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International audience; This paper presents an efficient simulated annealing algorithm for solving multi-objective layout problems where several rectangular components are placed, respecting non-overlap and non-protrusion constraints in the given space. Resolving layout problems can be very hard in some industrial cases because problems are over-constrained and computing feasible optimal layout designs are time consuming. In most practical problems, both real and virtual components exist. The virtual components represent the required accessible space allowing the user to access to the component. The virtual components can overlap with each other, while the overlap is not allowed for the real components. Considering the limited layout design space, the capacity of the layout problem is analyzed using constructive placing techniques. To explore the feasible layout space, a hybrid simulated annealing is proposed to determine the order of placement; then, a constructive placing strategy based on empty maximal space is developed. What’s more, an interactive visualization environment is introduced between the optimization and expert. The proposed algorithm is the first attempt to search feasible space of multi-objective layout design by constructive placing method.

Layout optimization plays an important role in the field of industrial engineering. The layout problem presented here involves the real and virtual rectangular components. The real components can be the devices or buildings depending on the application. The space of accessibility associated with the real component is virtual, which allows the user to access the real component in reality, such as facility maintenance. However, most of the layout problems are NP hard. The great complexity of layout problems increase the difficulty in finding a feasible layout design in a reasonable time. To resolve these problems, we propose a hybrid constructive placing strategy which makes the search of feasible designs easier. The multi-objective application presented in this study demonstrates the effectiveness and portability of the method. Since the number of optimal layout designs can be very large, a cluster approach is followed to group all similar solutions. First, the notion of pairwise similarity indicator is introduced to analyze the similarity among the optimized layout designs. Second, the visualization of the hierarchical clustering of similarity matrix is customized. Then for each design, the user can interact with it by locally modifying the position or rotation of the component. The interactivity helps the user evaluate performance of the designs and preferable results are typically achieved.

International audience; Electronic phased-array radars offer new possibilities for radar search pattern optimization by using bi-dimensional beam-forming and beam-steering. Radar search pattern optimization can be approximated as a set cover problem and solved using integer programming, while accounting for localized clutter and terrain masks in detection constraints. We present a set cover problem approximation for time-budget minimization of radar search patterns, under constraints of range, detection probability and direction-specific scan update rates. Branch&Bound is a classical optimization procedure for solving combinatorial problems. It is known mainly as an exact algorithm, but features interesting characteristics, making it particularly fit for solving optimization problems in real-time applications and producing just-in-time solutions.

International audience; Cognitive radars are systems capable of optimizing emission and processing by exploiting knowledge about environment and operational scenario. Those improvements are achieved by controlling new degrees of freedom offered by modern radar technology. In particular, active phased-array radars can perform bidimensional beam-steering and beam-forming. Those new capabilities allow adaptation of radar search patterns to localized constraints. We present an improvement from our previous set cover approximation for radar search pattern time-budget minimization, accounting for localized constraints of terrain masking and direction-specific scan update rates. The addition of those constraints however does not modify the underlying mathematical structure of the problem, which can be solved using integer programming methods.

International audience; Biomechanical motion simulation and dynamic analysis of human joint moments will provide insights into Musculoskeletal Disorders. As one of the mainstream simulation tools, OpenSim uses proportional scaling to specify model segment masses to the simulated subject, which may bring about errors. This study aims at estimating the errors caused by the specifying method used in OpenSim as well as the influence of these errors on dynamic analysis. A 3D scan is used to construct subject's 3D geometric model, according to which segment masses are determined. The determined segment masses data is taken as the yardstick to assess the errors of OpenSim scaled model. Then influence of these errors on the dynamic calculation is evaluated in the simulation of a motion in which the subject walks in an ordinary gait. Result shows that the mass error in one segment can be as large as 5.31\% of overall body weight. The mean influence on calculated joint moment varies from 0.68\% to 12.68\% in 18 joints. In conclusion, a careful specification of segment masses will increase the accuracy of the dynamic simulation. As far as estimating human segment masses, the use of segment volume and density data can be an economical choice apart from referring to population mass distribution data.

