Exoskeleton-type medical rehabilitation system with embedded sensors, designed using digital-twin solutions

INTRODUCTION: Exoskeleton-type medical rehabilitation systems are the main solution for recovery of the mobility of patients affected by strokes, spinal cord injuries, or muscular atrophy. These systems feature detection and actuation components, such as sensors and actuators, whose typology and integration are essential for the device's ability to withstand wear under intensive use conditions. OBJECTIVES: To increase the lifespan of exoskeletons, the main objective of the project presented in this article is to integrate sensors into the exoskeleton’s structure, for them to be better protected from external factors, such as shocks or moisture. METHODS: A virtual model of an exoskeleton component for the lower limb that ensures the plantar flexion (movement of the sole), made of polyurethane, was designed using a digital-twin modelling solution, namely the SolidWorks Simulation software. Our choice was motivated by the fact that the use of digital twin solutions allows functional testing, by simulating the impact factors existing in real systems, of the exoskeleton with embedded sensors, by coating with polyethylene and ethylene vinyl acetate (EVA) layers. Thus, it will be possible to observe the inconsistencies and defects that can appear on the surface of the materials used and to determine the best choice of material that can protect against wear. RESULTS: The values ​​of all parameters analyzed following the simulations demonstrate that polyethylene and EVA are materials that can be used to embedd sensors into the structure of exoskeletons. Layers with thicknesses of 0.5 mm, 1 mm, and 1.5 mm are resistant and display stable structures during the patient's walking, thus protecting the sensors integrated into a lower limb exoskeleton from wear factors. CONCLUSION: Following the comparative analysis of the results obtained from testing by digital simulations, the main conclusion is that the 1.5 mm thick ethylene vinyl acetate layer is the one that presents superior tribological properties, being the most useful for application in real systems.