Effect of Grasp Conditions on Upper Limb Load During Visual Inspection of Objects in One Hand

Abstract

Automated visual inspection systems based on image processing technology have been introduced to visual inspection processes. However, there are still technical and cost issues, and human visual inspection still plays a major role in industrial inspection processes. When a worker inspects small parts or products (e.g., lens for digital cameras, printed circuit boards for cell phones), they suffer from an upper limb load caused by handling objects in one hand and maintaining this awkward posture. Such workload causes damage to the hands, arms, and shoulders. So far, few studies have elucidated the effect of upper limb loads. Therefore, we conducted an experiment where the subjects were assumed to be visually inspecting small objects while handling them with one hand, and investigated the effect of grasp conditions on the upper limb load during tasks. We used electromyography, the joint angle, and subjective evaluation as evaluation indices. The results showed that the upper limb load due to the grasp condition differed depending on the upper limb site. Therefore, it is necessary to consider not only the muscle load but also the awkward posture, the duration of postural maintenance, and subjective evaluation when evaluating the upper limb load during such tasks.