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 Radar Search Pattern Optimization by using bi-dimensional beam-forming and beam steering, along both elevation and azimuth axes. The Radar Search Pattern Optimization problem can be approximated as a Set Cover problem and solved using Integer Programming methods. This approximation can be extended to account for direction-specific scan update rates constraints without the need to modify the optimization algorithm.

International audience; In this research, attempts are made to conduct concrete muscle fatigue analysis of arbitrary motions on OpenSim, a digital human modeling platform. A plug-in is written on the base of a muscle fatigue model, which makes it possible to calculate the decline of force-output capability of each muscle along time. The plug-in is tested on a three-dimensional, 29 degree-of-freedom human model. Motion data is obtained by motion capturing during an arbitrary running at a speed of 3.96 m/s. Ten muscles are selected for concrete analysis. As a result, the force-output capability of these muscles reduced to 60%-70% after 10 minutes' running, on a general basis. Erector spinae, which loses 39.2% of its maximal capability, is found to be more fatigue-exposed than the others. The influence of subject attributes (fatigability) is evaluated and discussed.

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.

International audience; Muscle fatigue is one of the reason leads to Musculo-Skeletal Disorder(MSD). Automation in today's industries makes human effort very less, but still there are many industries in which human have to do complex and repetitive tasks manually. The society/companies have to pay attention on this issue due to the new laws on penibility or repetitive tasks. The objective of this paper is to experimentally validate a new dynamic muscle fatigue model using electromyog-raphy (EMG) and Maximum voluntary contraction (MVC). A new model is developed by introducing a co-contraction factor 'n' in the Ruina Ma's dynamic muscle fatigue model. The experimental data of ten subjects are used to analyze the muscle activities and muscle fatigue during extension-flexion motion of the arm on a constant absolute value of the external load. The findings for co-contraction factor shows that the fatigue increases when co-contraction area decreases. The dynamic muscle fatigue model is validated using the MVC data, fatigue rate and co-contraction factor of the subjects.

International audience; Many engineering sectors are challenged by multi-objective optimization problems. Even if the idea behind these problems is simple and well established, the implementation of any procedure to solve them is not a trivial task. The use of evolutionary algorithms to find candidate solutions is widespread. Usually they supply a discrete picture of the non-dominated solutions, a Pareto set. Although it is very interesting to know the non-dominated solutions, an additional criterion is needed to select one solution to be deployed. To better support the design process, this paper presents a new method of solving non-linear multi-objective optimization problems by adding a control function that will guide the optimization process over the Pareto set that does not need to be found explicitly. The proposed methodology differs from the classical methods that combine the objective functions in a single scale, and is based on a unique run of non-linear single-objective optimizers.

Virtual reality techniques have been increasingly used for ergonomic applications. However, it is always important to know whether the results obtained in a virtual environment (VE) are representative of a real environment (RE) ones. This paper presents our preliminary experimental results on the relationship between ergonomic measurements in VE and RE for some typical “drilling” tasks. The same tasks were carried out by thirty male manufacturing factory workers in both VE and RE. Five evaluation indices – three objective (elbow angle, maximum force capacity reduction, and task completion time) and two subjective (BPD – Body Part Discomfort and RPE – Rated Perceived Exertion) – were used to evaluate the similarities between VE and RE for the selected “drilling” tasks. Four of these indices (all except elbow angle) were significantly higher (p Relevance to industry Using digital mock-ups and virtual reality simulations, industrial work activities can be evaluated to identify potential ergonomic problems during an early design stage, which reduces design time and costs, increases quality and improves customer satisfaction. A validated linear relationship can provide a reference for work design in virtual reality.

