A System Diagnosis through the Recognition of the Mode of Dynamic Motions of a Shaft by the Indirect Measurement in Journal Bearing

This work presents a method to develop a system diagnosis regarding to shaft in journal bearing. The timely righteous estimation and judgment of the states is very important for the safe operation in time domain system. The synthesis of this problem presumes that all state variables are observable for concerned system. But it seems that it is not feasible to measure all modes of states or velocities, accelerations directly. A practical solution to this problem, which should be tried, is the estimation of the states or its velocities by the use of an observer which can estimate a system characteristics of linear or nonlinear states and effects as a mode, so called, “ Indirect measurement”. For this procedure, the mathematical model of the concerned physical system which consists of a long shaft and two journal bearings at the ends of the shaft, is derived with the significant remarks such as friction, gravitation, and Coriolis force. This is a basic system. The concrete assignment is to design the observer that estimates the characteristics of the states and velocities based on the measurement vectors. The main artifice is to approximate the characteristics with a fictitious model that may describe the modes of system errors. As a practical and convenient fictitious model, the characteristics of nonlinear effects are assumed as approximately stepwise contact. An identity observer is obtained whose state variables are the estimate of the state variable of the corresponding “observer system”. It consists of a simulated model with a correction feedback of the estimation