Rotor unbalance is a basic concern in the design and operation of machinery because it is a major cause of excessive vibration. An early flexible- rotor balancing technique, was based on mode shapes (modal method). Moore demonstrated the practical application of the method to heavy rotating equipment. The controversy between modal and influence coefficient methods began with Goodman's formulation in 1962 of the influence coefficient methods Thearle for flexible rotors.
The exact-point speed method, which was developed for multiple planes and speeds, evolved into the least squares method. This method depends heavily on computers, good measurements, and rigid procedures whereas the modal approach involved physical insight. In the late 1970s, the opposing factions, represented by Parkinson of the U.K., an advocate of the modal method, and Smalley of the U.S., an advocate of the influence coefficient method, worked together to develop the unified method of flexible rotor balancing. This method includes aspects of both the modal and influence coefficient methods.
This presentation brings about in order to find out how to balance a flexible rotor.