Due to the flexibility and adaptability of human, manual handling work is still very important in industry, especially for assembly and maintenance work. Well-designed work operation can improve work efficiency and quality; enhance safety, and lower cost. Most traditional methods for work system analysis need physical mock-up and are time consuming. Digital mockup (DMU) and digital human modeling (DHM) techniques have been developed to assist ergonomic design and evaluation for a specific worker population (e.g. 95 percentile); however, the operation adaptability and adjustability for a specific individual are not considered enough. In this study, a new framework based on motion tracking technique and digital human simulation technique is proposed for motion-time analysis of manual operations. A motion tracking system is used to track a worker's operation while he/she is conducting a manual handling work. The motion data is transferred to a simulation computer for real time digital human simulation. The data is also used for motion type recognition and analysis either online or offline for objective work efficiency evaluation and subjective work task evaluation. Methods for automatic motion recognition and analysis are presented. Constraints and limitations of the proposed method are discussed.

Virtual human techniques have been used a lot in industrial design in order to consider human factors and ergonomics as early as possible. The physical status (the physical capacity of virtual human) has been mostly treated as invariable in the current available human simulation tools, while indeed the physical capacity varies along time in an operation and the change of the physical capacity depends on the history of the work as well. Virtual Human Status is proposed in this paper in order to assess the difficulty of manual handling operations, especially from the physical perspective. The decrease of the physical capacity before and after an operation is used as an index to indicate the work difficulty. The reduction of physical strength is simulated in a theoretical approach on the basis of a fatigue model in which fatigue resistances of different muscle groups were regressed from 24 existing maximum endurance time (MET) models. A framework based on digital human modeling technique is established to realize the comparison of physical status. An assembly case in airplane assembly is simulated and analyzed under the framework. The endurance time and the decrease of the joint moment strengths are simulated. The experimental result in simulated operations under laboratory conditions confirms the feasibility of the theoretical approach.

Multi-objective optimization is generally a time consuming step of the design process. In this paper, a Pareto based multi-objective genetic algorithm is proposed, which enables a faster convergence without degrading the estimated set of solutions. Indeed, the population diversity is correctly conserved during the optimization process; moreover, the solutions belonging to the frontier are equally distributed along the frontier. This improvement is due to an extension function based on a natural phenomenon, which is similar to a cyclical epidemic which happens every N generations (eN-MOGA). The use of this function enables a faster convergence of the algorithm by reducing the necessary number of generations.

International audience; Toward a multi-objective optimization robust problem, the variations in design variables and design environment pa-rameters include the small variations and the large varia-tions. The former have small effect on the performance func-tions and/or the constraints, and the latter refer to the ones that have large effect on the performance functions and/or the constraints. The robustness of performance functions is discussed in this paper. A post-optimality sensitivity analysis technique for multi-objective robust optimization problems is discussed and two robustness indices are introduced. The first one considers the robustness of the performance func-tions to small variations in the design variables and the de-sign environment parameters. The second robustness index characterizes the robustness of the performance functions to large variations in the design environment parameters. It is based on the ability of a solution to maintain a good Pareto ranking for different design environment parameters due to large variations. The robustness of the solutions is treated as vectors in the robustness function space, which is defined by the two proposed robustness indices. As a result, the designer can compare the robustness of all Pareto optimal solutions and make a decision. Finally, two illustrative examples are given to highlight the contributions of this paper. The first example is about a numerical problem, whereas the second problem deals with the multi-objective robust optimization design of a floating wind turbine.

International audience; Having a significant impact on the design of many products and industrial 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, layout design optimization is at the heart of scientific issues. The design of an optimal layout solution is a critical and complex task due to the increasing demands of designers working on varied projects. This paper proposes an integrated approach to solving layout optimization problems, from the needs expressed by the designer to the creation of an ideal solution. This generic and interactive method is based on a design process divided into four steps: the description, formulation, and solving of the problem, and the final decision. This process is based on a multiobjective modular optimization strategy that combines a genetic algorithm with local optimization modules. The method described in this paper is interactive because the designer participates in all processs steps. For example, in the final decision step, the approach includes an inno- vative exploration tool in order to let the designer choose an optimal solution according to his perceptions. The global method is applied to an industrial problem which deals with the search for an optimal layout of facilities in a shelter. Actually, this paper also presents an innovative software which ma- terializes the integrated optimization method presented in this paper. This tool includes the different steps of the optimization method and integrates the multiobjective solving of layout optimization problems.

