• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.355-361
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• 2000

In this study, active control magnetic actuator for reducing vibration of rotor system is performed. Identification, modeling, simulation, control system design, and evaluation of active magnetic damper system have been researched. Power amplifier modeling, connected magnetic actuator and augmented by system identification, is included to establish a magnetic damper simulation which provides close performance correspondence to the physical plant. A magnetic actuator, digital controller using DSP(Digital Signal Processor), and bipolar operational power supply/amplifiers are developed to show the effectiveness of reducing rotor vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent components is developed. Two kinds of test are executed as sliding and oil bearing. Results presented in this paper will provide a well-defined technical parameters in designing magnetic damper system for the proposed rotor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.439-443
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• 2006

In this paper, a design of milli-gripper using piezoelectric actuator and flexible hinge structure has been suggested, and the dynamic characteristics of the milli-gripper has been analysed and improved. The milli-gripper consists of the operating and amplifier parts, and the perfomance of the gripper be heavily influenced by base excitation disturbances. The dynamic characteristics of milli-gripper has been measured by the FRF based on experimental modal analysis. It has been found by a series of experiments that the performance of the milli gripper using PID control is made a remarkable improvement in terms of gripping forces.

• Wind and Structures
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• v.15 no.3
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• pp.263-283
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• 2012

This paper presents a framework of nonlinear dynamic analysis of a low-speed moving maglev (magnetically levitated) vehicle subjected to cross winds and controlled using a clipped-LQR actuator with time delay compensation. A four degrees-of-freedom (4-DOFs) maglev-vehicle equipped with an onboard PID (Proportional-Integral-Derivative) controller traveling over guideway girders was developed to regulate the electric current and control voltage. With this maglev-vehicle/guideway model, dynamic interaction analysis of a low-speed maglev vehicle with guideway girders was conducted using an iterative approach. Considering the time-delay issue of unsynchronized tuning forces in control process, a clipped-LQR actuator with time-delay compensation is developed to improve control effectiveness of lateral vibration of the running maglev vehicle in cross winds. Numerical simulations demonstrate that although the lateral response of the maglev vehicle moving in cross winds would be amplified significantly, the present clipped-LQR controller exhibits its control performance in suppressing the lateral vibration of the vehicle.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.9
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• pp.663-670
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• 2003

As the micro-technologies in the high precision manufacturing processes are developed, the demand for micro actuating device is increasing. But, it is difficult to achieve high resolution and wide operating range simultaneously with the conventional actuating systems which are contacting and type of dual servo system. So, the contact-free surface actuators whose movers are suspended or levitated were proposed. These systems can be applied to high precision stages and alignment apparatuses. The suspended mover can be assumed to be rigid body, but the mover is a structure in this study, therefore the vibration caused during the operating process has a serious adverse effect on the performance and it is very important to identify the vibrational characteristics. In this paper, a contact-free surface actuator is modeled in finite element method and updated by using the experimental modal data. Finally, the static and dynamic characteristics of the finite element model are predicted and then discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.630-637
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• 2003

This paper proposes a new modeling scheme to describe the hysteresis and the dynamic characteristics of piezoelectric actuators in the inchworm and develops a control algorithm for the precision motion control. From the analysis of piezoelectric actuator behaviors, the hysteresis can be described by the functions of a maximum input voltage. The dynamic characteristics are also identified by the frequency domain modeling technique based on the experimental data. For the motion control, the hysteresis behavior is compensated by the inverse hysteresis model. The dynamic stiffness of an inchworm is generally low compared to its driving condition, so mechanical vibration may degenerate the motion accuracy of the inchworm. Therefore, the sliding mode control and the Kalman filter are developed for the precision motion control of the inch-warm. To demonstrate the effectiveness of the proposed modeling schemes and control algorithm, experiment validations are performed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.770-774
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• 2003

We propose the re-design method of modal parameters to depress the 2nd resonance peak of the ultra-slim-height optical pick-up actuator. With the addition of tile counter mode near the 2nd resonance frequency, we can achieve the gain margin which is sufficient to meet the system requirement. It would alleviate the burden of the additional filter for a high-speed drive.

• KIEE International Transaction on Systems and Control
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• v.2D no.2
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• pp.65-71
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• 2002

In this paper, an experiment for the active vibration control of a cantilever beam uses electromagnet as an actuator and uses a laser sensor to measure the position of the bending beam, constituting a non-contacting control system. A mathematical model of the overall system is derived to analytically design an appropriate controller. Dynamic equations of the electromagnetic actuator and the beam are combined to find the transfer function from the actuator to the sensor. The effectiveness of the obtained model is verified by various experiments and an improper PID controller is designed based on the obtained model. According to analysis, the coefficient of the derivative controller is the most important parameter for handling the performance and the stability margin of the control system. The experimental results of the active control system are compared with those of the open loop system.

• 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 the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.139-146
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• 2009

In this study, an assessment is made for the helicopter vibration reduction of composite rotor blades using an active twist control concept. The piezoceramic shear actuation mechanism along with elastic couplings of composite blades is used for vibration reduction. The rotor blades are modeled as composite box-beams with actuator layers bonded on the outer surfaces of the thin-walled section. The governing equations of motion for helicopter blades are obtained using Hamilton's principle. A time domain unsteady aerodynamic theory with free wake model is used to obtain the airloads. Various rotor configurations with different elastic couplings with appropriate actuator placement are used to investigate the hub vibration characteristics. Numerical results show that a substantial reduction of $N_b$/rev hub vibration can be achieved using the optimal control algorithm.

• Journal of Mechanical Science and Technology
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• v.19 no.7
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• pp.1414-1423
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• 2005

This paper develops and evaluates several strategies for structural vibration control with the objective of attenuating broadband noise inside a rectangular enclosure. The strategies evaluated include model-independent collocated control, model-based feedback control and a new 'modal-estimate' feedback strategy. Collocated control requires no knowledge of model parameters and enjoys the advantage of robustness. However, effective broadband noise attenuation with colocated control requires a large number of sensor-actuator pairs. Model-based con-trollers, on the other hand, can be theoretically effective even with the use of a single actuator. However, they suffer from a lack of robustness and are unsuitable from a practical point of view for broadband structural vibration applications where the dynamic models are of large order and poorly known. A new control strategy is developed based on attenuating a few structural vibration modes that have the best coupling with the enclosure acoustics. Broadband attenuation of these important modes can be achieved using a single actuator, a limited number of accelerometers and limited knowledge of a few modal functions. Simulation results are presented to demonstrate the effectiveness of the developed strategy.