Usability and performance validation of an ultra-lightweight and versatile untethered robotic ankle exoskeleton

Abstract

Background Ankle exoskeletons can improve walking mechanics and energetics, but few untethered devices have demonstrated improved performance and usability across a wide range of users and terrains. Our goal was to design and validate a lightweight untethered ankle exoskeleton that was effective across moderate-to-high intensity ambulation in children through adults with and without walking impairment. Methods Following benchtop validation of custom hardware, we assessed the group-level improvements in walking economy while wearing the device in a diverse unimpaired cohort (n = 6, body mass = 42–92 kg). We also conducted a maximal exertion experiment on a stair stepping machine in a small cohort of individuals with cerebral palsy (CP, n = 5, age = 11–33 years, GMFCS I-III, body mass = 40–71 kg). Device usability metrics (device don and setup times and System Usability Score) were assessed in both cohorts. Results There was a 9.9 ± 2.6% (p = 0.012, range = 0–18%) reduction in metabolic power during exoskeleton-assisted inclined walking compared to no device in the unimpaired cohort. The cohort with CP was able to ascend 38.4 ± 23.6% (p = 0.013, range = 3–132%) more floors compared to no device without increasing metabolic power (p = 0.49) or perceived exertion (p = 0.50). Users with CP had mean device don and setup times of 3.5 ± 0.7 min and 28 ± 6 s, respectively. Unimpaired users had a mean don time of 1.5 ± 0.2 min and setup time of 14 ± 1 s. The average exoskeleton score on the System Usability Scale was 81.8 ± 8.4 (“excellent”). Conclusions Our battery-powered ankle exoskeleton was easy to use for our participants, with initial evidence supporting effectiveness across different terrains for unimpaired adults, and children and adults with CP. Trial registration Prospectively registered at ClinicalTrials.gov (NCT04119063) on October 8, 2019.

Feasibility evaluation of a dual-mode ankle exoskeleton to assist and restore community ambulation in older adults

“…Tekscan embedded fore-foot pressure sensors (A502) were used to identify stance and swing phase of a gait cycle, and inform the assistive and resistive high-level control strategies (Figure 1a). Additional details of the design can be found in our prior publication (Orekhov et al, 2021).

Figure 1.(a) Pictures of the exoskeleton on a participant with detailed views of the exoskeleton waist and ankle assemblies.

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Coordination Between Partial Robotic Exoskeletons and Human Gait: A Comprehensive Review on Control Strategies

“…For example, in ( Lai et al, 2013 ), the authors exploited the strong correlation between the knee angle and hip angular velocity during the swing phase of gait. Other sources of information were the pressure measurements between the thigh muscles and the exoskeleton straps ( Wu et al, 2015 ) for generating a velocity reference profile, or the biological moment of the ankle for generating assistive ( Fang and Lerner, 2021 ; Gasparri et al, 2019 ; Orekhov et al, 2020 , 2021 ) or resistive ( Conner et al, 2020 ) torque profiles.…”

Relationship Between Ankle Assistive Torque and Biomechanical Gait Metrics in Individuals After Stroke

“…For the majority of the control strategies, the parameter tuning is laborious, as therapists must manually adjust the parameters relying only on subjective feedback from the patients and visual assessments of the gait pattern [6], [7]. A few studies have shown that the process of tuning the control parameters requires the highest amount of time when setting up the device together with donning process [4], [8], [9]. Manual tuning might often lead to a sub-optimal set of parameters, and does not take advantage of the data gathered by the exoskeleton to facilitate the parameter tuning.…”