Showing papers by "Damien Chablat published in 2010"

A new muscle fatigue and recovery model and its ergonomics application in human simulation

Abstract: Although automatic techniques have been employed in manufacturing industries to increase productivity and efficiency, there are still lots of manual handling operations, especially for assembly and maintenance operations. In these operations, musculoskeletal disorder (MSD) is one of the major health problems due to overload and cumulative physical fatigue. With combination of conventional posture analysis techniques, digital human modeling and simulation (DHM) techniques have been developed and commercialized to evaluate the potential physical exposures. However, those ergonomic analysis tools are mainly based on posture analysis techniques, and until now there is still no fatigue index available in commercial software to evaluate the physical fatigue effectively. In this paper, a new muscle fatigue and recovery model is used to evaluate joint fatigue level in manual handling operations. The physical fatigue in a special application case is described and analyzed using digital human simulation techniques.

A framework for interactive work design based on motion tracking, simulation, and analysis

Abstract: Because of the flexibility and adaptability of humans, manual handling work is still important in industry, especially in 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-ups and are time-consuming. Digital mock-up (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 task. The motion data are transferred to a simulation computer for real-time digital human simulation. The data are 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. © 2010 Wiley Periodicals, Inc.

Optimal technology-oriented design of parallel robots for high-speed machining applications

Abstract: In this paper, a new methodology for the optimal design of parallel kinematic machine tools is proposed. This approach is based on the concept of the maximal inscribed parallelepiped and uses technology-oriented constraints that are motivated by particular applications. This methodology is applied on two translational parallel robots with three degrees-of-freedom (DOF): the Y-STAR and the UraneSX. An analysis of the size of their workspace as a function of the design constraints is made. It is shown that, for identical workspaces with similar properties, the size of the legs of the UraneSX are greater than for the Y-STAR, thus leading to larger deformations. However, the footprint surface needed in order to install the Y-STAR is about two times bigger than for the UraneSX. Therefore, it may be interested to use the UraneSX in order to save some place on ground in manufacturing centres.

Singularity Analysis of a Six-Dof Parallel Manipulator Using Grassmann-Cayley Algebra and Gröbner Bases

Abstract: The subject of this paper deals with the singularity analysis of a sixdof three-legged parallel manipulator for force-feedback interface. To this end, a geometric condition for the manipulator singularities is obtained by means of Grassmann-Cayley algebra; the parallel singularities of the manipulator are computed using Jacobian and Grobner basis. As a result, the algebraic relations of the singularities satisfied by the orientation variables are reported. Finally, the parallel singularities of the manipulator are plotted in its orientation workspace.

Cusp points in the parameter space of RPR-2PRR parallel manipulator

Abstract: This paper investigates the existence conditions of cusp points in the design parameter space of the R\underline{P}R-2P\underline{R}R parallel manipulators. Cusp points make possible non-singular assembly-mode changing motion, which can possibly increase the size of the aspect, i.e. the maximum singularity free workspace. The method used is based on the notion of discriminant varieties and Cylindrical Algebraic Decomposition, and resorts to Gr\"obner bases for the solutions of systems of equations.

A Framework for Interactive Work Design based on Digital Work Analysis and Simulation

Abstract: 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 (eg 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

A Framework for Interactive Work Design based on Digital Work Analysis and Simulation

Abstract: 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.

Fatigue evaluation in maintenance and assembly operations by digital human simulation

Abstract: 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.

