Pharmacy automation is becoming a key technology to cope with the increase in the demand of healthcare services. In this context, the Automated Drug Dispensing Systems allow for a large volume of dispensing compared to manual dispensing. In this paper, we address the medication assignment problem for an Automated Dispensing System based on a Free-Fall Flow-rack. The current use of these systems adopts a random distribution of drugs inside the rack. The research gap to be filled is to integrate the mutual use of certain drugs together and their placement in neighboring compartments. First, we use a network of Conflicting Timed Event Graphs (CTEGs), a class of timed Petri nets with shared resources, to model the dispensing system. Second, we develop a new method for controlling CTEGs under Mutual Exclusion Constraints (MECs) to solve the problem of drug assignment, using a control approach based on Min-Plus algebra. Finally, a case study of assigning drugs is given to illustrate the proposed methodology and show the efficiency of the developed control laws.

Automated Dispensing Systems; Drugs assignment; Mutual exclusion constraints; Discrete event systems; Conflicting timed event graphs; Min-Plus algebra; Control laws;