Trailer tongue length estimation using a hitch angle sensor

A system for estimating a tongue length of a trailer being towed by a vehicle, said vehicle including a pair of front wheels and a pair of rear wheels, where the front wheels are steered by an operator a the rear wheels are automatically steered by an on-board steering controller, said control system comprising:

• a front wheel angle sensor for providing a front w eel angle signal indicative of the angle of the front wheels of the vehicle;
• a rear wheel angle sensor for providing a rear w eel angle signal indicative of the angle of the rear wheels of the vehicle;
• a vehicle speed sensor for providing a vehicle speed signal indicative of the speed of the vehicle;
• a vehicle yaw rate sensor for providing a yaw rate signal indicative of the yaw rate of the vehicle;
• a hitch angle sensor for providing a measured hitch angle signal indicative of a hitch angle between the vehicle and the trailer;
• and
• a tongue length estimation controller for computing th estimate of the tongue length of the trailer, said estimation controller computing a estimated hitch angle signal based on the frontwheel angle signal, the rearwheel angle signal, the vehicle yaw rate signal, the vehicle speed signal and the measured hitch angle signal, said tongue length estimation controller including a first comparator f r comparing the estimated hitch angle signal to the measured hitch angle signal to generate a hitch angle error signal representative of the difference between the estimated hitch angle and the measured hitch angle, said estimation controller further including a proportional-integral-differential controller that is responsive to the itch angle error signal, said proportional-integral-differential controller converting the hitch angle error signal to a tongue length error signal, said estimation controller further including a second comparator for comparing the tongue length error signal to an initial tongue length estimation signal to provide a corrected tongue length estimation signal, wherein the corrected tongue length estimation signal becomes the estimated tongue length after a predetermined number of calculation periods.

A system comprising:

• a vehicle including a pair of front wheels and a pair of ear wheels, said vehicle further including a vehicle hitch post;
• a trailer including trailer wheels, said trailer further including a trailer hitch post;
• a hitch coupling the vehicle hitch post to the trailer hitch post;
• a hitch sensor for measuring a hitch angle between the vehicle hitch post and the trailer hitch post, said hitch sensor providing a hitch angle signal indicative of the measured hitch angle;
• and
• a controller, said controller computing a tongue length of the trailer based on the hitch angle signals wherein the controller compares the hitch angle signal to an estimated hitch angle, said estimated hitch angle being computed by an algorithm from inputs including an angle of the vehicle's front wheels, an angle of he vehicle's rear wheels, a yaw rate of the vehicle, a speed of the vehicle and the measured hitch angle.

A method of estimating a tongue length of a trailer being towed by a vehicle, comprising:

• determining the angle of front wheels of the vehicle;
• determining the speed of the vehicle;
• determining the yaw rate of the vehicle;
• determining a hitch angle between the vehicle and the trailer;
• and
• computing the estimate of the tongue length of the trailer based on the front wheel angle, the vehicle yaw rate, the vehicle speed and the hitch angle.