Detection of Unbalance in a Rotor-bearing Sys- Tem Using a Deterministic-stochastic Approach

Disk unbalance in rotating shaft of machines is a common problem. Direct measurement of unbalance forces due to disk unbalance is not possible, therefore, usually the unbalance forces are predicted via response measurements. In the present work, a model-based approach with joint input-state (JIS) estimation technique to detect the amount of unbalance present in a disc is proposed. The JIS technique is of a deterministic-stochastic type, therefore, capable of estimating the unbalance forces in noisy measurements. A numerical case study is presented for a single disk rotor system. The state-space form of a modally reduced order model for the rotor-bearing system and a limited set of response measurements are used. Mode shapes are obtained from a finite element analysis of the rotor-bearing system. Results are presented for different levels of measurement errors, and the effect of different vibration measurements (displacements and accelerations) are shown. The efficacy of the proposed method is validated for different unbalance conditions and rotor speeds.