Modal Identification of Truss Structures by Changing Stiffness Using Piezoelectric Actuator

Abstract

This study proposes a modal identification technique for truss structures by changing the stiffness using a piezoelectric actuator. The technique is formulated on the basis of the vibration characteristics of truss structures with a metal-sealed-type multilayer piezoelectric actuator installed in a specific truss member. The natural frequency of the truss is changed by the stiffness control of a truss member to identify the natural frequency of the truss structure; the axial stiffness of the truss member can be semi-actively controlled using piezoelectric materials and an electrical circuit. The frequency response amplitude is changed by the change of stiffness of the truss, then the change ratio of the frequency response amplitude can be used to identify the natural frequency of the truss, and then the excitation data are not required to be measured. The method is appropriate for the identification of space structures in orbit in the case when excitation data are not fully available because of unknown excitation forces and disturbances. Experimental demonstrations of the identification of the first bending modal frequency of a 10-bay truss with a piezoelectric actuator are presented. It is found that the estimated natural frequency is in good agreement with the exact frequency, even though excitation force data are not provided. Furthermore, the factors causing the identification error are discussed through theoretical sensitivity analyses. The results show that the identification error can be reduced when the frequency response amplitude of a specific excitation frequency derived from the natural frequency is used for the identification.