GB1421722A - Device for positioning a moving body in relation to fixed reference marks - Google Patents

Abstract

1421722 Position indicating system LANSING BAGNALL Ltd 20 Dec 1972 [20 Dec 1971] 59070/71 Heading G1A A system for indicating to the driver of a warehouse vehicle, the position of the vehicle relative to a particular required stopping position, comprises a plurality of pairs of horizontally displaced reflective strips e.g. 1, 2 each pair mounted adjacent a possible required stopping point along a path of travel of the vehicle, the vehicle carrying two similarly spaced photo-electric detectors 3a, 3b each having an associated light source 4a, 4b by which light is reflected to the detectors when they are opposite a strip, the outputs of the detectors being taken to a logic circuit 5 whereby if the correct activation sequence is produced prior to the simultaneous activation of the detectors, a pulse is applied to increment or decrement counters 6, 7. A keyboard 8, 9 mounted on the vehicle is operated to indicate a desired stopping position and this value is applied to a subtractor 12 together with the count at either counter 6 or 7 via gates 10 depending upon whether the setting at 8 is for an even-or an odd-numbered bay, since counter 6 is designed to count through the even nos. 2, 4, 6 ... and counter 7 the odd numbers 1, 3, 5 ... only, for in a typical warehouse, bay no. 2n will be opposite bay no.(2 n+1). The count at either 6 or 7 is also displayed at 11. When the number at 12 is less than a predetermined value, a lamp 13 will be illuminated to tell the vehicle driver to slow down. When the vehicle is within a very short distance of the required stopping point, a further logic circuit 14 is activated, and depending upon the sense of the sequence of activation of the detectors, illuminates one of the two lamps 15, 16 to tell the driver to move in one of the two directions. The correct position is reached when the detectors are simultaneously activated. In correct counting either due to hunting or a small reversal of direction during travel is prevented by the circuits 5, 14.