2,042 research outputs found

    Multi-Objective Optimisation Method for Posture Prediction and Analysis with Consideration of Fatigue Effect and its Application Case

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    Automation technique has been widely used in manufacturing industry, but there are still manual handling operations required in assembly and maintenance work in industry. 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 design and optimize the manual operations in design stage so as to avoid or decrease potential MSD risks. In these methods, physical fatigue is only considered as minimizing the muscle or joint stress, and the fatigue effect along time for the posture is not considered enough. In this study, based on the existing methods and multiple objective optimisation method (MOO), a new posture prediction and analysis method is proposed for predicting the optimal posture and evaluating the physical fatigue in the manual 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 & Space Company (EADS) in this paper

    Muscle Fatigue Analysis Using OpenSim

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    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

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

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    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

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

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    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 algorith

    Predictive model of the human muscle fatigue: application to repetitive push-pull tasks with light external load

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    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

    Integrating digital human modeling into virtual environment for ergonomic oriented design

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    International audienceVirtual 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

    Manual assembly modelling and simulation for ergonomics analysis

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    In manufacturing industry, although automation techniques have been employed widely, many tasks still require the flexibility and intelligence of human operators, especially in the product assembly process. Insufficient industrial ergonomics in the assembly process will cause the health problems and quality and productivity losses, ultimately increase costs of the final product. The purpose of this thesis is to integrate ergonomic considerations into the manual assembly process modelling and simulation in order to provide product/process design changes before their physical prototyping. In this research, a state-of-the-art commercial software tool - DELMIA - is adopted for the ergonomics simulation and analysis. Associated with its capabilities for the ergonomics solution, a series of human related issues in the manual assembly process is simulated and studied in order to demonstrate the benefits of a virtual assembly approach to the product deign, workplace deign, time and energy saving. Due to the poor repeatability and reproducibility of digital human postures in DELMIA manipulation, a posture prediction method is developed aiming at a practical and precise ergonomics analysis. A 10-degrees-of-freedom, 4-control-points digital human model concerned with assembly features and human diversity is established. The multi-objective optimisation method is applied to assembly posture prediction in which optimisation objectives (i.e. joint discomfort and metabolic energy expenditure) and constraints corresponding to manual assembly tasks are proposed and formulated. Following the verification of the posture prediction method, a series of posture strategies under different assembly conditions are investigated towards more comfortable and energy-efficient assembly postures. Thus far, the consideration on assembly operators in assembly sequencing is insufficient though it plays a key role in the integrative product and process design. In this research, the use of new ergonomic constraints into assembly sequencing optimisation is proposed. Feasible assembly sequences are generated and evaluated based on the product geometry, assembly workstation layout, operator characteristics and working posture. A new Liverpool Assembly Sequence Planning System (LASP) is developed to achieve the integration by applying two evaluation criteria, i.e. visibility criterion, accessibility criterion or both. With LASP, possible design faults with respect to restricted visibility and obstructed accessibility is obtainable during the early design stage. Meanwhile, the optimum sequences are provided to operators automatically for ease of manual assembly, facilitating higher assembly quality and efficiency

    Generalisable FPCA-based Models for Predicting Peak Power in Vertical Jumping using Accelerometer Data

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    Peak power in the countermovement jump is correlated with various measures of sports performance and can be used to monitor athlete training. The gold standard method for determining peak power uses force platforms, but they are unsuitable for field-based testing favoured by practitioners. Alternatives include predicting peak power from jump flight times, or using Newtonian methods based on body-worn inertial sensor data, but so far neither has yielded sufficiently accurate estimates. This thesis aims to develop a generalisable model for predicting peak power based on Functional Principal Component Analysis applied to body-worn accelerometer data. Data was collected from 69 male and female adults, engaged in sports at recreational, club or national levels. They performed up to 16 countermovement jumps each, with and without arm swing, 696 jumps in total. Peak power criterion measures were obtained from force platforms, and characteristic features from accelerometer data were extracted from four sensors attached to the lower back, upper back and both shanks. The best machine learning algorithm, jump type and sensor anatomical location were determined in this context. The investigation considered signal representation (resultant, triaxial or a suitable transform), preprocessing (smoothing, time window and curve registration), feature selection and data augmentation (signal rotations and SMOTER). A novel procedure optimised the model parameters based on Particle Swarm applied to a surrogate Gaussian Process model. Model selection and evaluation were based on nested cross validation (Monte Carlo design). The final optimal model had an RMSE of 2.5 W·kg-1, which compares favourably to earlier research (4.9 ± 1.7 W·kg-1 for flight-time formulae and 10.7 ± 6.3 W·kg-1 for Newtonian sensor-based methods). Whilst this is not yet sufficiently accurate for applied practice, this thesis has developed and comprehensively evaluated new techniques, which will be valuable to future biomechanical applications

