Post on 05-Feb-2016
description
transcript
About AS/RS (1/7)
About AS/RS (2/7)
Research areasStorage locations assignment
Storage and retrieval policy
Physical design
About AS/RS (3/7)
Storage locations assignment Randomized
Uniformly Closest open location
Class-based Turnover ratio
Dedicated
About AS/RS (4/7)
Storage and retrieval policySingle command (SC)
First-come-first-serve
Dual command (DC) First-come-first-serve Dynamic TSP problem
Assignment problem (static & dynamic) Nearest neighbor
About AS/RS (5/7)
Physical design Configurations of rack
Height & Length Velocity
Acceleration & Deceleration Dwell point
Bozer & White(1984) E(SC)=[ ] T
E(DC)=[ ] T
2b3
11
32
30
1b2
1
3
4b
About AS/RS (6/7)
Performance measureTravel time
Throughout
About AS/RS (7/7)
Load typesMini-load
Unit-load
Effects of relocation to AS/RS storage location policy with production quantity variation
Introduction Experiment design Simulation Result Conclusion
Introduction
The performance of will not be good if production quantity variation and current storage policy is kept
Find the tolerance limits and appropriate strategies for storage policy when production plan change
Random,2 and 3 class-based will be examined
Experiment design (1/3)
There are 20 items in the production plan
Production quantities vary between 10-80% Items are assumed as end products
For 2 class-based storageTop four items: first class
Experiment design (2/3)
For 3 class-based storage Top four items: first class Next six items: second class
For random storage 1500, 5000 and 95000 unit storage time
Relocation process will be done whenever the crane idles
Experiment design (3/3)
Simulation (1/4)
GPSS
Simulated for 900,000 unit time
Warn up 300,000
300,000~600,000 unit time: original
Repeat 10 times
Simulation (2/4)
Simulation (3/4)
Simulation (4/4)
Result (1/3) Random storage
Result (2/3) 2 class-based
Result (3/3) 3 class-based
Result(4/4)
Conclusion (1/2)
Conclusion (2/2)
Class-based storage policies perform better but have a lower tolerance
Class-based would be better if performance is the most critical issue
If performance is not critical and frequent production plan changes are expected, random storage would be better