Assessing usability of a prototype soft exoskeleton by involving people with gait impairments
Creators: name: Graf, Eveline
name: Bauer, Christoph
name: Schülein, Samuel
name: de Eyto, Adam
name: Power, Valerie
name: Bottenberg, Eliza
name: Weyermann, Bianca
name: O'Sullivan, Leonard
name: Wirz, Markus
Publisher: name: ZHAW Zürcher Hochschule für Angewandte Wissenschaften
Year: 2019
Subjects: User involvement
Assistive device development
Exoskeleton
User centered iterative design
610: Medizin und Gesundheit
620: Ingenieurwesen

description: Background: Gait impairment is prevalent among many growing clinical populations e.g. people with stroke, incomplete spinal cord injury (iSCI), older adults etc. Such populations may benefit from assistive devices such as exoskeletons to improve their walking ability. XoSoft (www.xosoft.eu) is a soft exoskeleton that is being developed for people with mild to moderate gait impairments to support their mobility by providing physical actuation across joints of the lower extremities. During the design and development of a device like XoSoft, it is crucial that Primary Users (PUs, e.g. patients) are involved and provide insight into their experiences and expectations regarding device usability. However, it is still not standard practice to include PUs in rigorous testing of highly technical exoskeletons. The XoSoft consortium took an iterative design approach to the development of the XoSoft prototypes. Data from usability testing with PUs are informing next iterations of the XoSoft concepts.
Purpose: The purpose of this study was to assess the PU experiences of the usability of a XoSoft prototype. This study should also highlight the importance of including PUs during the development of assistive devices.
Methods: Eleven participants were recruited (mean age: 73 years, mean height: 166 cm, mean mass: 65 kg). There were three categories of PUs: frail (n=5), stroke (n=1), iSCI (n=5). Participants had no cognitive impairment (Mini Mental State Examination score > 24). The prototype consisted of a leggings-style garment with Velcro straps as anchor points for actuators across the relevant joints (hip, knee, ankle). Actuation and control was provided by a modular pneumatic/sensor controlled system, which was added to the garment in modular fashion based on the PU needs. After independent donning and doffing by the participant, the garment was donned and the Velcro straps placed and secured by a researcher to ensure proper placement. Participants then performed walking tasks with active actuation followed by completion of the System Usability Scale (SUS, Brooke 1996, maximum score = 100).
Results: The scores for the SUS ranged from zero to 95 with a median rating of 52.5. The median rating corresponds to an “okay” score. According to the acceptability ranges by Bangor et al. (2008), 3 participants rated the prototype as acceptable, 3 as marginal, and 5 as not acceptable.
Conclusions: The scores indicate the need for improvement in the design of future XoSoft prototypes. The large variability in SUS scores indicated that the same device may be rated considerably differently by different users. This highlights the importance of including a variety of potential users of assistive devices during development.
Implications: Secondary Users (SUs) such as physical therapists are also involved in the development of XoSoft, providing insight into their own needs and the needs of their patients. The therapists also play a key role in motivating their patients to participate in research and development projects. To ensure that such assistive devices can be integrated into users’ lives and practices, it is essential to have both PUs and SUs actively involved in the technical development.