Mohamed Haddar

A new multi-criteria indicator for mechatronic system performance evaluation in preliminary design level

Optimizing a multidisciplinary integrated system design, taking into account multi-criteria interacting requirements, is a real challenge in mechatronic design. A new multi-criteria indicator for mechatronic system performance evaluation is formulated and described in this paper. An example of mechatronic system design is considered to validate the presented approach. It will be shown that the new indicator helps designers to evaluate and therefore optimize a mechatronic system design efficiently and rapidly.

Conceptual Model for Management of Digital Factory Simulation Information

Digital Factory (DF) aims at proposing simulation tools to design a product and its production system in parallel. Nevertheless, DF is marked by the multiplicity and heterogeneity of simulation models that are used, that slows down its usage in industry. We propose in this paper a conceptual model to manage the different simulation information created and manipulated through a DF project. This model is based on an analysis of the current design strategies and the used simulation tools. Finally, an industrial application has been developed to validate the completeness of this model.

Info Sim: Prototyping an information system for Digital Factory management

Digital Factory can be defined as a set of software tools and methodologies allowing the design, simulation, initiation and optimization of production systems, with regard to the product development process. However, it remains not widespread in the industries, essentially due to the insufficient capability to communicate between the different entities and actors implied in the product development process and so to ensure a global consistency of the product and its production system definition. In this research work, we propose an information system dedicated to the management of data and information of product, production and simulation, which allows the integration of different points of view and the communication between different actors who participate in the Digital Factory process. Such information system has been tested on a case study coming from an industrial context.

Acoustic analysis of hydrodynamic and elasto-hydrodynamic oil lubricated journal bearings

The purpose of the present paper is to investigate the effect of elastic deformation of bearing liner on the acoustic behavior of oil lubricated journal bearings. Analysis is performed for hydrodynamic(HD) and elasto-hydrodynamic (EHD) lubrications. Dynamic behavior and acoustical properties are investigated through an analysis of pressure fluctuation calculated from the Reynolds equation governing the flow in the clearance space of the journal bearing. This is solved numerically using the finite difference method with the successive over relaxation technique. In elasto-hydrodynamic lubrication, the finite element method with in iteration scheme is adopted to solve both Reynolds equation and the three-dimensional elasticity equation representing the displacement field in the bearing shell. The results show that the sound pressure level of the bearing is markedly influenced by the flexibility of the bearing liner, the viscosity of lubricant and the load applied to journal. HD analysis shows that the journal centre’s orbit, from a disturbed position, converges to the static equilibrium position faster than EHD lubrication. The results of the present paper could aid in the design of low-noise rotor-bearing systems supported by oil lubricated journal bearings.

Investigations on Crack Propagation and Strain Energy Release Rate in Notched Woven-Ply Thermoplastic Laminates at High-Temperature

The strain energy release rate G is of prime importance in composite materials fracture mechanics. In order to experimentally and numerically evaluate this parameter in the case of quasi-isotropic and angle-ply (AP) woven-ply thermoplastic (TP) laminates, single edge notched (SEN) specimens have been subjected to monotonic tensile loading at T > Tg when the toughness and the viscous behavior of the (TP) matrix are exacerbated. From the simulation standpoint, a particular attention was paid to the type of meshing as well as its refinement in the vicinity of the crack tip where the triaxiality rate leads to significant stress concentrations. For this purpose, a linear spectral viscoelastic and a generalized Norton-type viscoplastic models have been used. A comparison between two types of meshing (radiant and concentric) has been conducted. Both types of meshing allow us to define crowns in order to represent the surface of the integration ring around the crack tip. These crowns are necessary to evaluate the strain energy release rate GI in opening mode using Gθ-integral computation. Both overstress and overstrain profiles near the crack tip were investigated and validated using theoretical stress fields derived from the linear elastic fracture mechanics (LEFM) framework and overstrain fields obtained from digital image correlation (DIC) to verify the model’s ability to provide accurate mechanical fields at singularity zones.

