Virtual Ergonomic Assessment on Handheld Products based on Virtual Grasping by Digital Hand

The purpose of this research is to develop a system for virtual ergonomic assessment of products without real subjects and physical mockups by integrating a digital hand model with a product model. In previous work, we developed functions of a semi-automatic grasp planning for the digital hand and of quantitatively evaluating the grasp stability of the product based on the force-closure and the grasp quality in our system. We also confirmed the validity of the results from these functions by comparing them with the real grasp postures. However, only evaluating the grasp stability could not necessarily derive the appropriate grasp postures. To solve this problem, in this paper, we propose a new function of evaluating “ease of grasping (EOG)” for the grasp posture based on EOG-map constructed from principal component analysis for finger joint angles in real subjects’ grasps. We also developed another function of optimizing the grasp posture to avoid inappropriate postures by evaluating the posture similarity on EOG-map in the system.