Identification of steering system parameters by experimental measurements processing

Abstract

The object of this investigation is to propose a procedure for the parameter identification of a steering system, processing experimental measurements obtained on a test bench by means of a developed software. This allows the isolation of a set of parameters and the performance ratings of a steering system with an objective approach. The adopted approach overcomes problems of repeatability of the test, influence of driver style, and feelings associated with the subjective drivers evaluation method.

In this paper a two degrees of freedom (dof) model dependent by synthesis parameters is used. The model has been developed in Simulink environment, both for hydraulic and electrical power steering systems. The experimental data, obtained by an ad hoc collected set of measurements, are used to identify the parameters in two steps. A set of parameters is first computed by means of a simple signal processing procedure. Then, the model is controlled by an optimization tool, which varies the parameters values in order to reach the best fitting between experimental data and model output. Identification leads to a complete characterization of the steering system. In particular, the following parameters are identified: steering ratio, torsional stiffness, power-steering characteristic curve, friction forces, and damping.