Direct identification method of second order plus time delay model parameters

In this paper, we propose an identification method to estimate the second o rder plus time delay (SOPTD) model parameters. The proposed method directly obtains these parameters using a frequency-weighted integral transform and a least-squares method, without iterative calculation step. This calculati on procedure can be applied regardless of initial states, in contrast to al most all previous identification methods, which require the assumption of z ero initial states. In addition, it does not require any additional model r eduction steps to tune the PID controller. Using simulations, it is demonst rated that the proposed method provides better modeling performance than pr evious methods, in spite of its simplicity. The new method shows an accepta ble robustness to disturbance and measurement noise.