A hybrid Petri nets model of networked manufacturing systems and its control system architecture

Abstract

Purpose - To introduce a Petri nets model that describes a networked manufacturing system and its dynamics. Design/methodology/approach - A hybrid Petri nets model is constructed, the continuous part of which is to describe the dynamics of the production process within a manufacturing system and the discrete part of which is to describe the dynamics of the ordering and delivering process between every two manufacturing systems. In addition, the mathematical formulation of the dynamics of networked manufacturing systems is proposed to describe its behaviors in detail. Based on the model, the control system architecture of networked manufacturing systems is constructed to make and execute the production plan, solve the conflicts among manufacturing systems and realize the reconfiguration of the network. Findings - There are two key aspects in the dynamics of this hybrid system: first, in the continuous part of this hybrid system, the production process, the variables are discrete. Accordingly, the change of the systems states is not always continuous. Second, in the discrete part of this hybrid system the control variables are actually the safety and objective inventory levels and the minimum quantity of cumulative orders to trigger deliveries which determine the time and quantities of ordering or delivery. However, the relations between them are non-linear. Originality/value - Based on the model, the control system architecture of networked manufacturing systems can be constructed to make and execute the production plan, solve the conflicts among manufacturing systems and realize the reconfiguration of the network.