Steer-by-Wire: Universal Calculation of Production-Dependent,
Strongly Fluctuating Friction in Steering 2023-01-5082
In steer-by-wire (SbW) vehicles, understanding the steering rack force is
essential to replicate a realistic steering feel, allowing conclusions to be
drawn about road surface conditions by the decoupled manual actuator. Since
internal friction varies with each steering system manufactured and installed,
these models differ greatly in accuracy. This paper presents a concept for
continuously calculating fluctuating friction based on the internal steering
variables to avoid additional and complex individual measurements. An SbW system
offers the right approach by adjusting the driver’s desired steering angle and
the required motor control. The underlying steering clearance and the Kalman
filter are used to calculate the steering rack force. The validity of the
proposed concept is shown in drive tests according to ISO 13674 and ISO 7401 to
gauge high and low friction values in different speed ranges.
