Solving a flexible resource-constrained project scheduling problem under consideration of activity priorities

In the context of real-world optimization problems in the area of production and logistics, multiple objectives have to be considered very often. Precisely such a situation is also regarded in this work. For a resource-constrained project scheduling problem with activity selection and time flexibility, a new bi-objective extension is developed. Motivated by a steel industry production case, each of two already existing objective functions, makespan minimization and time balance maximization, is deployed together with a newly developed objective, the so-called activity priority maximization. To solve the resulting two bi-objective optimization problems and provide all existing trade-off solutions, the $$\epsilon $$-constraint method is used. A constraint programming model is presented and solved with the CP Optimizer of IBM ILOG CPLEX and the results are compared concerning solution quality and runtime, showing the competitiveness of the developed model.