Recently, as handheld information appliances, such as mobile phones, PDAs, have widely spread, the development of these appliances should pay more attention in their ergonomic design. However, the user tests for developing the “ergonomic” appliances are usually done by many real subjects testing a variety of these physical mockups, and the process of these tests usually requires the expensive cost and has to take a long time. So, we propose a software system of an automatic ergonomic assessment system for designing handheld information appliances by integrating the digital hand model with the product model of the appliance. Our system has the following four feature functions for ergonomic assessment: 1) Generation of kinematically and geometrically accurate digital hand models with rich dimensional variation, 2) automatic evaluation of the grasp posture stability by estimating the force-closure and the grasp quality, 3) automatic evaluation of ease of the finger motion in operating the user interface, 4) aiding the designers to re-design the housing shapes and user-interfaces in the product model. In this paper, we describe the 1) and 2) of the above functions. Moreover, we also describe the verification results of our system by comparing estimated grasp postures and these stability given from the system with the ones from experiments by real subjects.

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