A direct estimation method of second order plus time delay model parameters for PID controller autotuning

In this paper, we propose an identification method to estimate the second o rder plus time delay (SOPTD) model parameters. The proposed method obtains the parameters of the SOPTD model directly using a time weighted integral t ransform and a least square method, so model reduction steps can be avoided to tune the PID controller. It can also be applied regardless of the initi al states while almost all previous identification methods require the assu mption of zero initial states. Through extensive simulations, it is proved clearly that the proposed method gives acceptable estimation performances w hether initial states are zero or not. Moreover, it shows an acceptable rob ustness to the disturbances and measurement noise.