TechRxiv
UDWPaper.pdf (2.6 MB)
Download file

Kinematic compatibility of a wrist robot with cable differential actuation: effects of misalignment compensation via passive joints

Download (2.6 MB)
preprint
posted on 09.07.2021, 15:24 by Haider A. Chishty, Andrea Zonnino, Andria J. Farrens, Fabrizio SergiFabrizio Sergi

We present the UDiffWrist (UDW), a low-impedance 2-DOF wrist exoskeleton featuring a cable-differential transmission. To investigate the effect of different design strategies for achieving kinematic compatibility, we developed two versions of this robot: One version (UDW-C) achieves kinematic compatibility only in the case of perfect alignment between human and robot joints. The second version (UDW-NC) connects the human and robot via passive joints to achieve kinematic compatibility regardless of alignment between human and robot joints. Through characterization experiments, we found that the UDW-NC was more robust to misalignments than the UDW-C: the increase in maximum interaction torque associated with misalignments was greater for the UDW-C than the UDW-NC robot (p = 0.003). However, the UDW-NC displayed greater Coulomb friction (p < 0.001). Further, Coulomb friction increased more for the UDW-NC than the UDW-C in the presence of misalignments between the human and robot axes (p < 0.001). We also found that torque transfer was more accurate in the UDW-C than in the UDW-NC. These results suggest that for the small (10 deg) 2-DOF wrist movements considered, the advantages of the UDW-NC in terms of kinematic compatibility are likely overshadowed by the negative effects in friction and torque transfer accuracy.

Funding

National Science Foundation under Grant 1943712

History

Email Address of Submitting Author

fabs@udel.edu

ORCID of Submitting Author

0000-0003-3019-2958

Submitting Author's Institution

University of Delaware

Submitting Author's Country

United States of America

Usage metrics

Licence

Exports