Systems and methods for a friction estimation method for a steer-by-wire roadwheel actuator system based on closed-loop adjustment of a hysteretic gain coefficient

A method for friction estimation, the method comprising:

• receiving at least a rack position value associated with a rack of a steering system;
• determining whether the rack position value is within a rack position range;
• and
• in response to a determination that the rack position value is within the rack position range:
• determining a hysteresis force correction value based on a steering input signal;
• estimating a road friction value based on the hysteresis force correction value, and the rack position value;
• and
• selectively controlling at least one aspect of the steering system based on the estimated road friction value.

An apparatus for friction estimation, the apparatus comprising:

• a controller configured to:
• receive at least a rack position value associated with a rack of a steering system;
• receive a rack velocity value associated with the rack of the steering system;
• receive a vehicle velocity value;
• and
• in response to a determination that (i) the rack position value is within a rack position range, (ii) the rack velocity value is within a rack velocity range, and (iii) the vehicle velocity value is within a vehicle velocity range:
• determine a hysteresis force correction value based on a steering input signal;
• estimate a road friction value based on the hysteresis force correction value, the rack position value, the rack velocity value, and the vehicle velocity value;
• and
• selectively control at least one aspect of the steering system based on the estimated road friction value.