Abstract
Keywords - Seven Degree of Freedom vehicle model (7DOF), Multi-Input Multi-Output vehicle model (MIMO), Chassis Design Factors (CDF), Lagrange Equation formulation, Linear Time Invariant formulation (LTI)
ABSTRACT
Simulating the modal response of a seven degree of freedom (DOF) vehicle model has been the main objective behind the work presented in this paper. An independent front suspension, and a dependent rear suspension SUV vehicle has been the model analyzed throughout the study. Starting from the Kinematics and Kinetics of the 7DOF vehicle model, the seven equations of motion describing the model have been developed through Lagrange mathematical approach. The study goes on through transforming the equations of motion to the linear time invariant (LTI) form yielding fourteen state-space equations.
The analysis has been conducted using a MATLAB ® script specifically developed to perform a parametric analysis on the vibration response in the time domain of a 7DOF vehicle relative to the variation of several chassis parameters. Throughout the study, the dynamic response of the baseline design has been demonstrated relative to the inputs at the road-tire interface. The second stage of the study has been to investigate ways to enhance the ride quality, stability, and occupant safety by surveying the role of chassis parameters such as the anti-roll bar, weight distribution ratio, vehicle dimensions, suspension stiffnesses and damping factors.
The uniqueness of this research is the implementation of classical mechanics and modern dynamics systems using state-space formulation, which is appropriate for a Multi-Input Multi-Output
(MIMO) system. The effect of Roll motion on ride quality is also investigated. The input data is a realistic SUV data. The research shows that choosing the appropriate fitness between weight, location of C.G., weight distribution, stiffness and dimensions are affecting the ride quality significantly, and there is a need to satisfy some magic numbers in the design cycle of a motor vehicle on the highway for good ride performance.