• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.386.2-386
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• 2002

This paper reports the performance and the Algorithm of an 1/3-octave band spectrum control system. The system is developed to provide various required spectrums in a high intensity acoustic chamber. The required spectrums, which usually comes from launch vehicle specification, starts from 25㎐ band and ends 10,000㎐. Short settling time is required to guarantee the safety of test objects and reduce the amount of operating gas. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.10a
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• pp.142-147
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• 1996

For prediction and control of sound, acoustic systems must be modeled. Because sound systems like exhaust systems are very difficult to calculate mathematically, this study presents a method to determine experimentally the order of poles by transfer function. When designing a control system by traditional methods the exact model order and coefficient of the system to be controlled must be determined. But in acoustic systems, where systems to be controlled are very complex, mathematical interpretation is almost always impossible. Therefore transversal filters using trial and error methods to determine model order of a system are used to design a system. Compared to mathematical models with poles, transversal filters, in which the model order becomes relatively large, have the disadvantage of prolonged processing time and marked time delay. This study presents a method to determine experimentally the order of poles in a system model with poles and zeroes. Also, the validity of this method was verified mathematically and confirmed by application in general simple models and acoustic tube simulators.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.751-755
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• 2005

We propose a sound source localization method using the Head-Related-Transfer-Function (HRTF) to be implemented in a robot platform. In conventional localization methods, the location of a sound source is estimated from the time delays of wave fronts arriving in each microphone standing in an array formation in free-field. In case of a human head this corresponds to Interaural-Time-Delay (ITD) which is simply the time delay of incoming sound waves between the two ears. Although ITD is an excellent sound cue in stimulating a lateral perception on the horizontal plane, confusion is often raised when tracking the sound location from ITD alone because each sound source and its mirror image about the interaural axis share the same ITD. On the other hand, HRTFs associated with a dummy head microphone system or a robot platform with several microphones contain not only the information regarding proper time delays but also phase and magnitude distortions due to diffraction and scattering by the shading object such as the head and body of the platform. As a result, a set of HRTFs for any given platform provides a substantial amount of information as to the whereabouts of the source once proper analysis can be performed. In this study, we introduce new phase and magnitude criteria to be satisfied by a set of output signals from the microphones in order to find the sound source location in accordance with the HRTF database empirically obtained in an anechoic chamber with the given platform. The suggested method is verified through an experiment in a household environment and compared against the conventional method in performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1012-1015
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• 2004

There have been several kinds of attempts to actively control the deflected noise behind the noise barrier. Omoto's work in 1993 would be one of the fundamental studies, where he placed the control sources uniformly parallel to the noise barrier. Following this study, Yang pointed that the average distance between the noise source and control sources is more important than the arrangement of control sources such as a straight line or an arc type distribution. In 2004, Baek tried to show optimal arrangement of control sources while keeping the average distance between the noise source and control sources. He used simulated annealing algorithm which is one of the natural algorithms for the selections of optimal control source positions, but the searching technique was a hybrid of the simulated annealing and the sequential searching to adapt to the vast amount of searching time. This study is about the performance comparison between the pure sequential searching and the hybrid one. The simulation results show very similar performance and a pure simulated annealing searching will be more beneficial for the noise reduction performance but at the cost of computing time.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1833-1837
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• 2004

The two-inertia system, which has the torsion vibration, is typically found in several industrial applications. This torsion vibration will effect the quality of the rolled material as well as the stability of the drive system. Thus the speed and torsion vibration of the system have to be properly controlled. This paper, I-PDA controller designed by Coefficient Diagram Method to control a two-inertia system is proposed. The experimental result shows that both of transient and steady state specification can be fulfilled but the transient response still has long rise time. In order to improve the speed of the system response, a phase lag structure of feedforward controller is introduced to I-PDA control system. It is shown that the performance of the I-PDA control system with suitable FFC has shorter rise and settling times, no overshoot and the torsion vibration can be suppressed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.126-132
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• 1999

