To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ejor.2004.09.019 Byline: Inna G. Drobouchevitch (a), Suresh P. Sethi (b), Chelliah Sriskandarajah (b) Keywords: Scheduling; Robotic cells; Cyclic production; 1-unit cycles Abstract: We consider the scheduling problem of cyclic production in a bufferless dual-gripper robot cell processing a family of identical parts. The objective is to find an optimal sequence of robot moves so as to maximize the long-run average throughput rate of the cell. While there has been a considerable amount of research dealing with single-gripper robot cells, there are only a few papers devoted to scheduling in dual-gripper robotic cells. From the practical point of view, the use of a dual gripper offers the attractive prospect of an increase in the cell productivity. At the same time, the increase in the combinatorial possibilities associated with a dual-gripper robot severely complicates its theoretical analysis. The purpose of this paper is to extend the existing conceptual framework to the dual-gripper situation, and to provide some insight into the problem. We provide a notational and modelling framework for cyclic production in a dual-gripper robotic cell. Focusing on the so-called active cycles, we discuss the issues of feasibility and explore the combinatorial aspects of the problem. The main attention is on 1-unit cycles, i.e., those that restore the cell to the same initial state after the production of each unit. For an m-machine robotic cell served by a dual-gripper robot, we describe a complete family of 1-unit cycles, and derive an analytical formula to estimate their total number for a given m. In the case when the gripper switching time is sufficiently small, we identify an optimal 1-unit cycle. This special case is of particular interest as it reflects the most frequently encountered situation in real-life robotic systems. Finally, we establish the connection between a dual-gripper cell and a single-gripper cell with machine output buffers of one-unit capacity and compare the cell productivity for these two models. Author Affiliation: (a) Hitron Systems Inc., 109-19 Majeon-Ri, Samjuk-Myeon, Anseong-City, Kyungki-Do 456-881, Republic of Korea (b) The University of Texas at Dallas, School of Management, Box 830688, Mail Station SM30, Richardson, TX 75083-0688, USA Article History: Received 1 November 2001; Accepted 3 September 2004