Sensitivity Analysis of Ride Characteristics of Four-Wheel Vehicle under Random Road Surface Undulations

The vehicle performance is examined based on its specific performance indices. These specific performance indices include stability, ride comfort, steering ability, etc. The vehicle ride comfort is an important factor of vehicle quality and receiving large attention. The majority of previous investigations are focused on vertical vibration analysis of the sprung mass of the vehicle subjected to vertical excitations from the road surface. This study evaluates the ride characteristics of a coupled vertical-lateral 13 degrees of freedom (DoF) full-car model of a light passenger four-wheel vehicle developed with the Lagrangian method. The random vertical and lateral undulations of the road surface have been accounted for in the analysis and represented by the Power Spectral Density (PSD) function. The vehicle ride is assessed based on the International Organization for Standardization (ISO) 2631-1 annexure and the vehicle overall ride index is determined. The vehicle’s vertical-lateral dynamics are evaluated based on a 1-8 hr comfort boundary laid in ISO specifications. In a further study, the vehicle inertial, suspension, and geometric parameters, which critically influence the vertical and lateral ride, have been identified. The vehicle’s vertical ride covers a relatively wide band of frequencies under the discomfort level of ISO comfort boundaries and is found to be more crucial as compared with the lateral ride; the recommendations are made to improve the vertical ride in preference. The total value of weighted Root Mean Square (RMS) acceleration of the vehicle determined from the present analysis is 2.47 m/s², and the ride comfort index was found to be in the range “very uncomfortable” specified in ISO 2631-1 annexure. The present study provides a basis for the vehicle designer for the modification in the vehicle parameter values to obtain optimum ride comfort.