The smart passive system consisting of a magnetorheological (MR) damper and an electromagnetic induction (EMI) part
has been recently proposed. An EMI part can generate the input current for an MR damper from vibration of a structure
according to Faraday's law of electromagnetic induction. The control performance of the smart passive system has been
demonstrated mainly by numerical simulations. It was verified from the numerical results that the system could be
effective to reduce the structural responses in the cases of civil engineering structures such as buildings and bridges. On
the other hand, the experimental validation of the system is not sufficiently conducted yet. In this paper, the feasibility of
the smart passive system to real-scale structures is investigated. To do this, the large-scale smart passive system is
designed, manufactured, and tested. The system consists of the large-capacity MR damper, which has a maximum force
level of approximately ±10,000N, a maximum stroke level of ±35mm and the maximum current level of 3 A, and the
large-scale EMI part, which is designed to generate sufficient induced current for the damper. The applicability of the
smart passive system to large real-scale structures is examined through a series of shaking table tests. The magnitudes of
the induced current of the EMI part with various sinusoidal excitation inputs are measured. According to the test results,
the large-scale EMI part shows the possibility that it could generate the sufficient current or power for changing the
damping characteristics of the large-capacity MR damper.
KEYWORDS: Electromagnetic coupling, Control systems, Magnetism, Control systems design, Electromagnetism, Sensors, Head, Manufacturing, Bridges, Buildings
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.
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