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Challenges and Future Trends of Wearable Robotics

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Sensors and Robotics".

Deadline for manuscript submissions: closed (20 March 2023) | Viewed by 36185

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Special Issue Editors

Dr. Francesca Cordella

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Guest Editor

Unit of Advanced Robotics and Human-Centred Technologies, Department of Engineering, Università Campus Bio-Medico di Roma, 00128 Rome, Italy
Interests: biomedical robotics; human–machine multimodal interfaces; adaptive control strategies for collaborative robotics; vision-based approaches for motion reconstruction and human–robot interaction; psychophysiological assessment; closed-loop systems; sensory feedback restoration
Special Issues, Collections and Topics in MDPI journals

Dr. Emilio Trigili

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Guest Editor

BioRobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy
Interests: wearable robotics; exoskeletons; robotic rehabilitation; assistive devices; biomechatronics
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Jan Babič

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Guest Editor

Dept. of Automatics, Biocybernetics, and Robotics Jamova 39, 1000 Ljubljana, Slovenia
Interests: understand how the central nervous system process sensory information and transfer them to motor commands
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Wearable robotics is becoming more and more present in our life. These systems are in fact, among others, adopted in working environments with the aim of alleviating workers physical burden, as rehabilitation tools to enhance motor performance of people suffering from different pathologies, in teleoperation by representing a simple and natural interface to guide remote systems, as prostheses to replace a missed limb, as assistive devices to enhance or replace a motor functionality.

Despite these wide potentials, wearable systems are still far from being widely used in daily life due to some limitations related to usability, comfort, user intention recognition, costs and performance. Main current challenges are in fact related to i) mechanical design, that should be as unobtrusive and comfortable as possible while guaranteeing an effective human-like motion, ii) actuation and sensing, that have to estimate motion intention and to realize the motion with high torque density and high energy efficiency, and iii) control, that has to guarantee high accuracy, reliability and co-adaptation.

This special issue wants to outline the new advancements and challenges in the field of wearable robots paying particular attention to the hardware and software requirements for the deployment of wearable robots in the real world. Aspects related to sensing technologies, mechanical layout, control, acceptability, intuitiveness, clinical and daily use would be particularly considered.

Keywords:

Sensing, actuation and design of wearable robots
Teleoperation through wearable robots
Augmentation
Human-robot interfacing and co-adaptation
Soft wearable devices
Wearable robots for healthcare and sport
System performance evaluation
Motion intention recognition for wearable robots’ control
Prostheses
Machine learning methods for perception and control

This special issue fits the scope of Sensors aiming at providing a comprehensive view of the main challenges and future trends about wearable sensors and devices.

Dr. Francesca Cordella
Dr. Emilio Trigili
Prof. Dr. Jan Babič
Guest Editors

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Related Special Issue

Challenges and Future Trends of Wearable Robotics—2nd Edition in Sensors (1 article)

Published Papers (14 papers)

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Research

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17 pages, 2362 KiB

Open AccessArticle

Evaluation Methods and Measurement Challenges for Industrial Exoskeletons

by Ya-Shian Li-Baboud, Ann Virts, Roger Bostelman, Soocheol Yoon, Amaan Rahman, Lucia Rhode, Nishat Ahmed and Mili Shah

Sensors 2023, 23(12), 5604; https://doi.org/10.3390/s23125604 - 15 Jun 2023

Cited by 1 | Viewed by 1493

Abstract

In recent years, exoskeleton test methods for industrial exoskeletons have evolved to include simulated laboratory and field environments. Physiological, kinematic, and kinetic metrics, as well as subjective surveys, are used to evaluate exoskeleton usability. In particular, exoskeleton fit and usability can also impact the safety of exoskeletons and their effectiveness at reducing musculoskeletal injuries. This paper surveys the state of the art in measurement methods applied to exoskeleton evaluation. A notional classification of the metrics based on exoskeleton fit, task efficiency, comfort, mobility, and balance is proposed. In addition, the paper describes the test and measurement methods used in supporting the development of exoskeleton and exosuit evaluation methods to assess their fit, usability, and effectiveness in industrial tasks such as peg in hole, load align, and applied force. Finally, the paper includes a discussion of how the metrics can be applied towards a systematic evaluation of industrial exoskeletons, current measurement challenges, and future research directions. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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12 pages, 3754 KiB

