Skin Stretch Haptic Feedback to Convey Closure Information in Anthropomorphic, Under-Actuated Upper Limb Soft Prostheses

Abstract

Restoring hand function in individuals with upper limb loss is a challenging task, made difficult by the complexity of human hands from both a functional and sensory point of view. Users of commercial prostheses, even sophisticated devices, must visually attend to the hand to know its state, since in most cases they are not provided with any direct sensory information. Among the different types of haptic feedback that can be delivered, information on hand opening is particularly likely to reduce the requirement of constant visual attention. In recent years there has been a trend of using underactuated, compliant multi-fingered hands as upper limb prostheses, in part due to their simplicity and ease of use attributed to low degree-of-freedom actuation. The trend towards underactuation encourages the design of one degree of freedom (d.o.f.) haptic devices to provide intuitive sensory feedback from the prosthesis. However, mapping the closure of a multi-d.o.f. prosthetic hand to a simple and intuitive haptic cue is not a trivial task. In this paper we explore the use of a one d.o.f. skin stretch haptic device, the Rice Haptic Rocker, to provide intuitive proprioceptive feedback indicating overall hand closure of an underactuated prosthesis. The benefits and challenges of the system are assessed in multi-tasking and reduced vision scenarios for an object-size discrimination task, in an effort to simulate challenges in daily life, and are compared against the haptic resolution of the device using the Just Noticeable Difference. Finally, an evaluation done with a prosthesis user, in the form of a truncated version of the AM-ULA, shows possible benefits of the addition of haptic feedback in tasks with reduced visual attention.

A pilot study on locomotion training via biomechanical models and a wearable haptic feedback system

“…A study by Norman et al demonstrates the effectiveness of a simple fingerpad skin stretch device to guide a user's arm via haptic cues and real-time corrective feedback [24]. With the motivation to increase embodiment between amputees and their prosthetic device, Battaglia et al evaluated the ability of a rotational skin-stretch haptic wearable to convey proprioceptive information of a robotic hand [25]. For lower limb amputees, Husman et al proposes the use of a lateral skin-stretch haptic wearable to cue the user of gait events during ambulation [26].…”

“…Another wearable haptic device could deliver skin-stretch, pressure, and vibrotactile to convey information about the status of the teleoperated robot and it has been shown to effectively improve the user operation performance [37]. Skin stretch is a natural sensing mode for proprioception, thus making it ideal to intuitively convey proprioceptive information to the user [25], even when compared to vibrotactile feedback [38]. As an alert scheme, vibrotactile feedback was found to be superior to electrotactile feedback in terms of accuracy and user comfort [39].…”

Upper limb prostheses: bridging the sensory gap

“…Extradermal methods are composed of mechanotactile, vibrotactile or electrotactile activation of nerves underneath the skin. Mechanotactile feedback is provided by an external device that provides direct contact to the skin in the form of localized pressure or skin stretch (Battaglia et al., 2019). Vibrotactile feedback consists of wearable devices with small motors or linear resonant actuators vibrating at various frequencies on the skin (Miyahara and Kato, 2021).…”

Substitutive proprioception feedback of a prosthetic wrist by electrotactile stimulation

“…Homology and somatotopy are the priority factors affecting the acceptability of prosthetic sensory feedback methods because they affect the training periods that patients require ( Raspopovic et al, 2021 ) and acceptance of the feedback device ( Makin et al, 2017 ; Lan et al, 2019 ). In the literature, there are a variety of feedback methods, including invasive electrical stimulation ( Schiefer et al, 2016 ; Vu et al, 2022 ), skin stretching ( Battaglia et al, 2019 ), vibration ( Vargas et al, 2021b ), mechanical pressure ( Godfrey et al, 2016 ), audio ( Gonzalez et al, 2012 ), and electrotactile stimulation ( Franceschi et al, 2017 ; Chai et al, 2022 ). Although the sensations induced by electrotactile stimulation are not somatotopic, users can learn to interpret the feedback with a few days of training ( Bensmaia et al, 2020 ).…”