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A facility layout design is one of the most commonly faced problems in the manufacturing sectors. The problem is mixed-integer in nature and usually an NP-hard problem. Due to mixed-integer nature of the problem, it is difficult to solve the problem using classical optimization techniques. The classical optimization techniques are better for local search of the optimal solution. However, these algorithms are not efficient when there are multiple optimal solutions and alternate optimal solutions. To overcome these limitations, this paper proposed a new interactive evolutionary algorithm based local search algorithm for solving static facility layout problems with unequal compartments. This is an iterative based two steps algorithm. The evolutionary algorithm creates the new solutions for the local search algorithm to obtain a local optimal solution. The designer can interact between these processes to derive the best possible solution of the problem. The objective function of the problem is non-linear one in which the sum of the material handling cost has been minimized. Apart from the conventional evolutionary operators, i.e. selection, crossover, mutation and elitism, this paper has also proposed exchange and rotation operators. The rotation operator is used to avoid mixed-integer formulation of the problem for the local search problem. The use of rotation operator has also reduced the number of variables of the problem significantly. The performance of the model is tested over previously solved problems selected from the literature. The evaluation of the results shows that the performance of the proposed model is better than many existing algorithms and has the potential for real-world applications.

The accessibility verification of the assembly/disassembly plays an important role in the process of product design. In the last decade, the sampling based motion planners have been successfully applied to solve the accessibility verification. However, the narrow passage which is a common problem in the assembly tasks is still a bottleneck. Meanwhile, the requirement of perception and emotion assessment drives the interaction between users and automatic path planners in the virtual assembly process. In this paper, a curve matching method is used to explore the implicit relationship between the topological information of scenarios and the motion of objects, based on which an interactive motion planning framework that can learn from experience is constructed.Our framework consists of two main processes: a learning process and a motion generation process. In the former process, the motion segment (a part of motion path) and its related scenario segment (a part of workspace passed through by the object) are gathered, after an interactive motion planning process finds a collision-free motion path or reaches the conclusion of inaccessibility. According to the similarity between the skeletons of scenario segments, the gathered scenario segments and motion segments are organized by a hierarchical structure in the motion library. The latter process permits users to control only one point in the workspace for the selection of a new scenario, and then the similar scenarios are retrieved from the motion library, to help quickly detect the connectivity of the new scenario and generate a repaired motion path to guide users with feasible manipulations. We highlight the performance of our framework on a challenging problem in 2D, in which a non-convex object passes through a cluttered environment filled with randomly shaped and located non-convex obstacles. Maximal sphere sequence represents the scenario. The centerline of maximal sphere sequence represents the scenario skeleton.The motion of object has close relationship with the change of the skeleton and volume size of scenario.Motion learning is based on computing the similarity of scenarios by dynamic time warping (DTW).Scenario retrieval is highly efficient due to the hierarchical clustering in motion library.Releasing humans from rotation manipulation in complex assembly verification with learned motion experience.

International audience; Electronic Phased-Array Radars offer new possibilities for Optimization of Radar Search Pattern by using bi-dimensional beam forming and beam steering, along both elevation and azimuth axes. The minimization of the Time-Budget required for multiple Radar scanning missions in localized clutter, under constraints of range and detection probability, can be approximated as a Set Cover Problem. We present a Set Cover Problem approximation for Time-Budget minimization of the Radar Search Pattern, and solved this optimization problem using Integer Programming methods based on Branch&Bound and linear relaxation.

This paper presents a rational approach to the design of a catamaran's hydrofoil applied within a modern context of multidisciplinary optimization. The approach used includes the use of response surfaces represented by neural networks and a distributed programming environment that increases the optimization speed. A rational approach to the problem simplifies the complex optimization model; when combined with the distributed dynamic training used for the response surfaces, this model increases the efficiency of the process. The results achieved using this approach have justified this publication.

