All-wheel steering systems under computerized control for multi-trailer trains

Abstract The industrial trailer trains run at lower speeds and roll on stiffer wheels compared with the road vehicles, whence their motion is practically ruled by the rigid rolling constraint of the wheels with no side shift. Besides, the steering systems must consent paths with small radii to avoid collision with nearby obstacles. This study addresses front-back symmetric steering systems of a modified Bourlet-Davis type, which exactly respect the Ackermann condition. The same optimal motion is planned for the tractor and all the trailers, though with proper time delays for each unit. The length of the traction bar between two consecutive trailers is planned to change according to the hitch distance resulting from their required motions. A computing unit on the tractor manages the delayed commands for two planetary roller screws on each trailer, the one replacing the steering rod of the Bourlet-Davis mechanism, and the other ensuring the length variation of the traction bar. The motion of the whole train is calculated according to the desired kinematics, and all the inertia and traction forces are ultimately derived.