Steering System Simulation during the Concept Phase regarding Feedback Behavior

Abstract

Steering feedback has an important role in good vehicle guidance by the driver. However, the design of the steering feedback usually happens late in the development process with prototype vehicles, when significant changes to the steering system are hardly possible. Hence, a steering system model is developed for the early stages of vehicle development, which is able to predict the transmission behavior of a steering system. Therefore, this article verifies that the steering system can be modeled independently of the tires and axle for relevant amplitudes of the steering feedback. The developed steering system model is a two-mass model consisting of an effective rack mass and a combined steering wheel and steering column inertia. Both are connected via the spring stiffness of the steering column and a steering gear ratio. Friction has a very dominant influence on the transmission behavior of the steering system and is therefore modeled at the column and rack. Furthermore, a driver and a steering controller model are used to examine variations of configurations with a fixed and free steering wheel as well as an active and inactive assist motor. The validation of the model with measurement data shows good accuracy compared to a more complex state-of-the-art steering model.