Preventing Work-Related Musculoskeletal Disorders in Manufacturing by Digital Human Modeling

This research concerns the workplace design methodology, involving digital human models, that prevents work-related musculoskeletal disorders (WMSDs). We propose an approach that, in conjunction with one of the classic WMSD risk assessment methods, allows one to simplify simulations in a three-dimensional digital environment. Two real-life workstations from a manufacturing industry were modelled in a 3D Studio Max environment by means of an Anthropos ErgoMax system. A number of simulations show that, for the examined cases, classic boundary mannequins’ approaches can be replaced by using 50th percentile of a population individual, with a minimal impact on the WMSD risk. Although, the finding might not be suitable in all situations, it should be considered, especially where compromise solutions are being sought due to other criteria.

Virtual Modeling of User Populations and Formative Design Parameters

Human variability related to physical, cognitive, socio-demographic, and other factors can contribute to large differences in human performance. Quantifying population heterogeneity can be useful for designers wishing to evaluate design parameters such that a system design is robust to this variability. Comprehensively integrating human variability in the design process poses many challenges, such as limited access to a statistically representative population and limited data collection resources. This paper discusses two virtual population modeling approaches intended to be performed prior to in-person design validation studies to minimize these challenges by: (1) targeting recruitment of representative population strata and (2) reducing the candidate design parameters being validated in the target population. The first approach suggests the use of digital human models, virtual representations of humans that can simulate system interaction to eliminate candidate design parameters. The second approach suggests the use of existing human databases to identify relevant human characteristics for representative recruitment strata in subsequent studies. Two case studies are presented to demonstrate each approach, and the benefits and limitations of each are discussed. This paper demonstrates the benefit of modeling prior to conducting in-person human performance studies to minimize resource burden, which has significant implications on early design stages.

Natural Virtual Reality User Interface to Define Assembly Sequences for Digital Human Models

Digital human models (DHMs) are virtual representations of human beings. They are used to conduct, among other things, ergonomic assessments in factory layout planning. DHM software tools are challenging in their use and thus require a high amount of training for engineers. In this paper, we present a virtual reality (VR) application that enables engineers to work with DHMs easily. Since VR systems with head-mounted displays (HMDs) are less expensive than CAVE systems, HMDs can be integrated more extensively into the product development process. Our application provides a reality-based interface and allows users to conduct an assembly task in VR and thus to manipulate the virtual scene with their real hands. These manipulations are used as input for the DHM to simulate, on that basis, human ergonomics. Therefore, we introduce a software and hardware architecture, the VATS (virtual action tracking system). This paper furthermore presents the results of a user study in which the VATS was compared to the existing WIMP (Windows, Icons, Menus and Pointer) interface. The results show that the VATS system enables users to conduct tasks in a significantly faster way.

Ergonomic Assessment of Multi Calibre Individual Weapon System in Virtual Reality Platform

The primary objective of the study was to assess the compatibility of multi calibre individual weapon system (MCIWS) with the shorter, medium and larger individual users of Indian Army. Three dynamic digital human models (DHM) 5thp, 50thp, 95thp army pooled (AP) population were considered to accommodate wide range (more than 90 per cent) of the army population for ergonomic analysis of the weapon system with the help of digital human modelling software Jack. Solid model of MCIWS which was in Parasolid file format X_T (*.x_t) was imported into NX5 (solid model design software) and subsequently converted to JT (*.jt) format. This solid model was later translated into Jack 5.0.1 environment. Standing, squatting and crawling with the weapon were adopted for the study. Angular deviations of important joints, posture prediction using OWAS, and comfort discomfort assessment using Dreyfus 3D method were carried out in the study. The result of the study revealed that the operation in squatting and crawling conditions may increase postural load on neck, shoulder and upper arm. The pistol grip size, shape and contour are acceptable for the taller population. Removal of corrugated gripping surface, reduction of grip diameter and space adjustment for gloves use will be effective for optimal use. The position and size of fore grip seemed suitable for the taller users. Sight system could be accessed by all three user populations. It is advised to avoid holding the weapon for long duration with hands to prevent overuse injury or undue fatigue.