Kinematics of a 4-DoF Series-Parallel Robotic Thumb

Nicholas Baiata, Nilanjan Chakraborty

Keywords: Series-parallel mechanism, Thumb Design, Finger kinematics

TL;DR: We present the design and complete kinematic analysis of a novel 4-Degree-of-Freedom (4-DoF) series-parallel hybrid robotic thumb, and validate our findings via simulations, demonstrating position and velocity control in the task space.

Abstract:

Series-parallel robotic fingers offer a slender form factor, with excellent force transmission and potential controllability. A challenge in designing robotic hands with series-parallel fingers is that the fingertip position is hard to control because it is difficult to analyze the finger kinematics for fingers with 3–Degree-of-Freedom (3-DoF) or higher. In previous work [1], we have partially overcome this challenge by
designing and analyzing a 3-DoF series-parallel finger. However, the thumb is a special finger, which needs at least 4-DoF for it to be part of a versatile hand with the ability to do both opposable-thumb grasping as well as open-palm manipulation. The only current series-parallel hybrid hand available (AIDIN) has a fixed position thumb (3-DoF), resulting in the loss of open-palm manipulation, and a reduction in dexterity and manipulable object size. Therefore, in this paper, we present the kinematic design and analysis of a novel 4-Degree-of-Freedom (4-DoF) series-parallel hybrid robotic thumb. We present the forward, inverse, and differential kinematics, and show via simulation that we can do position control and velocity control of the thumb in joint space as well as task space.

Submission Number: 21