Development and Real World Use of a Vibratory Haptic Feedback System for Upper-Limb Prosthetic Users

Abstract

Introduction Sensory feedback is largely unavailable for persons with upper-limb amputation with conventional prostheses. The current study created a portable vibratory haptic feedback system integrated into the prosthesis to test its usefulness in gripping objects during daily life. Materials and Methods Development involved optimizing a mapping algorithm between the force sensor and the feedback tactor vibration, developing a custom process for mounting a wireless force sensor onto the prosthetic thumb with reliable output, and developing an instrumented object for testing grip force accuracy. Clinical testing involved optimizing tactor placement, measuring grip force accuracy, measuring the ability to perform daily gripping tasks, and surveying prosthetic users' opinion of the system after using the vibratory haptic device at home. A total of six individuals with unilateral transradial amputation participated in this study. Results The results demonstrated optimal tactor placement more proximal versus distal on the forearm. Accuracy with haptic versus no haptic feedback demonstrated that haptic feedback improved the grip force accuracy by 129% (adjusted P = 0.041) for light grip force target (2 lb or 0.9 kg) in the nonportable system and 21% (adjusted P = 0.051) for medium grip force target (10 lb or 4.5 kg) in the portable system. Haptic feedback did not statistically improve grip accuracy at strong grip forces (20 lb or 9.1 kg). Haptic feedback improved the gripping technique during the Assessment of Capacity for Myoelectric Control (ACMC) by 1.22 points, although this was not statistically significant (P = 0.27, n = 4). The participants provided specific positive examples of how the vibratory haptic system was useful at home. The overall usability score was 3.6 where 4 indicated excellent and 0 indicated poor. Conclusions This kind of system has potential to improve the lives of upper-limb prosthetic users.

Design and Integration of an Inexpensive Wearable Mechanotactile Feedback System for Myoelectric Prostheses

“…In an attempt to address these issues, researchers have developed low-cost wearable feedback systems. In the case of transradial amputations, systems have been developed to provide vibrational feedback against the skin in response to forces measured on the terminal device [22] – [24] . Tactors have been placed proximal to the prosthetic socket; in two studies the tactor was placed underneath the prosthetic liner [23] , [24] and in one it was secured within an elastic cuff [22] .…”

“…In the case of transradial amputations, systems have been developed to provide vibrational feedback against the skin in response to forces measured on the terminal device [22] – [24] . Tactors have been placed proximal to the prosthetic socket; in two studies the tactor was placed underneath the prosthetic liner [23] , [24] and in one it was secured within an elastic cuff [22] . These studies have demonstrated potential for reducing grasp force [24] , improving performance [22] , and improving grip force accuracy at low force levels [23] .…”

Comparison of vibrotactile and joint-torque feedback in a myoelectric upper-limb prosthesis

“…Markovic et al showed that there was no significant advantage with a vibrotactile bracelet in a box and blocks task [18]. Vibrotactile feedback was also shown not to have a significant effect on grip force accuracy at medium and high grip forces [19]. Given the mixed results on the benefits of haptic feedback for myoelectric prostheses, it becomes clear why haptic feedback of any modality has remained largely absent from commercial prostheses.…”

Simulated robotic device malfunctions resembling malicious cyberattacks impact human perception of trust, satisfaction, and frustration

“…When trying to control the force applied by the prosthetic hand, haptic feedback is helpful to reconnect this severed sensation of touch for the amputee, to give an indication about the applied force and enhance the grip force control. [24][25][26] Many noninvasive interfaces used by different research groups have been proposed for haptic feedback to restore the haptic experience, including vibrotactile stimulation, [27][28][29] electrotactile stimulation, [30][31][32][33] and mechanotactile feedback. [34][35][36] Passively powered pneumatic actuators have also been previously used to map the robotic fingertip forces to the residual limb of amputees, 36 A soft robotic armband with pump-driven pneumatic chambers for haptic feedback has also been designed in the past, which was previously tested with 10 human subjects who were able to recognize six discrete air pressure levels (10-35 kPa with 5 kPa increments) corresponding to six levels of robotic fingertip force.…”