An analysis of task assignment and cycle times when robots are added to human-operated assembly lines, using mathematical programming models

• Published in: International journal of production economics Vol. 242; p. 108292
• Main Authors: Koltai, Tamás, Dimény, Imre, Gallina, Viola, Gaal, Alexander, Sepe, Chiara
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2021
• Subjects: Assembly line balancing; Automation; Human-robot collaboration; Mathematical programming; Operations management; Operations management; Automation; Assembly line balancing; Human-robot collaboration; Mathematical programming
• ISSN: 0925-5273; 1873-7579
• DOI: 10.1016/j.ijpe.2021.108292

Adding robots to a human-operated assembly line influences both the short- and long-term operation of the line. However, the effects of robots on assembly line capacity and on cycle time can only be studied if appropriate task assignment models are available. This paper shows how traditional assembly line balancing models can be changed in order to determine the optimal number of workstations and cycle time when robots with different technological capabilities are able to perform a predetermined set of tasks. The mathematical programming models for the following three cases are presented and analysed: i) only workers are assigned to the workstations; ii) either a worker or a robot is assigned to a workstation; iii) a robot and a worker are also assigned to specific workstations. The data of an assembly line producing power inverters is used to illustrate the proposed calculations. Both the assignment of tasks and the changes of cycle time are analysed within the AIMMS modelling environment. The computational characteristics of the proposed mathematical programming models are also examined and tested using benchmark problems. The models presented in this paper can assist operations management in making decisions relating to assembly line configuration. •Assembly line balancing with the possibility of human-robot collaboration at some workstations.•Assembly line balancing problem when workers and robots can be used under various conditions.•Comparing three assembly line configurations with different levels of automation.•Linearisation of non-linear ALB problem for human-robot collaboration possibilities.•Constraint programming solution of non-linear assembly line balancing problems.