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11 CitationsSee all ›
14 ReferencesDesign and performance of a manual task evaluator
Abstract
The risk factors of high repetition, high force exertions, and awkward postures have been recognized as increasing the risk of cumulative trauma disorders of the upper extremities in certain jobs and tasks. Measurement of the reactive forces associated with hand tool use, an important component of an ergonomic evaluation, can be difficult in the field. The forces associated with powered hand tools have been measured at the object being worked upon, but few instances of direct instrumentation of non-powered hand tools have been reported. A system for field measurement of manual tasks is presented. System configuration and performance characteristics are detailed as well as the development rationale, system capabilities and limitations.
- CitationsCitations11
- ReferencesReferences14
- With the aim of progressing the quantitative study of tool use, this paper has demonstrated how data from sensors fitted to handles can provide data which is sufficiently reliable to distinguish levels of performance. This follows on from successful experimental work in instrumenting tools (Fellows and Freivalds, 1991; Kilbom et al., 1993; McGorry, 2001; McGorry et al., 2003; Murphy et al., 2000; Stoy and Aspen, 1999), and the interpretation of these data in terms of skilled performance is relatively novel in the ergonomics literature. Functional dynamics (Bril et al., 2010; Rein et al., 2013 ) provides a useful framework in which to explore differences in performance.
[Show abstract] [Hide abstract] ABSTRACT: Data from 15 jewellery students, in their 1st and 3rd years of training, were analysed to show how data collected from work settings can be used to objectively evaluate performance in the use of tools. Participants were asked to use a piercing saw to cut 5 lines in a piece of metal. Performance was categorised in terms of functional dynamics. Data from strain gauges and a tri-axial accelerometer (built into the handle of the saw) were recorded and thirteen metrics derived from these data. The key question for this paper is which metrics could be used to distinguish levels of ability. Principal Components Analysis identified five components: sawing action; grasp of handle; task completion time; lateral deviation of strokes; and quality of lines cut. Using representative metrics for these components, participants could be ranked in terms of performance (low, medium, high) and statistical analysis showed significant differences between participants on key metrics. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.- However, there are more traditional forms of sensor that are much cheaper and which could provide usable data, in the form of strain gauges. Murphy et al. [29] use strain gauges on the top and sides of a knife blade, near the handle, in order to measure forces applied during cutting. Memberg and Crago [27] designed a two sided handle, with strain gauges on each side.
[Show abstract] [Hide abstract] ABSTRACT: There are many ways to capture human gestures. In this paper, consideration is given to an extension to the growing trend to use sensors to capture movements and interpret these as gestures. However, rather than have sensors on people, the focus is on the attachment of sensors (i.e., strain gauges and accelerometers) to the tools that people use. By instrumenting a set of handles, which can be fitted with a variety of effectors (e.g., knives, forks, spoons, screwdrivers, spanners, saws etc.), it is possible to capture the variation in grip force applied to the handle as the tool is used and the movements made using the handle. These data can be sent wirelessly (using Zigbee) to a computer where distinct patterns of movement can be classified. Different approaches to the classification of activity are considered. This provides an approach to combining the use of real tools in physical space with the representation of actions on a computer. This approach could be used to capture actions during manual tasks, say in maintenance work, or to support development of movements, say in rehabilitation.- This requires that the data logger be able to identify the transducer being plugged in, then to retrieve the calibration constants for that transducer from a lookup table and convert the output to meaningful units prior to display and data collection. This could be accomplished manually by requiring the operator to identify the transducer by a code number or electronically sensing the transducer ID code (Murphy, McGorry, Teare, & Brogmus, 2000). More so-called intelligent microprocessor-based data acquisition boards are becoming available, some with the capability to enter a low power-utilization mode when no changes in the transducer signals are detected.
[Show abstract] [Hide abstract] ABSTRACT: The handheld computer promises to make data gathering faster and easier for ergonomists working in challenging field environments.- [Show abstract] [Hide abstract] ABSTRACT: As cumulative trauma disorders of the upper extremities have gained increasing attention, methods to quantify the associated workplace risk factors have been developed. This paper reviews some of the current workplace analysis techniques, and highlights the current need for better field measurement systems. This need has led to the development of a field measurement tool: the manual task evaluator (MTE). Results of a laboratory experiment and a field experiment using the MTE are presented. In the laboratory experiment, subjects performed a cutting task using a knife. Average peak torque levels, as measured by the system, were found to vary significantly as a function of the material being cut and the technique used to perform the cut. In the field experiment (at two poultry processing plants) similar cutting tasks were evaluated. Task- and person-related factors were found to influence the power required to perform the task. These studies demonstrate the utility of the MTE.Relevance to industryThe results of this study have implications regarding field evaluation of forces required to perform repetitive tasks as well as identification of areas for task redesign.
- [Show abstract] [Hide abstract] ABSTRACT: Quantification of the forces applied with or by hand tools can be a difficult but important component of an ergonomic evaluation. This paper describes a device for measuring gripping forces and the moments generated by a hand tool. Laboratory characterization indicated that the device had good linearity (r2 = 0.999) with minimal hysteresis or creep. The working range exceeds 700N for gripping forces, and 28 and 16Nm for the two applied moment axes. The device, configured as a boning knife, was sensitive to differences in grip forces and applied moments in a simulated meat cutting task requiring distinct levels of precision. Significant individual variation in the "efficiency" of grip force was also observed. The system design is flexible, allowing for additional tool configurations.
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