New Dynamics Model for Rail Vehicles and Optimizing Air Suspension Parameters Using GA


Department of Mechanical Engineering,Sharif University of Technology


In this paper, a complete four axle rail vehicle model with 70 Degrees Of Freedom (DOFs)
is addressed, which includes; a carbody, two bogies and four axles. In order to include track irregularity
e ects on vehicle behavior, a simpli ed track model for a straight line is proposed. As the performance
of the suspension components, especially for air springs, has signi cant e ects on rail-vehicle dynamics
and the ride comfort of passengers, a complete nonlinear thermo-dynamical air spring model which is
a combination of two di erent models is introduced and then implemented in the complete rail-vehicle
dynamics. By implementing the Presthus formulation [1], the thermo-dynamical parameters of an air
spring are estimated and then tuned, based on the experimental data. E ects of air reservoir volume and
connecting pipe length and diameter on system performances are investigated. For improving passenger
comfort during their trips, air suspension parameters of the modeled rail vehicle are tuned to minimize the
Sperling ride comfort index. Results showed that by modi cation of air suspension parameters, passenger
comfort is improved and the ride comfort index is reduced by about 10%. The Genetic Algorithm (GA)
optimization method is also used to optimize air suspension parameters. Results showed that improved
air suspension con gurations are more practical, compared to optimized ones.