Type of Document Master's Thesis Author Mohan, Anant Author's Email Address Anant.Mohan@framatome-anp.com URN etd-06252003-143151 Title Nonlinear Investigation of the Use of Controllable Primary Suspensions to Improve Hunting in Railway Vehicles Degree Master of Science Department Mechanical Engineering Advisory Committee
Advisor Name Title Ahmadian, Mehdi Committee Chair Ghorashi, Mehrdaad Committee Member Hendricks, Scott L. Committee Member Keywords
- Rail Vehicles
- Lateral Stability
- Semi-Active Suspension Control
- Hopf Bifurcation
Date of Defense 2003-06-20 Availability unrestricted AbstractHunting 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 eventual physical damage to wheels and rails.
A comprehensive study of the lateral stability of a single wheelset, a single truck, and the complete rail vehicle has been performed. This study investigates bifurcation phenomenon and limit cycles in rail vehicle dynamics. Sensitivity of the critical hunting velocity to various primary and secondary stiffness and damping parameters has been examined.
This research assumes the rail vehicle to be moving on a smooth, level, and tangential track, and all parts of the rail vehicle to be rigid. Sources of nonlinearities in the rail vehicle model are the nonlinear wheel-rail profile, the friction-creep characteristics of the wheel-rail contact geometry, and the nonlinear vehicle suspension characteristics. This work takes both single-point and two-point wheel-rail contact conditions into account.
The results of the lateral stability study indicate that the critical velocity of the rail vehicle is most sensitive to the primary longitudinal stiffness. A method has been developed to eliminate hunting behavior in rail vehicles by increasing the critical velocity of hunting beyond the operational speed range. This method involves the semi-active control of the primary longitudinal stiffness using the wheelset yaw displacement. This approach is seen to considerably increase the critical hunting velocity.
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