• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.12
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• pp.1942-1949
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• 2004

SLA(Scanned Linear Array) is a portable display unit for implementing next-generation virtual realities, utilizes a design that light generated by a line of LEDs is reflected from the rapidly oscillating mirror to generate a raster display. Reaction forces generated by the motions of the mirror and counter-balance mass cancel each other at the device base, reducing vibration. Metal leaf springs have been extensively applied in such portable units. Magnetic springs have been developed and adopted that can replace the metal spring and can avoid many disadvantages of metal springs. We model and analyze the dynamics of the structure with magnetic springs and present the simulation and experimental analysis results, which can be utilized for identifying and eliminating possible problem sources in removing shaking forces and moments, and oscillating the mirror at the required amplitude and frequency. Finally, we present the improved novel magnetic actuator model which can be applied in portable display units.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.223-229
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• 2016

This study proposes a new technology for a smart damper with flag-shaped behavior using the combination of magnetic friction and rubber springs. The magnet provides friction and, thus, energy dissipation, and the rubber springs with precompression contribute to present self-centering capacity of the damper. To verify their performance, this study conducts dynamic tests of magnet frictional dampers and precompressed rubber springs. For the purpose, hexahedron Neodymium (NdFeB) magnets and polyurethane rubber cylinders are used. In the dynamic tests, loading frequency varies from 0.1 to 2.0 Hz. The magnets provide almost perfect rectangular behavior in force-deformation curve. The rubber springs are tested without or with precompression. The rubber springs show larger rigid force with increasing precompression. Lastly, this study discusses combination of rigid-elastic behavior and friction to generate 'flag-shaped' behavior for a smart damper and suggests how to combine the magnets and the rubber springs to obtain the flag-shaped behavior.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.481-486
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• 2012

We discuss the design, fabrication, and testing of a large-displacement electromagnetic actuator with the meander springs partially exposed to a magnetic field. We compared two prototypes: a prototype (F) of the conventional actuator with the meander springs fully exposed to a magnetic field and a prototype (P) of the proposed actuator with the meander springs partially exposed to a magnetic field. For a 5 Hz square input current varying from 10.40 mA, P showed an increase of $16.9{\pm}1.2%$ in the amplitude, which was greater than the increase in the case of F. Thus, we experimentally demonstrated the large-displacement actuation performance of the proposed actuator in a small volume and at low currents (below 40 mA). The proposed electromagnetic actuator can be used for low-power and large-displacement manipulation of optical switches and optical choppers.

• ETRI Journal
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• v.28 no.3
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• pp.389-392
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• 2006

In this letter, a laterally-driven bistable electromagnetic microrelay is designed, fabricated, and tested. The proposed microrelay consists of a pair of arch-shaped leaf springs, a shuttle, and a contact bar made from silicon, low temperature oxide (LTO), and gold composite materials. Silicon-on-insulator wafers are used for electrical isolation and releasing of the moving microstructures. The high-aspect-ratio microstructures are fabricated using a deep reactive ion etching (DRIE) process. The tandem-typed leaf springs with a silicon/gold composite layer enhance the mechanical performances while reducing the electrical resistance. A permanent magnet is attached at the bottom of the silicon substrate, resulting in the generation of an external magnetic field in the direction vertical to the surface of the silicon substrate. The leaf springs show bistable characteristics. The resistance of the pair of leaf springs was $7.5\;{\Omega}$, and the contact resistance was $7.7\;{\Omega}$. The relay was operated at ${\pm}0.12\;V$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.359-364
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• 2013

In order to use a linear vibration motor for the actuator of a haptic interface, the motor must provide a higher reaction rate and longer service life than typical rotational motors with an eccentric mass. In this paper, we propose a linear vibration motor that is equipped with a voice-coil actuator and permanent-magnet springs. To concentrate the magnetic flux in the actuator, a Halbach-style magnetization pattern is used. Permanent-magnet springs replace mechanical springs to help increase the service life. We use the method of equivalent current sheets and the method of images to analyze and model the proposed vibration motor. These methods are validated using finite element analyses and experiments. A prototype motor is designed and fabricated. Tests with the prototype show the feasibility of the proposed linear vibration motor.

