Linking hybrid systems to ACD models: a case study in the fibre-glass industry

This paper is aimed at formalising and testing a model for hybrid systems where the interactions between the continuous process parts and the manufacturing sub-systems are given by minor stoppages. The proposed approach consists in representing the effects of the continuous process dynamics on discrete manufacturing sub-systems by means of autoregressive conditional duration (ACD) models originally conceived to treat high-frequency and irregularly spaced financial transaction data. The model has been applied to a real-life furnace and spooling-bushing department system of a fibre-glass production plant. Results conclude that the ACD-based model proved useful for representing the occurrence of fibre-glass breakage on the spooling-bushing machines and, in more general terms, that the proposed methodology could be really suitable for the logical modelling of the hybrid production systems where the relationships between the continuous and the discrete parts are given by the occurrence of minor stoppages.