Position-Based Control of Under-Constrained Haptics: A System for the Dexmo Glove

Friston, Sebastian, Griffith, Elias ORCID: 0000-0001-9360-381X, Swapp, David, Marshall, Alan ORCID: 0000-0002-8058-5242 and Steed, Anthony
(2019) Position-Based Control of Under-Constrained Haptics: A System for the Dexmo Glove. IEEE ROBOTICS AND AUTOMATION LETTERS, 4 (4). pp. 3497-3504.

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The Dexmo glove is a haptic exoskeleton that provides kinesthetic feedback in virtual reality. Unlike many other gloves based on string-pulleys, the Dexmo uses a free-hinged link-bar to transfer forces from a crank to the fingertips. It also uses an admittance-based controller parameterized by position, as opposed to an impedance-based controller parameterized by force. When setting the controller's target position, developers must use its native angular coordinate system. The Dexmo has a number of uninstrumented degrees of freedom. Mature forward models can reliably predict the hand pose, even with these unknowns. When it comes to computing angular controller parameters from a target pose in Cartesian space however, things become more difficult. Complex models that provide attractive visuals from a small number of sensors can be non-trivial or even impossible to invert. In this letter, we suggest side-stepping this issue. We sample the forward model in order to build a lookup table. This is embedded in three-dimensional space as a curve, on which traditional queries against world geometry can be performed. Controller parameters are stored as attributes of the sample points. To compute the driver parameters for a target position, the application constrains the position to the geometry, and interpolates them. This technique is generalizable, stable, simple, and fast. We validate our approach by implementing it in Unity 2017.3 and integrating it with a Dexmo glove.

Item Type: Article
Uncontrolled Keywords: Data gloves, force feedback, virtual reality, robot control
Depositing User: Symplectic Admin
Date Deposited: 13 Aug 2019 09:40
Last Modified: 19 Jan 2023 00:35
DOI: 10.1109/LRA.2019.2927940
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3051208