• Journal of Power System Engineering
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• v.17 no.2
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• pp.63-69
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• 2013

Most washing machines are now produced as a drum-type, where a washing drum mounted on a suspension system with springs and dampers, to minimize the transmittance of the vibration from the drum to the frame. A low-cost MR damper, using magneto-rheological fluids, can produce variable damping forces by changing the current values in the magnetic coil. Experimental results show the comparison of the vibration attenuation performances between two different dampers. One test set-up uses a passive damper and another one uses a MR fluid damper. The test results showed that the vibration amplitude of the washing machine with the MR damper is much smaller than the case with the passive damper.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1985-1987
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• 2002

Silicon bulk micromachined micromirrors are designed and fabricated for out-of-plane right angle reflection. The micromirror is comprised of a minor plate, springs, magnetic bars and electrodes. Single crystalline silicon is used for a flatness improvement of a mirror plate. Out-of-plane right angle reflection requires a 45 degree operation of the micromirror. The micromirrors are operated by applying a magnetic field, which is generated by a coil located below a substrate. For an individual mirror operation, each mirror is clamped using an electrostatic force against the electromagnetic force. Angular deflections are measured and compared with theoretical data. The micro mirror operates up to 45 degree when magnetic field is 4 kA/m which is generated by a 115 mA coil current Simple addressing is tested, and it is shown that a clamping voltage is less than 5V.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.47-55
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• 2012

This work deals with dynamic analysis of a monorail system with magnetic caterpillar where magnets are embedded inside each articulated element of the caterpillar, augmenting traction force of main rubber wheels to climb up slope up to 15 degree grade. Considerations are first given to determine stiffness of the primary and secondary suspension springs in order for the natural frequencies of car body and bogie associated with vertical, pitch, roll and yaw motion to be within generally accepted range of 1-2 Hz. Equations for calculating magnetic force needed to climb up given slope are derived, and a magnetic caterpillar system for 1/6 scale monorail is designed based on the derivation. To assess the hill climbing ability and cornering stability, and make sure smooth operation of the side and vertical guiding wheels which is critical for safety, a multibody model that takes into account of every component level design characteristics of car, bogie, and caterpillar is set up. Through hill climbing simulation and comparison with measurement of the limit slope, the validity of the analysis and design of the magnetic caterpillar system are demonstrated. Also by studying the curving behavior, maximum curving speed without rollover, functioning of lateral motion constraint system, the effects of geometry of guiding rails are studied.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.60-67
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• 2001

As a method of variable valve train(VVT), Electro-Mechanical Valve(EMV) has been studied. Compared with conventional VVT system, the EMV system has a relatively simple structure. The system has two electromagnets, springs and an armature. The system can be operated by reciprocal action between armature and two electromagnets. And, the operating event can be controlled by electrical signal from controller. Therefore, reduction of emission and fuel consumption can be achieved through valve event control at each engine operating condition. In this study, characteristics of EMV system were investigated by simulations and experiments. The results of simulation and experiment show that the core shape and material characteristics are dominant parameters on magnetic force and delay time. In order to apply the system to commercial engine, it has a compact size and high stiffness springs(50N/mm) to increase the valve speed. Because of high valve seating velocity, loud noise and high impact force generated, which can lead to reduction of actuator durability. Therefore, further research is required to reduce valve seating velocity.

• International journal of steel structures
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• v.18 no.4
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• pp.1325-1335
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• 2018

This study dealt with investigating the seismic performance of the smart and shape memory alloy (SMA) and magnets plus rubber-spring (MRS) dampers and their effects on the seismic resistance of multiple-span simply supported bridges. The rubber springs in the MRS dampers were pre-compressed. For this aim, a set of experimental works was performed together with developing nonlinear analytical models to investigate dynamic responses of the bridges subjected to earthquakes. Fragility analysis and probabilistic assessment were conducted to assess the seismic performance for the overall bridge system. Fragility curves were then generated for each model and were compared with those of as-built. Results showed dampers could increase the seismic capacity of bridges. Furthermore, from system fragility curves, use of damper models reduced the seismic vulnerability in comparison to the as-built bridge model. Although the SMA damper showed the best seismic performance, the MRS damper was the most appropriate one for the bridge in that the combination of magnetic friction and pre-compressed rubber springs was cheaper than the shape memory alloy, and had the similar capability of the damper.