초록 ▼

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 be

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.

대표청구항 ▼

[ What is claimed is:] [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 m

[ What is claimed is:] [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; anda 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.