Automatic modal balancing of flexible rotors during operation by using a single balancing head

Abstract

In this dissertation, modal unbalance control of a flexible rotating shaft using a wireless controlled balancing head is considered, and experiments on mannul and automatic balancing controls are performed with a general isotropic rotor bearing system during operation. Theoretical analysis for the possibility of single plane balancing head is also developed for general isotropic rotor bearing systems. In order to obtain modal data of the rotor bearing system, an efficient matrix reduction technique is developed by using the modal data of the isotropic undamped stationary parts. This method attains significant reduction in computation time and core size, while maintaining the accuracy and the flexibility in use. It does not require any intuition on mass lumping, mode selection and iterative procedures to improve the transformation matrix, necessitating only minor modifications to the existing FEM technique. The determination of an effective balancing head location is an important problem since modal properties are changed by imbedding the head. To determine the optimal location and the amount of correction unbalance required, the change in modal properties due to the presence of the balancing head has to be completely examined, which is often laborious and time consuming. A simple and effective method to determine the optimal location of the balancing head and the amount of correction unbalance adopting a Structural Dynamics Modification (SDM) approach, is presented. For the purpose of controlling flexible rotors at high speeds, much considration should be taken into account in designing the balancing head. A wireless controlled head is designed and constructed. The wireless controlled balancing head is simple to transfer the control data and strong enough to endure upto 5000 rpm. The detail analyses required in designing the head and in operating the control unbalances are also discussed. The experimental works with the balancing head are performed to overcome ...