Identification method for excitation force of rigid body vibration source by physical parameter identification (Method by characteristic matrix identification without using force signals)

Abstract

This paper proposes an identification method for the excitation force of a rigid body vibration source. This is done by constructing a characteristic matrix without a force signal during a preliminary excitation test. In mechanical products, if an abnormal vibration such as excessive vibration occurs after machine assembly, reworking is necessary to rectify the problem. This extends of the development period and increases cost. Therefore, quantitative vibration prediction at the design state is important. In order to predict quantitative vibration, it is necessary to understand the excitation force of the vibration source. The proposed method of excitation force does not use a force signal during the preliminary excitation test. Therefore, there is no restriction on the vibration method in the preliminary vibration test, and it solves the problem in the case where the excitation point cannot be secured. In this method, the modal mass is calculated using a rigid body mode vector of 6 degrees of freedom (acquired during the preliminary vibration test) and the mass of the vibration source. Then, after determining the mass normalized mode vector from the calculated modal mass, the characteristic matrix of the rigid body vibration source is identified. Finally, the excitation force when the machine is running is identified from the equation of motion in the frequency domain. As a result of testing the verify the validity of the method, the proposed method can identify the excitation with the same precision as when using the force signal and has demonstrated its usefulness.