Musculoskeletal disorder (MSD) is one of the major health problems in physical work especially in manual handling jobs. In several literatures, muscle fatigue is considered to be closely related to MSD, especially for muscle related disorders. In addition to many existing analysis techniques for muscle fatigue assessment and MSD risk analysis, in this paper, a new muscle fatigue model was proposed. The new proposed model reflects the influence of external load, workload history, and individual differences. This model is simple in mathematics and can be easily applied in realtime calculation, such as the application in realtime virtual work simulation and evaluation. The new model was mathematically validated with 24 existing static models by comparing the calculated METs, and qualitatively or quantitatively validated with 3 existing dynamic models. The proposed model shows high or moderate similarities in predicting the METs with all the 24 static models. Validation results with the three dynamic models were also promising. The main limitation of the model is that it still lacks experimental validation for more dynamic situations. Relevance to industry Muscle fatigue is one of the main reasons causing MSDs in industry, especially for physical work. Correct evaluation of muscle fatigue is necessary to determine work-rest regimens and reduce the risks of MSD., Comment: arXiv admin note: substantial text overlap with arXiv:0901.0222

Engineering design of complex systems is a decision making process that aims at choosing from among a set of options that implies an irrevocable allocation of resources. It is inherently a multidisciplinary and multi- objective process; nowadays, the designer has to face the continuous growing complexity of engineering problems, but also, the increasing economic competition that have led to a specialization and distribution of knowledge, expertise, tools and work sites. Products become more and more complex and their design is usually of large scale, characterized by an important number of design variables, parameters, requirements, constraints and objectives. Consequently, multi- objective optimization (MOO) and multidisciplinary design optimization (MDO) are more and more used to provide one optimal solution—by the use of a “a priori” or interactive preferences modelling—or a set of optimal solutions—in which the designer will have to choose “a posteriori” the one to be developed. The objective of this paper is to present an original and efficient Collaborative Optimization Strategy for Multi-Objective Systems (COSMOS) designed to find the sub-set of the design space that contains the best solutions – Pareto frontier – of the global system.

Employing three different active layer widths, aluminium gallium nitride-based double heterostructures have been grown on GaN template by metal–organic chemical vapour deposition. The crystalline quality of the heterostructures has been investigated using high-resolution X-ray diffraction analysis. Optical and decay time studies have been carried out using room-temperature photoluminescence and time-resolved photoluminescence, respectively. The interface recombination velocity (S) between active and barrier layers has been determined.

In this paper, two complementary methods are introduced to analyze the sensitivity of a three-degree-of-freedom (3-DOF) translational parallel kinematic machine (PKM) with orthogonal linear joints: the Orthoglide. Although these methods are applied to a particular PKM, they can be readily applied to 3-DOF Delta-Linear PKM such as ones with their linear joints parallel instead of orthogonal. On the one hand, a linkage kinematic analysis method is proposed to have a rough idea of the influence of the length variations of the manipulator on the location of its end-effector. On the other hand, a differential vector method is used to study the influence of the length and angular variations in the parts of the manipulator on the position and orientation of its end-effector. Besides, this method takes into account the variations in the parallelograms. It turns out that variations in the design parameters of the same type from one leg to another have the same effect on the position of the end-effector. Moreover, the sensitivity of its pose to geometric variations is a minimum in the kinematic isotropic configuration of the manipulator. On the contrary, this sensitivity approaches its maximum close to the kinematic singular configurations of the manipulator.

In the context of concurrent engineering, this paper presents a quite innovative approach to the collaborative optimization process, which couples a multi-objective genetic algorithm with an asynchronous communication tool. This optimization method allows the collaborative and multi-sites design to be performed without requiring significant investments or changes in the company organization. To illustrate this methodology, the collaboration of three European companies on the optimization of a ship hull is described. The hull shape is automatically optimised distributing the elements of the optimization loop among three distant sites. Our study demonstrates that when multi-objective optimization is carried out in a distributed manner it can provide a powerful tool for concurrent product design.

