Balancing and Scheduling U-Shaped Mixed-Model Assembly Lines with Human-Robot Collaboration Considering Ergonomic Risk

Abstract

The integration of collaborative robots (cobots) in assembly systems has gained prominence as a means of enhancing efficiency and supporting human operators in task execution. This study examines the U-shaped mixed-model assembly line balancing problem with human-robot collaboration (U-shaped Ergo-MMALBP-HRC), incorporating ergonomic risk factors into the task allocation process. A mixed-integer linear programming (MILP) model is formulated to minimize cycle time while ensuring an equitable distribution of physical, environmental, and psychosocial ergonomic risks across workstations. Ergonomic risks are assessed using the Quick Exposure Check (QEC), Occupational Repetitive Actions Index (OCRA), Rapid Entire Body Assessment (REBA), and the Copenhagen Psychosocial Questionnaire (COPSOQ), providing a comprehensive evaluation of human and cobot task assignments. A case study conducted on a dishwasher assembly line demonstrates the efficacy of the proposed approach, achieving up to a 15% reduction in cycle time and a 38% in ergonomic risk scores. Computational experiments with varying levels of robot integration indicate that cobot deployment enhances operational efficiency while significantly mitigating ergonomic risks. Sensitivity analysis reveals that prioritizing ergonomic objectives further decreases risk scores, albeit with a minor increase in cycle time. The findings underscore the necessity of balancing productivity and worker well-being in collaborative assembly environments. This study provides a structured methodology for integrating ergonomic considerations into assembly line balancing, offering valuable insights for industries seeking to optimize efficiency while ensuring a safer and more sustainable work environment. The proposed framework contributes to the advancement of human-centric manufacturing by facilitating the effective collaboration between human workers and robotic systems.