Open AccessArticle

Printed Directional Bending Sensor with High Sensitivity and Low Hysteresis for Human Motion Detection and Soft Robotic Perception

by Yi-Fei Wang, Ayako Yoshida, Yasunori Takeda, Tomohito Sekine, Daisuke Kumaki and Shizuo Tokito

Sensors 2023, 23(11), 5041; https://doi.org/10.3390/s23115041 - 24 May 2023

Cited by 3 | Viewed by 1733

Abstract

We present a high-performance flexible bending strain sensor for directional motion detection of human hands and soft robotic grippers. The sensor was fabricated using a printable porous conductive composite composed of polydimethylsiloxane (PDMS) and carbon black (CB). The utilization of a deep eutectic solvent (DES) in the ink formulation induced a phase segregation between the CB and PDMS and led to a porous structure inside the printed films after being vapored. This simple and spontaneously formed conductive architecture provided superior directional bend-sensing characteristics compared to conventional random composites. The resulting flexible bending sensors displayed high bidirectional sensitivity (gauge factor of 45.6 under compressive bending and 35.2 under tensile bending), negligible hysteresis, good linearity (>0.99), and excellent bending durability (over 10,000 cycles). The multifunctional applications of these sensors, including human motion detection, object-shape monitoring, and robotic perceptions, are demonstrated as a proof-of-concept. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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21 pages, 3225 KiB

Open AccessArticle

Effects of Walking Speed and Added Mass on Hip Joint Quasi-Stiffness in Healthy Young and Middle-Aged Adults

by Shanpu Fang, Vinayak Vijayan, Megan E. Reissman, Allison L. Kinney and Timothy Reissman

Sensors 2023, 23(9), 4517; https://doi.org/10.3390/s23094517 - 06 May 2023

Cited by 1 | Viewed by 1085

Abstract

Joint quasi-stiffness has been often used to inform exoskeleton design. Further understanding of hip quasi-stiffness is needed to design hip exoskeletons. Of interest are wearer responses to walking speed changes with added mass of the exoskeleton. This study analyzed hip quasi-stiffness at 3 walking speed levels and 9 added mass distributions among 13 young and 16 middle-aged adults during mid-stance hip extension and late-stance hip flexion. Compared to young adults, middle-aged adults maintained a higher quasi-stiffness with a smaller range. For a faster walking speed, both age groups increased extension and flexion quasi-stiffness. With mass evenly distributed on the pelvis and thighs or biased to the pelvis, both groups maintained or increased extension quasi-stiffness. With mass biased to the thighs, middle-aged adults maintained or decreased extension quasi-stiffness while young adults increased it. Young adults decreased flexion quasi-stiffness with added mass but not in any generalizable pattern with mass amounts or distributions. Conversely, middle-aged adults maintained or decreased flexion quasi-stiffness with even distribution on the pelvis and thighs or biased to the pelvis, while no change occurred if biased to the thighs. In conclusion, these results can guide the design of a hip exoskeleton’s size and mass distribution according to the intended user’s age. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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14 pages, 3275 KiB

Open AccessArticle

Validation of a Custom Interface Pressure Measurement System to Improve Fitting of Transtibial Prosthetic Check Sockets

by Lucy Armitage, Kenny Cho, Emre Sariyildiz, Angela Buller, Stephen O’Brien and Lauren Kark

Sensors 2023, 23(7), 3778; https://doi.org/10.3390/s23073778 - 06 Apr 2023

Viewed by 1552

Abstract

Achievement of fit between the residual limb and prosthetic socket during socket manufacture is a priority for clinicians and is essential for safety. Clinicians have recognised the potential benefits of having a sensor system that can provide objective socket-limb interface pressure measurements during socket fitting, but the cost of existing systems makes current technology prohibitive. This study will report on the characterisation, validation and preliminary clinical implementation of a low cost, portable, wireless sensor system designed for use during socket manufacture. Characterisation and benchtop testing demonstrated acceptable accuracy, behaviour at variable temperature, and dynamic response for use in prosthetic socket applications. Our sensor system was validated with simultaneous measurement by a commercial sensor system in the sockets of three transtibial prosthesis users during a fitting session in the clinic. There were no statistically significant differences between the sensor system and the commercial sensor for a variety of functional activities. The sensor system was found to be valid in this clinical context. Future work should explore how pressure data relates to ratings of fit and comfort, and how objective pressure data might be used to assist in clinical decision making. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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20 pages, 5418 KiB

