Pierre David

Reliability study of complex physical systems using SysML

The development of safety critical systems becomes even harder since the complexity of these systems grows continuously. Moreover, this kind of process involves the use of powerful design methods and precise reliability techniques that utilize dissimilar models and construction policy. In this article we propose a method to unify and enhance this process by linking functional design phase using SysML with commonly used reliability techniques such as FMEA and dysfunctional models construction in AltaRica Data Flow. We present how SysML models can be analyzed automatically in order to produce an FMEA and expose a parallel between SysML models and AltaRica Data Flow ones. The given approach is structured around a database of dysfunctional behaviors that supports the studies and is updated by the obtained results. We exemplify the approach to analyze a system of level controlling of a tank.

Mastering safety and reliability in a model based process

This article follows a line of papers focused on defining a method to improve the realization of reliability analysis during the System Engineering process. As MBSE becomes a fundamental concept for specifying and designing systems, our method takes full advantages of this approach and try to provide tools to ease the specification stage and the integration of RAMS early in the conception process. Our method called MeDISIS is related to the use of SysML to support MBSE and RAMS activities Currently, MeDISIS is used within an industrial project to design a hypersonic aircraft which is a relevant complex and critical system. During this project, MeDISIS has been adapted to take into account technologies devoted to embedded systems. Furthermore, MeDISIS had to comply with the tools, used by our industrial partners during the design stage. In this work, we present the new architecture of MeDISIS, and the process added recently.

Designing the database for a reliability aware Model-Based System Engineering process

This article outlines the need for a reliability database to implement model-based description of components failure modes and dysfunctional behaviors. We detail the requirements such a database should honor and describe our own solution: the Dysfunctional Behavior Database (DBD). Through the description of its meta-model, the benefits of integrating the DBD in the system design process is highlighted. The main advantages depicted are the possibility to manage feedback knowledge at various granularity and semantic levels and to ease drastically the interactions between system engineering activities and reliability studies. The compliance of the DBD with other reliability database such as FIDES is presented and illustrated.

Improving reliability studies with SysML

In this paper, we introduce a methodology for the reliability analysis of complex systems during their design. The challenge of such a method is to be efficient and accessible for system engineers. We gear this method towards the reuse of functional models expressed in the widely used languages of OMG (Object Management Group). We discuss the improvements brought by SysML for reliability studies in comparison with previous works using UML. Namely, we underline its utilization for the automatic synthesis of FMEA and indicate how it may be expanded for other reliability analyses. We describe a new approach for the analysis of system models that, thanks to its focus on flows, enables the revelation of the Failure Mode propagation deducted from the functional model. The technique presented here can be implemented on commercial tools, because it strictly respects the SysML metamodel. Regarding our experience in using SysML, we can conclude that this new modeling language is well-suited to support at least the first step of reliability analysis (i.e. FMEA-like analysis) and shows potential for integrating other analyses concurrently with system design (e.g. Fault Tree analysis, failure scenario studies).

A sensor placement approach for the monitoring of indoor scenes

Within the framework of a French project, which aims at developing a new human presence sensor, we intend to design a sensor system simulator. During the establishment of the requirements of that new sensor we raised that the mission of a global scene survey could only be performed by a collection of several systems using very diverse technologies. This article presents the development of a method for the placement of multi-technology and multisensor systems. The considered environments are room or set of rooms in office buildings or individual homes. We will explain how we managed to represent the use of different sensors considering their various environments. Then, the way of exploiting these models using genetic algorithms is discussed. Those models are oriented for finding system placement and therefore for helping sensor networks deployment.

A modelling language for assembly sequences representation, scheduling and analyses

The aim of this paper is to study the methods for assembly representation supporting the level of automation (LoA) decision process. Based on a literature review on the topic of LoA decision-making, a need for involving the assembly sequence in the decision was identified. The representation methods used in both assembly modelling and planning and other more generic approaches in the literature were studied and evaluated. The evaluation has been based on a requirements definition describing how the representation should support the decision about automation. Identified gaps in requirement satisfaction from the existing approaches led to the definition of the assembly sequence modelling language (ASML), a new modelling language that combines principles from and improvements on the studied methods and a standard vocabulary of assembly actions. The modelling language was demonstrated in an assembly example and was successfully evaluated with regard to the defined requirements. Thus, this new modelling approach, ASML, is offered as an innovative and intuitive support in the decision-making process for selecting automation levels in Assembly.

