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In conventional system modeling, some constitutive laws governing the performance of a major subsystem must be derived by testing existing hardware. However, if a system model is to be employed in the early stages of vehicle development, then separate models are required to generate the necessary subsystem constitutive laws strictly from basic design parameters and very simple component tests. This paper demonstrates how a computer model can generate the same complex kinematic data generated by a test for a vehicle suspension subsystem, and how these results can be integrated with a system-level, vehicle ride model. The suspension model presented is constructed primarily from design parameters, with some use of easier-to-obtain empirical data (such as load/deflection relationships of the jounce bumpers). This paper also discusses an improved approach to modeling the coil spring in a double A-arm suspension.

The Vehicle Handling Model (VHM) is representative of a new type of vehicle dynamics programs which can be easily used on a personal computer by vehicle development engineers. It consists of a simulation kernel which solves the vehicle equations of motion and a hypertext GUI which controls the model data input, execution, and post processing. The vehicle model has 5 DOF, including the vehicle lateral, vertical, yaw, pitch, and roll motions. The simulation also includes suspension compliance, a simple non-linear tire model, a wind gust model and a human driver model to provide realistic vehicle and steering inputs. The simulation program was generated by AUTOSIM which uses a high level description of the system to generate Fortran source code. The GUI allows an engineer to setup the model, run the analysis, and display the results with just a few clicks of the mouse.