    Contributions pour l’analyse ergonomique de mannequins virtuels

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    Physical fatigue in occupational activities leads to potential musculoskeletal disorder (MSD) risks, and it has received great attention to model the fatigue in order to prevent potential risks in ergonomics. Meanwhile, virtual human techniques have been used a lot in industrial design in order to consider human factors and ergonomics as early as possible. However, fatigue effect is considered sufficiently neither in conventional ergonomics tools nor in virtual human simulation tools. In this thesis, we are focusing on the modeling of muscle fatigue and recovery processes in manual handling operations, its potential applications, and the integration of fatigue effect into human operation evaluation and human simulation tools.At first, a simplified muscle fatigue model is proposed based on motor-unit pattern in muscle physiology to predict the reduction of physical strength in manual handling operations. Theoretical approach and experimental approach are used to validate the fatigue model. In theoretical way, comparisons have been made between the proposed model and existing maximum endurance models in static cases and other muscle fatigue models in dynamic cases. From theoretical analysis, fatigue resistance for a specific muscle group of a certain population can be determined by regression method. Secondly, in experimental method, a total of 40 subjects carried out the simulated drilling operation under posture constraints. Along the working process, the simulated job static strengths were measured as an index of the physical fatigue, and the posture of the upper limb was also captured in the operation. It has been found that the fatigue of most of the subjects followed the exponential function predicted by the fatigue model. At last, the fatigue model is integrated into our new virtual human simulation framework for evaluating industrial operations and predicting human posture in multi-objective optimization method.The fatigue and recovery model proposed in this thesis is useful for evaluating physical fatigue in manual handling operations, analyzing human posture, identifying the human fatigue and recovery properties, and optimizing the design of manual handling operations.La fatigue physique dans les activités professionnelles conduit à des risques éventuels de troubles musculo-squelettiques (TMS). Les recherches en ergonomie ont pour objectif la prévention des risques potentiels. Ainsi, la simulation de mannequins virtuels a été beaucoup utilisée dans l'industrie, afin d'examiner les facteurs humains et l'ergonomiques dès que possible. Cependant, l'effet de la fatigue n'est pas encore suffisamment considéré ni dans les analyses ergonomiques conventionnelles, ni dans les outils de simulation. Dans cette thèse, nous nous concentrons sur la modélisation de la fatigue et la récupération musculaire dans les opérations de manutention, et ses applications potentielles, et l'intégration de ses effets dans les évaluations des opérations et des outils de simulation.Dans un premier temps, un modèle simplifié de la fatigue musculaire est proposé sur la base de paramètres physiologiques pour prédire la réduction de la force physique dans les opérations de manutention. Une approche théorique et une approche expérimentale ont utilisé pour valider ce modèle. Dans la première approche, des comparaisons ont été faites entre notre modèle et les modèles d'endurance pour des cas statiques et des cas dynamiques. De l'analyse théorique, la résistance à la fatigue pour un groupe de muscles d'une certaine population ne peut être déterminée par la méthode de régression. Dans la deuxième approche, 40 ouvriers ont effectué la simulation d'opérations de perçage sous contraintes posturales. Outre le processus de travail, les forces exercées par les ouvriers dans la simulation des perçages ont été mesurées comme un indice de la fatigue physique, et la posture des membres supérieurs a également été mesurée grâce à un système de capture de mouvements. Il a été constaté que la fatigue de la plupart des sujets a suivi la fonction exponentielle prédite par le modèle de la fatigue. Enfin, le modèle de fatigue est implémenté dans notre logiciel de la simulation de mannequin pour évaluer des opérations de manutention et faire de la prédiction de postures de travail avec une méthode d'optimisation multi-objectifs.Les modèles de fatigue et de récupération proposés dans cette thèse sont utiles pour évaluer la fatigue physique lors d'opérations de manutention, pour analyser la posture de travail, pour identifier les propriétés de fatigue musculaire, et pour optimiser la planification des opérations de manutention

    Ergonomic Models of Anthropometry, Human Biomechanics and Operator-Equipment Interfaces

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    The Committee on Human Factors was established in October 1980 by the Commission on Behavioral and Social Sciences and Education of the National Research Council. The committee is sponsored by the Office of Naval Research, the Air Force Office of Scientific Research, the Army Research Institute for the Behavioral and Social Sciences, the National Aeronautics and Space Administration, and the National Science Foundation. The workshop discussed the following: anthropometric models; biomechanical models; human-machine interface models; and research recommendations. A 17-page bibliography is included
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