Improvement of Control Performance Concerning an Anti-Vibration Unit with Piezo-Element

Anti-vibration units have been developed to realize micro-vibration circumstance. Recently, the anti-vibration units using the piezo-elements have been widely developed. In these units, acceleration sensors were ordinarily used. However, in the literature 3), velocity sensors were attached to detect the vibration of structure. Then, the state-feedback theory was naturally applicable to the anti-vibration unit because both the velocity and displacement signals derived by integral action for the velocity could be used. While, the acceleration signal was not utilized as a feedback signal because its signal was not the state variable under the state feedback theory. However, more advanced performance concerning the transmissibility from the vibration of floor to that of isolated table has been expected by using the acceleration signal. In this paper, we propose to utilize the acceleration signal based on the state-feedback theory so as to improve the frequency response of the transmissibility. First, the acceleration signal is passed through a first-order lag filter with small time constant and its filter's output is inserted into the equation of motion. Next, the state-feedback theory is applied to this equation of motion. Finally, the derived controller becomes PID compensator for the velocity signal and it is shown that the feedback coefficients of the PID can be determined by using the optimal regulator design theory.