Bi-objective optimization for Scheduling and Multi-skilled Worker Assignments in the Hybrid Flow Shop

Abstract

This paper investigate a bi-objective scheduling and worker assignment problem in a hybrid flow shop. The difficulty of this problem lies in four aspects: (i) the workers differ with each other in both the quantity and proficiency of their acquired skilles; (ii) each processing stage is comprised of parallel unrelated machines; (iii) sequence dependent setup time should be considered and respected; (iv) both the makespan and the total flow time should be minimized simultaneously. To solve this bi-objective optimization problem, we first formulate it into a mixed integer linear programming model, then the commonly used exact solution method ϵ-constraint method is adopted to solve the model. A small instance is randomly generated and tested, the testing result demonstrates the effectiveness of the proposed model.