The collocated feedback is the direct negative definite feedback for flexible structures of velocities and/or displacements measured by sensors collocated with actuators, and preserves robust stability of the closed-loop systems. But, generally it does not insure sufficient low sensitivities for uncertainties or input disturbances ; therefore, an improvement for low sensitivities is necessary. In this paper, we show the condition of the Robust Model Matching to increase the dampings of the elastic oscillation by the collocated feedback and lessen the sensitivities simultaneously. Then we show experimental results using a flexible arm apparatus and discuss the performance.
