Suspension spring parameter´s optimization of an Indian Railway freight vehicle for better ride quality

Better ride quality of vehicle is the need of trains for damage free transportation of goods. Ride quality measures in terms of ride index. Lower ride index means better ride quality. Ride index improves with the effectiveness of suspension system. The secondary suspension system has snubber, outer and inner springs. Optimum wire diameter of suspension springs improves the ride index of freight vehicle. In the present study 70 degrees of freedom (DOF) model having 29 moving parts is considered for Multi Body Dynamics (MBD) analysis of a freight vehicle. The secondary suspension springs´ parameter i.e. wire diameters are selected as design variables to minimize the optimization function of Sperling´s ride index for BOXN wagon supported on CASNUB 22 HS bogies. The allowed deflection of springs, available clearance, constant stiffness and working height of springs are the factors for geometrical constraints. Genetic Algorithm (GA) tool of MATLAB R2009a is used as the optimization tool to find the possible wire diameter sets of suspension springs. The ADAMS/Rail software is used to find optimum wire diameter values of springs for ride index minimization. The new set of springs´ wire diameters as result, gives the idea to improve ride index value.