US Patent 9008913 Steering control system for a towed axle

A trailer includes a chassis having a hitch, an axle having a pair of tractive elements rotatably coupled to the chassis, an actuator coupled to the chassis and positioned to steer the pair of tractive elements, and a processing circuit. The processing circuit has an input for receiving a transmission gear of a tractor vehicle and a variable output for engaging the actuator. The processing circuit is configured to control the steering of the pair of tractive elements according to a control strategy that varies based on the transmission gear of the tractor vehicle.