IMM-UKF Versus Frequency Analysis [Past and Present]

In this article, we consider the degradation in the DAT loops performance caused by a gradual increase in backlash of the valve actuator (valve leakage) and several disturbances that occur in the process. The objective of this study is to develop automated strategies for fault detection, diagnosis, and isolation (FDDI) based on frequency and spectral analysis of the system response and an interactive multiple model (IMM) based on the unscented Kalman filter (UKF) estimation technique to the problem of FDDI of the valve actuator failures in DAT loops of the HVAC systems. The performance of the IMM-UKF is compared with that obtained by using the frequency analysis (FA). Both techniques are HVAC model driven-based, and the simulations results reveal the superiority of the IMM-UKF algorithm concerning its accuracy and robustness to the changes in the system structure parameters. The FDDI based on the IMM algorithm is implemented in a simulation environment, and the fault diagnosis results are presented for a several fault scenarios in terms of mode probabilities and active fault index.