Assistance Control of Human-Exoskeleton Integrated System for Balance Recovery Augmentation in Sagittal Plane

This article proposed a humanoid balance assistance strategy (BAS) to enhance balance recovery in sagittal plane. Numerical construction of balanced state manifold (BSM) which accounts for active intervention of human ankles is developed to detect imbalance criticality (IC). A human-in-the-loop balance judgment criterion is established to appropriately trigger the external assistance intervention. A unified assistive torque controller based on minimization modulation of virtual potential energy (VPE) towards BSM is designed to augment posture regulation. Exploitation of BAS leads to the following contributions: 1) ICs in 6 typical imbalance situations are accurately detected, with identification error within 23.7%. 2) Traversal imbalanced region of center of mass (CoM) is reduced by 44.2% (with imbalanced position/velocity range (IPR/IVR) by 35.6%/34.3%). 3) Position offset (PO) and velocity impact (VI) at landing collision are reduced by 39.3% and 59.4%. 4) Elapsed time of balance recovery is reduced by 160-580 ms. Experimental verification demonstrates the significant augmentation for balance recovery by BAS.