A new practical modal method for rotor balancing

A new practical modal balancing technique, which uses the modal ratio among measurement points (MRMP coefficient), has been developed. This new method is an improvement upon traditional modal balancing when the rotor to be balanced operates at the speed between the first and second critical speeds. The concept of the MRMP coefficient is introduced for the first time in this paper, on the basis of which the rotor-bearing system can be balanced at any one rotational speed between the first and second critical speeds by decomposing the modal components of unbalance and response simultaneously. Moreover, only one test run is required in three of the four balancing schemes provided in this paper to balance the rotor. In the new method, the test weights need not be orthogonal, so prior modal function knowledge is not necessary for calculation of the test weights, as required in the traditional modal balancing method. To verify the validity of the new technique, a balancing experiment using a rotating cantilever rotor is carried out. The results show that the new method can be applied effectively in field balancing.