OHT Job Assignment Using Linkage Transport and Congestion Prediction
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Solution Overview
Problem
Current overhead hoist transport control systems in semiconductor fabrication facilities do not consider post-unloading situations when allocating jobs, leading to congestion and delays when a section is overwhelmed with tasks.
Innovation Solution
A transport control system that assigns multiple jobs to an overhead hoist transport based on the availability of linkage transporting and the likelihood of transport congestion, determining a target transport by evaluating factors such as job alignment, transport paths, and idle states to prevent congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the OCS assigns jobs one-by-one to nearby OHTs based on current states, then the assignment is simple and fast, but congestion occurs in sections swamped with jobs causing delays
Solution Approach 1:
The system performs preliminary analysis of post-unloading situations and transport paths before assigning jobs. By evaluating future states and potential congestion points in advance, the OCS can prevent congestion before it occurs, rather than simply reacting to current conditions. This preliminary assessment allows the system to select OHTs that will not create future bottlenecks.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor the states of all OHTs and the distribution of jobs across sections. This feedback loop allows the OCS to adjust job assignments dynamically based on actual system performance and congestion patterns, improving overall productivity while preventing delays.
2Productivity
If multiple jobs are assigned to a single OHT based on linkage transporting availability, then transport operations become more efficient, but the risk of transport congestion increases
Solution Approach 1:
Before assigning multiple jobs to a single OHT, the system preliminarily evaluates the availability of linkage transporting and assesses potential congestion risks. By analyzing transport paths and OHT states in advance, the system can confidently bundle jobs together only when it's safe to do so, maximizing efficiency without compromising reliability.
Solution Approach 2:
The system uses real-time feedback on OHT states and transport path conditions to dynamically adjust job bundling decisions. When feedback indicates high congestion risk, the system reduces job bundling; when conditions are favorable, it increases bundling to improve efficiency. This feedback-driven approach balances productivity and reliability.
Data Source
AI summary
There is provided a transport control system assigning multiple jobs to an overhead hoist transport (OHT) based on the availability of linkage transporting and the likelihood of transport congestion. The transport control system includes: a plurality of transports, each of the plurality of transports transporting a carrier with a wafer loaded thereon; and a transport control apparatus controlling the plurality of transports and determining one of the plurality of transports as a target transport to which multiple jobs are to be assigned. The transport control apparatus determines one of the plurality of transports as the target transport based on a first element, which is the availability of linkage transporting, and a second element, which is the likelihood of transport congestion.