Model-Matching-Control of a Redundantly Actuated Steer-by-Wire-System

Steer-by-Wire (sbw) systems gain new importance with regard to autonomous driving since a permanently rotating steering wheel is undesired in such a vehicle. In addition, redundancies in the vehicle steering system must be provided for autonomous vehicles, which have been seen as an obstacle for sbw-systems until now. In this article, a control concept for redundantly actuated sbw-systems is presented. For this purpose, the mechanical model of a redundantly actuated sbw is described, in which the actuators of the steering are elastically connected to each other. Also a linear model of a conventional hydraulic power steering (hps) is derived as reference model, to describe the desired dynamic behavior of the controlled system. A dynamic model-matching controller based on norm minimization is designed to match the dynamics of the sbw-system to the dynamics of the hps-model. Finally, the characteristics of the controlled system are analysed. The controlled system matches the reference system in the relevant frequency range and shows the desired behavior on the test bed.