The paper presents the modeling and optimal control for the reduction of transverse vibration of simply supported beam under a moving mass. The equations of motion are derived by using assumed mode method. The coriolis and centripetal accelerations are accommodated in the equations of motion to account for the dynamic effect of the traveling mass. In order to reduce the transverse vibration of the beam, an optimal controller with full state feedback is designed based on the linearized equations of motion. The optimal actuator locations are determined with the evaluation of an optimal cost functional defined by the worst initial condition with the trade-off of controlled mode performance. Numerical simulations are performed with respect to various velocities and different traveling masses. Even if the velocity of the traveling mass reaches to the critical speed which can cause the resonance of the beam, the controller with two piezoelectric actuators shows the excellent performance under severe time-varying disturbances of the system.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.604-609
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• 2005

This paper presents an experimental study for optimizing the acceleration of AC servomotor using finite jerk (the first derivative of acceleration). The acceleration optimization with finite jerk aims at generating the smooth velocity profile of AC servomotor by experimentally minimizing vibration resulted from the initial friction of servomotor. The stick-slip motion of AC servomotor induced by initial friction can result in the positional errors that are not good for high-precision devices such as the assembly robot arms to be used in a 300mm wafer or a LCD (Liquid Crystal Display) stocker system. In this paper, experiments were made by using a PM (Permanent Magnet) type AC servomotor with MMC(R) (Multi Motion Controller) programmed in Visual C++(R). The experiments have been performed for finding the optimal duration time of finite jerk in terms of the minimization of vibration displacements when both the magnitude of velocity and the allowable acceleration are given. We have compared the proposed control with the conventional control with trapezoidal velocity profile by measuring vibration displacements. The effectiveness of the proposed control has been verified in that the experimental results showed the decrease of vibration displacement by about 24%.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.246-250
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• 2000

A distinctive feature in vibration control of a large civil infrastructure is the existence of large disturbances, such as wind, earthquake, and sea wave forces. Those disturbances govern the behavior of the structure, however, they cannot be precisely measured, especially for the case of wind-induced vibration control. The sliding mode fuzzy control (SMFC), which is of interest in this study, may use not only the structural response measurement but also the wind force measurement. Hence, an adaptive disturbance estimation filter is introduced to generate a wind force vector at each time instance based on the measured structural response and the stochastic information of the wind force. The structure of the filter is constructed based on an auto-regressive with auxiliary input model. A numerical simulation is carried out on a benchmark problem of a wind-excited building. The results indicate that the overall performance of the proposed SMFC is as good as the other methods and that most of the performance indices improve as the adaptive disturbance estimation filter is introduced.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.3
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• pp.269-276
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• 2006

Increasing requirements for the high quality of industrial robot performance made the vibration control issue very important because the vibration makes it difficult to achieve quick response of robot motion and may bring mechanical damage to the robot. This paper presents the vibration mechanism of an industrial robot which has flexible joints. The joint flexibility of the robot is modeled as a two-mass system and its dynamic characteristics are analysed. And some characteristics of the two-mass system, especially for the joint of industrial robots, such as disturbance, non-linearity and time-varying characteristics are studied. And finally, some considerations on controller design for the flexible joint of industrial robots are discussed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.8
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• pp.21-29
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• 2013

The functional behaviors of human standing postural control were investigated when they were exposed to long-term horizontal vibration in the sagittal plane. For complexity of human postural control, a useful alternative method that has been based on a black-box approach was taken; that is, where the feedback mechanism was lumped into a single element. A motor-driven support platform was designed as a source of vibration. The AC Servo-controlled motors produced continuous anterior/posterior (AP) motion. The data were analyzed both in the time and frequency domain. The cross-correlation and coherency functions were estimated. Subjects behaved as a non-rigid pendulum with a mass and a spring throughout the whole period of the platform motion, as consistent with the plan chosen for this study.