Open AccessArticle

Integration of Task-Based Exoskeleton with an Assist-as-Needed Algorithm for Patient-Centered Elbow Rehabilitation

by Pablo Delgado and Yimesker Yihun

Sensors 2023, 23(5), 2460; https://doi.org/10.3390/s23052460 - 23 Feb 2023

Cited by 5 | Viewed by 1743

Abstract

This research presents an Assist-as-Needed (AAN) Algorithm for controlling a bio-inspired exoskeleton, specifically designed to aid in elbow-rehabilitation exercises. The algorithm is based on a Force Sensitive Resistor (FSR) Sensor and utilizes machine-learning algorithms that are personalized to each patient, allowing them to complete the exercise by themselves whenever possible. The system was tested on five participants, including four with Spinal Cord Injury and one with Duchenne Muscular Dystrophy, with an accuracy of

91.22 %

. In addition to monitoring the elbow range of motion, the system uses Electromyography signals from the biceps to provide patients with real-time feedback on their progress, which can serve as a motivator to complete the therapy sessions. The study has two main contributions: (1) providing patients with real-time, visual feedback on their progress by combining range of motion and FSR data to quantify disability levels, and (2) developing an assist-as-needed algorithm for rehabilitative support of robotic/exoskeleton devices. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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16 pages, 7758 KiB

Open AccessArticle

Shape Memory Alloys in Textile Platform: Smart Textile-Composite Actuator and Its Application to Soft Grippers

by Jin Shin, Ye-Ji Han, Ju-Hee Lee and Min-Woo Han

Sensors 2023, 23(3), 1518; https://doi.org/10.3390/s23031518 - 30 Jan 2023

Cited by 10 | Viewed by 2897

Abstract

In recent years, many researchers have aimed to construct robotic soft grippers that can handle fragile or unusually shaped objects without causing damage. This study proposes a smart textile-composite actuator and its application to a soft robotic gripper. An active fiber and an inactive fiber are combined together using knitting techniques to manufacture a textile actuator. The active fiber is a shape memory alloy (SMA) that is wire-wrapped with conventional fibers, and the inactive fiber is a knitting yarn. A knitted textile structure is flexible, with an excellent structure retention ability and high compliance, which is suitable for developing soft grippers. A driving source of the actuator is the SMA wire, which deforms under heating due to the shape memory effect. Through experiments, the course-to-wale ratio, the number of bundling SMA wires, and the driving current value needed to achieve the maximum deformation of the actuator were investigated. Three actuators were stitched together to make up each finger of the gripper, and layer placement research was completed to find the fingers’ suitable bending angle for object grasping. Finally, the gripping performance was evaluated through a test of grasping various object shapes, which demonstrated that the gripper could successfully lift flat/spherical/uniquely shaped objects. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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14 pages, 6437 KiB

Open AccessArticle

A Cost-Effective, Integrated Haptic Device for an Exoskeletal System

by Maciej Rećko, Kazimierz Dzierżek, Rafał Grądzki and Jozef Živčák

Sensors 2022, 22(23), 9508; https://doi.org/10.3390/s22239508 - 05 Dec 2022

Cited by 1 | Viewed by 1239

Abstract

The paper presents an innovative integrated sensor-effector designed for use in exoskeletal haptic devices. The research efforts aimed to achieve high cost-effectiveness for a design assuring proper monitoring of joint rotations and providing passive force feedback. A review of market products revealed that there is space for new designs of haptic devices with such features. To determine the feasibility of the proposed solution, a series of simulations and experiments were conducted to verify the adopted design concept. The focus was set on an investigation of the force of attraction between one and two magnets interacting with a steel plate. Further, a physical model of an integrated joint was fabricated, and its performance was evaluated and compared to a similar commercially available device. The proposed solution is cost-effective due to the use of standard parts and inexpensive components. However, it is light and assures a 19 Nm braking torque adequate for the intended use as a haptic device for upper limbs. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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11 pages, 3809 KiB

Open AccessCommunication

Smart Pneumatic Artificial Muscle Using a Bend Sensor like a Human Muscle with a Muscle Spindle

by Norihiko Saga, Kunio Shimada, Douhaku Inamori, Naoki Saito, Toshiyuki Satoh and Jun-ya Nagase