Modeling and Simulation of Micro EDM Process

In contrast to Robust Design applications, the simulation of a mechatronic system including both mechanical and electrical parts requires a different strategy for the investigation of its robustness. Differences mainly results from interactions between the mechanical and the electrical part of the mechatronic system. Micro Electrical Discharge Machining (μEDM) is good example for mechatronics application. This paper presents an approach to evaluate robustness of mechatronic comfort systems. At the outset, this study revolves around modeling of the various constitutive blocs of the machine through the appliance of the ‘Matlab/Simulink’ as well as analyzing the strength of this model by resorting to the same software programme of simulation . Having gone through the phase of simulation, the main outcomes of this experience where noticed at the level of the parameters defining the drilling such as the gap and the position of the electrode.

CSP approach and interval computation for the coupling between static and dynamic requirements in the preliminary design of a compression spring

In this study, a new design approach based on an interval computation method and the constraint satisfaction problem technique (CSP approach) was discussed. It has been applied in the design of a compression spring, implemented in the vehicle suspension system. A design process is proposed and compared with what is done in conventional design. IT allows making static and dynamic sizing in one step. In fact, with the CSP, static and dynamic requirements can be coupled in the same step of sizing. In the CSP all requirements imposed can be integrated from the beginning. So it avoids falling on the loop “design-simulate-back to the initial step in case of failure”. In this study, the design parameters values of the compression spring generated by the CSP verify all requirements and the resulting simulation of the system behaviour respects all constraints required. The results obtained in this study affirmed that the suggested method is valid and potentially useful to the size dynamic system and can be applied easily and effectively.

Robust Optimization of Gear Tooth Modifications Using a Genetic Algorithm

Most studies in gear design analysis and optimization do not account for the presence of uncertainties inherent to the manufacturing and assembly precisions. In this paper, the issue of robustness of gear modifications with regard to transmission error fluctuations is addressed. An approach based on numerical integration (Gauss Quadrature) is adopted and a statistical optimization based on a genetic algorithm is used to determine the robust areas for tooth modifications. Finally, the influences of the gear quality grade and the probability law are analysed.

Effectiveness of an interval computation approach to the dynamic simulation of a MacPherson Suspension system

In this paper, a new design approach based on methods by intervals adapted to the integration of a simulation step at the earliest stage of preliminary design for dynamic systems is proposed. The general idea consists in using the interval computation method to make a simulation by intervals in order to minimize the number of simulations. These intervals represent the domains of possible values for the design parameters of the system. So the parameterized model of system is solved by interval. This avoids launching n simulations with n values for each design parameter. The proposed method is evaluated by several tests on a scalable numerical example. It has been applied to solve parameterized differential equations of a Macpherson suspension system and study its dynamic behavior. The dynamic model of the MacPherson suspension is nonlinear but linearisable. It was transformed into a parameterized state equation by intervals. The solution to this state equation is given in the form of a matrix exponential. Three digital implementations of exponential have been tested to obtain convergent results. Simulations results are presented and discussed.

An Effective Method for the Identification of Support Features in Multi-supported Systems

The mechanical properties of supports in a mechanical system strongly affect its dynamic behavior under real operating conditions. This work presents a new method for identifying the dynamical characteristics of local supports which has been developed along the lines of the work by Ozguven (Mech Syst Signal Process 4:53–63, 1990) and Debut et al. (Proceeding of the 19th international congress on sound and vibration, Vilnius, Lithuania, 2012), which combines measured frequency transfer functions and techniques from structural modifications . As typical for inverse problem , the noise in the frequency transfer functions lead to faulty identifications , so that regularization techniques have been implemented to mitigate noise amplification in the inverse problem . The proposed approach has been then numerically tested on a multi-supported structure, which can be seen as an idealized electricity generator rotor shaft. The results are satisfactory for noise-free data as well as under realistic noise levels.