Fotoohi A., Yousefi-Koma A.

Hunting is a very common instability exhibited by rail vehicles operating at high speeds. The hunting phenomenon is a self excited lateral oscillation that is produced by the forward speed of the vehicle and the wheel-rail interactive forces that result from the conicity of the wheel-rail contours and the friction-creep characteristics of the wheel-rail contact geometry. Hunting can lead to severe ride discomfort and eventually physical damage to wheels and rails. In this paper an active primary suspension is developed to improve Hunting in railway vehicles. The active suspension system consists of some actuators in both longitudinal and lateral directions on each bogie that control the yaw motion and lateral displacement of wheelset. Traditional model with passive primary suspension and model with additional active system have been analyzed and compared. The effects of suspension system on yaw motion and lateral displacement have been investigated in various rail conditions. Results show that semi-active suspension improves the Hunting and reduce wheelset displacements. All simulations were performed by integration of SIMULINK and ADAMS/Rail software packages.