Research On Fault Diagnosis Based On Control Loop

Regarding the complex industrial control system, a three-level configuration, which is composed of the component level, the loop level and the system level, is proposed as the basic framework for FDD system according to the production process. Oscillations in control loops, which are serious breakdown, are researched in the loop level in this thesis in the use of reciprocity between various variables. Moreover, for ease of carrying on the control algorithm as well as the fault diagnosis research, a water tank installation is designed, including hardware, electrical wiring as well as software realization. A primary cause of oscillation in the control loop is the stiction of the actuator, and its mathematical model is obtained by use of method based on data-driven in the article. Finally, methods based on the cross-correlation between control variable and loop output and that based on distinguishing between the shapes of the signals caused by a stiction actuator and an aggressive controller, using the ratio of the areas before and after the peak of the control error signal, are introduced to diagnose the oscillation. The simulation results have proven the effectiveness of the methods.