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1 Introduction The efficient and safe operation of civilian and military sys- tems requires that tasks, equipment, and the work environment be compatible with the users' capabilities. Too often equipment is designed as if it stood alone, and the task Is conceived as if it were independent of human characteristics. There are situa- tions in which equipment and system fmIure are believed to be caused by human error, despite the fact that the equipment or system was developed with little consideration of the capabilities and limitations of the people who operate and maintain it in a field environment. Due to exigencies of time, limited budgets, in- formation gaps, or just lack of consideration, these characteristics of the user are frequently ignored by the designer, engineer, and fabricator of the equipment. Even when people are considered, too often that consideration is incomplete or inaccurate owing to a lack of knowledge or thoroughness. Yet, in many instances, people may be the limiting factor in the effective use of this equipment. Since the interactions mnong the person, the equipment, the task, and the environment are complex, many researchers and en- gineers are concerned with the need for ergonomic models that describe the physical characteristics of people and their interac- tions with the task and equipment in the work environment. Such models should be representations of real systems designed to de- scribe and predict their essential characteristics and performance. In addition, if feasible, the development of a standard integrated

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2 ergonomic mode] would provide a means for extrapolating data across a variety of users and increase the data base. As noted in the following chapters, there have been numer- ous efforts to develop descriptive physical models of the human body (see especially Table 3-1, Biomechanical Models). In most instances, the development of anthropometric and biodynamic models has not extended beyond the requirements to meet the specific application needs of the moment. Such specialized models may serve their specific purposes well but usually give little help in predicting or solving general human-technology interaction prob- lems outside their specific boundaries. In addition, many of the existing models cannot be joined to form a more general mode! or be extended into an integrated ergonomic model. In the past, construction of models that describe people in "the real world" has been lirn~ted, due in large part to our inability to capture the versatility and mobility of the human body. In order to develop a universal ergonomic model, comprehensive and accurate representations are required for such factors as physical size, visual field perception, reach capabilities, loadings on muscles and bones, and their responses and strength capabilities. Precise examination of anthropometric and biodynamic data is facilitated by modern data management techniques such as com- puter graphics and relational data bases for studying physical in- teractions. The trend toward the use of common disciplinary (and interdisciplinary) structures, applications software, and data base formats by many researchers helps to provide a larger library of related information. The automation of static and dynamic mea- surement systems for data acquisition for body mapping, reach, kinematics of motion, and their interactions with independent variables such as work environments provides a wealth of detailed and accurate information. An integrated ergonomic mode! could encompass all three of the more primitive models, i.e., provid- ing anthropometric, biomechanical, and interface information for various populations, under various conditions, for various tasks, in their interactions with various technical components. To have the greatest utility, the integrated ergonomic mode} should be ca- pable of generalization and contain adequate refinement of detail to be applicable to other design, research, or analytic situations. At the same time, in order to be used it must be user-friendly and time- and cost-effective. Since anthropometric, biomechani- cal, and interface models provide the basis for the development of

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3 an integrated ergonomic model, any limitations and shortcomings of the former impose restrictions on the usefulness of the latter. The study group identified current anthropometric, biome- chan~cal, and interface models; determined that they were useful; and provided examples of their applications. Shortcomings of these models were described, and the additional research needed to increase their value was explored for each of these three classes of models. Among the shortcorn~ngs are the disparity and incom- patibility among the methods used by investigators to collect the data, frequently resulting from the use of samples that are too small to provide reliable data, and the variety of methods used for measurement and data collection. The workshop members determined that it was feasible to incorporate various models from these three classes into a general integrated ergonomic mode! or smaller modules and recommended a program of research for their development. The study group further recommended approaches to the collection of additional data using a standardized format and nomenclature and their incorporation into the overall mode! or modules. The following chapters describe the current status of devel- opment of anthropometric, biomechanical, and interface models, giving limitations and listing research needs specific to each. AN preaches to the development of integrated ergonomic models are discussed, and research recommendations are provided for further development of lower-level models.