Trip Detection and Foot Placement Estimator-Based Recovery Assistance Controller to Prevent Trip-Induced Falls

This study presents a method for trip detection using inertial sensors, and a controller for balance recovery in the sagittal plane after trip using exoskeleton devices. Trip detection was performed using a computed root mean square of the lower back angular acceleration in a sagittal plane and a fixed threshold resulting in mean detection times of 51 ± 16 ms. The foot placement estimator-based controller was designed for bilateral, pneumatic, constant-torque output exoskeleton devices to provide assistance to reposition the foot to prevent a fall. At the moment of detection, foot placement estimation (FPE) for recovery is calculated, and a human-inspired response (lift/lower) is chosen for the perturbed leg. A pendulum model is used to determine the necessary torque injections to achieve FPE. Sensitivity analysis of this pendulum model is performed to influence the outputs chosen. The controller is validated through simulation results of the applied strategies showing successful fall prevention.