Mechanical design of social robot Nancy

This paper presents the mechanical design of a social robot, Nancy, developed by Social Robotics Laboratory, Interactive and Digital Media Institute, National University of Singapore. The objective of our project is to introduce the social robot which is capable to interact with people, especially the elderly, based on fundamental, functional and social tasks. We developed Nancy with multi-module structure and 32 degrees of freedom (DOFs), including 24 and 8 DOFs in upper-body and lower-body, respectively. 8 DOFs are considered in each arm to make Nancy able to imitate human limbs' motion. Nancy's head involves eye and eyelid motions with 3 DOFs which is on top of a 2-DOFs neck. The wheeled-base is designed in such a way to facilitate the multi-directional movements for Nancy. One of our main objectives in Nancy's mechanical design is to obtain powerful and smooth motion, light-weight joints and simple kinematics. They are achieved by Bowden cable-pulley mechanism driven by actuators located in lower-body. Accordingly, all joints are designed to have intersected axes. Most joints are driven by brushless D.C. motors embedded with electrical brake system to stabilize the robot, especially in case of power loss.