Design of Augmented Observer for Rotor Systems

Abstract

Observers are widely used in state space control and model based fault diagnosis processes. However disturbances and model uncertainties often have large impact on the observation results regarding system states or outputs and result in reduced control or fault diagnosis performances. In rotor systems, observer design often faces two major problems: unbalances acting on the shaft are never known to full extent and in case of a rotor with large discs, gyroscopic effect results in variation of system behavior dependent on rotor rotary frequency. The predominant disturbances e.g. unbalance forces and model uncertainties caused by gyroscopic effect appear in rotor systems in a sinusoidal form with rotor rotary frequency. The influences of unbalance forces and gyroscopic effect can be considered as unknown inputs, and the signals of unknown inputs are also sinusoidal. Augmented observers that account for sinusoidal unknown inputs can be used to take advantage of this characteristic of rotor systems. The augmented observer can be applied in the control or fault diagnosis processes and can be used to estimate the distribution matrix of unknown inputs. According to the design purpose, different configurations of the augmented observer are investigated and their restrictions are discussed in this work. The performance of the augmented observer are presented and discussed with the respect to system states observation as well as fault detection and isolation.