Concept and Takagi–Sugeno descriptor tracking controller design of a closed muscular chain lower-limb rehabilitation device

Abstract

The authors consider the kinematic concepts of a new lower-limb rehabilitation device in closed muscular chain. The proposed control structure is based on a trajectory generator and a continuous non-linear tracking controller. The human efforts applied to this device are considered as external disturbances to the system's dynamics and as inputs to the trajectory generator and allow safe voluntary control of the system by the user. A H∞ control structure based on a Takagi–Sugeno descriptor model is proposed to track the desired trajectories and to attenuate external disturbances. Stability conditions are given in terms of linear matrix inequalities using a fuzzy Lyapunov function. Finally, the simulation results of the proposed control structure for the new rehabilitation device during isokinetic movements illustrate the efficiency of the proposed approach.