A Weighted Robust Two-Stage Stochastic Optimization Model for Supplier Selection and Order Allocation under Uncertainty

This paper presents an integrated model as a combination of fuzzy analytical hierarchy process (FAHP), scenario-based two-stage stochastic programming and robust optimization approaches for the problem of supplier selection and order allocation under supply risk conditions. Uncertainties in the supply of materials are considered under three scenarios: increased sanctions, stability of sanctions, and sanctions removal. In the first step, the main qualitative factors for the selection of suppliers are identified and a specific weight is assigned to each supplier through FAHP. In the second step, these weights are introduced as inputs to a two-stage stochastic programming model and affect the second-stage variables. In the third step, we use the Mulvey formulation and then linearize the resulted robust two-stage stochastic model. The model is a integer linear programming model solved by CPLEX for a case study and the results are discussed. Finally, a sensitivity analysis is performed on the parameters of the robust model and the balance between the total cost and the unfulfilled demand is shown.