Title: Throughput optimisation in reentrant circular regular robot cells

Authors: Ali Khebouche; Mourad Boudhar; El-Sedik Lamini

Addresses: RECITS Laboratory, Faculty of Mathematics, USTHB University, BP 32 Bab-Ezzouar, El-Alia 16111, Algiers, Algeria ' RECITS Laboratory, Faculty of Mathematics, USTHB University, BP 32 Bab-Ezzouar, El-Alia 16111, Algiers, Algeria ' RECITS Laboratory, Faculty of Mathematics, USTHB University, BP 32 Bab-Ezzouar, El-Alia 16111, Algiers, Algeria

Abstract: We consider robot cells of type reentrant circular flow shop served by a single-gripper central robot having the ability to swap. The objective is to find a cyclic sequence of robot moves that minimises the cycle time of one-unit required to produce a part or, equivalently, that maximises the throughput. We analysed three-machine robot cells in-depth showing that four of the feasible one-unit cycles dominate the remaining 17 cycles. We determined the parameter regions in which each of the four cycles is optimal. In the case of m machines, we gave two new lower bounds with an emphasis on four cycles that are specific among all one-unit cycles. Initially, cycle time formulas are created for the four cycles of one-unit. In addition, we established the parameter regions where each of the cycles is best. Finally, we showed that a specific cycle provides a 3/2-approximation for the remaining unique region.

Keywords: circular robot cells; chain-reentrant; throughput maximisation; cyclic production; flow-shop scheduling.

DOI: 10.1504/IJMOR.2023.133717

International Journal of Mathematics in Operational Research, 2023 Vol.26 No.1, pp.111 - 142

Received: 19 May 2022
Accepted: 04 Jul 2022
Published online: 02 Oct 2023 *

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