Technology acceptance and perceptions of robotic assistive devices by older adults - implications for exoskeleton design.

AIM: This study explored and interpreted insights expressed by a cohort of older adults related to their life experience, their experiences using or assisting someone with assistive devices, and their perceptions of robots and robotic assistive devices, including lower limb exoskeletons. METHOD: A grounded theory study was undertaken with 24 older adult participants over five months. Each participant participated in a structured interviewed regarding their experiences with technologies and in particular their perceptions of assistive technologies. Themes from the interviews were coded using Nvivo software. RESULTS: Five main themes emerged from this study - (1) Aging & life stage experiences, (2) Quality of Life, (3) Assistive Technologies, (4) Health Conditions & Care, (5) Products & Service Systems. These have influenced new constructs for a hybrid design tool that incorporates stages of Usability and TAMs (Technology Acceptance Models) to gauge (a) Perception, (b) Experience and (c) Perceived Impact by older adults of lower limb exoskeletons.Conclusions: Emerging technologies such as robotic assistive devices require a specific enquiry to understand how best to optimise acceptance by older adults and avoid feelings by them of frustration, embarrassment and ultimately abandonment of these devices.Implications for rehabilitationOlder adults frequently require rehabilitation and assistance with ambulationExoskeletons are forms of assistive technologies for rehabilitation, and they are moving from clinical use to more day care use, including as part of daily livingThese results help explain factors related to the perception of exoskeletons by older adults, which if considered during exoskeleton design, could improve the technology uptake and compliance with this technology use by these users.

Relationship Between Interface Pressures and Pneumatic Cuff Inflation Pressure at Different Assessment Sites of the Lower Limb to Aid Soft Exoskeleton Design.

OBJECTIVE: The aim was to develop a means of predicting interface pressure from cuff inflation pressure during circumferential compression at the lower limb, in order to inform the design of soft exoskeletons. BACKGROUND: Excessive mechanical loading of tissues can cause discomfort and soft tissue injury. Most ergonomic studies on exoskeletons are of interface pressure, but soft exoskeletons apply circumferential pressures similar to tourniquet cuffs by way of cuff inflation pressure. This study details the relationship between interface and cuff inflation pressures for pneumatic tourniquet cuffs. METHOD: Pneumatic cuffs of different widths were inflated to target pressures on (A) a rigid cylinder, (B) the dominant thigh and calf, and (C) knee of healthy participants standing still. Interface pressures were measured under the cuffs using a pressure-sensing mat. Average interface pressures were then compared to cuff inflation pressures. The influence of cuff width, cuff inflation pressure, and participants' anthropometric data on pressure transmission was assessed. RESULTS: A strong linear relationship between cuff inflation pressures and interface pressures was observed. Interface pressures were generally higher than cuff inflation pressures. The efficiency of pressure transmission to the lower limb depended on assessment site, adipose tissue thickness, cuff size, cuff inflation pressure, and possibly limb circumference. Regression equations were developed to predict interface pressures at the thigh, calf, and knee. CONCLUSION: Interface pressures under pneumatic cuffs are influenced by the cuff size, cuff inflation pressure, and tissue compressibility. Predicted interface pressure from cuff inflation pressure and vice versa can be used to aid the design of soft exoskeletons.

Pneumatic Quasi-Passive Actuation for Soft Assistive Lower Limbs Exoskeleton.

