Active fault tolerant control based on nonlinear subject to actuator and sensor faults for a parallel robot

In this paper, an Active Fault Tolerant Control (AFTC) strategy using a nonlinear H∞ control is proposed for a delta type parallel robot in the presence of actuator and sensor fault. First, dynamic modeling of the robot is accomplished using the Lagrange method. To measure the position and velocity, a super-twisting third-order sliding mode (STW-TOSM) observer is applied. The proposed scheme can accommodate both faults and uncertainties without velocity measurement. In addition, fast convergence and high accuracy is achieved because of applying the high-order sliding mode (HOSM) observer. In order to indicate the effectiveness of the FTC on the basis of nonlinear H∞, its performance is compared with conventional sliding mode and feedback linearization methods. The obtained results reveal the efficacy of the proposed FTC- H∞.