Joon-Mook Lim

A genetic algorithm for a single hoist scheduling in the printed-circuit-board electroplating line

Abstract In this paper, the problem of determining cyclic schedules for a material handling hoist in the printed-circuit-board(PCB) electroplating line is considered. The objective of this research is to determine an optimal simple-cycle schedule of the hoist which in turn maximizes the line throughput rate. Previous approaches to the cyclic hoist scheduling problem are all mathematical programming-based approaches to develop cyclic schedules(Mixed Integer Programming, Linear Programming based Branch and Bound, Branch and Bound Search Method and so on). In this paper, a genetic algorithm-based approach for a single hoist scheduling in the PCB electroplating line is described. Through an experiment for the well known example data, the proposed algorithm is shown to be more efficient than the previous mathematical programming-based algorithm.

Deriving an optimal dwell point of the storage/retrieval machine in an automated storage/retrieval system

Abstract The selection of the dwell point of the storage/retrieval (S/R) machine when it becomes idle in an automated storage/retrieval system (AS/RS) is discussed. Two existing models for dynamic control of the S/R machine are adopted for the analysis. They are transformed to the single-facility location problem with Tchebyshev distance, and the Tchebyshev minimax facility location problem, respectively. Algorithms are presented utilizing well known research results in location theory. Through computational tests, the algorithms are shown to be quite suitable for real-world applications.

A construction algorithm for designing guide paths of automated guided vehicle systems

A construction algorithm is suggested to design guide path networks for automated guided vehicle systems (AGVSs). This study uses the total travel time, including waiting and interference time, of vehicles as the decision criteria for determining the direction of path segments on unidirectional guide path layouts. The Q-learning technique is applied to estimate the travel times of vehicles on path segments. Computational experiments were performed to evaluate the performance of the proposed algorithm. The simulation results showed that the proposed algorithm is superior to Kim & Tanchocos (1993) algorithm in terms of the average travel time, the interference time and the number of deliveries.

Designing guide-path networks for automated guided vehicle system by using the Q-learning technique

This paper suggests a Q-learning technique for designing guide-path networks for automated guided vehicle systems. This study uses the total travel time as the decision criteria for constructing guide-path layouts. The Q-learning technique is applied to the estimation of the travel time of vehicles on each segment of the guide-path. Computational experiments were performed to evaluate the performance of the proposed algorithm. The simulation results showed that the proposed algorithm is superior to Kim and Tanchocos (1993) in terms of average travel time, interference time, and number of deliveries.

ECONOMIC DESIGN OF REFRIGERATED AUTOMATED STORAGE AND RETRIEVAL SYSTEMS

The objective of this paper is the development of a design model for refrigerated automated storage and retrieval systems (R-AS/RS). Compared with ordinary unit-load AS/RS, the R-AS/RS under this study has several different design and operating characteristics: (I) greater emphasis is placed on the storage function and so it has a double-depth lane in the storage rack; (2) cooling units are required to maintain a cold temperature environment in the system; (3) the maximum number of storage orders handled per unit time is limited by the system capacity. Considering the above characteristics, the design problem is formulated as a non-linear mixed integer programming problem in which the cost of the system is minimized. The decision variables are the storage volume, the number of storage and retrieval (S/R) machines, the type and number of cooling units, and the physical configuration of the building. A case problem is solved to illustrate the model.

Evaluation of operation policies for automatic delivery sequence sorting systems

The development of automatic delivery sequence sorting system entails enormous cost and time, yet it is still an essential element that determines the future of the postal service. In this paper, we select executive alternatives that consider restrictive conditions both in terms of physical environments as well as technical factors such as the location where the mail is sorted, the location where the addresses are read, and the types of video coding for unread addresses. Then, we evaluate the alternatives by performing cost and performance analyses on processing time, machine utilization and throughput. Lastly, we perform an analysis on the overall business to reflect on the qualitative factors.