Development of a Measurement System for Analyzing Periodic External Forces Acting on Rotating Machineries

In this study, a measurement system is developed to analyze periodic external forces acting on a rotating machinery. The dynamics of a rotating machineries are influenced by various periodic external forces such as unbalanced forces, oil film forces at a journal bearing, and seal contact forces. The characteristics of periodic external forces are dependent on the rotating conditions, rotational speed, and rotating orbit of the rotating shaft. The proposed system employs an active magnetic bearing (AMB), which is implemented using an adaptive feed-forward cancellation (AFC). The use of AFC ensures that the proposed system can realize the desired harmonic orbit assuming actual operations under the periodic external forces. Moreover, AFC can measure the periodic external forces in real-time using an adaptive algorithm. The effectiveness of the proposed system is verified experimentally. Experimental results show that the control system can control the rotating shaft to an accuracy of micrometer order using the implemented AFC. The measurement error of the periodic external forces acting on the rotating system is less than 2%.