Optimization of the Lateral Stability of Rail Vehicles

Abstract

The lateral stability of a rail vehicle is optimized using a combination of multibody dynamics, sequential quadratic programming, and a genetic algorithm. Several steps are taken to validate this integrated approach and to show its effectiveness. First, a hand-derived solution to a 17 degree of freedom linear rail vehicle model is compared to the simulation results from the A'GEM multibody dynamics software. Second, the calculation of the 'critical speed' (above which a rail vehicle response becomes unstable) using sequential quadratic programming is validated for a specific example. In the process, the existence of sharply-discontinuous 'cliffs' in the plots of critical speed versus suspension stiffnesses are identified. These cliffs, which are due to switching of the least-damped mode in the system, greatly hinder the application of gradientbased optimization methods. Two methods that do not require gradient information, a genetic algorithm and the Nelder-Mead's Simplex algorithm, are used to optimize the critical speed. The two algorithms and their results are compared. In recognition of the cliff phenomenon, the definition of critical speed is generalized to make it a more practical measure of lateral stability.

Sensitivity Analysis of Ride Behaviour of Indian Railway Rajdhani Coach using Lagrangian Dynamics

“…The values of existing parameters of a loaded Rajdhani coach of Indian Railway listed from Table 1. The values of creep coefficients for the wheel-track interaction have been taken from Yuping & McPhee [9]. The vertical PSD acceleration and lateral values for existing parameter values for Rajdhani coach are mentioned in Table 2 at certain frequencies within the frequency range of human comfort.…”

Stability and Eigenvalue Analysis of an Indian Railway General Sleeper Coach using Lagrangian Dynamics

“…The parameters of a loaded general sleeper coach, as listed inTable 1, are obtained from Indian Railways Research Department, Research Designs and Standards Organisation. The values of creep coefficients for the wheel-track interaction have been taken from Yuping & McPhee[3].…”

A magneto rheological hybrid damper for railway vehicles suspensions

“…where   Through a variable change, the system can be transformed into an ordinary differential equation system [6] which is treated using numeric methods: The equations (3) are employed both for the study of stability and the system's response using a numerical integration method of the movement equations, the Runge -Kutta method of 4 th order, for which a simulation software has been designed. To simulate the vehicle's response, the construction characteristics presented in Table 1 are utilized. As example, the response of the vehicle with the characteristics in Table 1, launched on a tangent track with periodic irregularities, running with 180 km/h -the maximal testing speed, is presented in figures 2 -4, indicating that the tracks' perturbations effect is slightly felt at the coach case level, as opposed to the bogie and axles where it persists during the coach's circulation.…”

“…The conventional suspension system for a passenger vehicle usually has two levels: the axle's suspension, stiffer, to provide safety and the suspension of the carbody, softer, to offer best ride quality [2]. Having in view the importance of the lateral oscillations phenomenon numerous authors have dedicated studies to this issue [3][4][5][6][7][8][9][10][11]. There are possibilities to increase vehicle's speed by an appropriate design of the passive suspension but this approach proves to have limits.…”