System and method for managing empty carriers in an automated material handling system
First Claim
1. An automated material handling system, comprising:
- a plurality of material carriers, a first subset of which contain material and a second subset of which are absent material;
a first stock area comprising a plurality of first bins, each of which are configured to store a material carrier drawn from either said first or said second subset;
a control system coupled to the first stock area for computing a first empty percentage calculated as the number of said first bins which contain material carriers from the second subset relative to the number of said first bins; and
a transportation system responsive to said control system for moving a material carrier drawn from said second subset between a staging area and the first stock area based on a comparison of the first empty percentage to a predetermined threshold.
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Accused Products
Abstract
A system and method for managing empty carriers in an automated material handling system. The system includes a plurality of material carriers, some of which are empty, and a plurality of stock areas which store the carriers while waiting for the contained material to be processed or after having been processed. The system also includes a transportation system for moving the carriers between the stock areas. The system also includes a control system which receives status information from the transportation system and stock areas and controls the movement of carriers, in particular empty carriers, within the system in order to avoid production inefficiencies due to time delays introduced by an empty carrier not being available at a stock area when needed. The control system accomplishes this by calculating status variables, such as the empty percentage of each stock area, the current move rate of carriers in the system, and the current empty move rate in the system. The control system controls the movement of empty carriers based on the status information in relation to control parameters. The empty carrier control system attempts to keep the empty percentage of each stock area within a range defined by minimum and maximum empty percentage control parameters. The empty carrier movement is performed subject to not exceeding a maximum system move rate control parameter, which serves to avoid exceeding the physical limitations of the system, and not exceeding a maximum empty carrier move rate control parameter, which serves as a damping factor to avoid introducing system instability. In one embodiment, the system is for handling semiconductor wafers. In one embodiment, the control system is a network of computers executing a distributed software application for controlling the empty carrier movement.
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Citations
47 Claims
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1. An automated material handling system, comprising:
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a plurality of material carriers, a first subset of which contain material and a second subset of which are absent material; a first stock area comprising a plurality of first bins, each of which are configured to store a material carrier drawn from either said first or said second subset; a control system coupled to the first stock area for computing a first empty percentage calculated as the number of said first bins which contain material carriers from the second subset relative to the number of said first bins; and a transportation system responsive to said control system for moving a material carrier drawn from said second subset between a staging area and the first stock area based on a comparison of the first empty percentage to a predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for managing empty material carriers in an automated material handling system comprising a plurality of material carriers, a plurality of stock areas, wherein each of the plurality of stock areas includes a plurality of bins for storing a portion of the plurality of material carriers, wherein each of said plurality of stock areas has an associated empty percentage, wherein said empty percentage is a percentage of said plurality of bins storing one of said plurality of material carriers which is empty, a transportation system for moving the plurality of material carriers between the plurality of stock areas, and a control system coupled to the plurality of stock areas, the method comprising:
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maintaining at least one control parameter; receiving event information from said plurality of stock areas; calculating an empty percentage for each of said plurality of stock areas in response to said event information; determining the relationship of said at least one control parameter and said empty percentage of at least one of said first and second of said plurality of stock areas; and controlling the movement of an empty one of said plurality of material carriers from a first of said plurality of stock areas to a second of said plurality of stock areas based on said relationship. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47)
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Specification