MILP model to decrease the number of workers in assembly lines with human-robot collaboration

The benefits of automatization in human-operated assembly lines are well known. When complete automatization is not possible, a combined production system, with both manual and automated parts, could be the best configuration. Adding robots to an only human-operated assembly line may decrease the number of stations and consequently the number of workers in the line. Even if, the number of stations cannot be decreased, the number of workers could be reduced in case of proper reallocation of tasks. In this paper, three mixed-integer linear programming (MILP) models are suggested to minimize in three steps the number of workers, the number of robots, and the cycle time in an assembly line with a predefined number of stations and partial automatization. The results for the optimization problems are shown based on the data of an assembly line producing power inverters. The proposed MILP model is implemented in the AIMMS modeling environment.