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