Remote Actuation Systems for Fully Wearable Assistive Devices: Requirements, Selection, and Optimization for Out-of-the-Lab Application of a Hand Exoskeleton

Abstract

Wearable robots assist individuals with sensorimotor impairment in daily life, or support industrial workers in physically demanding tasks. In such scenarios, low mass and compact design are crucial factors for device acceptance. Remote actuation systems (RAS) have emerged as a popular approach in wearable robots to reduce perceived weight and increase usability. Different RAS have been presented in the literature to accommodate for a wide range of applications and related design requirements. The push toward use of wearable robotics in out-of-the-lab applications in clinics, home environments, or industry created a shift in requirements for RAS. In this context, high durability, ergonomics, and simple maintenance gain in importance. However, these are only rarely considered and evaluated in research publications, despite being drivers for device abandonment by end-users. In this paper, we summarize existing approaches of RAS for wearable assistive technology in a literature review and compare advantages and disadvantages, focusing on specific evaluation criteria for out-of-the-lab applications to provide guidelines for the selection of RAS. Based on the gained insights, we present the development, optimization, and evaluation of a cable-based RAS for out-of-the-lab applications in a wearable assistive soft hand exoskeleton. The presented RAS features full wearability, high durability, high efficiency, and appealing design while fulfilling ergonomic criteria such as low mass and high wearing comfort. This work aims to support the transfer of RAS for wearable robotics from controlled lab environments to out-of-the-lab applications.

Wearable Robots: An Original Mechatronic Design of a Hand Exoskeleton for Assistive and Rehabilitative Purposes

“…Finally, the lack of an on-board power supply system, as also in In et al (2015), Polygerinos et al (2015), Randazzo et al (2017), Diez et al (2018), Rose and O'alley (2018), Yu et al (2019), and Dittli et al (2020) or in exomotion R , Carbonhand and Neomano devices among the commercially available ones, as visible in Table 1, prevented the device from being fully wearable and portable. Being an exoskeleton intended for assistive use, as already mentioned, this point was one of the most limiting since it forced the user to be connected to a power supply away from the hand.…”

“…Concerning the aim, such devices can have mainly rehabilitative (Dovat et al, 2008 ; Tong et al, 2010 ; Ho et al, 2011 ; Lambercy et al, 2013 ; Cempini et al, 2014 ; Polygerinos et al, 2015 ; Diez et al, 2018 ; Putzu et al, 2018 ; Wang et al, 2018 ; Bouteraa et al, 2019 ) and assistive (In et al, 2015 ; Randazzo et al, 2017 ; Yun et al, 2017 ; Cappello et al, 2018 ; Hadi et al, 2018 ; Yu et al, 2019 ; Dittli et al, 2020 ; Yurkewich et al, 2020 ) purposes. Exoskeletons or end-effector rehabilitation robots are used for treatments—typically in clinical settings—to recover from the loss of motor functions (Maciejasz et al, 2014 ; Zhang et al, 2018 ).…”

“…Indeed, more wearable and portable devices make possible rehabilitation therapy in different environments from the clinical one (e.g., at home), reducing the burden on therapists or in-patient facilities (Huang et al, 2017 ). Besides, devices designed for assistance or at-home rehabilitation (Lambercy et al, 2013 ; Polygerinos et al, 2015 ; Randazzo et al, 2017 ; Cappello et al, 2018 ; Putzu et al, 2018 ; Wang et al, 2018 ; Bouteraa et al, 2019 ; Dittli et al, 2020 ; Yurkewich et al, 2020 ) can always be available for the patient, who may find it stimulating and motivating to perform these therapies in a home setting by playing a computer game or during typical ADLs (Butter et al, 2008 ; Maciejasz et al, 2014 ). Despite the significant results achieved, robot-assisted and home-based therapy effectiveness remains an open research topic (Maciejasz et al, 2014 ; Huang et al, 2017 ; Duret et al, 2019 ).…”

“…Regarding the assisted movements, the number of driven fingers—usually defining the number of independent motors, unless passive couplings between fingers are used—the Degrees Of Freedom (DOFs), and the interactions between hand and exoskeleton may differ. In particular, HESs can have a single interaction point on each finger, in the case of single-phalanx mechanisms (Dovat et al, 2008 ), or more than one, in multi-phalanx configurations (Tong et al, 2010 ; Ho et al, 2011 ; Lambercy et al, 2013 ; Cempini et al, 2014 ; Yun et al, 2017 ; Diez et al, 2018 ; Wang et al, 2018 ; Bouteraa et al, 2019 ; Dittli et al, 2020 ).…”

“…The first ones (Bouzit et al, 2002 ; Tong et al, 2010 ; Ho et al, 2011 ; Lambercy et al, 2013 ; Cempini et al, 2014 ; Yun et al, 2017 ; Diez et al, 2018 ; Wang et al, 2018 ; Bouteraa et al, 2019 ) are made of metal or plastic, transmit motion through rigid kinematic chains, and usually exert higher force than soft ones (Chiaradia et al, 2018 ; Chu and Patterson, 2018 ). Indeed, on the other side, these are made of flexible materials (In et al, 2015 ; Polygerinos et al, 2015 ; Randazzo et al, 2017 ; Cappello et al, 2018 ; Hadi et al, 2018 ; Putzu et al, 2018 ; Yu et al, 2019 ; Dittli et al, 2020 ; Yurkewich et al, 2020 ) and are smaller and lighter than rigid ones. Recently, first hybrid solutions have been studied (Rose and O'alley, 2018 ) aiming to exploit the strengths of both.…”