Dynamic modelling of an off-road vehicle for the design of a semi-active, hydropneumatic spring-damper system

Ride and handling simulation of a heavy off-road military vehicle was simultaneously performed using DADS software. A non-linear vehicle simulation model, complete with a total of 66 degrees of freedom, was developed. After adding constraints, joints and a driver model, 14 unconstrained degrees of freedom remained. Ride comfort and handling/stability evaluations were combined in a single simulation run by driving the vehicle over Belgian paving whilst simultaneously performing a double lane change handling manoeuvre. The aim of the study was to determine the "best" spring and damper characteristics for ride comfort and handling/stability respectively. These characteristics will be used to design a semiactive, hydropneumatic spring-damper, able to switch both spring and damper characteristics electronically between two discrete values. The simulation results indicated that, for best ride comfort, the suspension natural frequency should be in the region of 0.6 Hz while the damper characteristic should be reduced to a value between 20 and 50% of the baseline damper value. For best handling and stability, a suspension natural frequency of 2 Hz is required while the baseline damping should be doubled.