A Study on the Project Scheduling Problem with Uncertainty of Resources: Focusing on Rental Resources Requiring Reservation

The inherent uncertainty of a project causes a difference between the project plan and execution, and efforts are needed to reduce the project loss caused by this difference. Accordingly, in research on the project scheduling problem, research on the deterministic model that finds the optimal combination of fixed elements, such as the Resource Contained Project Scheduling Problem (RCPSP), which considers resource constraints, and the Stochastic RCPSP (SRCPSP), which applies uncertainty probabilistically, are being actively studied. This study deals with the case where there are resources required for project execution that must be procured through external reservation (rental), and there is uncertainty in the availability of the corresponding resources at the time of schedule rewriting due to a change in the preceding schedule. To this end, a mathematical model was developed that probabilistically added uncertainty about the availability of resources that must be procured through external reservations (rentals) at the time of schedule rewriting that occurs in the SRCPSP model with uncertainty in the period, and the distribution of the usage points of specific activities that use resources that must be procured through reservations (rentals) was obtained using simulation techniques. Afterwards, the distribution of the usage points of specific activities was appropriately applied to the initial schedule, and an algorithm for improving the average objective function value was developed. According to the simulation results, under the same conditions, the average objective function value of the simulation using the initial schedule after improvement was improved compared to before improvement, proving the validity of the model presented in this study. This study differs from previous studies in that it additionally considered uncertainty about the availability of external rental resources as a probabilistic factor based on the existing SRCPSP model. In addition, it is significant in that the uncertainty about changes in external resources was applied to the schedule problem at the time of project reevaluation.