The increasing economic competition of all industrial markets and growing complexity of engineering problems lead to a progressive specialisation and distribution of expertise, tools and work sites. Most industrial sectors manage this fragmentation using the concurrent engineering approach, which is based on tools integration and shared databases and requires significant investments in design and work organisation. Besides, the multidisciplinary design optimisation (MDO) is more and more used as a method for optimal solutions search with regard to multiple coupled disciplines. The paper describes a quite innovative multidisciplinary optimisation method based on robust design techniques: MORDACE (multidisciplinary optimisation and robust design approaches applied to concurrent engineering). Managing uncertainty due to design teams collaboration, our automatic optimisation strategy allows concurrently designing different aspects or parts of a complex product. The method assures effective design work distribution and high optimisation results, containing the CPU time. In addition, our strategy is suited to the early stages of the design cycle, where evolutions of design goals and constraints are possible and exhaustive information about the design space is necessary. A roll stabiliser fin optimisation is presented as an example of this method applied to an industrial design problem.

International audience; The aim of designing wind turbine blades is to improve the power capture ability. Since rotor control technology is currently limited to controlling rotational speed and blade pitch, an increasing concern has been given to morphing blades. In this paper, a simplified morphing blade is introduced, which has a linear twist distribution along the span and a shape that can be controlled by adjusting the twist of the blade's root and tip. To evaluate the performance of wind turbine blades, a numerical code based on the blade element momentum theory is developed and validated. The blade of the NREL Phase VI wind turbine is taken as a reference blade and has a fixed pitch. The optimization problems associated with the control of the morphing blade and a blade with pitch control are formulated. The optimal results show that the morphing blade gives better results than the blade with pitch control in terms of produced power. Under the assumption that at a given site, the annual average wind speed is known and the wind speed follows a Rayleigh distribution, the annual energy production of wind turbines was evaluated for three types of blade, namely, morphing blade, blade with pitch control and fixed pitch blade. For an annual average wind speed varying between 5~m/s and 15~m/s, it turns out that the annual energy production of the wind turbine containing morphing blades is 24.5~\% to 69.7~\% higher than the annual energy production of the wind turbine containing pitch fixed blades. Likewise, the annual energy production of the wind turbine containing blades with pitch control is 22.7~\% to 66.9~\% higher than the annual energy production of the wind turbine containing pitch fixed blades.

This paper presents a novel interactive motion planning system for assembly/disassembly operations. Our system consists of three layers: interaction layer, learning layer and motion library layer. In interaction layer, user’s manipulation in difficult scenario is liberated by relaxing collision constraints. The resulting path is retracted and connected by random retraction method and BiRRT algorithm. A motion path which successfully passed through the narrow passage or information of geometrical interference in failed case is returned to user. In learning layer, motion primitives corresponding to prior similar scenario are selected by scenario comparison which is based on medial axis, and then transformed to generate new motions. Significant improvement for motion planning of non-convex object in challenging scenarios with narrow passages is obtained by interactive process. The introduction of learning mechanism can reduce global planning time and obtain experiential knowledge.

Part 9: PLM and Collaborative Product Development; International audience; Assembly and disassembly verification plays an important role in Product Lifecycle Management (PLM). Mass customization and personalized production require greater agility of industrial manufacturers, and consequently the time consumed in assembly processes (which often dominates costs) is of growing importance. Narrow passages which commonly exist in assembly tasks become a bottleneck in the assembly planning process reducing the time saved by using virtual assembly. In this paper, we present a novel interactive motion planning methodology for virtual assembly and disassembly operations. In our method, user’s manipulation with force feedback device in difficult scenario is liberated by relaxing collision constraints. The rough path is retracted by our random retraction method and then connected by BiRRT algorithm. For each user’s operation, a path successfully passing through the narrow passage is presented, or geometrical interference information in failed case is provided for motion re-planning and design modification. Significant improvement for trajectory planning of non-convex object is observed in challenging 2D scenarios with narrow passages.

