Dynamic Duo: Design and Validation of an Autonomous Frontal and Sagittal Actuating Hip Exoskeleton for Balance Modulation During Perturbed Locomotion

Humans are required to maintain balance during locomotion in challenging environments, which present an even bigger challenge for individuals with balance impairments. Exoskeleton-driven balance augmentation is a promising avenue to assist users in these environments, but there has been little work in developing exoskeleton devices for these applications. In this work, we present the design, realization, and validation of an autonomous robotic hip exoskeleton with frontal and sagittal actuation. This device contains four quasi-direct drive-actuated degrees of freedom, enabling both frontal and sagittal assistance at the hip joints. The device is relatively light-weight, weighing 7.76 kg, and low-profile in the frontal plane, enabling unimpeded arm swing of the user. We found that wearing the device did not change walking kinematics, validating that the design does not inhibit the user's natural motion. We validated the exoskeleton using a bilateral bang-bang controller that successfully modulated step width and length in all cardinal and ordinal directions (all p<0.001) during steady state and perturbed walking. We also found that step modulation capability is influenced by swing leg kinematics and perturbation context. Broadly, this work presents a lightweight, autonomous, powered exoskeleton that can be used to study control approaches for balance augmentation.