Haptic Perception of Virtual Spring Stiffness Using ExoTen-Glove

Abstract

This paper presents a study of haptic perception of virtual stiffness and the influence of visual feedback in virtual reality. In this study, a novel and lightweight haptic glove (ExoTen-Glove) based on Twisted String Actuation (TSA) system is presented and evaluated. This system has two independent TSA modules with integrated force sensors and small-size DC motors. ExoTen-Glove provides force feedback to the users during the execution of grasping virtual objects. The overall design, the controller and the preliminary experimental evaluation of the ExoTen-Glove have been shown in this paper. Different experiments have been performed in virtual reality environment using HTC VIVE headset with 2 degrees of freedom grasping tasks, squeezing a pair of virtual springs with the participant's thumb and index fingers. The aim of this study is to illustrate the benefit of using ExoTen-Glove to distinguish stiffness of a pair of virtual springs and the role of the visual feedback. The results show that the users use not only haptic cues but also use visual cues in detecting spring stiffness difference.

Hybrid Control Strategy for Force and Precise End Effector Positioning of a Twisted String Actuator

“…whereF z (t) andĥ(θ) are the estimated or measured values of F z (t) and h(θ), respectively. Substituting the above equation in (11) yields:…”

“…The high transmission ratio of TSAs is attractive for robotic systems [14,35], especially for applications where energy-efficient and costeffective solutions are required, such as robot manipulators [27,25] and grippers, anthropomorphic hands [15,22,20,34], and mobile robots [37], they provide lightweight and highly customizable solutions. Additionally, TSAs have been used successfully in functions that require compact and mechanically simple transmission with some level of compliance; among these, soft robotics [8] and human-machine interaction (HMI) devices like wearable robots and exoskeletons [36,4] or haptic devices [11,33,10,26].…”