Design and Evaluation of FALL-E: A Robotic Rollator for Studying Balance Response to Overground Perturbation

This paper presents the design and evaluation of a robotic rollator, FALL-E, developed to investigate how individuals respond to perturbations during overground walking with an assistive device. Drawing inspiration from perturbation methods used in treadmill and kinesthetic haptic studies, we introduce a novel overground perturbation technique that delivers brief, directional changes in velocity through the motorized rear wheels of FALL-E. We characterize the resulting stabilizing responses in able-bodied individuals at low risk of falls. Our findings show that changes in step length and anterior-posterior margin of stability (AP MOS) consistently aligned with the direction of the perturbation. In addition, assisted walking with FALL-E elicited distinct biomechanical adaptations not seen in unassisted conditions, including modifications in elbow flexion and trunk flexion. These results provide new insight into balance control strategies during perturbed, device-assisted walking.