There is a growing international interest in developing soft wearable robotic devices to improve mobility and daily life autonomy as well as for rehabilitation purposes. Usability, comfort and acceptance of such devices will affect their uptakes in mainstream daily life. The XoSoft EU project developed a modular soft lower-limb exoskeleton to assist people with low mobility impairments. This paper presents the bio-inspired design of a soft, modular exoskeleton for lower limb assistance based on pneumatic quasi-passive actuation. The design of a modular reconfigurable prototype and its performance are presented. This actuation centers on an active mechanical element to modulate the assistance generated by a traditional passive component, in this case an elastic belt. This study assesses the feasibility of this type of assistive device by evaluating the energetic outcomes on a healthy subject during a walking task. Human-exoskeleton interaction in relation to task-based biological power assistance and kinematics variations of the gait are evaluated. The resultant assistance, in terms of overall power ratio (Λ) between the exoskeleton and the assisted joint, was 26.6% for hip actuation, 9.3% for the knee and 12.6% for the ankle. The released maximum power supplied on each articulation, was 113.6% for the hip, 93.2% for the knee, and 150.8% for the ankle.

Circumferential tissue compression at the lower limb during walking, and its effect on discomfort, pain and tissue oxygenation: Application to soft exoskeleton design.

Soft exoskeletons apply compressive forces at the limbs via connection cuffs to actuate movement or stabilise joints. To avoid excessive mechanical loading, the interface with the wearer's body needs to be carefully designed. The purpose of this study was to establish the magnitude of circumferential compression at the lower limb during walking that causes discomfort/pain. It was hypothesized that the thresholds differ from those during standing. A cohort of 21 healthy participants were tested using two sizes of pneumatic cuffs, inflated at the thigh and calf in a tonic or phasic manner. The results showed lower inflation pressures triggering discomfort/pain at the thigh, with tonic compression, and wider pneumatic cuffs. The thresholds were lower during walking than standing still. Deep tissue oxygenation increased during phasic compression and decreased during tonic compression. According to the findings, circumferential compression by soft exoskeletons is preferably applied at anatomical sites with smaller volumes of soft tissue, using narrow connection cuffs and inflation pressures below 14 kPa.

The effect of simulated circumferential soft exoskeleton compression at the knee on discomfort and pain.

There is a lack of data and guidance on soft exoskeleton pressure contact with the body. The purpose of this research was to study the relationship between circumferential loading at the knee and discomfort/pain, to inform the design of soft exoskeletons/exosuits. The development of discomfort and pain was studied during standing and walking with circumferential compression using a pneumatic cuff. Our results show higher tolerance for intermittent than continuous compression during standing. Discomfort was triggered at pressures ranging from 13.7 kPa (continuous compression) to 30.4 kPa (intermittent compression), and pain at 52.9 kPa (continuous compression) to 60.6 kPa (intermittent compression). During walking, cyclic compression caused an increase in discomfort with time. Higher cuff inflation pressures caused an earlier onset and higher end intensities of discomfort than lower pressures. Cyclic cuff inflation of 10 kPa and 20 kPa was reasonably well tolerated. Practitioner summary Soft exoskeleton compression of the knee was simulated during static and dynamic compression cycles. The results can be used to understand how users tolerate pressure at the knee, and also to understand the levels at which discomfort and pain are experienced. Abbreviations: BMI: body mass index; DDT: discomfort detection threshold; EndVAS: end of experiment rating on visual analog discomfort scale; PDT: pain detection threshold; SD: standard deviation; SE: standard error; TSP: temporal summation of pain; VAS: visual analogue scale.

Discomfort/Pain and Tissue Oxygenation at the Lower Limb During Circumferential Compression: Application to Soft Exoskeleton Design.

OBJECTIVE: To establish the relationship between circumferential compression on the lower limb during simulated ramp and staircase profile loading, and the resultant relationship with discomfort/pain and tissue oxygenation. BACKGROUND: Excessive mechanical loading by exoskeletons on the body can lead to pressure-related soft tissue injury. Potential tissue damage is associated with objective oxygen deprivation and accompanied by subjective perception of pain and discomfort. METHOD: Three widths of pneumatic cuffs were inflated at the dominant thigh and calf of healthy participants using two inflation patterns (ramp and staircase), using a computer-controlled pneumatic rig. Participants rated discomfort on an electronic visual analog scale and deep tissue oxygenation was monitored using near infrared spectroscopy. RESULTS: Circumferential compression with pneumatic cuffs triggered discomfort and pain at lower pressures at the thigh, with wider cuffs, and with a ramp inflation pattern. Staircase profile compression caused an increase in deep tissue oxygenation, whereas the ramp profile compression decreased it. CONCLUSION: Discomfort and pain during circumferential compression at the lower limb is related to the width of pneumatic cuffs, the inflation pattern, and the volume of soft tissue at the assessment site. The occurrence of pain is also possibly related to the decrease in deep tissue oxygenation during compression. APPLICATION: Our findings can be used to inform safe and comfortable design of soft exoskeletons to avoid discomfort and possible soft tissue injury.

