This invention concerns a method for self guidance of unmanned vehicles along pre-defined paths using an on-board one dimensional optical sensor and light reflective targets placed at intervals along and to one side of its path.
Autonomously guided (autoguided) vehicles are in common use in factories and warehouses. Some are guided by wires buried in the floor but this type of installation has the disadvantages of a relatively high installation cost, limited flexiblity of path changes, and unsuitablility on soft floor or those with metal reinforcement rods. For these reasons, several different types of alternative guidance schemes have been invented.
One type uses optical paths painted on the floor. However optical paths tend to wear away or can be obscured by dirt. Other types use overhead light beams either emitted from the vehicle to stationary reflectors, or light beams from stationary locations to passive receivers on the vehicle. These systems must reject ambient lighting and also must be mounted high off the ground to insure that the beams are not interruped by traffic and equipment. This height can interfere with loading the vehicle. The presence of the flashing or spinning light beams can also interefere with the visual systems of pedestrians and workesr in the area.
Still other types use optical sensors to detect targets placed at known locations in the building. Guidance is achieved by triangulation. Best accuracy is achieved by using targets that are widely separated in angle. However these types have the disadvantage of requiring two dimensional sensors and a need to see over obstructions.