Research on mechanism and control methods of carbody chattering of an electric multiple-unit train

Carbody chattering is an abnormal vibration that severely deteriorates the ride quality of a railway vehicle. However, systematic studies on the mechanisms and control methods of carbody chattering are inadequate. Hence, in-situ tests, wheel and rail profile tests, modal parameter tests, and root locus analyses were conducted for an electric multiple-unit train to study the carbody chattering mechanism. Results show significant concave wear on wheel treads that have not yet met their wheel-turning mileages. When the vehicle moves from a carbody non-chattering to a chattering section, the wheel–rail contact positions are scattered and jumping is observed; then, the wheel–rail contact conicity increases rapidly, causing the modal damping ratio of the bogie hunting motion to reduce to 0, the bogie to change from stable to critical-unstable state, and bogie hunting motion frequency to increase close to the modal frequency of the carbody diamond-shaped deformation, thereby triggering synchronous movement. This amplifies the modal vibration, causing carbody chattering. Therefore, three control methods are proposed for carbody chattering—turning worn wheels; grinding rail profiles in the carbody chattering section; and synchronous optimisation of the primary longitudinal and lateral positioning stiffness, node stiffness, and damping coefficient of the yaw damper—according to the multi-objective synchronisation optimisation method to improve operational stability and ride quality. Test results show that all three methods effectively control carbody chattering; compared to the original vehicle, the amplitude of carbody chattering acceleration at 10 Hz can be reduced by 90%, 40% and 60% for the three methods.