Improve Hunting of a Railway Vehicle Using Semi-Active Primary Suspension

Hunting is a very common instability phenomenon in rail vehicles operating at high speeds. The hunting phenomenon is a self excited lateral oscillation produced by the forward speed of the vehicle and the wheel-rail interactive forces caused by 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 eventual physical damage to wheels and rails. This research is conducted to demonstrate advantages of semi-active primary suspension in railway vehicle for control of hunting phenomenon. Semi-active suspension consists of some actuators on each bogie located in primary suspension position in addition to vertical passive dampers. A simple on-off switching is used here and the actuator force is determined regarding to wheelset displacement. An integration of a control design tool, i.e. MATLAB, together with a tool for railway vehicle simulation, i.e. ADAMS/Rail is utilized for modeling and control design simultaneously. Analysis has been performed on a traditional bogie model with passive primary suspension and on a new bogie model with semi-active suspension. The effects of semi-active suspension system on lateral displacement and yaw motion of wheelset have also been investigated. Results show that the semi-active suspension improves the stability by controlling displacement magnitude.