Browsing by Author "Varela, Leonilde"
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- Autonomous production control: a literature reviewPublication . Martins, Luis; Fernandes, Nuno O.; Varela, LeonildeAutonomous production control (APC) aims at improving production systems performance through fast and flexible reaction to changes in dynamic production environments. APC shifts the power of decision from a central planning unit, towards single intelligent and distributed logistic objects that can cope with the rising complexity of today’s manufacturing systems. The purpose of this research is to analyse the current state of art on APC in discrete manufacturing industries, throughout a systematic literature review. The study’s objectives were to: (1) identify specialists in APC; and (2) identify theoretical developments and practical implementations. The reviewed was obtained by searching the Scopus database - a total of 49 papers have been analysed. The findings revealed that there is not much work carried out on APC until now, and that most of the contributions are theoretical. It is hoped that this literature review will contribute to enhance research in this science field.
- A comparison of production control systems in a flexible flow shopPublication . Silva, Cristóvão; Reis, V.; Morais, A.; Brilenkov, I.; Vaz, J.; Pinheiro, T.; Neves, M.; Henriques, M.; Varela, Leonilde; Pereira, G.; Fernandes, Nuno O.; Silva, Sílvio do CarmoProduction control in make-to-order must address the companies’ need for short delivery times and on-time deliveries. Several production control systems may be used to meet these needs. This paper presents a simulation study to evaluate the delivery performance of the TKS, GKS and POLCA production control systems, in the context of a make-to-order flexible flow shop. Since TKS is used for make-to-stock manufacturing, an adaptation of it is made to use in make-to-order. Results of a simulation study show that the adapted TKS outperforms POLCA, but performs worse than GKS. The study is a contribution for the alignment of production control theory to the industrial practice.
- Literature review on autonomous production control methodsPublication . Martins, Luis; Varela, Leonilde; Fernandes, Nuno O.; Silva, Sílvio do Carmo; Machado, JoséProduction environments are becoming more complex and dynamics. This is influenced by external factors related with products’ characteristics and costumers’ requirements and internal factors related with processing times variability, machine failures, setup times, between others. To face this increasing complexity and dynamics, it is crucial to have effective production control methods, considering Interoperability Enablers for Cyber-Physical Systems. However, production control methods most in used today, are focused on centralised decision-making and planning, and considered inadequate to deal with the increasing dynamics of these systems. Autonomous Production Control (APC) may be an adequate alternative to face this complexity, allowing flexible and rapid reaction to possible disturbances that may occur in the production system. However, as APC is the relatively new concept, there are no existing surveys. Therefore, we review and discuss the literature on APC methods to bring more attention to this promising topic of research, highlighting future research directions.