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In 2008 the Australian National Transport Commission (NTC) published a reference document titled Performance Based Standards Scheme - The Standards And Vehicle Assessment Rules [1]. This document describes a series of testing requirements known as Performance Based Standards (PBS) to be used for certifying truck configurations acceptable for the Australia highway system. The PBS specification allows for both in-vehicle testing and numerical analysis using simulation tools such as TruckSim [2]. Several of the PBS tests require a Low-Speed 90° Turn, used to measure tracking behavior and tire friction utilization. This test presents an unusual simulation challenge because the driver is required to closely track a path with the outer sidewall of the outside front tire. A human driver must learn the response of the vehicle in order to steer it accurately through the test.

The increasing use and implementation of computer simulation in the vehicle engineering process has allowed for complex vehicles to be designed and tested in a virtual environment prior to a full-size vehicle being built. This approach is of particular importance in the commercial truck markets of Australia, New Zealand, and South Africa where large truck-trailer combinations, often referred to as “road trains”, are becoming more common. Such trucks can carry more freight per vehicle; however their overall length and mass means additional safety standards must be in place to ensure a safely operating vehicle. To that end the National Transport Commission (NTC) Australia has been developing vehicle specifications called Performance Based Standards, or PBS. Performance Based Standards include specifications for longitudinal performance such as Startability, Gradeability, Acceleration Capability, and Tracking ability on a straight path.

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.