A Bi-Objective Optimal Task Scheduling Model for Two-Machine Robotic-Cell Subject to Probable Machine Failures

In this study, we model a stochastic scheduling problem for a robotic cell with two unreliable machines susceptible to breakdowns and subject to the probability of machine failure and machine repair. A single gripper robot facilitates the loading/unloading of parts and cell-internal movement. Since it is more complicated than the other cycles, the focus has been on the S2 cycle as the most frequently employed robot movement cycle. Therefore, a multi-objective mathematical formulation is proposed to minimize cycle time and operational costs. The -constraint method is used to solve small-sized problems. Non-dominated Sorting Genetic Algorithm II (NSGA-II), is used to solve large-sized instances based on a set of randomly generated test problems. The results of several test problems were compared with those of the GAMS software to evaluate the algorithm s performance. The computational results indicate that the proposed algorithm performs well. Compared to GAMS software, the average results for maximum spread (D) and Non-Dominated Solutions (NDS) are 0.02 and 0.04, respectively.