Iterative control in automotive testing

Abstract

Road simulator test rigs investigate both the durability and the squeak and rattle characteristics of vehicle structures. The test specimens are the whole vehicle or a sub-structure taken from the vehicle. In laboratory simulation tests, random time series of strain, displacement, or acceleration, which represent service conditions, are reproduced at specified locations within the structure. These responses are formulated from measurements made on the road or at a specialized proving ground. The premise is that reproducing these responses recreates service strain throughout the structure. The test rigs are normally driven by hydraulics and form multiple channel non-linear dynamic systems. Time series drive files that reproduce the strain are generated to excite the test rig. These are determined using an iterative procedure that overcomes the deficiencies of the hydraulics, channel interaction, and non-linearity in the system. The current paper outlines a new iterative algorithm with better convergence than the commonly used iterative algorithm which does not always converge. This new iterative algorithm is demonstrated in numerical simulations that represent typical automotive engineering systems.