Adaptive rear-wheel steer open-loop control for vehicle-trailer system

A control system for providing an open-loop rear-wheel steering assist signal for a vehicle/trailer combination, said system comprising:

• a hand-wheel angle sensor for providing a hand-wheel angle signal of the hand-wheel position of a vehicle hand-wheel;
• a vehicle speed sensor for providing a vehicle speed signal of the speed of the vehicle;
• a vehicle yaw rate sensor for providing a measured vehicle yaw rate signal of the yaw rate of the vehicle;
• a steady-state processor responsive to the vehicle yaw rate signal, said steady state processor determining if the vehicle yaw rate signal has reached steady state and generating a vehicle yaw rate steady-state signal;
• a rear-wheel steering processor responsive to the vehicle speed signal and the hand-wheel angle signal, said rear-wheel steering processor generating nominal rear-wheel steering values;
• a rear-wheel adapter processor responsive to the vehicle speed signal and the vehicle steady-state signal, said rear-wheel adapter processor generating new feed-forward rear/front (R/F) ratio values;
• an adapter for updating the nominal rear-wheel steering values with the new feed-forward rear/front (R/F) ratio values;
• and
• a multiplier for multiplying the updated feed-forward rear/front (R/F) ratio values and the hand-wheel angle signal and generating a rear-wheel steering command signal that provides the rear-wheel steering assist signal.

A method for providing an open-loop rear-wheel steering assist signal for a vehicle/trailer combination, said method comprising:

• providing a hand-wheel angle signal of the position of a vehicle hand-wheel;
• providing a vehicle speed signal of the speed of the vehicle;
• providing a measured vehicle yaw rate signal of the yaw rate of the vehicle;
• and
• adapting the open-loop steering signal for different trailers or the same trailer with different configurations using only vehicle parameters by using the hand-wheel angle signal, the vehicle speed signal and the vehicle yaw rate signal.