P-Temporal Petri Nets for Hoist Scheduling Problem

This paper aims to present P-Temporal Petri Net models for a specific kind of real industrial problems. This class of problems is known in the literature as CHSP, Cyclic Hoist Scheduling Problem. Several jobs have to flow through a production line according to an ordered bath sequence. Firstly, they enter the line from a loading buffer. Then, they will be soaked sequentially in a series of tanks containing specific chemical baths. Finally, they will leave the line at the unloading buffer. The processing time duration of each job in each tank is not constant but confined in a time interval. Moreover the transport of jobs between tanks is insured by a transport resource called hoist. In this paper, we propose a linear programming model to determine an optimal production plan of the studied system while determining the exact beginning and ending instants of each task. The second contribution of the paper is to propose P-Temporal Petri net models describing the behavior of many configurations of the production line. The proposed modeling approach enables to describe the system and validate its qualitative properties using the simulation tool Visual Object Net ++.