Optimization of dynamically sensitive parameters of Linke Hofmann Busch coach considering suspended equipment using design of experiment

Abstract

The high speed coach running on irregular track is always accompanied by inferior comfort for the passengers. The optimal design of coach parameters improving comfort level can be achieved through response analysis. The present study is concerned with the optimization of Linke Hofmann Busch rail coach design parameters to augment comfort level. The coach body and bogie frame under four degrees of freedom are modeled with the finite element method to obtain dynamic parameters of the coach, that is, eigenvalues and eigenvectors. The sensitivity analysis based on partial derivatives against frequency response function displacement with respect to various design parameters is conducted, and most influential coach parameters are optimized through computer experimentation using central composite design and response surface methodology of design of experiment (DOE). Using modal parameters obtained as above and Indian Rail Road power spectral density of track irregularities, both vertical and lateral responses are determined at vicinity to the center mass of coach body in a 0.1– 40 Hz frequency range of interest. Results conclude that peak vertical responses occur in 0 – 10 Hz, whereas peak lateral responses fall at still lower frequency representing long wavelength irregularities of track that causes discomfort to vehicle riders. Findings of the research work embodied herein reveal that the left end bio toilet tank mass has least effect on response. Also, these findings suggest scope for further attainment in comfort level by computer experimentation for combinations of three coach design parameters (wheel base, equivalent primary, and secondary suspension stiffness) on minimizing the response level without altering the basic design of the coach model. The present paper represents a significant move forward on the dynamic analysis of coach body considering suspended equipment, sensitivity analysis through mathematical approach rather than step parametric variation, and its optimization through DOE, which have not been addressed earlier. The outcome of the paper may help rail coach designers to modify coach design parameters for better comfort level, even in the low frequency range of operation.