Investigation of low damped carbody oscillation for Korean high-speed EMU experimental train

Abstract

This study describes the low damped carbody oscillations of the HEMU-430X, a high-speed electric-multiple-unit experimental train of Korea. The HEMU-430X had already undergone a kind of hunting problem in the test period, but it was effectively suppressed through several measures and the test was finished successfully. However, recently, the HEMU-430X again experienced the similar but slightly different problem after its wheel profile was changed to XP55, which is widely used in high-speed trains in Korea. In this paper, the eigenbehavior and system damping ratio are analyzed using a linearized vehicle model to more systematically investigate the cause of the carbody oscillation of the HEMU-430X. The results show that the bogie lateral movement coupled with carbody upper sway has the least damping ratio in the case of the HEMU-430X and the magnitude of yaw directional constraints of the bogie plays an important role in causing the carbody oscillation. Parametric studies for suspension, equivalent conicity and creep coefficients are carried out. A solution is suggested and it is validated using field tests.

Suspension parameters for low-damped carbody oscillation of high-speed railway vehicle

“…As the vehicle model was linearized for small perturbations at equilibrium points, high-order terms were neglected, and the wheelset's roll motion was constrained by the equivalent conicity and lateral motion of the wheelset. 5 Thus, the linearized vehicle model has 17 DOFs (four wheelsets with two DOF, two bogie frames with three DOF, and one carbody with three DOF). Because the state-space equation of the linearized vehicle model has been studied by various researchers, [4][5][6]11,12 this study briefly introduces its configuration:…”

“…5 Thus, the linearized vehicle model has 17 DOFs (four wheelsets with two DOF, two bogie frames with three DOF, and one carbody with three DOF). Because the state-space equation of the linearized vehicle model has been studied by various researchers, [4][5][6]11,12 this study briefly introduces its configuration:…”

“…As the longitudinal stiffness of the primary suspension and the series stiffness of the yaw damper mainly affect the magnitude of the yaw directional stiffness of the bogie, which is important for reducing the carbody oscillation, 5 these two suspension properties should be included in the design variables. However, to secure the critical speed for the worn wheel, other suspension properties such as the lateral stiffness of the primary suspension, and damping coefficients of the yaw and lateral dampers can also be considered.…”

“…2 It has been recognized that this phenomenon occurs at relatively low vehicle speeds, and disappears at high speeds beyond the resonance zone 3 ; however, in some countries where high-speed railways are widely operated, it is reported that the deterioration of ride quality owing to the carbody oscillation also occurs in high-speed vehicles even when they are traveling above mid-speeds. [3][4][5] This carbody oscillation can be suppressed by increasing the damping ratio of the coupled mode, and several measures have been introduced based on modified suspension properties. [3][4][5][6] However, these suspension properties affect the lateral stability, safety, curving performance, and ride comfort, and some of their performances are conflicting; they should be carefully designed to balance each performance.…”

“…[3][4][5] This carbody oscillation can be suppressed by increasing the damping ratio of the coupled mode, and several measures have been introduced based on modified suspension properties. [3][4][5][6] However, these suspension properties affect the lateral stability, safety, curving performance, and ride comfort, and some of their performances are conflicting; they should be carefully designed to balance each performance. As highspeed railway vehicles typically operate on large curves, their curving performance is generally not a priority.…”