal maintenance scheduling in the system. We formulate the problem as a multidepot vehicle routing and scheduling problem with time windows and synchronisation constraints, in a multiday time schedule. The requirement that some tasks require the simultaneous presence of more than one engineer means that task synchronisation must be considered. A multi-stage constructive framework is proposed, which first distributes maintenance tasks using a clustering formulation. Following this, a Constraint Programming (CP) based approach is used to generate feasible monthly plans for large instances of practical interest. Experimental results indicate that the proposed framework can generate feasible solutions and schedule a monthly plan of up to 1000 tasks for eight crew members, in a reasonable amount of computational tim

A hybrid Constraint Programming/Mixed Integer Programming framework for the preventive signaling maintenance crew scheduling problem

This research has been carried out as part of the PhD research project funded by Technical University of Denmark and Banedanmark company which is responsible for the operation and maintenance of the Danish railway network. This work has been partially funded by the DAASE project, EPSRC programme grant EP/J017515/1

A mesoscopic model for inter-yarn friction

Friction between yarns is a crucial phenomenon in fabric manufacturing processes, and it becomes more complex when using lubrication agents to improve processing. This work presents an experimental investigation of the frictional behaviour of different combinations of yarns under dry and wet conditions, as occurring in overbraiding processes. The experiments were designed to maintain a constant yarn tension, and subsequently also a constant normal force and contact area during the test. Both the inter-yarn angle and the normal force significantly influence the friction coefficient. The additional contribution of the capillary force results in consistently higher friction coefficients for the water-lubricated yarns compared to the dry yarns. An anisotropic friction model is proposed to capture the influence of the inter-yarn angle, normal force, and capillary effects observed during the experiments. The model shows that the friction follows Amontons’ friction at high external normal forces and Howell’s friction at moderate normal forces