• Journal of KSNVE
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• v.8 no.4
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• pp.683-689
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• 1998

A control algorithm for multi-stage dampers is developed based on the mode skyhook control concept, and implemented on the full vehicle system environment. The test vehicle system is equipped with the real time controller, four-stage variable dampers and sensors. The real time controller is developed using a digital signal processor(DSP), digital I/O, A/D and D/A converters. The dampers are driven by the electromagnetic actuators of less than 20 msec response time. The sensors include accelerometers, relative displacement transducers, and steering wheel rate sensors, etc. Through a series of tests in laboratory and proving ground, the performance of the semi-active suspension system is evaluated and it is shown that the vehicle dynamic characteristics is improved with the developed damping system. Futhermore, the parameter tuning methods to enhance vehicle dynamic performance are propsoed.

• Journal of KSNVE
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• v.9 no.3
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• pp.577-586
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• 1999

Estimation of damping ratio for vibration signals measured on the passenger car's sear is useful for the objective evaluation of impact harshness in car. The vibratio signal is a transient signal represented by many coupled modes of suspension system. Wavelet transform automatically decouples these modes in the time-frequency domain. Damping ratios for decoupled modes are obtained by logarithmic treatment for the Wavelet transformed signal. The objective evaluation using Wavelet transform has been well corresponded with subjective evaluation done by skilled engineers.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.263-263
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• 2000

Electromagnetic Suspension(EMS) System produces no noise, friction and heat through non-contacting operation Therefore, the applicable device using EMS system has a lot of attraction in case of the high-speed and non-contacting transmission EMS with nonlinear properties requires a precise airgap position control and stable kinematics characteristics under the disturbances, In this study, the nonlinear system was linearized by a Nonlinear Feedback Lineariztion(NFL) method. The NFL method requires that the modelling should be exact, and the state variables should be measured and a rapidly operating controller be necessary on account of a heavy data calculating In the experiments. the ideal control characteristics of the NFL was acquired through simulation at first. then the characteristics of the actual system were compared with those of simulation. In addition, the results by NFL were examined and analysed considering the characteristics of the PID control. The Control by NFL shows much stable control characteristics than the PID control. Whereas, the steady state errors occur for various disturbances. hence a robust control design is remained for a further study.

• Journal of KSNVE
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• v.5 no.1
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• pp.29-35
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• 1995

This paper presents the simultaneous optimal design of structure and LQG control systems for the improvement of riding comforts of active vehicle suspension systems. The performance index of riding comforts is extended to include frequency-weighted acceleration in the quadratic cost functional. Janeway human response curve with respect to acceleration is used to verify the usefulness of the presented method. The method is applied to a half model of an active vehicle suspension systems with elastic body moving on randomly profiled road. The values of stiffness of suspensions are used for the structural design variables. The conjugate gradient method is used for optimization. The simulated results of simultaneous optimization with frequency-weighted cost functional are compared with those without frequency- weighted cost functional.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.3
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• pp.144-153
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• 1996

The magnetic levitation system has many advantages, such as little friction, no lubrication, no noise and so on. For this reason, the magnetic levitation system is utilized in the magnetic bearing of high-speed rotor. The method to obtain magnetic force is both the repulsive suspension method and the attraction suspension method need a stabilizing controller because it is a unstable system in natural. This paper presents the design of robust stabilizing servo controller in spite of being the model uncertainties in the magnetic levitation system by $\textit{H}_{\infty}$ control theory using the free parameter. And we investigated the validity of a designed controller through results of the simulation and the actual experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.5
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• pp.100-110
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• 1995

The human subject perception response according to vertical vibration and pitching was analyzed with a five degree of freedom model. The vehicle dynamic system with the delayed colored noise excitation and the passenger perception response was arranged as an integrated viration system and could be analyzed simultaneously for seven different combination of vehicle suspension. ISO2631 and BS6841 was adapted for analyzing the passenger perception reponse. Simulation results shows that passenger feel relatively less discomfort due to pitching compared to vertical vibration and road type was not necessary to be considered as a design parameter in view of comfort analysis.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.912-918
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• 1994

Poor speech intelligibility in an air traffic control room is frequently a result of many, quite different causes and occasionally leads to complaints of the controller personnel. The paper describes a sequence of successful tasks performed in a local control room. The initial measurements included an investigation of the background noise (caused by fans, air condition, computer and radar equipment) and performance checks of the electronic audio and communication equipment with respect to the audio transmission behavior. The spectral composition of the noise as well as the characteristics of the audio communication path between the controllers and the pilots(which showed a loss of spectral information in the audio band due to built-in notch filters for the suppression of control tones) required adaptations of the amplitude behavior of the amplifiers through user adjustable tone controls. The radar console fans, which contributed significantly to the overall noise floor of the room, underwent a substantial reconstruction by replacing the tight mounting with an elastic double suspension, reducing the noise level by 50%. Finally, a possible source of untimely fatigue of the controllers during their working hours has been found in strong spectral components of the noise above the audio band, radiated by numerous video monitors in the control through vibrating components excited by the line frequency of the video signal.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.1-8
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• 2012

Multidisciplinary design optimization (MDO) for a suspension component of the vehicle front suspension was performed in this research. Shapes and thicknesses of the subframe were optimized to satisfy multi-disciplinary design requirements; weight, fatigue, crash, noise, vibration, and harshness (NVH), and kinematic and compliance (K&C). Analyses procedures of the performance disciplines were integrated and automated by using the process integration and design optimization (PIDO) technique, and the integrated and automated analyses environments enabled various types of analytic design methodologies for solving the MDO problem. We applied an approximate optimization technique which involves sequential sampling and metamodeling. Since the design variables for thicknesses should be dealt as discrete variables. the evolutionary algorithm is selected as optimization technique. The MDO problem was formulated three types of problems according to the order of priorities among the performance disciplines, and the results of MDO provided design alternatives for various design situations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.333-338
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• 2011

This paper describes the design process of floor damping material optimization to reduce structure borne noise. This process uses finite element analysis(FEA) along with experimental techniques to complement each other. The objective of this approach was to develop an optimized damping material application layout and thickness at the initial design stage. The first step is to find the sensitivity areas of vehicle body without damping material applied using FEA. In order to determine the high vibration areas of the floor panel, the velocity was measured using a scanning laser vibrometer from 20 Hz to 300 Hz. To excite the floor panel vibration, shaker was placed at the front suspension attachment point. The second step is the optimization process to determine the light weight solution of damping material. The design guideline of damping material was suggested that the lightweight solution was verified using test result of road noise. Design engineer could efficiently decide the design variable of damping material using parameter analysis results in early design stage.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.2 s.95
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• pp.135-147
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• 2005

As automobile technology advances, a smoother ride with less noise is desired. In order to achieve these purposes, a study on the vibration and noise produced by a moving automobile was carried out and a model for tire vibration characteristics which influence the ride performance was developed. The model was verified through simulations and experiments. The developed model was then applied to a half car model and automobile vibrations were analyzed. The effects of tire design parameters on the automobile vibration energy were investigated. The results from laboratory and field tests confirm the validity of the analytical model. The 17-DOF half-car model was built to analyze automobile vibration. The characteristics of the nonlinear model for a shock absorber were applied to this model. The results from the present 17-DOF half car model incorporating the analytical tire model with tire design parameters, were compared with the 5-DOF half car model where the tire was modeled with linear springs. The results of the 17-DOF model are close to the experimental results. Using the 17-DOF model, the influence of tire design parameter were considered. According to the analysis results, the vibrations at seat/body/wheel were predicted by simulation and experiment.