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In inertially-reacted road test simulations, spindle accelerations that are acquired in the field can be replicated precisely and their replication improves the accuracy of the simulations versus simulations in which spindle accelerations are not replicated. In fixed-reacted road test simulations, on the other hand, spindle accelerations are often not replicated due to the belief that doing so will introduce unrealistic loads into the test specimen. Although this is true with regards to the lower frequency range of the control band, it is shown in this paper that replicating spindle accelerations in the upper frequency range of the control band can improve the accuracy of fixed-reacted road test simulations. In order to analyze the effects of spindle vertical acceleration control on suspension loads, models were created for a half vehicle on the road and on a fixed-reacted road test simulator.

Road test simulators are widely used for vehicle durability tests in the automotive industry. In order to develop road simulator durability tests, on-road load data is acquired. Then, the road test simulator (RTS) is set up according to the vehicle dimensions such as track, wheel base and tire rolling radius, so that the on-road load data can be dynamically replicated. The drive files, which are the time histories that control the simulator, are then developed by an iterative process. The fidelity of the resulting simulation is a function of both the simulator, including geometric and kinematic characteristics and the degree to which the drive files replicate the on-road data. However, there is often conflict between different load channels during simulation development. On a 4-degree-of-freedom (4DOF) simulator in particular, replicating both horizontal spindle loads and the camber moment about the spindle axis is frequently difficult.