Questionnaire results of user experiences with wearable exoskeletons and their preferences for sensory feedback

Human-exoskeleton interaction portrait

Human-robot physical interaction contains crucial information for optimizing user experience, enhancing robot performance, and objectively assessing user adaptation. This study introduces a new method to evaluate human-robot interaction and co-adaptation in lower limb exoskeletons by analyzing muscle activity and interaction torque as a two-dimensional random variable. We introduce the interaction portrait (IP), which visualizes this variable's distribution in polar coordinates. We applied IP to compare a recently developed hybrid torque controller (HTC) based on kinematic state feedback and a novel adaptive model-based torque controller (AMTC) with online learning, proposed herein, against a time-based controller (TBC) during treadmill walking at varying speeds. Compared to TBC, both HTC and AMTC significantly lower users' normalized oxygen uptake, suggesting enhanced user-exoskeleton coordination. IP analysis reveals that this improvement stems from two distinct co-adaptation strategies, unidentifiable by traditional muscle activity or interaction torque analyses alone. HTC encourages users to yield control to the exoskeleton, decreasing overall muscular effort but increasing interaction torque, as the exoskeleton compensates for user dynamics. Conversely, AMTC promotes user engagement through increased muscular effort and reduces interaction torques, aligning it more closely with rehabilitation and gait training applications. IP phase evolution provides insight into each user's interaction strategy formation, showcasing IP analysis's potential in comparing and designing novel controllers to optimize human-robot interaction in wearable robots.

A qualitative study to elicit user requirements for lower limb wearable exoskeletons for gait rehabilitation in spinal cord injury

OBJECTIVE

We aim to determine a comprehensive set of requirements, perceptions, and expectations that people with spinal cord injury (SCI) and the clinicians in charge of their rehabilitation have regarding the use of wearable robots (WR) for gait rehabilitation.

BACKGROUND

There are concerns due to the limited user acceptance of WR for gait rehabilitation. Developers need to emphasize understanding the needs and constraints of all stakeholders involved, including the real-life dynamics of rehabilitation centers.

METHODS

15 people with SCI, 9 without experience with WR and 6 with experience with these technologies, and 10 clinicians from 3 rehabilitation centers in Spain were interviewed. A directed content analysis approach was used.

RESULTS

78 codes grouped into 9 categories (physical results, usability, psychology-related codes, technical characteristics, activities, acquisition issues, context of use, development of the technologies and clinical rehabilitation context) were expressed by at least 20% of the users interviewed, of whom 16 were not found in the literature. The agreement percentage between each group and subgroup included in the study, calculated as the number of codes that more than 20% of both groups expressed, divided over the total amount of codes any of those two groups agreed on (≥ 20%), showed limited agreement between patients and clinicians (50.00%) and between both types of patients (55.77%). The limited accessibility and availability of lower limb exoskeletons for gait rehabilitation arose in most of the interviews.

CONCLUSIONS

The limited agreement percentage between patients and clinicians indicates that including both types of users in the design process of these technologies is important, given that their requirements are complementary. Engaging users with prior technology experience is recommended, as they often exhibit strong internal consensus and articulate well-defined requirements. This study adds up the knowledge available in the literature and the new codes found in our data, which enlighten important aspects that ought to be addressed in the field to develop technologies that respond to users' needs, are usable and feasible to implement in their intended contexts.

APPLICATION

The set of criteria summarized in our study will be useful to guide the design, development, and evaluation of WR for gait rehabilitation to meet user's needs and allow them to be implemented in their intended context of use.

Utility and Usability of Two Forms of Supplemental Vibrotactile Kinesthetic Feedback for Enhancing Movement Accuracy and Efficiency in Goal-Directed Reaching

Recent advances in wearable sensors and computing have made possible the development of novel sensory augmentation technologies that promise to enhance human motor performance and quality of life in a wide range of applications. We compared the objective utility and subjective user experience for two biologically inspired ways to encode movement-related information into supplemental feedback for the real-time control of goal-directed reaching in healthy, neurologically intact adults. One encoding scheme mimicked visual feedback encoding by converting real-time hand position in a Cartesian frame of reference into supplemental kinesthetic feedback provided by a vibrotactile display attached to the non-moving arm and hand. The other approach mimicked proprioceptive encoding by providing real-time arm joint angle information via the vibrotactile display. We found that both encoding schemes had objective utility in that after a brief training period, both forms of supplemental feedback promoted improved reach accuracy in the absence of concurrent visual feedback over performance levels achieved using proprioception alone. Cartesian encoding promoted greater reductions in target capture errors in the absence of visual feedback (Cartesian: 59% improvement; Joint Angle: 21% improvement). Accuracy gains promoted by both encoding schemes came at a cost in terms of temporal efficiency; target capture times were considerably longer (1.5 s longer) when reaching with supplemental kinesthetic feedback than without. Furthermore, neither encoding scheme yielded movements that were particularly smooth, although movements made with joint angle encoding were smoother than movements with Cartesian encoding. Participant responses on user experience surveys indicate that both encoding schemes were motivating and that both yielded passable user satisfaction scores. However, only Cartesian endpoint encoding was found to have passable usability; participants felt more competent using Cartesian encoding than joint angle encoding. These results are expected to inform future efforts to develop wearable technology to enhance the accuracy and efficiency of goal-directed actions using continuous supplemental kinesthetic feedback.

