Ergonomic evaluation of manual assembly operations using direct and indirect observation workstations in sitting and standing positions

Abstract

This research evaluated the traditional or direct observation workstation and the newly developed indirect observation workstation in manual assembly operations. The direct observation workstation requires the bending of the head and trunk in order to perform the task. The indirect observation workstation uses a video camera to project the work area onto a television monitor directly in front of the worker. Muscle activities of the trapezius and anterior deltoid muscles were quantified using Electromyography (EMG). This research found that static load on the trapezius muscle was lower when using the indirect observation workstation particularly in the standing position. The internal between the activation of motor unit potential is measured in micropauses. Duration in micropauses or micro-breaks were longer when using the indirect observation workstation for both the trapezius and anterior deltoid muscles. This research also found that excessive bending of the head can be reduced by using the indirect observation workstation. Productivity, however, is slower when using the indirect observation workstation compared to the direct observation workstation due to the two dimensional image projected by the television monitor. Dynamic workstation which utilizes a combination of direct and indirect observations, in the sitting and standing positions, shows an improvement in productivity but is accompanied by an increase in static load and shorter duration in micropauses particularly in the trapezius muscle. (Abstract shortened by UMI.)