Active Control of Lateral Vibrations in a Railway Carriage

As trains are continually designed for higher and higher speeds the problems of railway carriage vibration are on the increase. Lateral vibrations in a railway carriage are noticeable to passengers if the vibration frequencies are lower than approximately 20 Hz. Below this frequency discomfort is a common problem for the passengers and below approximately 1 Hz motion sickness is a problem. The passive solution of stiffening the carriage chassis to shift the vibrational frequencies higher up results in inflated manufacturing and running costs, and opposes higher travel speeds due to increased weight. Semi-passive solutions such as modifying the structural dynamics of the carriage body by decoupling heavy underfloor equipment do not reduce the vibrations sufficiently. However, by appending a multi-reference feedforward active vibration control system, one way expect a substantial reduction in the lateral vibration level. Using a dynamic computer model of a railway carriage simulating the lateral vibration, and using as input bogie acceleration data measured on a running train, multiple-input/single-output coherence spectra were shown to constitute a suitable set of reference signals for an active control system. Control simulations based on the Feedforward Multiple-Input/Single-Output Filtered-x LMS Algorithm are carried out using different reference signal combinations. The control results indicate lateral vibration attenuation on the order of 15dB at the objective frequency of 10Hz