Comparing the Exteroceptive Feedback of Normal Stress, Skin Stretch, and Vibrotactile Stimulation for Restitution of Static Events

M Reza Motamedi,Vincent Duchaine,David Florant

doi:10.3389/frobt.2017.00006

M Reza Motamedi, Vincent Duchaine + Show 1 more

Open Access

https://doi.org/10.3389/frobt.2017.00006

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Abstract

This paper investigates the effectiveness of three types of haptic feedback: normal stress, tangential force, and vibrotactile stimulation. Modern prosthetic limbs currently available on the market do not provide a wide range of sensory information to amputees, forcing amputees to mainly rely on visual attention when manipulating objects. We aim to develop a haptic system that can convey information to the central nervous system (CNS) through haptic feedback. To this end, we aim to find out which type of feedback performs best under static conditions, so that it can be used to restore a sense of grasping force to amputees. We tested the three main stimulation methods by inputting a series of five force magnitudes to each haptic device, so that the device applied the corresponding feedback to the participants’ finger pads. The participants then pressed on a force sensor, with the goal of applying the same level of force to a force sensor as they believed the haptic device had initially conveyed to them via their finger pads. While the subjects pressed on the force sensor, the haptic device applied a level of feedback to their forearms that corresponded to the pressure they were applying to the sensor. These tests provided fifteen numerical data per subject and a total of 180 trials for all twelve subjects. The end results indicate that even though all the stimulation methods provided a sufficient level of feedback, normal stress seems more effective than either tangential force, or vibrotactile stimulation, at conveying the sense of pressure to the finger pad.

Highlights

Prosthetic upper limbs require the user to establish an adequate safety margin during objectmanipulation tasks, in order to prevent object damage or slippage (Damian et al, 2012)
The straight lines represent the desired level of the forces that were applied from the devices, and the margins around the lines indicate the feedback from the participants at that specific level
When we examined the data based on the critical statistical parameters, normal stress lead to a better restitution of static conditions than the other two types of stimulation at all five force levels

Summary

Introduction

Prosthetic upper limbs require the user to establish an adequate safety margin during objectmanipulation tasks, in order to prevent object damage or slippage (Damian et al, 2012). This safety margin is primarily determined by visual attention, as current commercially available prosthetic limbs are not equipped with full tactile sensing capabilities. Most amputees are unable to hold an egg for more than a few seconds The regulation of grasping force depends on having adequately regulated this force during similar events in the past

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