The aim of designing the wind turbine blades is to improve the power capture ability. Since the rotor control technology is currently limited to controlling the rotor rotational speed and the pitch of the blades, an increasing concern has been given to the morphing blades. In this paper, a simplified morphing blade is introduced, which has a linear twisted distribution along the span and its shape can be controlled by adjusting the root twisted angle and the tip twisted angle of the blade. Moreover, to evaluate the performances of the wind turbine blades, a numerical code based on the blade element momentum theory is developed and validated. The blade of the NREL Phase VI wind turbine is taken as a reference blade, and the optimization problems associated with the morphing blade and pitch control blade are both formulated. The optimal results show that the morphing blade gives better results than the pitch control blade in terms of produced power. Under the assumption that in a given site, the annual average wind speed is known and the wind speed follows the Rayleigh distribution, we can evaluate the annual energy produced by these three blade types. While the annual average wind speed varies from 5 m/s to 15 m/s, the results show that the optimal morphing blade can increase 23.9 percent to 71.4 percent in annual energy production while the optimal pitch control blade can increase 22.5 percent to 67.4 percent in annual energy production, over the existing twisted pitch fixed blade.

Human muscle fatigue is considered to be one of the main reasons for Musculoskeletal Disorder (MSD). Recent models have been introduced to define muscle fatigue for static postures. However, the main drawbacks of these models are that the dynamic effect of the human and the external load are not taken into account. In this paper, each human joint is assumed to be controlled by two muscle groups to generate motions such as push/pull. The joint torques are computed using Lagrange's formulation to evaluate the dynamic factors of the muscle fatigue model. An experiment is defined to validate this assumption and the result for one person confirms its feasibility. The evaluation of this model can predict the fatigue and MSD risk in industry production quickly., Comment: Advances in Robot Kinematics, Innsbruck : Austria (2012)

The aim of designing the wind turbine rotors is to improve the power capture ability. Since the rotor control technology is currently limited to controlling the rotor rotational speed and the pitch of the blades, an increasing concern has been given to the morphing blades. In this paper, a numerical code has been developed and validated based on the blade element momentum theory (BEMT). Then we compare the performance improvements through these different methods. The NREL phase VI wind turbine is selected as a reference wind turbine, and then the performances of six different wind turbines are compared. The results show that the rotor rotational speed control ones can improve the power capture ability well. Toward the variable speed wind turbines, the pitch control and the morphing blade improve the power capture ability hardly. Toward the constant speed wind turbines, the morphing blade has better performance than the pitch control one.

Layout design optimization has a significant impact in the design and use of many engineering products and systems, such as the subdivision of a ship, the layout of facilities in a plant or further still the assembly of parts of a mechanism. The search for an optimal layout configuration is a critical and complex task due to the increasing demands of designers working on varied projects. A layout optimization process is generally divided into different steps: the description, formulation and solving of the problem and the final decision. This process consists in writing an optimization problem that transform designer’s requirements into variables, constraints and objectives. Then, an optimization algorithm has to be used in order to search for optimal solutions that fit with product’s specifications. This paper focuses on the last step which consists, for the designer, in making a choice on the solutions generated by the optimization algorithm. This choice is made according to the global performances of the designs and also the personal judgment of the designer. This judgment is based on the expertise of the designer and the subjective requirements that could not be integrated on the formulation of the problem. This paper proposes a perceptive exploration method, based on an Interactive Genetic Algorithm (IGA), used to explore designs, taking into account the subjective evaluation of the designer. The objective of this method is to select an ideal solution that realizes the best trade-off between the quantitative and qualitative performance criteria. This interactive process is tested on an industrial layout application which deals with the search for an optimal layout of facilities in a shelter.Copyright © 2012 by ASME

International audience; With the increasing of computer capabilities, Computer aided ergonomics (CAE) offers new possibilities to integrate conventional ergonomic knowledge and to develop new methods into the work design process. As mentioned in [1], different approaches have been developed to enhance the efficiency of the ergonomic evaluation. Ergonomic expert systems, ergonomic oriented information systems, numerical models of human, etc. have been implemented in numerical ergonomic software. Until now, there are ergonomic software tools available, such as Jack, Ergoman, Delmia Human, 3DSSPP, and Santos, etc. [2-4]. The main functions of these tools are posture analysis and posture prediction. In the visualization part, Jack and 3DSSPP produce results to visualize virtual human tasks in 3-dimensional, but without realistic physical properties. Nowadays, with the development of computer technology, the simulation of physical world is paid more attention. Physical engines [5] are used more and more in computer game (CG) field. The advantage of physical engine is the nature physical world environment simulation. The purpose of our research is to use the CG technology to create a virtual environment with physical properties for ergonomic analysis of virtual human.

