Workload Assessment with Ovako Working Posture Analysis System (OWAS) in Japanese Vineyards with Focus on Pruning and Berry Thinning Operations

Abstract

A questionnaire survey was conducted in Yamanashi Prefecture in the course of adapting a wearable robotic suit, which was originally developed for assisting human care (Yonetake and Toyama, 2005), to agriculture. Among various farm operations, farmers had a heavy workload when grape berry thinning followed by cluster shaping and pruning, and 58% of farmers hoped to buy a wearable agri-robot suit that may support their arms, legs, and back. Using the main Ovako Working Posture Analysis System (OWAS), physical workload was evaluated during pruning and berry thinning in vineyards on a slope and flatland; pruning was a heavier workload than berry thinning irrespective of the farm topography and, for both operations, working on the slope was a heavier workload. According to the second OWAS working posture percentages for the relative proportions of the postures of different body parts, workers have to maintain a static posture by raising the arms at or above shoulder level for more than 70% of the total working time in berry thinning. The arm posture in berry thinning was classified as AC3 and corrective measures are necessary as soon as possible. In the OWAS analysis system, although pruning was evaluated to have a higher level of physical stress than berry thinning, farmers felt that it is a lighter workload because it involves various postures, such as walking and sitting, whereas in berry thinning the farmer has to maintain the same posture by raising the arms and farmers especially felt arm fatigue while berry thinning. These results suggested that a mechanical support system is necessary to reduce the workload of grape farmers. Thus, in Japanese grape production, a wearable agri-robot suit focused on a support system for the back, arms and legs with free and rapid movement of the wearer might be an alternative solution to reduce the workload of grape farmers.