Recently, vibration requirements are getting stricter as precise equipments need more improved vibration environment to
realize their powerful performance. Though the passive pneumatic vibration isolation tables are frequently used to
satisfy the rigorous vibration requirements, the specific vibration problem, especially continuous sinusoidal or periodic
vibration induced by a rotor system of other precise equipment, a thermo-hygrostat or a ventilation system, is still left.
In this research, the application procedure of Filtered-X LMS algorithm to pneumatic vibration isolation table with
piezo-stack actuators is proposed to enhance the isolation performance for the continuous sinusoidal or periodic
vibration. In addition, the experimental results to show the isolation performance of proposed system are also presented
together with the isolation performance of passive pneumatic isolation table.
Magnetorheological (MR) dampers are one of the most advantageous control devices for civil engineering applications to
natural hazard mitigation due to many good features such as small power requirement, reliability, and low price to
manufacture. To reduce the responses of a structural system by using MR dampers, a control system including a power
supply, control algorithm, and sensors is needed. The control system becomes complex, however, when a lot of MR
dampers are applied to large-scale civil structures, such as cable-stayed bridges and high-rise buildings. Thus, it is
difficult to install and/or maintain the MR damper-based control system. To overcome the above difficulties, a smart
passive system was proposed, which is based on an MR damper system. The smart passive system consists of an MR
damper and an electromagnetic induction (EMI) system that uses a permanent magnet and a coil. According to the
Faraday law of induction, the EMI system that is attached to the MR damper can produce electric energy and the
produced energy is applied to the MR damper to vary the damping characteristics of the damper. Thus, the smart passive
system does not require any power at all. Besides the output of electric energy is proportional to input loads such as
earthquakes, which means the smart passive system has adaptability by itself without any controller or sensors.
In this paper, the integrated design method of a large-scale MR damper and Electromagnetic Induction (EMI) system is
presented. Since the force of an MR damper is controllable by altering the input current generated from an EMI part, it is
necessary to design an MR damper and an EMI part simultaneously. To do this, design parameters of an EMI part
consisting of permanent magnet and coil as well as those of an MR damper consisting of a hydraulic-type cylinder and a
magnetic circuit that controls the magnetic flux density in a fluid-flow path are considered in the integrated design
procedure. As an example, a smart passive control system for reducing stay cable responses is considered in this
investigation and it will be fabricated and tested through experiment in the future.
Terfenol-D is one of magnetostrictive materials with the property of converting the energy in magnetic field into mechanical motion, and vice versa. We designed and fabricated a linear magnetostrictive actuator using Terfenol-D as a control device. In order to grasp the dynamic characteristics of the actuator, a series of experimental and numerical tests were performed. Induced-strain actuation displacements of the actuator measured by the test and predicted by magnetic analysis agreed well. And blocked forces according to the input currents were estimated from the testing results. Modeling method representing the exerting force of the actuator was confirmed through some testing results. We also explored the effectiveness of the linear magnetostrictive actuator as a structural control device. A series of numerical and experimental tests was carried out with simple aluminum beam only supported at each end by the actuator. After the equation of motion of the controlled system was obtained by the finite element method, a model reduction was performed to reduce the numbers of degree of freedom. A linear quadratic feedback controller was realized on a real-time digital control system to damp the first four elastic modes of the beam. Through some tests, we confirmed the possibility of the actuator for controlling beam-like structures.