The magnitude of external fall-inducing forces in subjects using the DreamMotion exoskeleton prototype in static body positions - a pilot study.

Purpose: Exoskeleton robots are becoming increasingly popular due to improved robotic technologies and the positive perception of users. Lower limb exoskeletons are the most widely used as assistive devices for people with disabilities. The aim of the study was to determine the magnitude of forces necessary to induce the fall of a person using the Polish prototype of the exoskeleton robot. Methods: Sixteen volunteers used DreamMotion prototype designed to perform medical tasks was tested. Measurements of the fall-inducing forces were performed in compliance with safety standards. Assessed were fall-inducing forces acting in various directions in 3 static, vertical body positions. In each test position, 10 trials were completed resulting in the effective measurement. Results: In the 2-leg standing with posterior vector direction, the lowest value of fall-inducing force was recorded (mean 1.50 kG). Also, in 1-leg standing position, the lowest value of the fall-inducing force was recorded with posterior vector direction (1.66 kG). In the step position, the highest fall-inducing forces were recorded with the posterior (8.58 kG) and anterior (6.37 kG) vector directions, the lowest - with the lateral vector direction towards the stepping limb (3.26 kG). Conclusions: The forces required to induce a fall in a person wearing the exoskeleton robot are relatively low, with relative forces ranging from 1.45% to 8.30% of the subject-ER setup weight. In both the 2-leg and 1-leg standing positions, the lowest fall-inducing forces were recorded when the force vector was directed posteriorly. The exoskeleton robot's design will likely need to be modified to enhance safety in this particular direction.