DETERMINATION OF RIGID-BODY CHARACTERISTICS FROM TIME-DOMAIN MODAL TEST DATA

A new method is presented to identify the characteristics of a rigid body and its supports, such as the center of gravity, the moment of inertia, and the stiffness and damping matrices, based on the measured time domain vibration data. Transformation matrices are formed using only the geometric co-ordinates relative to an arbitrarily selected origin to relate the pure translational measurement to both translation and rotation of the rigid body system. The rigid body modes and mode shapes, carefully selected from the accurately determined modes and mode shapes (rigid body and structural), are used, together with the special matrix structure, such as symmetry. The test result shows that the center of gravity and the moment of inertia are determined with good accuracy. The simple test procedure makes it an easily implementable method in practice.