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| DOI： |
| Received:April 26, 2004Revised:August 10, 2004 |
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| Pick sequencing optimization problem in the rotary rack S/R system |
| Pan Zhang, Lei Jia,Guohui Tian |
| (School of Control Science and Engineering, Shandong University, 250061 Jinan Shandong, China) |
| Abstract: |
| The problem of pick sequencing in the rotary rack S/R system (PPS-RRS) is investigated with the objective of minimizing the execution time. The rotary rack S/R system consists of one S/R machine and multiple levels of carousels that can rotate independently in bi-directions. The routing policy, namely the decision on the storage or retrieval sequence, dominates the efficiency and the throughput for such S/R systems, due to the complicated relationship between all levels of carousels and the S/R machine. For the purpose of optimizing the PPS-RRS, a computational model is developed in terms of execution time for picking multiple items in one trip. Characteristics of the PPS-RRS are analyzed and a local search heuristic based on a newly proposed neighborhood is presented. Integrated with the proposed local search procedure a new hybrid genetic algorithm is developed. Experimental results demonstrate the structure characteristics of good sequence and the efficiency and effectiveness of the proposed sequencing algorithms. |
| Key words: Rotary rack S/R system Hybrid genetic algorithm Sequencing problem Level-blank neighborhood Local search |
