This report describes the experiments for the development of the ultrasonic underwater imaging system and the subbottom profiling system.
Subbottom profiling system using the concave cross-array type ultrasonic transducer and the mono-pulse ultrasonic waves to use the electromagnetic induction type transmitter has been built and tested.
Ultrasonic underwater imaging system using sector scanning cross-array transducer has been built and tested for offshore underwater constructions.
From the results of these experiments, we found out that the subbottom profiling system is suitable for detecting subbottom buried objects, and the ultrasonic underwater imaging system, for supervising underwater construction works and inspecting results of the works.

抄録全体を表示

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.

抄録全体を表示