Natural frequencies and mode shapes are to important modal information that define the system. If the real system and FE(finite element) model don`t have the same local physical parameters, there will be a difference between modal data from real system and FE model. Because there is little difference in displacement mode shapes measured by accelerometers, modal updating based on displacement mode shapes contaminated by measurement errors may not be successful. In this research, strain mode shapes are used as modal informations because the strain mode shapes measured by strain gauges are more sensitive than the displacement mode shapes with respect to the change of parameters concerned in the FE stiffness matrix. We modified the system to increase the sensitivity of the strain mode shapes with respect to the change of parameters using feedback control. The modification makes it possible to update the FE model with more precision in computer simulation. Finally, through experiment using a cantilevered beam, we verified that the model updating using strain mode shapes is more precise compared to the one using displacement mode shapes.
