The Performance Monitoring Unit (PMU) is a real-time sensor that is easily mounted on the bogie, i.e. on the undercarriage-carrying wheelsets.
Each PMU is equipped with a GPS and an accelerometer that measures motion in three dimensions. These measurements give an acceleration profile for each part of the track. The data is processed with Artificial Intelligence methods that continuously analyze and classify signals into warning trends and defects for each acceleration profile.
Since the acceleration profile differs for different kinds of faults, the PMU can detect and interpret any fault arising. For example, it can discriminate between frozen brakes and a wheel flat. Railway Metrics and Dynamics has produced an extensive database of acceleration profiles for distinctive types of faults in different types of carriage and locomotive.
The systems detect and provide an alert concerning any fault arising on the locomotive or carriage – in real time. As the warning is given in good time before a major breakdown, damage can be avoided. The system also analyses and warns if damage has arisen on the track since the previous PMU passage.
Efficient wagon registration
The PMU can also be equipped with Near-Field Communication (NFC), which facilitates highly efficient wagon registration. Many companies use handwritten notes as a way to make sure that the wagons are positioned in the correct order before departure. With an NFC-equipped PMU, you simply scan each wagon with a smartphone instead.
The sensors communicate with each other, and with the main unit within the locomotive, through radio signals. The sensors also communicate with the cloud through any available internet connection – anything from GPRS to 4G.
The information from the system is presented in real time in a digital interface – a dashboard that is customised to suit each customer’s unique needs and is available via computer, tablet or smartphone. In addition to warning signals, the interface can also display utilisation and keep track of maintenance cycles.
Through the Railway Metrics and Dynamics app My Train, the driver also gets access to the train’s information in real time. Using the app the driver can add his or her own operational observations into the system.