Design and Verification of Parallel Hip Exoskeleton Considering Output Torque Anisotropy

In rehabilitation training, it is crucial to consider the compatibility between exoskeletons and human legs in motion. However, most exoskeletons today adopt an anthropomorphic serial structure, which results in rotational centers that are not precisely aligned with the center of the hip joint. To address this issue, we introduce a novel exoskeleton called the Parallel Hip Exoskeleton (PH-Exo) in this paper. PH-Exo is meticulously designed based on the anisotropic law of output torque. Considering the friction of the drive components, a dynamic model of the human–machine complex is established. Simulation analysis demonstrates that PH-Exo not only exhibits outstanding torque performance but also achieves high controllability in both flexion/extension and adduction/abduction directions. Additionally, a robust controller is designed to address model uncertainty, friction, and external interference. Wearing experiments indicate that under the control of the robust controller, each motor achieves excellent tracking performance.