• Energy Research

Mobile Global Navigation Satellite System (GNSS) measurements carried out on the railway consist of using satellite navigation systems to determine the track geometry of a moving railway vehicle on a given route. Their purposes include diagnostics, stocktaking, and design work in railways. The greatest advantage of this method is the ability to perform measurements in a unified and coherent spatial reference system, which effectively enables the combining of design and construction works, as well as their implementation by engineering teams of diverse specialties. In the article, we attempted to assess the impact of using three types of work mode for a GNSS geodetic network [Global Positioning System (GPS), GPS/Global Navigation Satellite System (GLONASS) and GPS/GLONASS/Galileo] on positioning availability at three accuracy levels: 1 cm, 3 cm and 10 cm. This paper presents a mathematical model that enables the calculation of positioning availability at these levels. This model was also applied to the results of the measurement campaign performed by five GNSS geodetic receivers, made by a leading company in the field. Measurements with simultaneous position recording and accuracy assessment were taken separately on the same route for three types of receiver settings: GPS, GPS/GLONASS and GPS/GLONASS/Galileo in an urban area typical of a medium-sized city. The study has shown that applying a two-system solution (GPS/GLONASS) considerably increases the availability of high-precision coordinates compared to a single-system solution (GPS), whereas the measurements with three systems (GPS/GLONASS/Galileo) negligibly increase the availability compared to a two-system solution (GPS/GLONASS).

The paper proposes a novel approach to modeling electrified transportation systems. The proposed solution reflects the mechanical dynamics of vehicles as well as the distribution and losses of electric supply. Moreover, energy conversion losses between the mechanical and electrical subsystems and their bilateral influences are included. Such a complete model makes it possible to replicate, e.g., the impact of voltage drops on vehicle acceleration or the necessity of partial disposal of regenerative braking energy due to temporary lack of power transmission capability. The modeling methodology uses a flexible twin data-bus structure, which poses no limitation on the number of vehicles and enables modeling complex traction power supply structures. The proposed solution is suitable for various electrified transportation systems including suburban and urban systems. The modeling methodology is applicable i.a. to Matlab/Simulink, which makes it broadly available and customizable, and provides short computation time. The applicability and accuracy of the method were verified by comparing simulation and measurement results on an exemplary trolleybus system operating in Pilsen, Czech Republic. Simulation of daily operation of an area including four supply sections and maximal simultaneous number of nine vehicles showed a good conformance with the measured data, with the difference in the total consumed energy not exceeding 5%.

Electric rail vehicles use current collection system which consists of overhead contact line and a current collector (pantograph) mounted on the roof of a vehicle. A pantograph is equipped with contact strips, which slide along the contact wire, ensuring steady electric contact. Contact strips are made of carbon layer, fixed to an aluminum carrier. The carbon layer wears down due to friction. Using overly worn contact strips increases the rate of contact wire wear and, significantly, the risk of contact line damage. Therefore, thickness of carbon strips has to be inspected periodically. In previous work a 3D-scanning system has been proposed for recording data of contact strips when vehicles pass an inspection point on a railway line. However, the system has to be complemented with data analysis algorithm to estimate the thickness of the carbon layer. Data processing has to be performed quickly and automatically to prevent faulty pantographs from being used. The main difficulty of wear analysis is caused by diverse altitude and tilt of scanned contact strips. To determine the smallest thickness of carbon layer, the carbon surface data have to be normalized with respect to an aluminum carrier. The location and shape of the aluminum carrier can be extracted from the registered data. Due to the fact that the profile of the carrier is highly distorted, a robust Whittaker approximation algorithm has been proposed in order to deal with the noise and the missing data.

Construction and technical condition of current collectors is crucial to reliability and safety of railway transportation. According to the Technical Specifications for Interoperability railway vehicles in the European Union should be equipped with carbon contact strips. Excessive wear or defects of contact strips degrade the capability of undisturbed power transmission, cause faster wear of contact wire, and can even result in catenary rupture. The technical condition of contact strips is assessed manually during periodical services performed by rolling stock operators. However, rail infrastructure companies are also interested in pantographs inspection of the vehicles running within their network. A novel inspection system for current collectors contact strips is presented. The system uses a specialized camera and a laser line generator to scan the contact strips surface. The scanning is performed on a railway line, when a vehicle passes the inspection point. A prototype of the system was tested in the target conditions and sample scanning results were recorded. Basic algorithms for automatic analysis of contact strips wear were introduced. Accuracy and repeatability of the measurement were assessed. The potential of commercial implementation of the system was confirmed.