Modeling and scheduling of ratio-driven FMS using unfolding time Petri nets

In this paper, we focus on the analysis of a cyclic schedule for the determination of the optimal cycle time and minimization of the Work in Process (WIP for short). Especially, this paper deals with product ratio-driven FMS cyclic scheduling problem with each other products and ratios using Timed Petri nets unfolding (TPN for short). TPN slicing and unfolding are applied to analyze this FMS model. We can divide original system into subsystem using TPN slices and change iterated cycle module into acyclic module without any loss of other behavior properties.     

On the performance of the base-stock inventory system under a compound Erlang demand distribution

In this paper, we propose a new method for determining the optimal base-stock level in a single echelon inventory system where the demand is a compound Erlang process and the lead-time is constant. The demand inter-arrival follows an Erlang distribution and the demand size follows a Gamma distribution. The stock is controlled according to a continuous review base-stock policy where unfilled demands are backordered. The optimal base-stock level is derived based on a minimization of the total expected inventory cost. A numerical investigation is conducted to analyze the performance of the inventory system with respect to the different system parameters and also to show the outperformance of the approach that is based on the compound Erlang demand assumption as compared to the classical Newsboy approach. This work allows insights to be gained on stock control related issues for both slow and fast moving stock keeping units.     

A New Cyclic Scheduling Algorithm for Flexible Manufacturing Systems

Flexible manufacturing system control is an NP-hard problem. A cyclic approach has been demonstrated to be adequate for an infinite scheduling problem because of maximal throughput reachability. However, it is not the only optimization criterion in general. In this article we consider the minimization of the work in process (WIP) as an economical and productivity factor. We propose a new cyclic scheduling algorithm giving the maximal throughput (a hard constraint) while minimizing WIP. This algorithm is based on progressive operations placing. A controlled beam search approach has been developed to determine at each step the schedule of the next operations. After presenting the main principles of the algorithm, we compare our approach to several most known cyclic scheduling algorithms using a significant existing example from the literature.     

Integration of FMS performance evaluation models using patterns for an information system design

The objective of our work is to create an information system able to integrate different view points concerning the design and the control of a Flexible Manufacturing System. Numerous methods based on generic reference frameworks have been proposed for the modeling of all the aspects of production systems. These models have to be instantiated in order to be applied to specific systems. The difficulties are then to integrate pre-existing models of the studied systems with those obtained by the instantiation of the generic reference framework.

The proposed approach tackles the problem from the information system point of view. A meta-modeling bottom-up approach is presented based on the notion of patterns in order to facilitate the integration step.

An example concerned with the performance evaluation and scheduling of a production system is presented to show how the product viewpoint can be built in order to be integrated later with other viewpoints.     

Correction to: Risk‑aware business process management using multi‑view modeling: method and tool

Requirements Engineering - A correction to this paper has been published: https://doi.org/10.1007/s00766-021-00356-2     

Risk-aware business process management using multi-view modeling: method and tool

Requirements Engineering - Risk-aware Business Process Management (R-BPM) has been addressed in research since more than a decade. However, the integration of the two independent research streams...     

Indirect monitoring of the failures of a flexible manufacturing system under cyclic scheduling

We are interested in flexible manufacturing systems and more particularly in their well functioning. In such a context, we opted for a deterministic and cyclic command, which optimizes several criteria such as Work in Process and workflow. In order to supervise the system functioning, we propose to survey the system output and compare it to the deterministic schedule. We will give a diagnostic principle to identify the root cause of the detected symptoms.     

Formal Approach of FMS Cyclic Scheduling

This correspondence is related to the determination of both control and scheduling of flexible manufacturing systems under cyclic command. Different approaches can be found in the literature, but we focus on those which respect the optimal throughput while minimizing the work in process. So, we recall methods of performance evaluation developed during the last 20 years. The last part is devoted to a new approach of cyclic scheduling using a Petri net. This method uses algebraic tools (dioids) developed for the study of marked graphs. In this way, the problem of the scheduling is progressively transformed into a problem of the search of solution(s) on a system of equations     

A new approach for loop machine layout problem integrating proximity constraints

This paper focuses on the machine arrangement problem on common loop network in a flexible manufacturing system. Existing studies aim to place machines at pre-fixed positions around a loop network. This problem is considered as a permutation problem that aims to find the best combination to reduce generated costs. In this work, we try to add more complexity to this problem by respecting the proximity constraints, defined by the experts, between the machines. To do this, we propose an algorithm based on direct distance measure. Logically, proximity constraints are checked using direct distances but costs are calculated using travelled distances. Throughout this study, we seek the best machine layout in four transport system configuration types to minimise the sum of flow time distances. Comparing our algorithm results with two hybrid genetic algorithms, the empirical results show that the proposed algorithm provides the most suitable solutions.     

On-line fault diagnosis of FMS based on flows analysis

Any flexible manufacturing system (FMS) may face fault which may disrupt the production and cause delays. Thus, the identification of the source of failure is very important to intervene rapidly. This paper aims to develop an indirect and incremental diagnostic approach to identify the root cause of the observed delay in the context of a single fault occurrence. In this study the observation is done only at the output of the system to measure the output dates of each part and to detect the eventual delay. For this purpose, a mathematical model is developed to model the proposed diagnostic approach of FMS under cyclic scheduling. This cyclic approach provides intermediary reference points to detect any discrepancy with regard the predictive scheduling. These intermediary reference points correspond to the end of each cycle defined by the scheduling. To solve this problem, the constraint programming technique is used. Finally, the performance of the proposed approach is evaluated with respect to the literature. The major merit of this study is to prove the capacity to diagnose efficiently the progressive faults of a plant without the necessity to add sensors dedicated to its monitoring.