Adaptive Phase-Aligned Delayed Output Feedback Control Based on Adaptive Frequency Oscillator for Hip Exoskeletons

Abstract

Traditional delayed output feedback control (DOFC) for hip exoskeletons provides a model-free and computationally efficient approach for gait assistance. However, fixeddelay DOFC is susceptible to phase mismatch under variable cadence conditions. To address this issue, a DOFC framework based on an adaptive frequency oscillator (AFO) is proposed to achieve dynamic phase alignment. By acting as a realtime cadence estimator, the AFO continuously updates the DOFC delay parameter. Simulation results demonstrate that the proposed method achieves accurate frequency tracking, maintains improved torque-velocity phase alignment across different walking speeds, and reduces antagonistic negative work compared with fixed-delay DOFC under the tested conditions.