Chopstick-type Gripper Mechanism for Meal-Assistance Robot Capable of Adapting to Size and Elasticity of Foods T. Oka 1(&) , D. Matsuura 1 , Y. Sugahara 1 , J. Solis 2 , A. L. Lindborg 3 , and Y. Takeda 1 1 Department of Mechanical Engineering, Tokyo Institute of Technology, Tokyo, Japan {oka.t.aa,matsuura.d.aa,sugahara.y.aa, takeda.y.aa}@m.titech.ac.jp 2 Karlstad University, Karlstad, Sweden jorge.solis@kau.se 3 Camanio Care AB, Nacka, Sweden annlouise.lindborg@camanio.com Abstract. This paper proposed a chopstick-type gripper for a meal-assistance robot, which is capable of adapting its shape and the contact force with the target food according to the size and the elasticity of the food. Solely using position control of the driving motor for the mechanism, this feature was enabled without relying on force sensors. The gripper was designed based on the concept of under-actuation and a planar mechanism with 2 DOF composed of a combi- nation of 2 four-bar mechanisms having a torsion spring in a passive joint. To clarify the gripping motion and relationship among the contact force, food’s size and elasticity, a simulation based on kineto-elasto-static analysis was performed. Finally, to verify the theoretical analysis, a simple prototype was manufactured and an experiment to measure the contact force has been conducted. Keywords: Mechanism design  Meal-assistance robot Chopstick-type gripper  Under-actuated mechanism Kineto-elasto-static analysis 1 Introduction Undernutrition is a large problem amongst the elderly. In order to enable frail elderly to live independently and to keep track of their food intake, we started a joint project under a Japan-Sweden Academia-Industry International Collaboration Program on Innovative Solutions, Community Design and Services for Elderly People [1]. Our research aims at making a mock-up of a multi grip tool and a camera system for a commercialized robotic assistive eating device Bestic [2] which was developed to enable frail elderly to get the food from the plate to the mouth according to the control by themselves. This paper is focused on the development of the multi grip tool, which is the alternative tool for a spoon to enable to pick up Japanese foods. © Springer Nature Switzerland AG 2019 A. Gasparetto and M. Ceccarelli (Eds.): MEDER 2018, MMS 66, pp. 284–292, 2019. https://doi.org/10.1007/978-3-030-00365-4_34