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This paper proposes an active disturbance rejection and fuzzy impedance control (ADRFIC) framework for two-degrees-of-freedom (2-DOF) lower limb exoskeleton robots. By utilising the differential flatness theory, the underlying robotic system is decomposed into two subsystems that are easy to control. On this basis, extended state observers (ESOs) are designed individually to realise disturbance estimation for each subsystem. Considering that human-robot interaction can cause obvious observation error, nonlinear state error feedback-based fuzzy impedance controllers (NSEF-FICs) are designed. The proposed ADRFIC framework is composed of tracking differentiators (TDs), ESOs and NSEF-FICs. A simulation example is finally given to demonstrate the excellent trajectory-tracking and impedance performance of the proposed control framework. And this framework can be easily generalised to robotic systems with more DOFs.
Fei et al. (Thu,) studied this question.