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.

In the presence of multiple optimal solutions in multi-modal optimization problems and in multi-objective optimization problems, the designer may be interested in the robustness of those solutions to make a decision. Here, the robustness is related to the sensitivity of the performance functions to uncertainties. The uncertainty sources include the uncertainties in the design variables, in the design environment parameters, in the model of objective functions and in the designer’s preference. There exist many robustness indices in the literature that deal with small variations in the design variables and design environment parameters, but few robustness indices consider large variations. In this paper, a new robustness index is introduced to deal with large variations in the design environment parameters. The proposed index is bounded between zero and one, and measures the probability of a solution to be optimal with respect to the values of the design environment parameters. The larger the robustness index, the more robust the solution with regard to large variations in the design environment parameters. Finally, two illustrative examples are given to highlight the contributions of this paper.

International audience; Layout optimization problems deal with the search for an optimal spatial arrangement of components inside a container. Global performances of many engineering products and systems sharply depend on layout design. Because of the great complexity of most real-world layout applications, recent studies focus on the development of efficient optimization algorithms used to solve layout problems. These algorithms, which have to take into consideration multi-constraint and multi-objective optimization problems, aim to be generic to adapt to lots of layout problems. However, the solving of these layout problems is time consuming and designers know if an optimal solution is available for their problem at the end of the optimization process. Designer cannot know a priori if the layout problem can be solved. Then, this paper proposes a new indicator to assess the feasibility of layout problems. This indicator is based on the layout description of the problem and the formulation of designer's requirements. In particular, it takes into account the non-overlap constraints between layout components. It allows the designer to know if the layout problem can be solved before running the optimization algorithm. After defining the new indicator of feasibility, this paper tests it on a simple layout application.

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)

Pushing/Pulling tasks is an important part of work in many industries. Usually, most researchers study the Push/Pull tasks by analyzing different posture conditions, force requirements, velocity factors, etc. However few studies have reported the effects of fatigue. Fatigue caused by physical loading is one of the main reasons responsible for MusculoSkeletal Disorders (MSD). In this paper, muscle groups of articulation is considered and from joint level a new approach is proposed for muscle fatigue evaluation in the arms Push/Pull operations. The objective of this work is to predict the muscle fatigue situation in the Push/Pull tasks in order to reduce the probability of MSD problems for workers. A case study is presented to use this new approach for analyzing arm fatigue in Pushing/Pulling., 19th CISM-IFToMM Symposium on Robot Design, Dynamics, and Control, Paris : France (2012)

During the conceptual and prototype design stage of an industrial product, it is crucial to take assembly/disassembly and maintenance operations in advance. A well-designed system should enable relatively easy access of operating manipulators in the constrained environment and reduce musculoskeletal disorder risks for those manual handling operations. Trajectory planning comes up as an important issue for those assembly and maintenance operations under a constrained environment, since it determines the accessibility and the other ergonomics issues, such as muscle effort and its related fatigue. In this paper, a customer-oriented interactive approach is proposed to partially solve ergonomic related issues encountered during the design stage under a constrained system for the operator's convenience. Based on a single objective optimization method, trajectory planning for different operators could be generated automatically. Meanwhile, a motion capture based method assists the operator to guide the trajectory planning interactively when either a local minimum is encountered within the single objective optimization or the operator prefers guiding the virtual human manually. Besides that, a physical engine is integrated into this approach to provide physically realistic simulation in real time manner, so that collision free path and related dynamic information could be computed to determine further muscle fatigue and accessibility of a product design, Comment: International Journal on Interactive Design and Manufacturing (IJIDeM) (2012) 1-12. arXiv admin note: substantial text overlap with arXiv:1012.4327

International audience; Layout design optimization has a significant impact in the design and use of many engineering products and systems. Real-world layout problems are usually considered as complex problems because of the geometry of components, the problem density and the great number of designer's requirements. Solving these optimization problems is a hard and time consuming task. This paper proposes an interactive modular optimization strategy which allows the designer to find optimal solutions in a short period of calculation time. This generic strategy is based on a genetic algorithm, combined with specific optimization modules. These modules improve the global performances of the algorithm. This approach is adapted to multi-objective optimization problems and interactivity between the designer and the optimization process is used to make a final choice among design alternatives. This optimization strategy is tested on a real-world application which deals with the search of an optimal spatial arrangement of a shelter.