Comparison of Planar Parallel Manipulator Architectures Based on a Multi-Objective Design Optimization Approach

Abstract: This paper deals with the comparison of planar parallel manipulator architectures based on a multi-objective design optimization approach. The manipulator architectures are compared with regard to their mass in motion and their regular workspace size, i.e., the objective functions. The optimization problem is subject to constraints on the manipulator dexterity and stiffness. For a given external wrench, the displacements of the moving platform have to be smaller than given values throughout the obtained maximum regular dexterous workspace. The contributions of the paper are highlighted with the study of 3-P RR, 3-RP R and 3-R RR planar parallel manipulator architectures, which are compared by means of their Pareto frontiers obtained with a genetic algorithm.Copyright © 2010 by ASME

Stiffness Analysis of Parallel Manipulators with Preloaded Passive Joints

Abstract: The paper presents a methodology for the enhanced stiffness analysis of parallel manipulators with internal preloading in passive joints. It also takes into account influence of the external loading and allows computing both the non-linear "load-deflection" relation and the stiffness matrices for any given location of the end-platform or actuating drives. Using this methodology, it is proposed the kinetostatic control algorithm that allows to improve accuracy of the classical kinematic control and to compensate position errors caused by elastic deformations in links/joints due to the external/internal loading. The results are illustrated by an example that deals with a parallel manipulator of the Orthoglide family where the internal preloading allows to eliminate the undesired buckling phenomena and to improve the stiffness in the neighborhood of its kinematic singularities.

Cusp Points in the Parameter Space of RPR-2PRR Parallel Manipulators

Abstract: This paper investigates the existence conditions of cusp points in the design parameter space of the RPR-2PRR parallel manipulators. Cusp points make possible non-singular assemblymode changing motion, which can possibly increase the size of the aspect, i.e. the maximum singularity free workspace. The method used is based on the notion of discriminant varieties and Cylindrical Algebraic Decomposition, and resorts to Grobner bases for the solutions of systems of equations.

Stiffness Modelling of Parallelogram-Based Parallel Manipulators

Abstract: The paper presents a methodology to enhance the stiffness analysis of parallel manipulators with parallelogram-based linkage. It directly takes into account the influence of the external loading and allows computing both the non-linear “load-deflection” relation and relevant rankdeficient stiffness matrix. An equivalent bar-type pseudo-rigid model is also proposed to describe the parallelogram stiffness by means of five mutually coupled virtual springs. The contributions of this paper are highlighted with a parallelogram-type linkage used in a manipulator from the Orthoglide family.

Technology-Oriented Optimization of the Secondary Design Parameters of Robots for High-Speed Machining Applications

Abstract: In this paper, a new methodology for the optimal design of the secondary geometric parameters (shape of links, size of the platform, etc.) of parallel kinematic machine tools is proposed. This approach aims at minimizing the total mass of the robot under position accuracy constraints. This methodology is applied to two translational parallel robots with three degrees-of-freedom (DOF): the Y-STAR and the UraneSX. The proposed approach is able to speed up the design process and to help the designer to find more quickly a set of design parameters.Copyright © 2010 by ASME

Joint space and workspace analysis of a two-DOF closed-chain manipulator

Abstract: The aim of this paper is to compute of the generalized aspects, i.e. the maximal singularity-free domains in the Cartesian product of the joint space and workspace, for a planar parallel mechanism in using quadtree model and interval analysis based method. The parallel mechanisms can admit several solutions to the inverses and the direct kinematic models. These singular configurations divide the joint space and the workspace in several not connected domains. To compute this domains, the quadtree model can be made by using a discretization of the space. Unfortunately, with this method, some singular configurations cannot be detected as a single point in the joint space. The interval analysis based method allow us to assure that all the singularities are found and to reduce the computing times. This approach is tested on a simple planar parallel mechanism with two degrees of freedom.

Integrating Digital Human Modeling Into Virtual Environment for Ergonomic Oriented Design

Abstract: Virtual human simulation integrated into virtual reality a plications is mainly used for virtual representation of theuser in virtual environment or for interactions between the user an d the virtual avatar for cognitive tasks. In this paper, in order t o prevent musculoskeletal disorders, the integration of virtua l human simulation and VR application is presented to facilitate ph ysical ergonomic evaluation, especially for physical fatigueevaluation of a given population. Immersive working environmen ts are created to avoid expensive physical mock-up in conventi onal evaluation methods. Peripheral motion capture systems are used to capture natural movements and then to simulate the physic al operations in virtual human simulation. Physical aspects o human’s movement are then analyzed to determine the effort lev el of each key joint using inverse kinematics. The physical fat igue level of each joint is further analyzed by integrating a fati gue 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 ph ysical fatigue for a given population and its usefulness for wo rker selection.