Technology Assisted Rehabilitation Patient Perception Questionnaire (TARPP-Q): development and implementation of an instrument to evaluate patients' perception during training

BACKGROUND

The introduction of technology-assisted rehabilitation (TAR) uncovers promising challenges for the treatment of motor disorders, particularly if combined with exergaming. Patients with neurological diseases have proved to benefit from TAR, improving their performance in several activities. However, the subjective perception of the device has never been fully addressed, being a conditioning factor for its use. The aims of the study were: (a) to develop a questionnaire on patients' personal experience with TAR and exergames in a real-world clinical setting; (b) to administer the questionnaire to a pilot group of neurologic patients to assess its feasibility and statistical properties.

METHODS

A self-administrable and close-ended questionnaire, Technology Assisted Rehabilitation Patient Perception Questionnaire (TARPP-Q), designed by a multidisciplinary team, was developed in Italian through a Delphi procedure. An English translation has been developed with consensus, for understandability purposes. The ultimate version of the questionnaire was constituted of 10 questions (5 with multiple answers), totalling 29 items, exploring the patient's performance and personal experience with TAR with Augmented Performance Feedback. TARPP-Q was then administered pre-post training in an observational, feasible, multi-centric study. The study involved in-patients aged between 18 and 85 with neurological diseases, admitted for rehabilitation with TAR (upper limb or gait). FIM scale was run to control functional performance.

RESULTS

Forty-four patients were included in the study. All patients answered the TARPP-Q autonomously. There were no unaccounted answers. Exploratory factor analyses identified 4 factors: Positive attitude, Usability, Hindrance perception, and Distress. Internal consistency was measured at T0. The values of Cronbach's alpha ranged from 0.72 (Distress) to 0.92 (Positive attitude). Functional Independence Measure (FIM®) scores and all TARPP-Q factors (Positive attitude, Usability, Hindrance perception, except for Distress (p = 0.11), significantly improved at the end of the treatment. A significant positive correlation between Positive attitude and Usability was also recorded.

CONCLUSIONS

The TARPP-Q highlights the importance of patients' personal experience with TAR and exergaming. Large-scale applications of this questionnaire may clarify the role of patients' perception of training effectiveness, helping to customize devices and interventions.

The effect of limited sensory information on exoskeleton performance in people with complete spinal cord injury

Despite the absence of somatosensory information from the lower extremities, people with complete spinal cord injury (SCI) can maintain postural stability in an exoskeleton. This is partly because humans are able to reweigh the relative dependence on each of the senses. However, when the sensory environment is changed, people with complete SCI are limited in their ability to reweigh their sensory organization towards more dependence on somatosensory information. The aim of this study was to investigate the effect of limited visual and/or auditory information on exoskeleton performance in people with complete SCI. Three experienced exoskeleton users performed twelve walking trials in the ReWalk exoskeleton. In each trial, the presence or absence of visual and/or auditory information was varied. Exoskeleton performance was operationalized as the walking distance covered and the amount of crutch loading. In one participant, the distance covered decreased when visual information was limited. The other two participants did not show substantial differences in distance covered between sensory conditions. Two participants decreased crutch loading when visual information was restricted, and one participant decreased crutch loading when auditory information was limited. The current study suggests a limited influence of the presence or absence of visual and auditory information on the distance covered in people with complete SCI walking in an exoskeleton. Interestingly, crutch loading seemed to decrease rather than increase when visual or auditory information was limited.

Sensors and Actuation Technologies in Exoskeletons: A Review

Exoskeletons are robots that closely interact with humans and that are increasingly used for different purposes, such as rehabilitation, assistance in the activities of daily living (ADLs), performance augmentation or as haptic devices. In the last few decades, the research activity on these robots has grown exponentially, and sensors and actuation technologies are two fundamental research themes for their development. In this review, an in-depth study of the works related to exoskeletons and specifically to these two main aspects is carried out. A preliminary phase investigates the temporal distribution of scientific publications to capture the interest in studying and developing novel ideas, methods or solutions for exoskeleton design, actuation and sensors. The distribution of the works is also analyzed with respect to the device purpose, body part to which the device is dedicated, operation mode and design methods. Subsequently, actuation and sensing solutions for the exoskeletons described by the studies in literature are analyzed in detail, highlighting the main trends in their development and spread. The results are presented with a schematic approach, and cross analyses among taxonomies are also proposed to emphasize emerging peculiarities.