This article presents a generic method to solve 2D multi-objective placement problem for free-form components. The proposed method is a relaxed placement technique combined with an hybrid algorithm based on a genetic algorithm and a separation algorithm. The genetic algorithm is used as a global optimizer and is in charge of efficiently exploring the search space. The separation algorithm is used to legalize solutions proposed by the global optimizer, so that placement constraints are satisfied. A test case illustrates the application of the proposed method. Extensions for solving the 3D problem are given at the end of the article., Comment: ASME 2009 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, San Diego : United States (2009)

Although automatic techniques have been employed in manufacturing industries to increase productivity and efficiency, there are still lots of manual handling jobs, especially for assembly and maintenance jobs. In these jobs, musculoskeletal disorders (MSDs) are one of the major health problems due to overload and cumulative physical fatigue. With combination of conventional posture analysis techniques, digital human modelling and simulation (DHM) techniques have been developed and commercialized to evaluate the potential physical exposures. However, those ergonomics analysis tools are mainly based on posture analysis techniques, and until now there is still no fatigue index available in the commercial software to evaluate the physical fatigue easily and quickly. In this paper, a new muscle fatigue and recovery model is proposed and extended to evaluate joint fatigue level in manual handling jobs. A special application case is described and analyzed by digital human simulation technique., Comment: IDMME - Virtual Concept, Beijing : Chine (2008)

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’.

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.

Nowadays products become more and more complex and their design is usually of large scale, characterized by an important number of design variables, constraints and objectives. Besides the traditional economic point of view, more recent industrial requirements, such as robustness and performance of the design, but also marketing criteria have appeared and quickly become important characteristics of the design and of the optimization process. In the same time, the structure in which the design process takes place has evolved a lot. Enterprises have grown in complexity. The increasing economic competition has led to a specialization and distribution of knowledge, expertise, tools and work sites. Enterprises have reduced their competencies to be finally specialized in one (or several) discipline(s); in this context, the use of subcontractors is now really common and the extended enterprise is the common companies’ structure model. Such a structure requires efficient optimization methodologies that take into account the decomposition of the product into several disciplines that are simultaneously optimized in different structures (team, division, subcontractors) and places. This kind of structures can be considered as complex systems and defined as assemblies of interacting members that are difficult to understand as a whole. Such complex systems can be decomposed by several ways: object, aspect, sequential and model-based. Object decomposition divides a system by physical components. Aspect (or discipline) decomposition divides the system according to different disciplines or specialities. Object and aspect partitioning are ”natural” partitions and typically large companies employ both types of partitions simultaneously (mixed partition) in a matrix management organization. Sequential decomposition is applicable when partitioned sub-problems are organized by work-flow or process logic and presumes unidirectionality of design information. Hierarchical decomposition: Complex systems are composed of several sub-systems that form subsystems and multilevel: Figure 1 on the following page shows the structural decomposition of a plane. Such decomposition can be pursued until the basic members of the system appear. Actually, basic members are either components or disciplines that can be more easily optimized that the complex system. Interaction between sub-systems: Interactions betweens sub-systems exist at any level of the decomposition. However, they do not appear at the system level (level zero). Such interactions are usually called ”coupling functions”. They are output data for one of the sub-systems that are needed as input data by one or several others sub-systems. They ensure the system’s coherence and synergy between members. Non-hierarchical systems: Frequently, complex systems are non-hierarchical what means that there is no reason to process the optimization of one sub-system before another. In the optimization process of such systems, the presence of coupling functions and their recognition constitutes a real challenge for researchers.

