Identification method for commercialized PI control using Laguerre function

This paper presents an identification method for noisy PI control operating data. A general pre-filtering procedure is not required in this method. A three-step procedure for estimating a process model is proposed. In the first step, the closed loop transfer function model (called the Laguerre model) is estimated from noisy PI control operating data by using orthonormal properties of Laguerre functions. In the second step, the process transfer function model is extracted from the Laguerre model. Finally, the estimated process model can be replaced with low order model by considering the placement of poles and zeros. The proposed method is validated by simulation. As a result, the estimated process model corresponds with the true model. Simulation results show that the proposed method is effective in closed loop identification.