A review of cost estimation models for determining assembly automation level

The importance of early phase cost estimation is presented and argued.Most appropriate literature cost models to the issue are identified and reviewed.The suitability of literature cost models is assessed and discussed.Relevant cost drivers are identified.A cost estimation outline is proposed to support assembly cost prediction. The aim of this research is to support early phase cost estimation for assembly systems design and automation decision. During this phase, various alternatives of assembly systems with different automation levels can be generated. The alternatives generation is performed using available information on product design, assembly sequences, and planned production information. The issue is to assess given alternatives, identify, and opt for the most appropriate one. Several criteria have to be considered in this decision. The economic aspect represents one of the most preponderant, including cost and profitability prediction. The importance and challenges of this complex issue are highlighted in this paper with feedbacks from manufacturers and the literature. The literature in the field is reviewed, presented, and analyzed. For this sake, a selection of cost models is performed covering a wide chronological range, journals, and fields including assembly and manufacturing models. Classification techniques of cost estimation works are presented and exploited in the proposed review. It is used to filter and discuss models suitability for the defined assembly automation decision issue. The most appropriate models are more thoroughly reviewed and discussed. Useful literature costing techniques, features, and relevant cost drivers are also identified. They cover multiple aspects as production information, resources features or performances. Finally, the review findings are illustrated by a cost estimation outline proposal to support early phase cost prediction for assembly systems design and automation decision.

A cost estimation model to support automation decision in assembly systems design

Cost analysis is crucial in the design of assembly systems and the decision on their level of automation (LoA). This paper presents a cost estimation model of assembly system that is used to decide their LoA during the early phase of projects. Based on an extensive literature review, a complete cost model integrating multiple cost drivers is proposed. This model is then exploited to create the objective function of an integer linear programme model utilised to solve the LoA decision problem. The work provides a way to perform cost estimation of assembly systems alternatives and to decide the most appropriate LoA in assembly. The cost estimation model is built with a parametric approach allowing the definition of various optimisation objectives. The proposed integer programme, complement this approach by proposing the suitable constraints set, that describes the LoA decision problem.

Standardized Vocabularies for Assembly Systems Modelling and Automation Alternatives Description

The aim of this research is to support assembly lines designers in conceiving new processes with optimal automation levels selection. Several alternatives with various automation options may exist. Graphic representations and analyses of the different designs are needed. The finality is to offer a quick, exhaustive, and reliable way of modelling alternatives based on a given product design. In this sense we propose a new assembly tasks vocabulary to be combined to an existing lower layer vocabulary of elementary motions and a graphic modelling language. These developments deal with an existing automation decision approach as an extension allowing to overcome identified gaps and to ease its implementation and computerization. The proposal facilitates assembly systems alternatives generation with automation options consideration based on an initial representation. The generated alternatives are then subject to further analyses with regard to automation criteria and performance indicators considering planned production targets.

Methods for Selecting Level of Automation: A Critical Comparison of Approaches and Integrated Proposal

The purpose of this paper is to first review and then propose methods for determining the appropriate levels of automation for assembly operations. Based on a literature review in decision making methods, an evaluation against method requirements is made. The analysis shows that no single method fulfills all the defined requirements, yet two methods are identified that jointly address all the requirements: Boothroyd’s and Dewhurst (B&D) method and the Dynamo method. B&D and Dynamo methods are then combined into a new method, exploiting elements of each. An additional step for graphical modeling of the assembly processes using the Assembly Sequence Modeling Language (ASML) is integrated to facilitate alternative exploration. This newly proposed method is discussed and revealed promising in the field of assembly systems Level of Automation (LoA) measurement and improvement.Copyright