International audience; This paper presents a robustness study of 3R manipulators and aims at answering the following question: are generic manipulators more robust than their non-generic counterparts? We exploit several properties specific to 3R manipulators such as singularities, cuspidality, homotopy classes, and path feasibility, in order to find some correlations between genericity and robustness concepts. It turns out that the farther a manipulator is from non-generic ones, the more robust it is with respect to homotopy class and number of cusps. Besides, we state that the proximity of a manipulator to non-generic frontiers may severely affect its robustness with respect to path-feasibility. Finally, we notice that the dexterity and the accuracy of 3R manipulators do not depend on genericity.

In engineering, designers are often faced with decisions involving conflicting objectives. Although existing Multi Criteria Decision Making (MCDM) “methods” can aid decisionmakers in satisfying the required trade-offs, a basic understanding of the assumptions and limitations underlying the approaches is required. It is important to note that all of these so called MCDM “methods” have fundamental shortcomings, which render them inappropriate for carte blanche application. Making an educated decision, as to which method to choose for a particular problem, however, is confounded by the fact that over 70 MCDM methods have thus far been proposed within the literature. Although many approaches, aimed at facilitating the selection of the most suitable MCDM approaches for a particular task, have been proposed, these are misleading since they suggest the existence of a “best” method for a particular problem at hand. The very description of the MCDM techniques as methods is a misnomer, as the majority of them constitutes nothing more than attention directing tools and should be treated as such -with caution. Nevertheless, these attention directing tools, when used appropriately in a proper context, may have a significant amount of utility. It is for this reason that we advocate careful reflection (with regard to the problem at hand, the underlying assumptions/limitations of the attention directing tool considered, and interpretation of results) before selection.

This paper presents the implementation of a distributed optimisation method applied to the ship design domain. The approach takes into account the present industrial requirements linked to the distant work and the concurrent engineering deployment. The increasing economic competition of all industrial markets and the growing complexity of the 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 based on distant shared tools and databases. This paper presents the implementation of a multi-objective optimisation process in a concurrent engineering context. Our study aims to demonstrate that when multi-objective optimisation is carried out in a distributed manner it can provide a powerful toll for concurrent product design. To illustrate our methodology, three European companies’ collaboration on the optimisation of a ship hull is described. The results of this real scale experiment suggest that significant improvements of the present industrial design method are possible.

The paper aims at dimensioning a mechanism in order to make it robust, and synthesizing its dimensional tolerances. The design of a mechanism is supposed to be robust when its performance is as little as sensitive as possible to variations. First, a distinction is made between three sets to formulate a robust design problem; (i) the set of Design Variables (DV) whose nominal values can be selected between a range of upper and lower bounds, they are controllable; (ii) the set of Design Parameters (DP) that cannot be adjusted by the designer, they are uncontrollable; (iii) the set of performance functions. DV are however under uncontrollable variations although their nominal value can be adjusted. Moreover, two methods are described to solve robust design problems. The first method is explicit and solves problems that aim at minimizing variations in performance. The second method, an optimization problem, aims at optimizing the performance and minimizing its variations, but only when the ranges of variations in DV and DP are known. Besides, we define and compare some robustness indices. From the explicit method, we develop a new tolerance synthesis method. Finally, three examples are included to illustrate these methods: a damper, a two-dof and a three-dof serial positioning manipulator.

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.

Product variation is a key piece of information that flows from the design function to manufacturing function in an enterprise. Every, engineering design is subject to variation that can arise from a variety of sources, including manufacturing operations, variation in material properties, and at the operating environment. Engineers must deal with variations in the products they design and manufacture. They have to produce robust designs by assessing the expected size of variation and determining the risk of failure. The best time to reduce the impact of variation is in the early stages of design process. Variation analysis in mechanical design becomes an essential practice.

In this paper, a novel method of positional tolerance analysis is discussed. These tolerances are critical in the assembly analysis. The statistical approach is introduced and its performance is evaluated on a best case study. Industries claim that statistical tolerance analysis is necessary in order to perform a a reduction of the cost of manufacturing, assembly and inspection process. Some applications are given to highlight the advantages of our statistical 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.

