Standard Guide for Assessing Fit Accommodation of Exoskeletons for Manufacturers and Designers

Importancia y uso:

4.1 Improperly fitted exoskeletons may cause discomfort, distraction, stress, disuse, accidents, and therefore, may cause unacceptable risk of injury or damage to the health of users (1).5 An improperly fitted exoskeleton can also cause a loss of cognitive fit and task failure. According to Ref (2), “Cognitive fit refers to supporting the perception–cognition–action decision process of the human when wearing the exosystem.” This characteristic is relevant to exosystem fit as the operator’s cognitive capability must be maintained such that operational tasks, including decision making, can be adequately performed. Thus, manufacturers and designers may consider user anthropometry and fit when designing exoskeletons. This guide provides a set of recommendations for considering the anthropometry (body size and shape) of the intended user population of an exoskeleton. These recommendations can provide guidance to designers on fit criteria. They will also facilitate the consistent (repeatable) estimation of accommodation rates. This guide further highlights important considerations in the design of exoskeletons which are impacted by human physical variation as well as range of motion and clearances, which are critical safety concerns. Additionally, anthropometric considerations also extend to kinematic and kinetic parameters; however, these concepts are beyond the scope of this guide. Lastly, this guide assumes the reader understands the fundamentals behind anthropometry and human biomechanics.

4.1.1 In estimating how much (that is, what percentage) of the population is accommodated by an exoskeleton, it is critical to use the appropriate anthropometric database. The anthropometric data upon which the design is based should match the target user population as closely as possible. This can be a challenge, particularly for civilian populations where detailed anthropometric data are often not widely available. A list of readily available anthropometric databases is provided in Appendix X1. A limited number of civilian datasets are available in the public domain (that is, free). There are more extensive anthropometric datasets that are available for purchase.

4.1.2 When discussing accommodation, disproportionate disaccommodation is an essential conversation in the context of groups not considered. Disproportionate disaccommodation occurs when one group (for example, men) is accommodated at a rate different than that of other groups (for example, women) or at rates different than their relative presence in the overall population. Best practices of estimating fit include consideration of available anthropometric data and attention to sub-populations that may not be fully accommodated.

4.2 Considering anthropometry during exoskeleton design will result in information useful to end users. Information may include who may safely and effectively use an exoskeleton and how to correctly measure body dimensions to determine size requirements. Sizing information may also include criteria to determine if the exoskeleton is fitting properly and how to adjust the exoskeleton for a better fit. Possible limitations to the end user’s range of motion and guidance regarding the use of clothing, PPE, or other equipment may also be provided to the end user.

4.3 Not every element of this guide may be applicable to all exoskeletons, nor are the recommendations in this guide intended to be prescriptive (that is, manufacturers may already provide a variable level of adjustability inherent in the exoskeleton design which may be described in their guidance).

4.4 Static and dynamic fit are related to, but not the same as, comfort. Static fit refers to the alignment between dimensions of the human and exoskeleton in one or a small number of predefined, standardized postures, with no consideration of movement. An example of static fit is a user in a standing posture with their hands by their side. This would allow for shoulder breadth measurements to be taken. Dynamic fit, on the other hand, relates to the fit of the human and exoskeleton interaction with each other through functional range of motion (ROM) activities. An example of dynamic fit is a user moving the shoulder complex through the range of motion for flexion/extension and adduction/abduction. This would allow for changes in the shoulder complex to be noted and measured.

4.4.1 The environment is an important factor in dealing with evaluations of comfort or discomfort. According to Ref (3), discomfort was reported to be related to the physical characteristics of an environment. However; in the absence of discomfort, the user experiences a neutral subjective state. To notice comfort, something positive may be experienced, such as rest, security, relaxation, or indulgence; therefore, comfort and discomfort are considered two independent constructs. Nevertheless, in equipment evaluation, both discomfort and comfort can be related to an equipment’s physical features (4, 5), albeit, comfort may also include the visual pleasure of a design as well (6, 7). For example, when wearing an exoskeleton, fit is a parameter of the exoskeleton. However, if the exoskeleton does not fit from an anthropometric perspective, this could mean discomfort from the exoskeleton device. Thus, the opposite of non-fitting or of discomfort would be fit and comfort.

Subcomité:

F48.02

Volúmen:

15.13

Palabras clave:

accommodation; anthropometry; anthropomorphic; dynamic fit; ergonomics; exoskeleton; Seven-Step Paradigm; static fit; univariate;