Realtime Driving Simulation Using A Modular Modeling Methodology

The use of driving simulation in vehicle design and development is growing. For maximal benefit, vehicle models used in the driving simulator must be rapidly reconfigurable and easy to develop. To evaluate potential modeling concepts, vehicle dynamics and vehicle subsystems are developed using modular model components. These are integrated with simulator cueing subsystems, using the same modeling concepts, to build a complete driving simulator. It was found that the vehicle dynamics and the simulator could be reconfigured easily to meet user needs. INTRODUCTION Over the past twenty years offline vehicle dynamics simulations have been used extensively in the automotive industry. As computer performance increased vehicle dynamics applications were introduced into hardware in the loop simulation and operator in the loop simulation. To meet the needs of vehicle designers the complexity and fidelity of the vehicle dynamics used in operator in the loop simulation has been increasing. Currently, driving simulators are being used to assess the impact of new systems such as active safety devices, active suspension systems, and advanced powertrain designs [1][2]. To evaluate these systems in the simulator, a model of the new system must be introduced into the vehicle dynamics. The purpose of this paper to develop a modular modeling methodology that supports an easily reconfigurable realtime vehicle dynamics model into which new vehicle subsystems can be rapidly introduced. This modeling methodology will be applied to both the vehicle dynamics and the complete driving simulator to maximize the reconfiguration speed and model flexibility. The modular components will be developed and assembled in SimCreator a graphical simulation tool from Realtime Technologies, Inc. The vehicle dynamics model will be introduced first, followed by the rest of the simulator. VEHICLE DYNAMICS The vehicle dynamics model can be broken down into several modules: powertrain, brake system, steering system, tire model, and suspension [3][4]. Each of these systems can in turn be broken down into additional submodules. The vehicle powertrain for example has been modeled previously in the both EASY5 a graphical simulation package from Boeing Computer Services [5] and Simulink a graphical simulation package from the Mathworks, Inc. [6] using a modular approach. Ciesla [5] developed powertrain modules for the engine, torque converter, differential, gears, and tires. The selection of how the vehicle model is broken down into modules directly effects the reconfigurability of the simulation. For the current analysis, the top level of the vehicle dynamics was broken down into the components shown in Figure 1.