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Soft modular biomimetic exoskeleton to assist people with mobility impairments

Periodic Reporting for period 2 - XoSoft (Soft modular biomimetic exoskeleton to assist people with mobility impairments)

Reporting period: 2017-08-01 to 2019-01-31

Advances in healthcare and medicine, and other comforts of modernity, enable us live longer than our ancestors. The life expectancy of the average European has nearly doubled during the last century. As life expectancy increases, however, so does the number of older people with mild to moderate disabilities. There are 3.2 million wheelchair users in Europe, and another 40 million who cannot walk without an aid. People with movement limitations of their legs can now use a variety of assistive devices. However, current assistive aids are typically bulky, relatively inflexible and often only partially support movements. Further, they typically do not encourage or support the activation of legs, which is essential to prevent further atrophy.

XoSoft is a soft exoskeleton device for users who need low to moderate levels of mobility assistance. XoSoft comprises a modular actuation system for the ankle, knee and hip, which can be configured and customized to fit any specific user (for example, post-stroke patients or frail elderlies in unilateral/bilateral configurations). The sensors embedded in the system identify the motion of the user and adjusts the control system to the specific movement. Actuation provides task specific assistance, i.e. during walking to increase foot clearance, improve the gait symmetry or provide stability during stance phase. In addition to providing lower limb assistance, XoSoft monitors lower leg movement kinematics, and classifies the data to monitor mobility levels and activity type (e.g. walking, standing, stairs negotiation, sit to stand, and stand to sit).

XoSoft is designed to be easy to wear, comfortable, serviceable and compatible with the user’s daily life activities, helping augment autonomy and individual performance by the users. These aspects will ensure high user acceptability, being applied not only in clinical environments, but also at home and in everyday life. The use of novel technologies in smart materials, advanced algorithms for biomimetic control, user centred design, and an energy efficient implementation, provides the technology with a user needs design focus to accomplish XoSoft.
The first prototype of the system (Alpha) was developed using existing technologies and was divided in separate modules for sensing and actuation. In particular, some of the modules were still using hard technologies for actuation and soft technologies for sensing.

The Beta 1 prototype was the first to include soft technologies to integrate sensing and actuation on the garment. The garment of the Beta 1 prototype was fitted to the subject and enabled actuation of the hip and knee flexion (unilateral) with a quasi-passive actuation system, using an electromagnetic clutch connected to an elastic band through a bowden cable. Different technologies were evaluated to measure the user’s motion (insole sensors, IMUs and capacitive sensors in knee and ankle).

The Beta 2 prototype represented a big step towards a complete soft system. The actuation system was replaced by a novel type of quasi passive actuation based on elastic bands and custom made pneumatic soft clutches. The new design of the garment enabled a high degree of configuration of the system, with the possibility to assist the flexion/extension of the hip, flexion/extension of the knee and dorsi/plantar flexion of the ankle, in any configuration (including unilateral and bilateral), with a maximum of 8 simultaneous actuators. The sensory system was an evolution of the one present in the Beta 1 prototype, with important developments in the control system.

Finally, the Gamma prototype further improved the XoSoft design, with important changes in the garment and optimisation of the pneumatic system. One of the main changes in the Gamma garment design was the ability to adjust it to a wider variety of persons. The Gamma prototype was classified as a medical device Class I, passing all the conformity tests required by the pertinent regulations.

Different versions of the connected monitoring system, and feedback to the different types of users, were integrated with the different prototypes. The full-connected system is easily adaptable to different situations, is able to monitor, store, analyse and evaluate XoSoft data.

In the later stages of the project, different public demonstrations of the system were performed: International Festival of Robotics 2017 (Pisa, IT), GNB2018 (Milan, IT), IROS2018 (Madrid, ES), WeRob2018 (Pisa, It), Dutch Design Week 2018 (Eindhoven, NL). Furthermore, a final project event entitled “Exoskeletons and soft wearable robotics day” was organised in Amsterdam, with the participation of key researchers, institutions, projects and industry in Europe in the area of Exoskeletons.

In total, 25 scientific contributions have been published during the project, with a further 10 under review or in preparation. Most of the publications involve collaboration between partners, in particular between engineering/technical and clinical partners.
Each prototype of the system includes technologies that go beyond the state of the art in different areas. The Beta 1 prototype incorporated soft sensors based on capacitive technologies directly integrated in the garment to measure knee and ankle angles/motion. Several solutions for soft actuation were evaluated, with some concepts integrated for the first time onto a wearable soft assistive device.

The Beta 2 and Gamma prototypes incorporated a novel type of pneumatic soft clutches, which provided the quasi-passive actuation to the system. This novel type of clutch enabled complete integration of the actuation system into the garment, while the auxiliary pneumatic equipment was placed on the person’s back.

The Gamma garment prototype includes several advances with respect to the state of the art. This garment is able to accommodate a wide variety of user’s size, and also multiple configurations of the actuation system, which allows the assistance of different patients’ conditions and pathologies.

Capacitive sensors were also integrated directly into the pneumatic soft clutches, allowing in a single component to provide the control of the quasi-passive actuation and the measurement of joint motion.

The different prototypes include different versions of the adaptive biomimetic control structure, using the information coming from the soft and wearable sensors to estimate the subject’s movement, and triggering the adequate reaction of the actuation system. The complete setup uses information from the insole pressure sensors, IMUs and knee soft sensors to segment the swing and stance phase of both legs and modulate with a high degree of precision and flexibility the actuation system.

In total, 15 different subjects participated in the different testing and validation stages of the three prototypes (Beta 1, Beta 2 and Gamma). In particular, a post-stroke patient with a low unilateral disability participated in the laboratory testing of the Beta 1 prototype. Four subjects (1 post-stroke and 3 iSCI patients) participated in the laboratory testing of the Beta 2 and Gamma prototypes. Seven and five elderly subjects participated in the clinical validation of the Beta 2 and Gamma prototypes respectively. Four subjects (2 iSCI and 2 post-stroke patients) participated in the home-simulated environment validation with the Gamma prototype.
XoSoft Gamma
XoSoft Prototypes