Abstract
This paper is concerned with an active control system using piezoelectric actuators to isolate vibrations which are transmitted from machines to hull plates in ships. First, a large size multilayer piezoelectric actuator with a cross section of 30 × 40 mm was developed. Even under a dead load of 5 tons it can expand and contract to a magnitude of 70% as much as it can under no load. Secondly, a stable control method to isolate random vibration was derived for a two degree-of-freedom model. The piezoelectric actuator was inserted in the supporting system of an excited mass and driven by the feedback signal based on the acceleration of the mass and the force transmitted through the actuator. As the feedback signal represents the double integrated value of the exciting force which is independent of the movement of the actuator, the control is stable. Vibration isolation was further improved by the addition of active damping based on the transmitted force to the control system. Finally, experimental results were shown in which the transmitted force was reduced by 20 to 40 dB.
