Anti-jackknife control for vehicle-trailer backing up using rear-wheel steer control

A method of selectively providing rear-wheel steering for a vehicle backing-up a trailer, said method comprising:

• determining a steering angle of the vehicle;
• determining a speed of the vehicle;
• determining a measured hitch angle between the vehicle and the trailer;
• calculating an equilibrium hitch angle between the vehicle and the trailer that is a steady-state hitch angle position;
• calculating a pseudo-equilibrium hitch angle between the vehicle and the trailer that is a steady-state hitch angle position at a maximum rear-wheel steering input;
• determining whether a predetermined relationship exists between the measured hitch angle, the equilibrium hitch angle and the pseudo-equilibrium hitch angle, wherein the predetermined relationship includes determining the orientation of the steering angle of the vehicle, determining whether the measured hitch angle is within a range set by the equilibrium hitch angle and the pseudo-equilibrium hitch angle, determining a rate of change of the measured hitch angle and determining whether the measured hitch angle is converging towards or away from the equilibrium hitch angle and the pseudo-equilibrium hitch angle;
• providing rear-wheel steering of the vehicle if the predetermined relationship does exist;
• and
• removing the rear-wheel steering if the predetermined relationship no longer exists when the rear-wheel steering is being provided.

A system for selectively providing rear-wheel steering for a vehicle backing-up a trailer, said system comprising:

• a steering angle sensor for determining a steering angle of the vehicle;
• a speed sensor for determining a speed of the vehicle;
• a hitch angle sensor for measuring a hitch angle between the vehicle and the trailer;
• and
• a controller for selectively providing the rear-wheel steering to the vehicle if a jackknife condition is probable, said controller calculating an equilibrium hitch angle between the vehicle and the trailer that is a steady-state hitch angle position, calculating a pseudo-equilibrium hitch angle between the vehicle and the trailer that is a steady-state hitch angle position at a maximum rear-wheel steering input, determining whether a predetermined relationship exists between the measured hitch angle, the equilibrium hitch angle and the pseudo-equilibrium hitch angle, and providing the rear-wheel steering to the vehicle if the predetermined relationship does exist.