Design and Kinematic Analysis of a Novel Series-Parallel Hybrid Finger for Robotic Hands

Interacting Robotic Systems Laboratory, Stony Brook University

Thiha Zaw, Dasharadhan Mahalingam, Nicholas Baiata, Aditya Patankar, Nilanjan Chakraborty

Introduction

Dexterous robotic hands are the key to enabling the use of robots in many applications, including service robotics, assistive robotics, and healthcare. These applications require the ability of robots to manipulate engineered objects designed for humans and require manipulation capabilities beyond pick-and-place tasks. A key to making robotic hands dexterous is to have fingers such that finger tip motion and forces are controllable, while ensuring that the fingers are compact and akin to the size of an average human, so that the hand can manipulate objects designed for humans. Although a wide range of hands have been proposed in the literature, there is no readily available robotic hand that is compact, dexterous, reliable, and cost-effective. Therefore, with a view towards building compact reliable dexterous robotic hands, we studied the fundamental problem of designing a robotic finger with abduction/adduction and flexion/extension capabilities and size similar to a human finger such that the fingertip motion and forces can be controlled.

Proposed Design

The kinematic design of our linkage-driven finger mechanism is as shown on the right side. The left panel shows the CAD model of the finger. It has three digits or phalanges and three joint connections similar to a human finger. The MCP joint is designed with a universal joint connection so that it has abduction/adduction and flexion/extension motions. The PIP joint and DIP joint are designed with revolute joints so that both have flexion/extension motions. The PIP and DIP joints of our finger are coupled and connected together with a cross four-bar linkage, so that they move together, similar to natural human finger motion during grasping, where the PIP and DIP joints do not move independently [14]. Thus, the whole finger mechanism consists of 4 joint motions with three degrees of freedom.

Kinematics Analysis

The forward and inverse kinematics of the mechanism was analyzed, and position forward, inverse, and Jacobian matrix are developed. Detail analysis and mathematical derivations can be found in the paper. With the position forward and inverse kinematics, it is possible to control both the joint space position and the fingertip task space position, and with the Jacobian matrix, it is possible to control the task space fingertip velocity. To the best of our knowledge, this is the first 3-DoF linkage-driven finger with abduction/adduction as well as flexion/extension, where the kinematics is well understood and the task space controls are possible.

Reachable Workspace of the finger

(a) 3D View

(b) Left Side View

(c) Back Side View

Simulations of the Controllablity of the Finger

The video provides simulation of the possible joint space, task space, and velocity controls of the finger mechanism. The task space control was demonstrated by letting the fingertip follow the predetermined path using the resolved motion rate control. Moreover, the multi-fingers coordinated task space control ability was demonstrated with three finger hand.

More about the research work can be learned at

Zaw, T., Mahalingam, D., Baiata, N., Patankar, A., and Chakraborty, N. (October 29, 2024). "Design and Kinematic Analysis of a Novel Series-Parallel Hybrid Finger for Robotic Hands." ASME. J. Mechanisms Robotics. doi: https://doi.org/10.1115/1.4067024