معرفی روش تجزیه و تحلیل کمی داخل محیط مجازی برای زمان واقعی و ارزیابی ارگونومیک مستمر

This paper presents our work on methods to link virtual environments (VE) and quantitative ergonomic analysis tools in real time for occupational ergonomic studies. We pursued two distinct approaches: (a) create methods to integrate the VE with commercially available ergonomic analysis tools for a synergistic use of functionalities and capabilities; (b) create a built-in ergonomic analysis module in the VE. The first approach provides the use of established, off-the shelf tools integrated with the VE to create a hybrid application. This integration is performed through the use of APIs provided by the software vendor and existing Internet and communications technologies. The commercial ergonomics tool and the VE run concurrently and integrate their capabilities. The second approach provides the capability to do ergonomic evaluations in a self-contained VE application. In this method, the required ergonomics calculations are built into the VE. Each approach has its own distinct advantages. The use of a commercially available ergonomics tool integrated with a VE provides significant more capability and should be used where detailed and complex ergonomics evaluations are required. However, the process of integration in this approach is more difficult and time consuming. The self-contained VE application is more suited for simple ergonomic evaluations or in cases where the ergonomics algorithms are readily accessible and easily implemented. The two integration strategies are methodically explained and demonstrated using case studies conducted with industry partners. This integrated capability facilitates integration of ergonomic issues early in the design and planning phases of workplace layouts. It provides functionality beyond the capabilities of current commercial off-the-shelf (COTS) solutions. In addition, it contributes to a new trend in the integration of different technology fields for synergistic use in industry.

In the past, workplace ergonomic considerations have often been reactive, time-consuming, incomplete, sporadic, and difficult. Ergonomic experts who were consulted after problems occurred in the workplace examined data from injuries that had been observed and reported. There are now emerging technologies supporting simulation-based engineering to address this in a proactive manner. These allow the workplaces and the tasks to be simulated even before the facilities are physically in place. In recent times, virtual reality has emerged as one such technology attaining maturity and gaining acceptance in industry [1]. Application of this technology spans health-care, national security, design and manufacturing [2], education, and training [3]. One natural application domain of these immersive technologies is in ergonomic studies such as reach, visibility, and visual inspection through the use of CAD models in immersive environments. However, most of the virtual environments used for ergonomic evaluations only allow for subjective and qualitative evaluations based on verbal/written participant and observer feedback of comfort and effectiveness. At present various commercial systems are available for ergonomic analysis of human posture and workplace design. However, these methods provide primarily static analysis of the task at hand, i.e. one can create a static “snapshot” of the posture or situation to be evaluated and then perform an analysis using the tool. In the work presented in this paper, we synergize the ergonomic modeling and setup capability of a virtual environment with ergonomic analysis tools and methods to allow a more rigorous analysis of the underlying ergonomic aspects during the simulation in the immersive environment (Fig. 1). The key contribution of this is that it provides a monitoring system that analyzes the entire process continuously, in real-time, as the participant goes thru the motions required by the task and is able to automatically flag postures that are not ergonomically recommendable. This presents a very effective approach to take the evaluation capabilities of VEs to the next level.Thus, the key questions to be answered through this research were: can linking an immersive system with quantitative ergonomic analysis functionality create a continuous ergonomics monitoring tool? How can we formulate an integration system to accomplish this by linking the VE (which is dynamic in nature) with a commercial package (that performs static posture analysis); what is the necessary data streaming that is necessary in both directions? What is the methodology required to create a simple ergonomic analysis capability within a VE? We would like to emphasize that the focus of this study was not to actually perform a detailed ergonomic analysis and provide recommendations but to create the integrated technology and verify that it had the potential to be useful for industrial ergonomics studies. As always, it can be argued that in some cases an expert ergonomist can make good recommendations with just a paper and pencil, without the need for this kind of relatively expensive environments. But the creation of this synergistic tool is justified since it is one more resource that would be appropriate and useful in more complex situations.

Both approaches presented in this paper enhanced the functionality of the VE by allowing more rigorous ergonomic analysis functionality and eliminating manual and paper/pencil data capture process. The first approach that used the COTS application Jack had the advantages of decreased effort and risk of development and higher reuse of software as far as the basic ergonomic analysis functionality. However, this method required greater effort in terms of configuration, communication, and compatibility issues for the hybrid system. Also, there was an inability to meet certain requirements because of the pre-packaged functionality provided by the ergonomics analysis software. Data sharing between the two applications needs to be through a reliable medium. Shared memory used in the current implementation is fast and reliable but cannot be used in distributed environments. The frame rates and data rates need to be synchronized between the two applications to avoid excessive lag or jerky movements in either system. Another important issue relates to the calibration of the human model. The VADE human model used was created as a 50th percentile human. But a person with a different size and shape can be immersed in the environment. VADE uses a parametrically defined human model (defined by 13 size parameters) in Pro/Engineer. This parametric human model can be used to generate humans of various sizes and shapes. Jack also allows a segment-by-segment modification of the human model. If multiple people participate in these integrated environments, methods need to be implemented to also integrate the human model size and shape across the two systems. In the second approach, the ergonomic capability developed to create a single unit VE was highly customizable since it was created in-house. However, each ergonomic analysis capability needs to be implemented individually in the VE. In essence, the VE ergonomic capability development parallels the development of any ergonomic analysis system and that seems to be a wasted duplication of effort. In addition, there will be a need for ergonomics experts in this method to identify the proper analysis methods to be implemented. Considering the complexity of the real human body system, more trackers need to be utilized in this approach to more accurately represent the posture of the human.The integration methods described in this paper create a novel way to bring quantitative ergonomic analysis into virtual environments. This in turn allows different postures and assembly processes to be examined in a more rigorous manner in order to identify problems in work environments. This work also offers a prototype that could be extended for further integration of other CAE tools to add more functionality to VR-based applications. Since many immersive visualization systems are custom developed and the interactions vary largely based on the application, it is important that the value of these customized tools not be diminished because of a lack of certain analysis capabilities that are required in the application. The integration approach presented in this paper allows these custom developed applications to integrate ergonomic analysis capabilities and provide a more useful tool to industry. This technology and the implementation illustrate the possibilities of using both off-the shelf software and in built methods in a VE environment, thus combining advanced visualization systems, human modeling systems, and advanced ergonomics capabilities. Initially all immersive applications needed to be created as stand alone applications. In the recent past, engineering applications and ergonomics applications have embraced “open architecture” concepts. This, combined with advances in distributed computing, collaboration applications, and systems integration has now opened the doors to complete integration of complex ergonomics evaluation capabilities found in commercial systems and custom immersive applications.