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Technical Paper

Simulation of the Performance Based Standards (PBS) Low-Speed 90° Turn Test in TruckSim by Jumping Back in Time

2013-09-24
2013-01-2374
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.
Technical Paper

Mechanics of Brake Steering Pull on Heavy Trucks

2015-05-13
2015-36-0024
Heavy trucks with solid front axles commonly use steering systems that have left to right asymmetry. The asymmetry creates the potential to cause steering pulls during brake application which are by their nature undesirable since they require an input in the steering wheel by the driver to maintain the correct path of the vehicle. Brake forces acting in the tire contact patches create toe-out moments around the kingpin axes that are resisted by the steering linkages. However asymmetry of the linkage allows unbalanced toe-out steer angle deviations at the wheels resulting in a path deviation of the truck that is perceived as brake steering pull. The factors influencing steering pull include the compliance properties of the steering linkages, road wheel geometry, drag link geometry and spring windup properties. The mechanics of the brake force interactions with these steering and suspension properties are explained here.
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