Open Loop Response Identification During Non-Stationary Operation of Actively Controlled Rotating Systems

Abstract. One of the challenges in designing actively controlled rotating systems is finding the appropriated controller gains of the feedback system. Some strategies of finding the controller gains require that the open loop response of the system be known or identified experimentally. This can be done by exciting the system in a given rotating speed (stationary condition). However, the most critical situations that justify controlling occur during run-up and run-down (non-stationary conditions). In these non-stationary conditions, unbalance strongly affects the results and must be considered in the analysis. In this work, one presents a methodology for identifying the open loop response of an actively controlled rotating system during non-stationary conditions. One takes advantage of the fact that, in these conditions, frequency changes with time and can be used for exciting the system. Unbalance can be disregarded in signal processing by measuring the unbalance response during run-up and forced + unbalance response during run-down. Experimental results show the feasibility of finding the open loop response of the system after a single run-up and run-down operation. Phase identification is critical and some precautions during the response measurement procedure are suggested. At the end, the obtained open loop response functions can be further used to find the controller gains of the system for non-stationary operation.