Design, Modeling and Optimal Control Strategy for an Under-Actuated Anthropomorphic Robotic Finger

In this paper, we describe the design and optimal control strategy of an under-actuated, anthropomorphic robotic finger. A compliance element (silicon rubber skin) and series elastic actuators are incorporated in the design to reduce the number of actuators, and for robotic finger control. Manufacturing of the robotic finger is further simplified by the basic joint design and a 3D printing technique. The proposed metacarpophalangeal (MCP) joint structure allows flexion-extension and adduction-abduction motions of the robotic finger to be controlled easily and independently. However, due to the under-actuated system, and joint stiffness caused by the compliance element, the design is limited by inverse kinematics issues, preventing some of the desired joint angles from being achieved. We analyzed this problem and proposed an optimal control strategy to address this issue. Our experimental results showed that good performance of the optimal control strategy of the under-actuated anthropomorphic robotic finger prototype.