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The major actions that move a highway vehicle are the forces and moments generated between the tire and ground; hence, the validity of a simulated vehicle test depends on the quality of both the tire model and the characterization of the ground surface. Other actions come from aerodynamic forces and moments that are affected by the relation of the vehicle body to the ground surface. This paper describes how the ground can be characterized to cover features of interest for most vehicle simulation scenarios involving pavements or other rigid surfaces. The 3D surface is built from tabular data related to specified properties of a road surface such as horizontal geometry, design elevation changes related to curves and drainage (i.e., banking of turns, cross-slope, ditches, etc.), elevation changes due to hills and other major grades, and disturbances and unique features such as bumps and holes. Broadband random-type road roughness is also included.

This paper describes modeling methods used in the commercial BikeSim® simulation package to represent alternative suspension design concepts. The modeling method used for automotive suspensions is applied to define generic suspensions for motorcycles. This method can represent multi-link suspension systems as well as traditional motorcycle suspensions with telescopic front forks and rear swing arms. Comparisons of two suspension types show a multi-link suspension can provide advantages over the traditional system for braking, acceleration (throttle), and cornering. Similar comparisons made with a chain-drive powertrain and a shaft-drive powertrain show less jacking with the chain-drive design. Although the math models include complex nonlinear motions, the computational efficiency supports fast operation; on a 2.8 GHz PC the simulation runs eight times faster than real time.

The use of computer simulation of vehicle dynamics as a development tool has come into its own over the past few decades. “Simulated” testing on a computer makes possible a degree of control and repeatability that allows the automotive engineer to determine the influence of design variables on different aspects of dynamic performance in ways that would be difficult or impossible by experimental methods. One of the software tools receiving wide acceptance for simulating trucks and combination vehicles is Truck-Sim™. The attraction of this program arises in part from its foundation of truck modeling methods developed at the University of Michigan Transportation Research Institute over the past two decades, and the use of an advanced graphical user interface to make the software both easy to understand and easy to use by design and development engineers.

The ability to accurately simulate vehicle dynamics behavior with a mathematical model is limited by the quality of the tire model. In fact, the tire is often the single most important component in determining correlation between a mathematical vehicle model and measured experimental results. Tire data for heavy trucks are more difficult and expensive to acquire than passenger car and light truck data, and, consequently, there has been little published experience testing or modeling these tires. This paper shows how the analysts can integrate heterogenous tire modeling methods into one coherent tire model suitable for the simulation of an over-the-road 18-wheel tractor-trailer configuration. The methods used in this paper are: Tire F&M modeling that represents the effect of tread wear, water depth, and speed, as well as combined longitudinal and lateral slip conditions.

This paper describes the architecture and use of a simulation graphical user interface (SGUI) that uses new (1990's) computer hardware and software concepts to provide an easy-to-use environment for simulating vehicle dynamics. The user interacts with windows, buttons, and pop-up menus, in a multitasking environment such as UNIX, Windows®, or Mac OS®. The SGUI reduces the level of computer expertise required of the user. Most information is shown in a graphic context, and “what if?” options are selected by clicking buttons and selecting from pop-up menus. The SGUI is organized as a data base of vehicles, vehicle parts, vehicle inputs, and simulation results. The organization makes it easy for users to assemble the component data needed to (1) simulate new systems, (2) run simulation programs automatically, and (3) view the results graphically. The SGUI is assembled from low-cost software components.