The Identification of the Modal Parameters of Orbital Machines using Dynamic Structural Approach

Document Type: Research Paper


Department of Mechanical Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran


The researcher measured the least number of frequency response functions required for the identification of modal parameters, in order to simplify the identification of modal properties of such systems. In this work, the orbital machines are supposed to be a combination of orbital and non-orbital components. Structural Approach specified the identification of dynamic properties only to those phrases that contain responses to a driving force. It has been revealed that the identification of dynamic properties distinguishes the orbital and non-orbital components of the structures and as a result, non-symmetric sections of the space coordinate matrixes become obvious. The application of the above approach was examined on two different structures. The first examination was on a computer-simulated rotor model with four degrees of freedom. In this case, the theoretical properties of this approach were evaluated, while the noise factor was disregarded. The second examination was done on a true machine, whereby the probable problems of the implementation of the suggested approach were clarified. The complete modal identification of an orbital system takes place without the need to measure a complete row of FRF matrixes. The number of the elements to be measured in an FRF matrix depends on the number of degrees of freedom of the system and on the non-symmetric sections of the stuffiness and damping matrixes. The number of elements of the left specific axis that should be measured directly from the evaluated data depends on the matrix sub-ranks, which is composed of non-symmetric sections of space-featured matrixes.