SELF-IDENTIFICATION EXPERIMENTS USING VARIABLE INERTIA SYSTEMS FOR FLEXIBLE BEAM STRUCTURES

摘要

The concept of self-identification and its feasibility are experimentally investigated. The modal parameters changed multiple times by the control input of variable inertia parameter are used to obtain linear equations about unknown structural parameters to overcome the lack of modes. We derive the controllability of the modal parameters as the requested conditions for implementing self-identification using sensitivity analyses of the modal parameters with respect to the control input. Also, a criterion for the self-identification is proposed to measure the controllability. Then, the self-identification experiments are performed to examine the present method using a flexible cantilevered beam structure with variable inertia systems, which include controllable additional mass attached to the beam. As a result, the bending stiffness and mass per unit length of the test beam are accurately identified when the controllable and observable lower modes are appropriately excited by input force and their changes due to the variable inertia are accurately estimated from the combinations of a few strain gage sensors output and a cubic spline interpolation technique. The results also indicate that the identification accuracy of higher modes is affected by the accuracy of the estimated controllable mode shape, which is sensitive to the locations of sensors. As the proposed criterion is larger, the identification accuracy becomes more insensitive to the estimation error of the mode shapes.