Sensors 2022, 22(22), 8975; https://doi.org/10.3390/s22228975 - 19 Nov 2022

Cited by 1 | Viewed by 1685

Abstract

Shortage of labor and increased work of young people are causing problems in terms of care and welfare of a growing proportion of elderly people. This is a looming social problem because people of advanced ages are increasing. Necessary in the fields of care and welfare, pneumatic artificial muscles in actuators of robots are being examined. Pneumatic artificial muscles have a high output per unit of weight, and they are soft, similarly to human muscles. However, in previous research of robots using pneumatic artificial muscles, rigid sensors were often installed at joints and other locations due to the robots’ structures. Therefore, we developed a smart actuator that integrates a bending sensor that functions as a human muscle spindle; it can be externally attached to the pneumatic artificial muscle. This paper reports a smart artificial muscle actuator that can sense contraction, which can be applied to developed self-monitoring and robot posture control. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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32 pages, 11796 KiB

Open AccessArticle

Piton: Investigating the Controllability of a Wearable Telexistence Robot

by Abdullah Iskandar, Mohammed Al-Sada, Tamon Miyake, Yamen Saraiji, Osama Halabi and Tatsuo Nakajima

Sensors 2022, 22(21), 8574; https://doi.org/10.3390/s22218574 - 07 Nov 2022

Cited by 2 | Viewed by 3516

Abstract

The COVID-19 pandemic impacted collaborative activities, travel, and physical contact, increasing the demand for real-time interactions with remote environments. However, the existing remote communication solutions provide limited interactions and do not convey a high sense of presence within a remote environment. Therefore, we propose a snake-shaped wearable telexistence robot, called Piton, that can be remotely used for a variety of collaborative applications. To the best of our knowledge, Piton is the first snake-shaped wearable telexistence robot. We explain the implementation of Piton, its control architecture, and discuss how Piton can be deployed in a variety of contexts. We implemented three control methods to control Piton: HM—using a head-mounted display (HMD), HH—using an HMD and hand-held tracker, and FM—using an HMD and a foot-mounted tracker. We conducted a user study to investigate the applicability of the proposed control methods for telexistence, focusing on body ownership (Alpha IVBO), mental and physical load (NASA-TLX), motion sickness (VRSQ), and a questionnaire to measure user impressions. The results show that both the HM and HH provide relevantly high levels of body ownership, had high perceived accuracy, and were highly favored, whereas the FM control method yielded the lowest body ownership effect and was least favored. We discuss the results and highlight the advantages and shortcomings of the control methods with respect to various potential application contexts. Based on our design and evaluation of Piton, we extracted a number of insights and future research directions to deepen our investigation and realization of wearable telexistence robots. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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19 pages, 6432 KiB

Open AccessArticle

Data-Driven Predictive Control of Exoskeleton for Hand Rehabilitation with Subspace Identification

by Erkan Kaplanoglu and Gazi Akgun

Sensors 2022, 22(19), 7645; https://doi.org/10.3390/s22197645 - 09 Oct 2022

Cited by 1 | Viewed by 1957

Abstract

This study proposed a control method, a data-driven predictive control (DDPC), for the hand exoskeleton used for active, passive, and resistive rehabilitation. DDPC is a model-free approach based on past system data. One of the strengths of DDPC is that constraints of states can be added to the controller while performing the controller design. These features of the control algorithm eliminate an essential problem for rehabilitation robots in terms of easy customization and safe repetitive rehabilitation tasks that can be planned within certain constraints. Experiments were carried out with a designed hand rehabilitation system under repetitive and various therapy tasks. Real-time experiment results demonstrate the feasibility and efficiency of the proposed control approach to rehabilitation systems. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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21 pages, 8098 KiB

Open AccessArticle

Assistive Mobility Control of a Robotic Hip-Knee Exoskeleton for Gait Training

by Chuan Changcheng, Yi-Rong Li and Chun-Ta Chen

Sensors 2022, 22(13), 5045; https://doi.org/10.3390/s22135045 - 04 Jul 2022

Cited by 1 | Viewed by 2545

Abstract

In this paper, we present an assistive mobility control for a robotic hip-knee exoskeleton intended for gait training. The robotic hip-knee exoskeleton is designed with an active flexion/extension and a passive abduction/adduction at each hip joint and an active flexion/extension at each knee joint to comply with the movement of lower limbs. While facilitating walking with the robotic exoskeleton, model-free linear extended state observer (LESO)-based controllers are proposed for gait control, in which the LESO is used to deal with each user’s different lower limb parameters and unknown exerted torques. Walking and ascending experiments were conducted to evaluate the performance of the proposed methods, and the results are shown with respect to walking parameters. Moreover, a preliminary study for an extended application to the recovery of normal gaits that relieves the freezing of gait (FOG) in Parkinson’s disease (PD) patients is also investigated in the paper. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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Review

