Maria Di Mascolo

An Analytical Method for Performance Evaluation of Kanban Controlled Production Systems

The aim of this paper is to develop a general purpose analytical method for performance evaluation of multistage kanban controlled production systems. We consider a single-part type production system decomposed into stages in series. Each stage consists of a manufacturing cell and an output buffer. With each stage is associated a given number of kanbans. The kanban controlled production system is modeled as a queueing network with synchronization mechanisms. The basic principle of the proposed approximation method is to decompose the original kanban system into a set of subsystems, each subsystem being associated with a particular stage. Each subsystem is analyzed in isolation using a product-form approximation technique. An iterative procedure is then used to determine the unknown parameters of each subsystem. Numerical results show that the method is fairly accurate.

On the design of generalized kanban control systems

Considers a class of control systems known as generalized kanban control systems (GKCS) which can be used to implement a pull control mechanism in a manufacturing system. In a GKCS, the production system is decomposed into stages, where each stage consists of a production sub‐system. There are two design parameters per stage: one controls the work‐in‐process in the stage and the other determines the maximum number of finished products of this stage. Investigates the influence of these design parameters on the efficiency of generalized kanban control policies by deriving qualitative properties as well as using experimental results on the behaviour of GKCS.

Analysis of assembly systems controlled with kanbans

This paper deals with the problem of evaluating the performance of assembly systems managed with kanbans. In particular we analyze kanban systems functioning with different control policies depending on how kanbans are released in assembly stages. Simultaneous and independent releases of kanbans are considered in the analysis as alternative control policies to be used in assembly systems. Queuing network techniques are used to calculate the major system performance measures such as throughput of the system, percentage of satisfied orders, average level of finished products and average time delay of unsatisfied orders. Simultaneous and independent kanban assembly systems are compared in some numerical cases. The differences, in terms of performance, between the two alternative kanban control policies are evaluated so that the proper control policy can be selected in the design phase of the system. Simulation results are also reported to validate the approximation of the analytical method used to calculate the performance of assembly kanban systems.

A Multi-class Approximation Technique for the Analysis of Kanban-Like Control Systems

Analytical methods have been proposed in the literature for performance evaluation of kanban control systems. Among them, the method presented by Di Mascolo and colleagues appears to be of special interest since it can handle manufacturing stages consisting of any number of machines and it is fairly accurate. This paper presents a new way of deriving the analytical method presented by Di Mascolo et al. The approach is to see the queueing network of the kanban control system as a multiclass queueing network in which each kanban loop is represented by a class of customers. This allows one to use the general technique proposed in Baynat and Dallery for analysing multiclass queueing network using product-form approximation methods. In terms of equations, the new method is equivalent to that previously presented. However, the computational algorithm is much more efficient since it avoids the two levels of iterations involved in the original algorithm. Another major advantage of the new method over that originally proposed is that it provides a general framework for the analysis of more general kanban systems. Indeed, it is shown in this paper how this approach can easily be extended in order to handle kanban systems with multiple consumers and multiple suppliers, kanban-controlled assembly systems and generalized kanban systems.

Fault diagnosis for discrete event systems: Modelling and verification

Abstract This paper proposes an effective way for diagnosis of discrete-event systems using a timed-automaton. It is based on the model-checking technique, thanks to time analysis of the timed model. The paper proposes a method to construct all the timed models and details the different steps used to obtain the diagnosis path. A dynamic model with temporal transitions is proposed in order to model the system. By “dynamical model”, we mean an extension of timed automata for which the faulty states are identified. The model of the studied system contains the faultless functioning states and all the faulty states. Our method is based on the backward exploitation of the dynamic model, where all possible reverse paths are searched. The reverse path is the connection of the faulty state to the initial state. The diagnosis method is based on the coherence between the faulty occurrence time and the reverse path length. A real-world batch process is used to demonstrate the modelling steps and the proposed backward time analysis method to reach the diagnosis results.

Buffer sizing of a Heijunka Kanban system

Heijunka is a key-element of the Toyota production system which levels the release of production kanbans in order to achieve an even production flow over all possible types of products, thus, e.g. reducing the bullwhip effect. In this paper we analyze a kanban controlled and heijunka leveled production system where the arriving demands are controlled and limited by a kanban loop. The production system is modeled as a queueing network with synchronization stations. The aim is to determine the optimal number of production kanbans, and thus the buffer size that guarantees a given service level.

Health smart home for elders - a tool for automatic recognition of activities of daily living

Elders live preferently in their own home, but with aging comes the loss of autonomy and associated risks. In order to help them live longer in safe conditions, we need a tool to automatically detect their loss of autonomy by assessing the degree of performance of activities of daily living. This article presents an approach enabling the activities recognition of an elder living alone in a home equipped with noninvasive sensors.

Makespan minimisation on parallel batch processing machines with non-identical job sizes and release dates

The problem we study in this paper arises from the washing step of hospital sterilisation services. Washers in the washing step are capable of handling more than one medical device set as long as their capacity is not exceeded. The medical device set sizes and arrival times to the sterilisation service may be different, but they all have the same washing duration. Thus, we model the washing step as a batch scheduling problem where medical device sets are treated as jobs with non-identical sizes and release dates, but equal processing times. The main findings we present in this paper are the following. First, we study two special cases for which polynomial algorithms are presented. We then develop a 2-approximation algorithm for the general problem. Finally, we develop a MILP model and compare it with another MILP model from the literature. Computational results show that our MILP model outperforms the model from the literature.

Warehouse performance measurement: a literature review

As the supply chains get more complex, the variety of indicators and tools to measure warehouse performance has also increased. Furthermore, the metrics that are used for performance evaluation are assessed in different manners and hence there is not clear definition for some of these metrics. To address these issues, this literature review focuses on operational warehouse performance measurement, for which the warehouse managers need to carry out periodic analysis. Using the content analysis method, performance indicators are acquired from selected papers and are classified according to time, cost, quality and productivity dimensions. The contributions of this literature review are as follows: we present a synthesis of the literature on operational warehouse performance, we provide the definitions for the performance indicators and a framework to demonstrate their boundaries and, finally, based on the literature analysis, we also provide some discussions on current trends in warehouses and propose future research directions on warehouse performance evaluation.

A generic simulation model to assess the performance of sterilization services in health establishments.

The work presented here is with a view to improving performance of sterilization services in hospitals. We carried out a survey in a large number of health establishments in the Rhône-Alpes region in France. Based on the results of this survey and a detailed study of a specific service, we have built a generic model. The generic nature of the model relies on a common structure with a high level of detail. This model can be used to improve the performance of a specific sterilization service and/or to dimension its resources. It can also serve for quantitative comparison of performance indicators of various sterilization services.