Stiffness Analysis of Parallel Manipulators with Preloaded Passive Joints

Abstract: The paper presents a methodology for the enhanced stiffness analysis of parallel manipulators with internal preloading in passive joints. It also takes into account influence of the external loading and allows computing both the non-linear “load-deflection” relation and the stiffness matrices for any given location of the end-platform or actuating drives. Using this methodology, it is proposed the kinetostatic control algorithm that allows to improve accuracy of the classical kinematic control and to compensate position errors caused by elastic deformations in links/joints due to the external/internal loading. The results are illustrated by an example that deals with a parallel manipulator of the Orthoglide family where the internal preloading allows to eliminate the undesired buckling phenomena and to improve the stiffness in the neighborhood of its kinematic singularities.

Using virtual human for an interactive customer-oriented constrained environment design

Abstract: For industrial product design, it is very important to take into account assembly/disassembly and maintenance operations during the conceptual and prototype design stage. For these operations or other similar operations in a constrained environment, trajectory planning is always a critical and difficult issue for evaluating the design or for the users' convenience. In this paper, a customer-oriented approach is proposed to partially solve ergonomic issues encountered during the design stage of a constrained environment. A single objective optimization based method is taken from the literature to generate the trajectory in a constrained environment automatically. A motion capture based method assists to guide the trajectory planning interactively if a local minimum is encountered within the single objective optimization. At last, a multi-objective evaluation method is proposed to evaluate the operations generated by the algorithm

Comparison of Planar Parallel Manipulator Architectures based on a Multi-objective Design Optimization Approach

Abstract: This paper deals with the comparison of planar parallel manipulator architectures based on a multi-objective design optimization approach. The manipulator architectures are compared with regard to their mass in motion and their regular workspace size, i.e., the objective functions. The optimization problem is subject to constraints on the manipulator dexterity and stiffness. For a given external wrench, the displacements of the moving platform have to be smaller than given values throughout the obtained maximum regular dexterous workspace. The contributions of the paper are highlighted with the study of 3-RPR, 3-RPR and 3-RPR planar parallel manipulator architectures, which are compared by means of their Pareto frontiers obtained with a genetic algorithm.

Using virtual human for an interactive customer-oriented constrained environment design

Abstract: For industrial product design, it is very important to take into account assembly/disassembly and maintenance operations during the conceptual and prototype design stage. For these operations or other similar operations in a constrained environment, trajectory planning is always a critical and difficult issue for evaluating the design or for the users' convenience. In this paper, a customer-oriented approach is proposed to partially solve ergonomic issues encountered during the design stage of a constrained environment. A single objective optimization based method is taken from the literature to generate the trajectory in a constrained environment automatically. A motion capture based method assists to guide the trajectory planning interactively optimizationif a local minimum is encountered within the single objective optimization. At last, a multi-objective evaluation method is proposed to evaluate the operations generated by the algorithm. efficiency. However, sometimes, the path can be trapped in a

Integrating digital human modeling into virtual environment for ergonomic oriented design

Abstract: 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.

Performance evaluation of parallel manipulators for milling application

Abstract: This paper focuses on the performance evaluation of the parallel manipulators for milling of composite materials. For this application the most significant performance measurements, which denote the ability of the manipulator for the machining are defined. In this case, optimal synthesis task is solved as a multicriterion optimization problem with respect to the geometric, kinematic, kinetostatic, elastostostatic, dynamic properties. It is shown that stiffness is an important performance factor. Previous models operate with links approximation and calculate stiffness matrix in the neighborhood of initial point. This is a reason why a new way for stiffness matrix calculation is proposed. This method is illustrated in a concrete industrial problem.