Diagnosis between sinusoidal oscillations and oscillatory colored noise

The practice of oscillation compensation in control loops depends on the source of the oscillation. While retuning the controller is required to compensate the oscillations caused by aggressive controller tuning, it is not an effective approach to compensate oscillations due to valve problems or sinusoidal disturbances. Thus, it is of great value to distinguish between oscillations which are truly caused by the controller tuning from oscillations due to other kind of sources. The paper discusses the special properties of oscillations caused by controller tuning and proposes a method to distinguish it from sinusoidal disturbances. The method is based on analyzing the auto correlation function of the signals for both detection and diagnosis of oscillations in the presence of multiple oscillations.