International audience; In ergonomics and biomechanics, muscle fatigue models based on maximum endurance time (MET) models are often used to integrate fatigue effect into ergonomic and biomechanical application. However, due to the empirical principle of those MET models, the disadvantages of this method are: 1) the MET models cannot reveal the muscle physiology background very well; 2) there is no general formation for those MET models to predict MET. In this paper, a theoretical MET model is extended from a simple muscle fatigue model with consideration of the external load and maximum voluntary contraction in passive static exertion cases. The universal availability of the extended MET model is analyzed in comparison to 24 existing empirical MET models. Using mathematical regression method, 21 of the 24 MET models have intraclass correlations over 0.9, which means the extended MET model could replace the existing MET models in a general and computationally efficient way. In addition, an important parameter, fatigability (or fatigue resistance) of different muscle groups, could be calculated via the mathematical regression approach. Its mean value and its standard deviation are useful for predicting MET values of a given population during static operations. The possible reasons influencing the fatigue resistance were classified and discussed, and it is still a very challenging work to find out the quantitative relationship between the fatigue resistance and the influencing factors.

International audience; Component and facility layout plays an important role in the design and usability of many engineering products and systems as mechanical design, process plan, management and architecture including ship compartment layout,... Because of the great complexity of most industrial layout problems, the decision of the acceptable layout is a hard and critical task since the special layout can have a significant consequence on the user satisfaction, the economic cost and broadly speaking the global performances. Thus, in order to propose to the designer an optimal spatial arrangement in a reasonable time, this paper develops an interactive optimization strategy based on a genetic algorithm coupled with a separation algorithm. The proposed method is tested on the layout problem of a shelter. The resolution of this problem is innovative because it introduces the concept of space of accessibility in the layout problem formulation.

International audience; Layout design plays an important role in the design and usability of many engineering products and systems. Because of the great complexity of most of industrial layout problems, the decision of the acceptable layout is a hard and critical task since the special layout can have a significant consequence on the global performances. Thus, in order to propose to the designer an optimal spatial arrangement in a reasonable time, this paper develops an interactive optimization strategy that is tested on the facilities layout problem of a shelter. This problem is innovative because it introduces the concept of space of accessibility.

Automation techniques have been widely used in the manufacturing industry, but there are still many manual handling operations required in assembly and maintenance work. Inappropriate posture and physical fatigue might result in musculoskeletal disorders (MSDs) in such physical jobs. In ergonomics and occupational biomechanics, virtual human modelling techniques have been employed to optimize manual operations in the design stage so as to avoid or decrease risk of MSD. In these methods, physical fatigue is only considered to minimize muscle or joint stress, while the effect of fatigue along time on posture is not often considered, although worker's motion strategies and postures under physical fatigue are different from those under non-fatigue conditions. In this paper, based on related literatures and multiple-objective optimisation method (MOO), a new posture prediction and analysis method is proposed for predicting the optimal posture under non-fatigue and fatigue conditions and evaluating the physical fatigue in manual material handling operation. The posture prediction and analysis problem is mathematically described, and a special application case is demonstrated for analyzing a drilling assembly operation in European Aeronautic Defence and Space Company (EADS).

This paper presents a program for the automatic generation of a closed form solution of the symbolic inverse geometric model of some structures of six degree of freedom robots. These structures are characterized by the possibility of decoupling the inverse geometric problem of six unknowns into two problems with three unknowns. The solution is given whatever the values of the geometric parameters (angles and distances between successive axes) not conditioning the structure. The given program constitutes a module of the software package of symbolic modelling of robots ‘SYMORO’.

