Abstract
The recent developments and innovations in manufacturing techniques have changed the mode of manufacturing activities from manual to automatic. However, maintenance activities for repairing machinery have still not been automated, because such tasks depend on the skill and experience of the workers. During maintenance activities, workers are required to maintain a fixed posture according to the structure of the machinery. Therefore, workers involved in manufacturing activities, including those performing maintenance tasks, may experience damage to the fingers, forearms, shoulders, neck, and the lumbar region. Accordingly, we consider that the maintenance of a comfortable work environment is important for these workers. To this end, we focused on analyzing the process of insertion of pin connectors, an activity that is frequently employed in the field of maintenance activities. In this study, we investigated the relationship between the work position and the physical work load during insertion of pin connectors. Ten healthy male subjects participated in this experiment. They were asked to insert pin connectors under two horizontal-distance conditions (length of forearm-fingertip or upper limb) and three height conditions (the height of socket connector at the wrist, elbow, or shoulder). We estimated the control force and the maximum torque ratio of the upper-limb joints using a load cell and a three-dimensional attitude-measurement sensor. We also measured the upper-limb and dorsal-muscle activities by performing electromyography. Further, we recorded subjective ease of inserting pin connectors. The results showed that the physical work load decreased and subjective ease in inserting the pin connector increased when the socket connector was set at the height of the elbow and the horizontal distance of the forearm-fingertip length.
