Parameter identification of a rigid body with flexible appendages using sensitivity analysis.

For the attitude and vibration control of a flexible structure, such as a spacecraft having flexible appendages, it is important to know design parameters such as the moment of inertia and the location of the center of gravity. But, generally, it is very difficult to calculate these design parameters in the case of a structure whose configuration is very complex. Thus, it is necessary to develop a technique to determine these parameters from vibration test data. The test data of a flexible structure such as natural frequencies, modal damping ratios, and mode shapes are different from those of a structure regarded as a rigid body, because of the interaction between a rigid body motion and flexible appendage motions. Therefore, this paper proposes a method of direct identification of these parameters from vibration test data measured in the state in which a flexible structure is supported by elastic mounts. The method is based on the motion equation taking into account elastic deformation of flexible appendages. The usefulness of the proposed method is illustrated by carrying out identification of a calculation model and an actual simple structure composed of a rigid body and two flexible appendages.