The increasing need of high quality products, leads industry to improve the tolerancing of their products. It is thus necessary to calculate, as precisely as possible, every tolerance to achieve functional requirements and to take into account the influence of manufacturing processes and the results of the final assembly. An algebraic method is proposed which can help tolerance analysis and synthesis, and in particular tolerance transfer. It is a continuation of previous work developed particularly by Louis Rivest, Clement Fortin and others. The method allows the algebraic determination whether a tolerance can be transferred, and what will be its shape after transfer. This result is obtained from a second degree equation. The study of this equation determines whether the transfer is possible. The calculation time is reduced since no simulation is required. Finally, two examples are used to show that the method can solve some complex cases.

Functional gaging techniques can be used to check the conformance of a part with Maximum Material Condition features, but the cost of this gages can be expensive. A Coordinate Measurement Machine can simulate the gage for simple cases. Unfortunately, when the datum reference frame of the feature is not unique, the inspection of the parts defined with MMC using CMM becomes more complex, and it is currently not supported. To resolve this problem a method using a kinematic model is proposed, which simulates the gaging control. The method takes into account the possible rotation of the DRF, and it obtains all possible situations of the DRF for which the parts conforms. And the actual value of the feature can be calculated.

This paper proposes an automatic and adaptive method for the digitization of numerical parts using Coordinate Measuring Machines (CMM). We present a methodology for scanning inspired by optimization algorithms and contour determination in Computer Aided Design. Relevance of the proposed method and its advantages compared to existing methods are illustrated by an example of industrial application consisting in measuring the profile curves and sections of parts of revolution. We finally set up the bases of an algorithm devoted to the surface digitization of any mechanical part.

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.

The paper presented by Gautier and Khalil (see ibid., vol.6, no.3, p.368-73, 1990) gives a direct and efficient method of calculating most of the minimum inertial parameters of serial robots. Some parameters concerning the translational links between the first two rotational joints that are not parallel need particular calculation; partial results concerning the case where these links are either perpendicular or parallel are given in the above paper. This correspondence presents a direct solution of this particular case, such that all the minimum inertial parameters can be obtained directly without calculating the energy or the dynamic model of any link. >

This document presents a technique developed to switch between different behavioral models in the interactive simulation of a mechanical object. When conducting interactive simulations several behavioral models may be required, due to limitations of the models' validity domain. In other cases, alternative models are developed to improve the accuracy or the precision of the estimated response. Smaller time of response is also another feature that fosters model creation. In this work, an all-available model approach is proposed to perform interactive simulations where using only one model during the simulation may not be desirable, since its validity domain is finite and its advantages may appear only in a specific range of behavior. This paper proposes coupling several available models to cover a reasonable validity domain, and in particular, to improve the overall time of response. A selector, based on the Takagi-Sugeno-Kang method of inference, is constructed to dynamically switch between models, accordingly to the environment's status. This flexible model, created from a collection of sub-models, may also adapt itself to manage the accuracy/precision-time relation. The concept has been implemented in the simulation of the mechanical response of a simple structure, and performed better than the sub-models that it integrates.

International audience; Biomechanical motion simulation and kinectic analysis of human joints and muscles provide insights into Musculoskeletal disorders. OpenSim is an open-source platform that give easy access to biome-chanical analysis, especially of muscles. The biomechanical analysis in OpenSim is based on pre-defined human models. Among the dozens of models available right now, none covers the muscles and joints of all the body parts. In view of the fact that most human motions are systemic, the lack of a comprehensive model prohibits synthesized and systemat-ical biomechanical analysis. The aim of this research is to develop an OpenSim model which enables the full-chain dynamic analysis of tasks involving multi-bodies. The model is developed based on two existing models. It consists of 45 body segments, 424 muscles and 39 degrees of freedom. The model was then used to simulate an overhead drilling task. Six drilling postures are analyzed, and the estimated joint moments and muscle activations are compared.

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.