Improving Disturbance Rejection Performance of EID-Based Control by Employing PLTD.

This paper proposes an improved equivalent-input-disturbance (IEID) approach to further suppress the exogenous disturbances. A predictor linear tracking differentiator (PLTD) is suggested as a replacement for the first-order low-pass filter in the traditional EID method and constructs the IEID approach. The controller based on the IEID approach includes a PLTD, a Luenberger state observer, the internal model of the input signal and the state feedback gain. The PLTD can be easily designed by adjusting the damping ratio to change the resonance peak and superimposing a differential unit to compensate for the phase loss; the frequency domain properties of the PLTD explain why the IEID estimator has better disturbance-rejection performance than the conventional EID approach. The closed system can be divided into two subsystems for design and stability analysis. The state feedback gain can be obtained using the linear quadratic regulator (LQR) control method; the state observer gains are achieved by the perfect regulation method; and the stability of the system is analyzed according to the small-gain theorem. The simulation results of a rotational control system show the validity of the proposed method and superiority over the conventional EID approach, a high-order EID (HEID) approach, the DOB method and the ADRC method.