1. About AS/RS (1/7)

2. About AS/RS (2/7) Research areas  Storage locations assignment  Storage and retrieval policy  Physical design

3. About AS/RS (3/7) Storage locations assignment  Randomized Uniformly Closest open location  Class-based Turnover ratio  Dedicated

4. About AS/RS (4/7) Storage and retrieval policy  Single command (SC) First-come-first-serve  Dual command (DC) First-come-first-serve Dynamic TSP problem  Assignment problem (static & dynamic)  Nearest neighbor

5. 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

6. About AS/RS (6/7) Performance measure  Travel time  Throughout

7. About AS/RS (7/7) Load types  Mini-load  Unit-load

8. Effects of relocation to AS/RS storage location policy with production quantity variation

9. Introduction Experiment design Simulation Result Conclusion

10. 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

11. 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 storage  Top four items: first class

12. 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

13. Experiment design (3/3)

14. Simulation (1/4) GPSS Simulated for 900,000 unit time Warn up 300,000 300,000~600,000 unit time: original Repeat 10 times

15. Simulation (2/4)

16. Simulation (3/4)

17. Simulation (4/4)

18. Result (1/3) Random storage

19. Result (2/3) 2 class-based

20. Result (3/3) 3 class-based

21. Result(4/4)

22. Conclusion (1/2)

23. 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