Exoscore: A Design Tool to Evaluate Factors Associated With Technology Acceptance of Soft Lower Limb Exosuits by Older Adults.

OBJECTIVE: This pilot study proposed and performs initial testing with Exoscore, a design evaluation tool to assess factors related to acceptance of exoskeleton by older adults, during the technology development and testing phases. BACKGROUND: As longevity increases and our aging population continues to grow, assistive technologies such as exosuits and exoskeletons can provide enhanced quality of life and independence. Exoscore is a design and prototype stage evaluation method to assess factors related to perceptions of the technology, the aim being to optimize technology acceptance. METHOD: In this pilot study, we applied the three-phase Exoscore tool during testing with 11 older adults. The aims were to explore the feasibility and face validity of applying the design evaluation tool during user testing of a prototype soft lower limb exoskeleton. RESULTS: The Exoscore method is presented as part of an iterative design evaluation process. The method was applied during an exoskeleton research and development project. The data revealed the aspects of the concept design that rated favorably with the users and the aspects of the design that required more attention to improve their potential acceptance when deployed as finished products. CONCLUSION: Exoscore was effectively applied to three phases of evaluation during a testing session of a soft exoskeleton. Future exoskeleton development can benefit from the application of this design evaluation tool. APPLICATION: This study reveals how the introduction of Exoscore to exoskeleton development will be advantageous when assessing technology acceptance of exoskeletons by older adults.

Cuff Pressure Algometry in Patients with Chronic Pain as Guidance for Circumferential Tissue Compression for Wearable Soft Exoskeletons: A Systematic Review.

In this article, we report on a systematic review of the literature on pressure-pain thresholds induced and assessed by computerized cuff pressure algometry (CPA). The motivation for this review is to provide design guidance on pressure levels for wearable soft exoskeletons and similar wearable robotics devices. In our review, we focus on CPA studies of patients who are candidates for wearable soft exoskeletons, as pain-related physiological mechanisms reportedly differ significantly between healthy subjects and patients with chronic pain. The results indicate that circumferential limb compression in patients most likely becomes painful at ∼10-18 kPa and can become unbearable even below 25 kPa. The corresponding ranges for healthy control subjects are 20-42 kPa (painful limits) and 34-84 kPa (unbearable levels). In addition, the increase of pain with time tends to be significantly higher, and the adaptation to pain significantly lower, than in healthy subjects. The results of this review provide guidance to designers of wearable robotics for populations with chronic pain regarding rates and magnitudes of tissue compression that may be unacceptable to users.

Computerized Cuff Pressure Algometry as Guidance for Circumferential Tissue Compression for Wearable Soft Robotic Applications: A Systematic Review.

In this article, we review the literature on quantitative sensory testing of deep somatic pain by means of computerized cuff pressure algometry (CPA) in search of pressure-related safety guidelines for wearable soft exoskeleton and robotics design. Most pressure-related safety thresholds to date are based on interface pressures and skin perfusion, although clinical research suggests the deep somatic tissues to be the most sensitive to excessive loading. With CPA, pain is induced in deeper layers of soft tissue at the limbs. The results indicate that circumferential compression leads to discomfort at ∼16-34 kPa, becomes painful at ∼20-27 kPa, and can become unbearable even below 40 kPa.