The wrist joint has complex kinematics such that achieving compatibility between an exoskeleton and the human body is difficult to accomplish.
The goal of this project is to develop a transparent, high-performance wrist exoskeleton and to examine how design complexity and kinematic compatibility affect robot transparency, dynamic characteristics, and position control accuracy.
We have developed two configurations of a high power, low-impedance, low-friction wrist exoskeleton based on a cable differential transmission. The first design (colocated design, shown above) requires precise alignment between the human and robot joints during 2DOF wrist rotations. The second design (non-colocated design) does not require precise alignment through the inclusion of several passive joints introduced to achieve compatibility.
We are currently conducting characterization of both designs to gain insight on the trade-off between design complexity and kinematic compatibility in cable-driven wrist exoskeletons.
Publications on this topic
A. Zonnino, F. Sergi, “Optimal design of cable differential actuation for 2-DOF wrist robots: effect of joint misalignments on interaction force”, IEEE Engineering in Medicine and Biology Conference (EMBC) 2016, pdf.