The paper describes the use of a recently introduced relay shifting method for estimation parameters of a second order time delayed model. The aim is to obtain a process model for setting PID control parameters. For this purpose, an algorithm is designed for estimation of model parameters from two frequency response points obtained from a single relay feedback test without any assumptions about a model transfer function. The relay shifting method is slightly modified here by using an integrator to receive the frequency response points in positions more suitable for model fitting. This modification enables to better estimate the static gain even under constant load disturbance. The proposed solution is demonstrated on simulated examples.
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