Robust Adaptive Control of Knee Exoskeleton-Assistant System Based on Nonlinear Disturbance Observer

This study presents a control design of an angular position for the exoskeleton knee assistance system based on model reference adaptive (MRAC) strategy. Three schemes MRAC have been proposed: classical MRAC, with disturbance observer, and nonlinear observer. The stability analysis each scheme has conducted developed Lyapunov theorem to prove uniform ultimate bound tracking estimation errors. In addition, laws proposed according analysis. effectiveness state output feedback controllers verified via computer simulation. results numerical simulation shown that observer could give better robustness characteristics performance in terms errors as compared other controllers.