Kazuto Seto

Development of Seismometer-Type Absolute Displacement Sensor Aimed for Detecting Earthquake Waves With Large Magnitude and Long Period

This paper proposes a novel seismometer-type absolute displacement sensor aimed at detecting earthquake waves with a large magnitude and long period. However, since the measuring range of the displacement sensor is higher than the natural frequency of itself, it is difficult to detect a low frequency vibration below 1 Hz using conventional seismic-type displacement sensors.In order to provide an absolute displacement detection which is capable of lowering the natural frequency and enlarging the detectable amplitude without causing a structural defect, the relative signals of displacement, velocity, and acceleration between a detected object and the auxiliary mass of the sensor are fed back into the sensor. In addition, phase lag compensation is inserted to adjust phase angles, which are below a frequency lower than 1Hz.It has been demonstrated that a developed sensor with a small size and lightweight has a detecting range from 0.2 Hz to 10Hz for absolute displacement and velocity. As an additional advantage, the measurement displacement amplitude has been expanded to about 40dB (100 times) for detecting earthquake waves with large magnitude and long period.© 2012 ASME

403 Performance Evaluation of Complementary Connected Control Method for a Combination of Three-dimensional Base-isolated and Conventional Structures

In this paper, a novel combination of structures for connected-control mechanism(CCM) is presented. By coupling base-isolation and ordinary structures, the vibration suppression effect of CCM is expected to be expanded, while the stroke of base-isolation layer is hopefully suppressed. Experimental structures and CCM mechanism using magnetic dampers are built and excitation experiments are carried out. The effectiveness of CCM applied to base-isolation and ordinary structures is confirmed.

Levitation and Vibration Supression of an Elastic Rotor by Using Active Magnetic Bearings

This paper presents a novel modeling method and a control system design procedure for a flexible rotor with many elastic modes using active magnetic bearings. The purpose of our research is to let the rotor rotate passing over the 1st and the 2nd critical speeds caused by flexible modes. To achieve this, it is necessary to control motion and vibration of the flexible rotor simultaneously. The new modeling method named as Extended Reduced Order Physical Model is presented to express its motion and vibration uniformly. By using transfer function of flexible rotor-Active Magnetic Bearings system, we designed a local jerk feedback control system and stability analysis by using root locus is carried out. Levitation experimentation is performed and stable levitation and significant vibration suppression effect is achieved.Copyright

Control System Design for Active Isolator Taking Dynamical Property of Elastic Load Into Account

This paper deals with the control system design for active isolation table[1][2][3]. It aims at controlling vibration of the installed object and isolation table. An experimental isolation table with flexible loaded object is built. Control simulations are carried out by using feedback controller designed according to sub-optimal control theory.Copyright

Modeling and Vibration Control of a Flexible Rotor by Using Magnetic Bearings

This paper presents a new modeling method and a control system design procedure for a flexible rotor with many elastic modes using active magnetic bearings. The purpose of our research is to let the rotor rotate passing over the 1st and the 2nd critical speeds caused by flexible modes. To achieve this, it is necessary to control motion and vibration of the flexible rotor simultaneously. The new modeling method named as Extended Reduced Order Physical Model is presented to express its motion and vibration uniformly. By using transfer function of flexible rotor-Active Magnetic Bearings system, we designed a Local Jerk Feedback Control system and conducted stability discrimination with root locus. In order to evaluate this modeling and control method, levitation experimentation is conducted.Copyright

Modeling and Control of Active Vibration Isolation System Taking the Dynamics of Elastic Load Into Account by Using the Reduced Order Physical Model

This paper deals with the control system design for active isolation table[1][2][3] . It aims at controlling vibration of the installed object and isolation table. An experimental isolation table with flexible loaded object is built. Control simulations are carried out by using feedback controller designed according to LQ optimal control theory.Copyright

Research on Complementary Connected Control Method of Two-Axes for a Combination of Base-Isolated and Conventional Structures

In this paper, a novel combination of structures for connected-control mechanism (CCM) is presented. By coupling baseisolation and ordinary structures, the vibration suppression effect of CCM is expected to be expanded, while the stroke of base-isolation layer is hopefully suppressed. Experimental structures and CCM mechanism using magnetic dampers are built and excitation experiments are carried out. The effectiveness of CCM applied to base-isolation and ordinary structures is confirmed.Copyright