HBI Haerter AG, headquartered in Zurich, Switzerland, is a leading firm for engineering consultancy in the field of tunnel ventilation, prediction of emissions, safety issues as well as the aerodynamics and thermodynamics of road and rail tunnels.
In public transport, recent efforts focus on the reduction of journey time and the impact on the environment while increasing passenger comfort. Tunnels allow for a more direct routing and reduce the noise emission. Accentuated by the increased speed of travel, the pressure changes generated at the entrance and exit of a tunnel are of great importance for the environment and passenger comfort. Furthermore, the boundary layer development along the train has an impact on the contact forces of the pantograph towards the catenary.
It is important and required by regulation to validate the design parameters with measurements on and in the vehicle. The instrumentation of a full-size train is challenging both due to its size (typical lengths are 200m), accessibility (high voltage safety regulations) and the harsh environment (rain, snow, electromagnetic environment, etc.).
HBI commissioned streamwise with the development of a wireless sensor system for full-scale public transport applications to increase the measurement capability while simplifying the installation. The approach is to have a set of battery-powered and time-synchronized sensing modules that can be mounted easily anywhere on the vehicle and can be operated and monitored wirelessly. Without wires, the sensors can be placed with more freedom (especially in the high-voltage environment of the train pantrograph) and with minimal effort. The possibility of putting the modules to sleep allows for an installation several days ahead of the actual measurement campaign. The data can be logged on-board of each module in case any temporary connection loss occurs.
To maintain a high level of flexibility, a wireless communication module capable of handling communication, data-logging and power distribution was developed. The basis module can be equipped with any sensor devices capable of communicating on a digital bus. Besides a modular design, emphasis was put on size and power consumption. The modules communicate over a radio network and can be put into sleep mode to minimize power consumption or data acquisition mode via dedicated software. For its first application on the occasion of a measurement run with an ICE S train, a module equipped with pressure sensor and Pitot-static tube was fitted to the pantograph. The system mounted 12 h prior to the measurements and activated over radio operated without any problems and recorded velocity data at 100 Hz over 24 h. The increase in sensor and mounting options while reducing time and cost of installation allows to run more tests with more data points and therefore improves the understanding of the physical phenomena involved.