Muscle fatigue is defined as the point at which the muscle is no longer able to sustain the required force or work output level. The overexertion of muscle force and muscle fatigue can induce acute pain and chronic pain in human body. When muscle fatigue is accumulated, the functional disability can be resulted as musculoskeletal disorders (MSD). There are several posture exposure analysis methods useful for rating the MSD risks, but they are mainly based on static postures. Even in some fatigue evaluation methods, muscle fatigue evaluation is only available for static postures, but not suitable for dynamic working process. Meanwhile, some existing muscle fatigue models based on physiological models cannot be easily used in industrial ergonomic evaluations. The external dynamic load is definitely the most important factor resulting muscle fatigue, thus we propose a new fatigue model under a framework for evaluating fatigue in dynamic working processes. Under this framework, virtual reality system is taken to generate virtual working environment, which can be interacted with the work with haptic interfaces and optical motion capture system. The motion information and load information are collected and further processed to evaluate the overall work load of the worker based on dynamic muscle fatigue models and other work evaluation criterions and to give new information to characterize the penibility of the task in design process., International Conference On Industrial Technology, Chengdu : Chine (2008)

International audience; A distributed framework for knowledge modelling in interactive design will be presented in this article. A multi-agent approach is proposed in order to support distributed partners in the creation of coherent models for engineering analysis. A granular modelling process is proposed to ensure a coherent construction of models and their analysis. It consists of a global and a local analysis based on a networked Product Life Cycle (PLC). A set of ‘Tutor Agents' (TA) intends to guide each partner to extract relevant information from his/her technical domain while a ‘Standardisation Process' (SP) is performed with supplied information to find potential redundancies. A coherent model is then obtained that is ready to be analysed by traditional inference engines such as optimisation solvers and constraint satisfaction programming. Furthermore, a case will be presented in order to clarify the framework. The results will enable design teams to integrate constraints from throughout the PLC in order to optimise the evolution of design concepts in distributed design.

International audience; A methodology for distributed knowledge modeling will be presented in this article, in order to contribute to a better decision making during design problems analysis. An optimal design process refers to setting up coherent numerical models and it requires a well structured problem definition. However, a lack of downstream information in early stages of product development leads to a complicated elicitation task that became an issue due to nowadays distributed environments. A Multi-Agent approach is proposed to support the distributed knowledge elicitation process. A set of agents will guide members from the distributed design team, throughout the product life cycle, to extract relevant information and analyze it. The interaction among agents will highlight potential incoherencies during the modeling process, in order to enable partners to avoid inconsistent information. A coherent knowledge base is then constructed and ready to be used to create models to be analyzed by traditional inference engines such as optimization solvers, constraint satisfaction programming, etc.

16 pages; International audience; This paper introduces the concept of granular modelling as a strategy to construct human-centred virtual prototype and environment models. This approach aims at providing a granular strategy for virtual prototype models in order to allow the change from a coarse-grain description to a fine-grain one according to the level of specification desired. The granular model is built from the aggregation of several component models and their interaction models, representing the interaction between two components. Component models must include information not only about themselves but also about the environmental part related to them. This is important as environmental conditions may have different effects at different scales/levels. Additionally, it leads to a higher level of communication, only allowed through the interaction models. This implies that new different objects might be integrated only by including their component models and their required interaction. The foreseen advantage is that the human is integrated in a simple manner: a component model corresponding to a haptic interface and an interaction model relating it to the virtual product. The first step, identification and organic description, consists of establishing an interaction graph from the hierarchical structure of the virtual product and all the objects that will be present in its future environment. Subsequently, the component and interactions models are constructed. The model is expected to be implemented into a multi-agent system where every component model derives into a component agent.

The increasing economic competition of all industrial markets and growing complexity of engineering problems lead to a progressive specialization and distribution of expertise, tools and works. On the other hand, engineering products becomes more and more complex and the designer has to face with an increase design variables and design objectives. Besides multi-objective optimization (MOO) and multi-disciplinary design optimization (MDO) are more commonly used as methods to provide optimal solutions for complex design problems. The paper describes an innovative mixing between genetic algorithms (MOGA) and collaborative optimization (CO) as a tool to: 1) increase the convergence rate when a design problem can be broken up regarding design variables, and 2) provide an optimal set of design variables in case of multi-level design problem. This method gives multidisciplinary optimization the advantages AG has brought to multi-objective optimization. The method, tested on test functions, assures high optimization results containing CPU times.Copyright © 2005 by ASME

