Design of an Integrated Observer Structure for Robust Fault Detection

An integrated observer structure consisting of an unknown input observer and proportional integral observer with an additional fading term for robust fault detection is presented. First, a brief overview of each observer is outlined with the associated advantages. The design equations of each observer is required for the design of combined observer structure termed as PIFUIO. It is shown that the fading term of this observer plays a key role in reliable estimation of faults decoupled from the unknown disturbance or vice versa. The robust detection of sensor fault is also considered with the presence of unknown inputs. A numerical example is provided to illustrate the advantage of PIFUIO.