Track sensor arrangement

A method for determining a position of an automated vehicle operating on a grid-based rail system, the rail system comprising a first plurality of parallel rails arranged in a first direction and a second plurality of parallel rails arranged in a second direction, the rails in the first direction and the second direction intersecting perpendicularly to form of plurality of intersections defining a plurality of grid access openings, each rail provided with either a single track or a pair of parallel tracks for wheels of the vehicle, each track being in the form of a groove defined by upwardly projecting track walls said track walls terminating at terminal ends at the intersections, the vehicle being able to change its direction of travel from the first direction to the second direction by alternately raising or lowering sets of wheels into and out of the tracks, a first set of wheels arranged for travel in the first direction and a second set of wheels arranged for travel in the second direction, the method comprising:

• providing a sensor, the sensor comprising:
• a sensor body having a recess arranged to receive a track wall of a track when the first set of wheels is lowered into the track;
• and
• a plurality of emitters, each arranged to emit a beam of energy, and one or more corresponding detectors arranged to detect the beams of energy from the emitters;
• wherein the emitters and the corresponding detector or detectors are arranged on opposite sides of the recess, such that the track wall blocks the beam emitted from the emitters from reaching their corresponding detectors when the first set of wheels is lowered into the track;
• attaching the sensor to the vehicle at a position whereby a beam from an emitter is capable of reaching its corresponding detector while a predetermined part of the vehicle is positioned over an access opening of interest;
• lowering the first set of wheels of the vehicle into a track in order for the vehicle to travel in the first direction, whereby the sensor is also lowered such that the track wall enters the recess and blocks the beams from the emitters from reaching their corresponding detectors;
• causing the vehicle to travel in the first direction until the beam from an emitter passes the terminal end of a track wall at an intersection adjacent to the access opening of interest;
• and
• stopping the vehicle when the sensor is positioned relative to the adjacent intersection such that the predetermined part of the vehicle is aligned over the access opening of interest.