Pediatric Robotic Lower-Limb Exoskeleton: An Innovative Design and Kinematic Analysis

Lower-limb exoskeletons enhance motor function in patients, benefiting both clinical rehab and daily activities. Nevertheless, pediatric exoskeletons remain largely underdeveloped. To address this gap, this study presents a new robotic lower-limb exoskeleton (LLE) design specifically tailored for children. Utilizing anthropometric data from the target demographic, the LLE has a size-adjustable design to accommodate children aged 8 to 12. The design incorporates six active joints at the hip and knee, actuated using Brushless DC motors in conjunction with Harmonic Drive gears. This study conducts a rigorous analysis of forward and inverse kinematics applied to the robotic LLE. While forward kinematics are essential for dynamic modeling and model-based control formulation, inverse kinematics play a crucial role in facilitating balance control. The study uses an algebraic-geometric method to solve the inverse kinematics of LLEs with four DOFs per leg, including one in the frontal plane and three in the sagittal plane. A unique model of validation and verification is then employed using the Simulink (R) and SimscapeTM computational environments. The accuracy of the forward kinematic analysis is confirmed by comparing separately modeled outcomes in both environments. The validity of the inverse kinematic model is verified by implementing sequential forward and inverse kinematic analyses, comparing the forward kinematic inputs with inverse kinematic outputs. Simulation results conclusively validate both the forward and inverse kinematic analyses, suggesting the exoskeleton's potential in accommodating standard gait patterns.