Effects of Spring Stiffness on Suspension Performances Using Full Vehicle Models

Suspension system has significant influence on the passenger safety, providing comfortable ride, stability, and handling of the vehicle. The aims of the present research are to investigate and quantify the effect of spring weakness on suspension performance. This is based on a MATLAB simulation analysis of a seven degree-of-freedom (7-DOF) model for a full vehicle. In the simulation, the suspension faults were seeded by reducing the spring stiffness by 25%, 50% and 80%. The model was validated using experimental data, collected by driving the vehicle across bumps. The simulation results for varying degrees of spring stiffness indicated that the ride comfort was decreased as the spring stiffness was increased for excitation frequencies close to resonant frequencies of the vehicle body (approximately 1 Hz). As spring stiffness was increased at excitation frequencies below 1 Hz, the suspension travel was reduced. Within the zone of resonant frequency of sprung mass, the deformation amplitudes were increased as the spring stiffness increased. Moreover, Fr equency Response Functions analysis has been used for fault detection of reduction of spring’s stiffness by 25%, 50% and 80%.