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31 pages, 15239 KiB

Open AccessReview

Myoelectric Control Systems for Upper Limb Wearable Robotic Exoskeletons and Exosuits—A Systematic Review

by Jirui Fu, Renoa Choudhury, Saba M. Hosseini, Rylan Simpson and Joon-Hyuk Park

Sensors 2022, 22(21), 8134; https://doi.org/10.3390/s22218134 - 24 Oct 2022

Cited by 14 | Viewed by 4550

Abstract

In recent years, myoelectric control systems have emerged for upper limb wearable robotic exoskeletons to provide movement assistance and/or to restore motor functions in people with motor disabilities and to augment human performance in able-bodied individuals. In myoelectric control, electromyographic (EMG) signals from muscles are utilized to implement control strategies in exoskeletons and exosuits, improving adaptability and human–robot interactions during various motion tasks. This paper reviews the state-of-the-art myoelectric control systems designed for upper-limb wearable robotic exoskeletons and exosuits, and highlights the key focus areas for future research directions. Here, different modalities of existing myoelectric control systems were described in detail, and their advantages and disadvantages were summarized. Furthermore, key design aspects (i.e., supported degrees of freedom, portability, and intended application scenario) and the type of experiments conducted to validate the efficacy of the proposed myoelectric controllers were also discussed. Finally, the challenges and limitations of current myoelectric control systems were analyzed, and future research directions were suggested. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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25 pages, 9307 KiB

Open AccessReview

Soft Wearable Robots: Development Status and Technical Challenges

by Yongjun Shi, Wei Dong, Weiqi Lin and Yongzhuo Gao

Sensors 2022, 22(19), 7584; https://doi.org/10.3390/s22197584 - 06 Oct 2022

Cited by 15 | Viewed by 5095

Abstract

In recent years, more and more research has begun to focus on the flexible and lightweight design of wearable robots. During this process, many novel concepts and achievements have been continuously made and shown to the public, while new problems have emerged at the same time, which need to be solved. In this paper, we give an overview of the development status of soft wearable robots for human movement assistance. On the basis of a clear definition, we perform a system classification according to the target assisted joint and attempt to describe the overall prototype design level in related fields. Additionally, it is necessary to sort out the latest research progress of key technologies such as structure, actuation, control and evaluation, thereby analyzing the design ideas and basic characteristics of them. Finally, we discuss the possible application fields, and propose the main challenges of this valuable research direction. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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Other

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25 pages, 4125 KiB

Open AccessSystematic Review

Transcutaneous Functional Electrical Stimulation Controlled by a System of Sensors for the Lower Limbs: A Systematic Review

by Layal Chaikho, Elizabeth Clark and Maxime Raison

Sensors 2022, 22(24), 9812; https://doi.org/10.3390/s22249812 - 14 Dec 2022

Cited by 2 | Viewed by 2607

Abstract

In the field of transcutaneous functional electrical stimulation (FES), open-loop and closed-loop control strategies have been developed to restore functions of the lower limbs: walking, standing up, maintaining posture, and cycling. These strategies require sensors that provide feedback information on muscle activity or biomechanics of movement. Since muscle response induced by transcutaneous FES is nonlinear, time-varying, and dependent on muscle fatigue evolution, the choice of sensor type and control strategy becomes critical. The main objective of this review is to provide state-of-the-art, emerging, current, and previous solutions in terms of control strategies. Focus is given on transcutaneous FES systems for the lower limbs. Using Compendex and Inspec databases, a total of 135 review and conference articles were included in this review. Recent studies mainly use inertial sensors, although the use of electromyograms for lower limbs has become more frequent. Currently, several researchers are opting for nonlinear controllers to overcome the nonlinear and time-varying effects of FES. More development is needed in the field of systems using inertial sensors for nonlinear control. Further studies are needed to validate nonlinear control systems in patients with neuromuscular disorders. Full article

(This article belongs to the Special Issue Challenges and Future Trends of Wearable Robotics)

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