Tolerancing is one of the most important but complex activities in design. Tolerance information takes place at every phase of design activity. It represents the fundamental link between the theoretical model of the mechanical product and the actual one. During the two previous decades, engineering projects and scientific researches demonstrated that ongoing miniaturization increased the influence of geometric tolerances. They also admit that mass production is mainly based on statistical techniques. On the other hand, the decomposition of the global tolerancing process into functional-level, assembly-level, part-level, and manufacturing-level, reduces dramatically the domain of the solution. In this paper, the global tolerancing process is described and a novel method for statistical analysis of geometrical tolerances is discussed. Then the statistical approach is introduced and its performance is evaluated on a best case study. The analysis of the technical drawing of a part is given in order t...

The utilization of robots, for mechanical part assemblies, is a current practice. Existing methods and software permit to simulate tasks and program them off line using the perfect geometry of the parts. However, as the parts to be assembled are never perfect the adjustment time of these programs is often too long. It is indispensable to find models that can integrate these manufacturing uncertainties at the simulation level. The method proposed can replace the verification using manual functional gauges and can be integrated to a simulation software. In relation to the existing methods, it is especially suitable for the intended parts to be assembled and the datum reference frame (DRF) is defined at maximum material condition. This paper proposes a method for all situations of the DRF where the part is in conformance. It can be applied to inspection, as well as to tolerance analysis and synthesis. A kinematic model is used to represent the permissible motion of the DRF.

In the context of concurrent engineering, this paper presents a quite innovative approach to the collaborative optimisation process, which couples a multi-objective genetic algorithm with an asynchronous communication tool. To illustrate this methodology, three European companies’ collaboration on the optimisation of a ship hull is described. Our study demonstrates that when multi-objective optimisation is carried out in a distributed manner it can provide a powerful tool for concurrent product design.

Usually, the design of mechanisms and assemblies uses the perfect model of the part. This type of model can be used within a software application to simulate and to verify the kinematics and dynamic behavior of such mechanisms. However, the analysis of the manufacturing uncertainties is also necessary to control the sensitivity and robustness of the mechanism assembly. To take into account these uncertainties, the designer deals with a class of interchangeable and functionally equivalent parts. When specifying tolerances, he essentially defines the authorized variations of the envelope of the parts and a number of classes can represent the various domains of acceptance of the parts. Since we need to take into account the infinite number of parts allowed by the variational class, the analysis of variational assembly is a hard task. In this paper, an extension of our previous work to calculate the virtual and resultant parts is proposed. The proposed method takes into account the datum chaining in the toleranced part. A kinematics model and robotic parameterisation is used to simulate the possible “motion” of the tolerance zone, allowed by MMC and LMC modifiers. Thus, the analysis of the infinite number of parts is reduced to analyse only two parts for each variational class. The analysis of the Jacobian matrix of the mechanism effectively generates the intersection and the union of all the boundaries of the features of the part. The paper presents also a significant application of this approach.

This paper deals with the problem of product mechanical design within the framework of integrated design. It proposes a technique based on the fuzzy logic approach. The design process is divided in several sub-problems (professions or points of view : Pov). Fuzzy approach allows the comparison of the PoV to each other and the final solution emerges through a global compromise. This approach allows the design process to be distributed in parallel tasks. The neural network (NN) tool is used in order to encapsulate data and the analysis of each design PoV. So it allows a flexible decision making in design process. Numerical advantage of this approach is discussed.

Accessibility of measured points to touch probes is crucial in planning dimensional inspection of mechanical parts by Co-ordinate Measuring Machines (CMM). This paper presents a new method to define the kind of touch probe needed to measure the various points of a mechanical part. The limits of the notion of visibility as it is usually defined for machining purposes are shown. We propose a new definition of visibility, dedicated to measurement. A method allowing the determination of the probe’s characteristics (maximum length of the stylus, sufficient number of styli) is described.

Within the context of mechanical parts machining, it is useful to reduce the number of manufacturing sequences required for a workpiece. In the case of milling, we must choose milling machine configuration and a workpiece setup. The collisions between the tool and the finished part are an essential stage to be taken in account; this study is based on the notion of visibility. By comparing those visibilities with the milling machine abilities, it is possible to known if the piece can be machined in only one phase.

