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Process scheduling system, method, and program

  • US 9,409,230 B2
  • Filed: 05/06/2010
  • Issued: 08/09/2016
  • Est. Priority Date: 05/13/2009
  • Status: Active Grant
First Claim
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1. A method for determining a sequence of slabs fed to a hot rolling mill from an inventory slab sequence and a direct slab sequence according to processing of a computer, comprising the steps of:

  • representing data of the inventory slab sequence and data of the direct slab sequence on a storage device operatively connected to a processing unit of the computer as a data structure arranged respectively in first and second directions;

    forming a grid graph having intersections as nodes, from the data of the inventory slab sequence in the first direction and the data of the direct slab sequence in the second direction, wherein each node in the grid graph includes both;

    (a) an inventory slab subnode for an inventory slab in an i position of the inventory slab sequence, wherein i is an integer; and

    (b) a direct slab subnode for a direct slab in a j position of the direct slab sequence, wherein j is an integer;

    weighting edges in the grid graph based on attributes of each slab in the inventory slab sequence and attributes of each slab in the direct slab sequence, wherein the weighting is performed using three indices that are inter-slab connectivity, a hot rolling idle time, and a direct slab wait time, said weight of each edge in the grid graph being calculated as a function of said three indices, an indice having a direct slab or inventory slab and corresponding direct slab subnode or inventory slab subnode as arguments;

    determining a combined slab sequence of the inventory slab sequence and the direct slab sequence, by a shortest path search through a sequence of nodes from a start point to an end point in the weighted grid graph, said shortest path search traversing through either one of;

    said inventory slab subnode or said direct slab subnode at each node of said sequence;

    wherein said processing unit performs one or more said forming, weighting and determining;

    wherein the inter-slab connectivity is determined by the function;

    connectivity(slab1, slab2);

    =C1*abs(slab1.width−

    slab2.width)+C2*abs(slab1.thickness−

    slab2.thickness); and

    wherein slab1.width is width of slab1, slab2.width is width of slab 2, slab1.thickness is thickness of slab1, slab2.thickness is thickness of slab2, andwherein C1 and C2 are positive constants and abs is a function that returns an absolute value; and

    using the combined slab sequence to schedule feeding slabs to the hot rolling mill.

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