Internal Model Impedance Control for a Lower Limb Rehabilitation Robot in the Presence of Uncertainty

Abstract

Internal Model Impedance Control (IMIC) method is introduced here, and applied to control the contact impedance between a Lower Limb Rehabilitation Robot (LLRR) and environment e.g. the patient's limb. In rehabilitation process, contact force between patient's limbs and the robot is an important issue. Impedance control aims at enforcing a desired dynamics to the interactions of a robot. However, uncertainties of all types, i.e. unknown external disturbances, model imperfections, and unmodeled dynamics, frustrate the efforts. In the proposed method, internal model strategy is utilized to compensate for the uncertainty. Thus, the proposed impedance controller, IMIC, considers the contact mechanical impedance between robot and environment, while it is a robust structure against the uncertainties. Simulations results confirm the robustness, efficiency, and high performance of the proposed controller.