Kinematic design of a 7-DOF cable-driven humanoid arm: a solution-in-nature approach

Abstract

A solution-in-nature approach has been adopted in the design of a 7-DOF humanoid robotic arm. Similar to a human arm, the proposed robotic arm consists of three sequentially connected modules, i.e., a 3-DOF shoulder module, a 1-DOF elbow module, and a 3-DOF wrist module. To mimic the driving scheme of the human arm, all of the three arm modules are driven by cables which are functionally equivalent to human muscles (can pull but cannot push). Such a robotic arm has the advantages of light weight, high dexterity, and large reachable workspace. Hence, it can be an ideal versatile arm for various service robots to perform human-like operations. Two critical design analysis issues, i.e., displacement analysis and cable-tension analysis are addressed in more details. The closed form solution is derived for the forward displacement analysis, while the inverse displacement solution is obtained through an optimization technique. An effective cable-tension analysis algorithm is proposed in light of the analysis method for force-closure grasps.