Stadler Rail using MSR Mini Data Loggers to quantify rail transportation comfort

Comparing subjective ride comfort with measured data

Rather than subjective opinions of passengers, what is needed is repeatable hard data to give a quantitative indication of ride quality. Miniature, autonomous simple-to-use universal data loggers are commercially available that feature built-in highly sensitive sensors for a wide variety of parameters, and, being small, are convenient and unobtrusive to install. MSR Electronics GmbH(Switzerland) manufactures tiny lightweight loggers that can sense almost any physical and electrical measurement: temperature, humidity, pressure, brightness, vibrations, or other voltage-based sensor output values. Stadler Rail has used MSR’s data loggers in many different applications, such as for the investigation of sudden vibrations or other vibration phenomena in rail vehicle operation. According to Stadler’s engineers, the qualities of these data loggers - autonomous, self-powered, very small, very large memory – make them ideal for mobile vibration studies, and they can also be rapidly deployed for spontaneous measurements. These tiny data recorders can be installed quickly and unobtrusively, and provide fast set-up vibration monitoring that can quantify actual train riding comfort. "Passenger requirements for ride comfort, which is greatly affected by vibration behavior, have grown increasingly stringent in recent years," said Tillmetz. "Our tests monitor three-axis acceleration on the vehicle floor, on the chassis, and in the center of the car with MSR data loggers, so we can provide objective measurements and thus give a numerical indication of ride comfort."

Stadler’s experiments have detected vehicle vibrations in a frequency range of up to 100 Hz. The MSR data logger’s sampling rate was set to 400 Hz by test engineer Kossmann, but the MSR165 logger could be set for as many as 1600 measurements per second. The loggers were quickly mounted to the carpet floor base with spikes for data recording. While some of the test journeys were made at constant speeds at up to 200 km/h for short durations, it was found to be even more beneficial to take measurements over a period of several days. For data analysis, the engineers exported the logged data via a csv file into FAMOS™ measurement evaluation software. The program was set to filter the signals according to the European standard EN 12299 Driver Comfort (or UIC 513) and an evaluation was made using frequency analysis, statistics and target comparisons. Although ride comfort measurements were made by the Stadler team on existing operational rail stock, they are now able with these loggers to investigate prototype vehicle behavior and also to provide initial inspection data on production vehicles, ensuring that specified customer comfort values are verified.

New model variants: Developing for the Future

According to Tillmetz and Kossmann, Stadler’s testing pushed the MSR data loggers to their limits. So the two engineers desired equipment with even more precise resolution for their measurement tasks. The 15 g sensor built into the MSR165 data loggers has an accuracy of ± 0.15 g with a resolution of 0.005 g. While this is sufficient for their applications in most cases, Kossmann thought that an accuracy of 0.003 g would be preferable. She could have specified a different type of MSR data logger – for instance, the MSR160 has four analog input channels for use with external custom sensors, to allow measurements exactly matching the desired measuring range of the sensors’ specifications. But since these sensors would have to be mounted externally, they would not be entirely suitable for most Stadler applications. According to MSR Electronics GmbH’s CEO Wendelin Egli, the 15 g measurement range of the MSR165 data logger design was because the logger was targeted at shock measurements. However, because of high demand for applications in the field of transport monitoring, MSR has now expanded the range of its available internal sensors up to 200 g, so stronger shock events with significantly greater forces can thus be recorded.

But what about logger variants with a smaller range? "Yes, we can do that!" says MSR’s Egli. "Vibration measurements with different measurement variants are an area in which we continue to expand." Since the MSR165 data logger is well established in the marketplace, he frequently gets requests from different fields of application and he sees many other potential application opportunities. "Our data loggers are designed for a niche market," said Egli, "but our entrepreneurial success means that, being close to our customers, we can better meet their custom requirements more effectively and faster than larger companies who are focused on the broader marketplace. If our customers want sensors with a different range, then we do our utmost to meet these desires." Stadler, for one, would welcome an MSR165 with a sensor with a smaller range. For now, as Kossmann and Tillmetz state, they use the existing MSR165 data logger with 15 g sensor because "it allows us quick and accurate statements as well as uncomplicated and time-efficient measurements, and at a reasonable cost."