International audience; Cumulative local muscle fatigue may lead to potential musculoskeletal disorder (MSD) risks {\color{red}, and subject-specific muscle fatigability needs to be considered to reduce potential MSD risks.} This study was conducted to determine local muscle fatigue rate at shoulder joint level based on an exponential function derived from a muscle fatigue model. Forty male subjects participated in a fatiguing operation under a static posture with a range of relative force levels (14\% - 33\%). Remaining maximum muscle strengths were measured after different fatiguing sessions. The time course of strength decline was fitted to the exponential function. Subject-specific fatigue rates of shoulder joint moment strength were determined. Good correspondence ($R^2>0.8$) was found in the regression of the majority (35 out of 40 subjects). Substantial inter-individual variability in fatigue rate was found and discussed.

International audience; This paper presents the development of a new software in order to manage objects, robots and mannequins in using the possibilities given by the haptic feedback of the Phantom desktop devices. The haptic device provides 6 positional degree of freedom sensing but three degrees force feedback. This software called eM-Virtual Desktop is integrated in the Tecnomatix's solution called eM-Workplace. The eM-Workplace provides powerful solutions for planning and designing of complex assembly facilities, lines and workplaces. In the digital mockup context, the haptic interfaces can be used to reduce the development cycle of products. Three different loops are used to manage the graphic, the collision detection and the haptic feedback according to theirs own frequencies. The developed software is currently tested in industrial context by a European automotive constructor.

International audience; Repetitive tasks in industrial works may contribute to health problems among operators, such as musculo-skeletal disorders, in part due to insufficient control of muscle fatigue. In this paper, a predictive model of fatigue is proposed for repetitive push/pull operations. Assumptions generally accepted in the literature are first explicitly set in this framework. Then, an earlier static fatigue model is recalled and extended to quasi-static situations. Specifically, the maximal torque that can be generated at a joint is not considered as constant, but instead varies over time accordingly to the operator's changing posture. The fatigue model is implemented with this new consideration and evaluated in a simulation of push/pull operation. Reference to this paper should be made as follows: Sakka, S., Chablat, D., Ma, R. and Bennis, F. (2015) 'Predictive model of the human muscle fatigue: application to repetitive push-pull tasks with light external load', Int.

International audience; Virtual human simulation integrated into virtual reality applications is mainly used for virtual representation of the user in virtual environment or for interactions between the user and the virtual avatar for cognitive tasks. In this paper, in order to prevent musculoskeletal disorders, the integration of virtual human simulation and VR application is presented to facilitate physical ergonomic evaluation, especially for physical fatigue evaluation of a given population. Immersive working environments are created to avoid expensive physical mock-up in conventional evaluation methods. Peripheral motion capture systems are used to capture natural movements and then to simulate the physical operations in virtual human simulation. Physical aspects of human's movement are then analyzed to determine the effort level of each key joint using inverse kinematics. The physical fatigue level of each joint is further analyzed by integrating a fatigue and recovery model on the basis of physical task parameters. All the process has been realized based on VRHIT platform and a case study is presented to demonstrate the function of the physical fatigue for a given population and its usefulness for worker selection.

International audience; To avoid flops, the control of the risks in product innovation and the reduction of the innovation cycles require valid and fast customer's assessments. A methodology must be proposed to the designer to take into account the perceptions of the user. The method presented is based on an iterative process of user selection of representative CAD models of the product. An IGA is used to interpret the user's choices and introduce new products. In the center of this methodology, the user who, thanks to his decisions, will guide the evolution of the algorithm and its convergence. After a description of the IGA, a study on the convergence of the IGA is presented, according to the tuning parameters of the algorithm and the size of the design problem. An experiment was carried out with a set of 20 users on the application case proposed a steemed glass. The implementation of the perceptive tests and the analysis of the results, using Hierarchical Ascendant Classification (HAC) is described. The main contributions of the paper are proposals of (1) an interactive product optimization methodology; (2) a procedure for parameterizing interactive genetic algorithms; (3) a detection of perceptive trends that characterize customer expectations; (4) an experimental application on a real life product.