Estimating rotor unbalance from a single run-up and using reduced sensors

The earlier model-based rotor mass unbalance estimation methods have used two orthogonal sensors per bearing pedestal. It is generally believed that the vibration measurement at two orthogonal directions provides the bigger picture of machine dynamical behaviour. However, in the present study, the concept of the earlier method is applied again but with using only one sensor at a bearing pedestal, rather than the usual pair of sensors arranged in orthogonal directions. The significant reduction in the number of vibration sensors without necessarily compromising the valuable information required for the diagnosis is of great benefit to industries that have huge rotating machines with numerous bearings. The reason is that the computational effort in the complex signal processing will reduce considerably and hence the machine down time will reduce significantly. The concept is applied to experimental rigs with single as well as multiple balancing planes and supported on either side through a stiff ball bearing on a somewhat flexible foundation. The paper presents the experimental apparatus, unbalance estimation and comparison of several unbalance estimations of various scenarios. The results indicate the potentials of the proposed technique for practical applications.