MiL: the beginning of the process

MiL testing involves using a mathematical model of a system component as the testing environment.

This allows engineers to evaluate and validate the behavior and functionality of specific aspects of a system before the actual hardware implementation takes place.

Driving simulators have boosted the vehicle design with the introduction of human beings in the simulation loop.

For a realistic functioning, the steering system must provide an accurate behaviour, since the hand wheel is a crucial human interface.

Despite a large diffusion of steering models, this paper deals with the creation of a specific solution for real-time applications, characterized by precise features as numerical stability and low computational cost.

The mechanical model is composed by two DOF:

1. The first one composed by the: steering wheel, steering column and hooke joints
2. The second one is composed by the pinion, rack and tie rods.

The two  masses are connected by the torsion bar modelled as a simple torsional spring and damper.

The HPS is modelled by a simple function in two variables which are the torsion bar torque and vehicle velocity plus a first order delay to approximate the system dynamic response.