Using Postural Synergies to Animate a Low-Dimensional Hand Avatar in Haptic Simulation

Abstract

A technique to animate a realistic hand avatar with 20 DoFs based on the biomechanics of the human hand is presented. The animation does not use any sensor glove or advanced tracker with markers. The proposed approach is based on the knowledge of a set of kinematic constraints on the model of the hand, referred to as postural synergies, which allows to represent the hand posture using a number of variables lower than the number of joints of the hand model. This low-dimensional set of parameters is estimated from direct measurement of the motion of thumb and index finger tracked using two haptic devices. A kinematic inversion algorithm has been developed, which takes synergies into account and estimates the kinematic configuration of the whole hand, i.e., also of the fingers whose end tips are not directly tracked by the two haptic devices. The hand skin is deformable and its deformation is computed using a linear vertex blending technique. The proposed synergy-based animation of the hand avatar involves only algebraic computations and is suitable for real-time implementation as required in haptics.

Hand synergies: Integration of robotics and neuroscience for understanding the control of biological and artificial hands

“…In [170], this approach was applied to whole hand avatar animation, considering only two contact points for the thumb and the index with a haptic interface. Exploiting synergistic information, the forces necessary to track real finger trajectories through virtual springs (between the avatar’s tips and the corresponding operator’s tips) were transformed in the synergy-space of general forces.…”

A Synergy-Based Optimally Designed Sensing Glove for Functional Grasp Recognition

“…However, these optimal design techniques were validated only in simulation. In [ 14 ], a hand avatar with 20 DOFs used in virtual grasping applications with two three-DOF haptic devices was animated only relying on the knowledge of kinematic constraints defined by hand postural synergies, but no sensor glove or advanced tracker with markers was used. To summarize, to the best of our knowledge, the techniques described in [ 12 , 13 ] represent the first attempt to use synergy information to advance reconstruction accuracy, i.e.…”

Design, development, and preliminary evaluation of a highly wearable exoskeleton

“…2a). In accordance with [30], we modeled the metacarpophalangeal (MCP) joint of the index, middle, ring and pinky fingers as a 2-DoF universal joint (one for adduction/abduction and another for flexion/extension). The proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints have one DoF each.…”