Wearable robotic exoskeleton for gait reconstruction in patients with spinal cord injury: A literature review

Objectives

Wearable robotic exoskeletons (WREs) have been globally developed to achieve gait reconstruction in patients with spinal cord injury (SCI). The present study aimed to enable evidence-based decision-making in selecting the optimal WRE according to residual motor function and to provide a new perspective on further development of appropriate WREs.

Methods

The current review was conducted by searching PubMed, Web of Science, and Google Scholar for relevant studies published from April 2015 to February 2020. Selected studies were analysed with a focus on the participants’ neurological level of SCI, amount of training (number of training sessions and duration of the total training period), gait speed and endurance achieved, and subgroup exploration of the number of persons for assistance and the walking aid used among patients with cervical level injury.

Results

A total of 28 articles (nine using Ekso, three using Indego, ten using ReWalk, one using REX, five using Wearable Power-Assist Locomotor) involving 228 patients were included in the analysis. Across all WREs, T6 was the most frequently reported level of SCI. The amount of training showed a wide distribution (number of training sessions: 2–230 sessions [30–120 min per session]; duration of the total training period: 1–24 weeks [1–5 times per week]). The mean gait speed was 0.31 m/s (standard deviation [SD] 0.14), and the mean distance on the 6-min walking test as a measure of endurance was 108.9 m (SD 46.7). The subgroup exploration aimed at patients with cervical level injury indicated that 59.2% of patients were able to ambulate with no physical assistance and several patients used a walker as a walking aid.

Conclusion

The number of cervical level injury increased, as compared to the number previously indicated by a prior similar review. Training procedure was largely different among studies. Further improvement based on gait performance is required for use and dissemination in daily life.

The translational potential of this article

The present review reveals the current state of the clinical effectiveness of WREs for gait reconstruction in patients with SCI, contributing to evidence-based device application and further development.

Wearable rehabilitation exoskeletons of the lower limb: analysis of versatility and adaptability

PURPOSE

To analyse the versatility and adaptability of commercially available exoskeletons for mobility assistance and their adaptation to diverse pathologies through a review of clinical trials in robotic lower limb training.

DATA SOURCES

A computer-aided search in bibliographic databases (PubMed and Web of Science) of clinical trials published up to September 2020 was done.

METHODS

To be selected for detailed review, clinical trials had to meet the following criteria: (1) a protocol was designed and approved, (2) participants were people with pathologies, and (3) the trials were not a single case study. Clinical trial data were collected, extracted, and analysed, considering: objectives, trial participants, number of sessions, pathologies involved, and conclusions.

RESULTS

The search resulted in 312 potentially relevant studies of seven commercial exoskeletons, of which 135 passed the preliminary screening; and 69 studies were finally selected. Of the 69 clinical trials included in the review about 50% involved Spinal Cord Injury participants, while roughly 25% focussed on stroke and two trials corresponded to patients with both disorders. The rest were composed of neurological diseases and trauma disorders.

CONCLUSIONS

The use of a single wearable robot for different medical conditions in various diseases is a challenge. Based on this comparative, the properties of the exoskeletons that improve the working ability with different pathologies and patient conditions have been evaluated. Suggestions were made for developing a new lower-limb exoskeleton based on various modules with a distributed control system to improve versatility in wearable technology for different gait pattern progression.Implications for rehabilitationWearable robotic exoskeletons for gait assistance have been analysed from the perspective of adaptation to different diseases.This paper emphasizes the importance of personalized therapies and adaptive assistive technology.Suggestions were made for a new modular exoskeleton capable of addressing the issue of low versatility characterizing currently wearable assistive technology.

Immediate Effects of Force Feedback and Plantar Somatosensory Stimuli on Inter-limb Coordination During Perturbed Walking

Single-sided motor weakness, also known as hemiparesis, is the most prevalent gait impairment among stroke survivors, which often results in gait asymmetry. Studies on robot-assisted gait training (RAGT) have shown positive effects of force feedback on spatial symmetry; somatosensory stimulation is thought to facilitate recovery of temporal symmetry. Despite the known importance of sensorimotor integration for motor recovery, interventions that incorporate RAGT and somatosensory stimuli have been largely overlooked so far. In this paper, we explore how gait symmetry can be restored in healthy subjects following unilateral foot perturbations, using adaptive assistive forces and plantar vibrotactile stimuli provided by a bilateral powered ankle-foot orthosis. Results suggest that combined force feedback and vibrotactile stimuli may be more effective than force feedback alone in reducing spatial asymmetry. Further, force feedback did not produce significant improvements in temporal symmetry, unlike the combined modality. We discuss possible implications of these preliminary findings for future training paradigms for RAGT.