A Robust Adaptive Admittance Controller for Lower Limb Exoskeleton

In this paper, an admittance control scheme for an augmentation lower body exoskeleton is presented. The design basically consists of, on the one hand, a composite adaptive controller which utilizes a feedback law in order to compensate the modeled dynamics and, a robust term to overcome the unmodeled dynamics, and on the other hand, an admittance relation which is founded based on a small multiplication of the exoskeleton dynamics. The admittance control is employed to substitute the new admittance - as the apparent dynamics - for the robot’s forward dynamics. lt is proved that based on the resulting controller, the tracking error converges to zero. Moreover,utilization of a composite adaptation law results the convergence of parameter estimations to their right values. Finally, the design is evaluated by means of simulations.