Jose Antonio Diego-Mas

Using Kinect™ sensor in observational methods for assessing postures at work

This paper examines the potential use of Kinect™ range sensor in observational methods for assessing postural loads. Range sensors can detect the position of the joints at high sampling rates without attaching sensors or markers directly to the subject under study. First, a computerized OWAS ergonomic assessment system was implemented to permit the data acquisition from Kinect™ and data processing in order to identify the risk level of each recorded postures. Output data were compared with the results provided by human observers, and were used to determine the influence of the sensor view angle relative to the worker. The tests show high inter-method agreement in the classification of risk categories (Proportion agreement index = 0.89 κ = 0.83) when the tracked subject is facing the sensor. The cameras point of view relative to the position of the tracked subject significantly affects the correct classification of the postures. Although the results are promising, some aspects involved in the use of low-cost range sensors should be further studied for their use in real environments.

A method to design job rotation schedules to prevent work-related musculoskeletal disorders in repetitive work

Job rotation is an organisational strategy widely used in human-based production lines with the aim of preventing work-related musculoskeletal disorders (WMSDs). These work environments are characterised by the presence of a high repetition of movements, which is a major risk factor associated with WMSDs. This article presents a genetic algorithm to obtain rotation schedules aimed at preventing WMSDs in such environments. To do this, it combines the effectiveness of genetic algorithms optimisation with the ability to evaluate the presence of risk by repeated movements by following the OCRA ergonomic assessment method. The proposed algorithm can design solutions in which workers will switch jobs with high repeatability of movements with other less demanding jobs that support their recovery. In addition, these solutions are able to diversify the tasks performed by workers during the day, consider their disabilities and comply with restrictions arising from the work organisation.

Solving facility layout problems with strict geometric constraints using a two-phase genetic algorithm

This article puts forward a two-phase genetic algorithm that is able to solve facility layout problems strictly respecting the geometric constraints imposed on activities. In the first phase the algorithm attempts to locate an optimum slicing tree to group the activities appropriately. In the second phase the layout is obtained from this tree. In order to assess the slicing trees in the first phase we propose an evaluation function able to predict if, by making the appropriate cuts, the tree structure is able to generate layouts that satisfy the geometric restrictions imposed on the facilities to be arranged, and to minimize the cost of transporting materials between the production activities. It also permits the determination of the most suitable aspect ratio of the layout zone in order to minimize non-compliance with the geometric restrictions. The algorithm and the method of calculating the indicator proposed in the evaluation function are described, and the results obtained in the experiments carried out are also given.

Influences on the use of observational methods by practitioners when identifying risk factors in physical work

Most observational methods for musculoskeletal disorder risk assessment have been developed by researchers to be applied in specific situations, and practitioners could find difficulties in their use in real-work conditions. The main objective of this study was to identify the factors which have an influence on how useful the observational techniques are perceived to be by practitioners and to what extent these factors influence their perception. A survey was conducted on practitioners regarding the problems normally encountered when implementing these methods, as well as the perceived overall utility of these techniques. The results show that practitioners place particular importance on the support the methods provide in making decisions regarding changes in work systems and how applicable they are to different types of jobs. The results of this study can serve as guide to researchers for the development of new assessment techniques that are more useful and applicable in real-work situations. Practitioner Summary: A survey about the use of ergonomics assessment methods for identifying risk factors in physical work was conducted among practitioners. The reasons to find a method more or less useful were analysed. The support the methods provide in making decisions regarding changes in work systems and how applicable they are to different types of jobs were found to be the main reasons.

Slicing tree's geometric potential: an indicator for layout problems based on slicing tree structure

In this paper we propose an indicator to measure the capacity of a slicing tree to generate geometrically acceptable solutions for layout problems based on the slicing tree structure. This indicator can predict if, by making the appropriate cuts, the tree structure is able to generate layouts that satisfy the geometrical restrictions imposed on the items to be arranged. It also permits the determination of the most suitable aspect ratio of the layout zone in order to minimize non-compliance with the geometric restrictions. The method of calculating the indicator and its application to the facility layout problem are described, and the results obtained in the experiments carried out are also given.

Errors Using Observational Methods for Ergonomics Assessment in Real Practice

Objective: The degree in which practitioners use the observational methods for musculoskeletal disorder risks assessment correctly was evaluated. Background: Ergonomics assessment is a key issue for the prevention and reduction of work-related musculoskeletal disorders in workplaces. Observational assessment methods appear to be better matched to the needs of practitioners than direct measurement methods, and for this reason, they are the most widely used techniques in real work situations. Despite the simplicity of observational methods, those responsible for assessing risks using these techniques should have some experience and know-how in order to be able to use them correctly. Method: We analyzed 442 risk assessments of actual jobs carried out by 290 professionals from 20 countries to determine their reliability. Results: The results show that approximately 30% of the assessments performed by practitioners had errors. In 13% of the assessments, the errors were severe and completely invalidated the results of the evaluation. Conclusion: Despite the simplicity of observational method, approximately 1 out of 3 assessments conducted by practitioners in actual work situations do not adequately evaluate the level of potential musculoskeletal disorder risks. Application: This study reveals a problem that suggests greater effort is needed to ensure that practitioners possess better knowledge of the techniques used to assess work-related musculoskeletal disorder risks and that laws and regulations should be stricter as regards qualifications and skills required by professionals.

A computer based system to design expressive avatars

Abstract Avatars are used in different contexts and situations: e-commerce, e-therapy, virtual worlds, videogames, collaborative online design… In this context, a good design of an avatar may improve the user experience. The ability of controlling the way an avatar convey messages and emotions is capital. In this work, a procedure to design avatar faces capable of conveying to the observer the most suitable sensations according to a given context is developed. The proposed system is based on a combination of genetic algorithms and artificial neural networks whose training is based on perceptual human responses to a set of faces.

Measuring the Project Management Complexity: The Case of Information Technology Projects

Complex projects require specific project management (PM) competences development. However, while no complex projects have standards that are recognized to guide their management, complex projects do not have guides to deal with their complexity. To lead complex projects to success, this complexity must be measured quantitatively and, in our opinion, project management complexity assessment should be based on existing PM standards. In this work, the main project complexity assessment approaches based on PM standards are analyzed, observing that International Project Management Association (IPMA) approach is the closest to a tool that can be used as a complexity quantitative measurement system. On the other hand, several authors have shown that the inherent complexity of specific kind of projects must be measured in a particular way. The main objective of this research is to propose a project management complexity assessment tool for IT projects, providing a Complexity Index that measures the impact that complexity factors inherent to IT projects have under a specific complexity scenario. The tool combines the use of complexity factors defined by IPMA approach and the use of complexity factors found in the literature to manage inherent complexity of IT projects. All these factors were validated by expert survey and the tool was applied to a study case.