7. Wireless communication network for monitoring of freight car condition
- A system using a 920MHz band has been proposed, in response to the need for information about the status of each freight car in a consist when train compositions are changed; the system automatically composes the network and sends it to the driver’s cab on the locomotive.
- This system is able to check the state of a freight car’s hand brake in approximately half the time required for a visual inspection, and can also be used to monitor freight car conditions.
Before freight train departs from a station, it is necessary to verify the release status of each freight car's hand brake for safety purposes. Today, these checks are carried out visually, which time is consuming when having to check a whole rake of freight cars. In order to facilitate this verification work from the locomotive or the control centre, a network of wireless sensors between each freight car could be built, however, this would require a flexible means of communication which could adapt to train composition being modified and distinguish between freight cars on different train compositions. It is also necessary to take into account possible interference with other wireless networks and the electromagnetic environment.
A proposal was therefore made for a wireless communications network using a 2.45GHz band for the network between cars on the same train and a 920MHz band for communication with other cars. A method was developed to build a network offering the necessary flexibility to allow changes in train composition (Fig. 1). The method employs the space beneath the freight cars as the propagation path, then, while the quality of data transmission is verified at each relay device the network builds automatically and collects data. Furthermore, each relay device automatically selects the path requiring the minimum number of transmissions thereby controlling battery consumption by the network connecting cars on the same train.
A prototype was installed on a locomotive and freight cars. Results of tests revealed that the direct transmission distance is approximately 100m. The test assumed a consist of 26 freight cars, and results also showed that it took 6 and half minutes for the network to set itself up and to collect data.
The new system cuts the visual inspection time needed to check freight car hand brake status by about half, and feeds this information back to the driver's cab. In addition it is hoped that this method will help prevent failures to visually identify non-released brakes.
This system can be adapted to general train vehicles, and can also be used for data transmission between vehicles during operation, offering a means of communication to collect vehicle data.