Monitoring an axle of a railway vehicle

A method of monitoring an axle of a wheelset assembly of a railway vehicle, the wheelset assembly comprising an axle mounted between opposed wheels, each wheel being fitted to a respective opposite end of the axle, the method comprising the steps of:

• a. providing a wireless sensor node fitted to the wheelset assembly, the wireless sensor node comprising a vibration energy harvester for converting mechanical energy from vibration in the wheelset assembly into electrical energy, a sensor for measuring a parameter, wherein the sensor is an accelerometer mounted to an end of the axle, and a wireless transmitter for wirelessly transmitting the measured parameter or data associated therewith;
• b. while the railway vehicle is in motion, the vibration energy harvester receiving input vibration energy which is converted into electrical energy to power the wireless transmitter;
• c. while the railway vehicle is in motion, measuring an axle percussion resonant vibration frequency, due to impacts on the wheelset assembly form a wheel/track interface, using the sensor, wherein the sensor measures resonant vibration along the axle and the resonant vibration occurs at the resonant frequency of the wheelset assembly which comprises the axle mounted between the opposed wheels;
• d. while the railway vehicle is in motion, wirelessly transmitting the measured axle percussion resonant vibration frequency or data associated therewith using the wireless transmitter;
• and
• e. processing the measured axle percussion vibration frequency of the resonant vibration along the axle to produce processed data.