• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.898-902
• /
• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation ${\Large f}_1\;and\;{\Large f}_2$ respectively, the displacement at the center of the plate has the strongest component at frequency ${\Large f}_1$. The angular displacement of the plate has strong components at ${\Large f}_1-{\Large f}_2$ and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. Part of these simulation results are proved analytically.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.9 s.114
• /
• pp.958-963
• /
• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation $f_1\;and\;f_2$, respectively, the displacement at the center of the plate has the strongest component at frequency $f_1$. The angular displacement of the plate has strong components at $f_1-f_2$ and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shaker with low frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.81-85
• /
• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation ${\Large f}_1\;and\;{\Large f}_2$, respectively, the displacement at the center of the plate has the strongest component at frequency ${\Large f}_1$. The angular displacement of the plate has strong components at ${\Large f}_1-{\Large f}_2$, and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shatter with low frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.182-186
• /
• 2002

If a sinusoidal excitation force moves back and forth along a structure with a certain frequency, the structure will be excited with the difference frequency of these two frequencies. A low frequency vibration shaker has been developed using this force frequency shifting without actually moving a shaker. The shaker consists of an ordinary eccentric mass shaker, a plate, constant springs, and time varying dampers. The dampers are turned on and off in a sequential manner to simulate a traveling slide of an excitation force. The operation of the shaker is simulated by solving the equations of motion of the shaker. Characteristics of the shaker have been found and they will be utilized to design efficient low frequency shakers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.324.2-324
• /
• 2002

If a sinusoidal excitation force moves back and forth along a structure with a certain frequency, the structure will be excited with the difference frequency of these two frequencies. A low frequency vibration shaker has been developed using this force frequency shifting without actually moving a shaker. The shaker consists of an ordinary eccentric mass shaker, a plate, constant springs, and time varying dampers. The dampers are fumed on and off in a sequential manner to simulate a traveling slide of an excitation force. (omitted)

• 제어로봇시스템학회:학술대회논문집
• /
• 1996.10a
• /
• pp.362-367
• /
• 1996

In this paper, the eigenstructure of a class of linear time varying systems, termed as linear quasi-time invariant(LQTI) systems, is investigated. A system composed of dynamic devices such as linear time varying capacitors and resistors can be an example of the class. To effectively describe and analyze the LQTI systems, a generalized differential operator G is introduced. Then the dynamic systems described by the operator G are studied in terms of eigenvalue, frequency characteristics, stability and an extended convolution. Some basic attributes of the operator G are compared with those of the differential operator D. Also the corresponding generalized Laplace transform pair is defined and relevant properties are derived for frequency domain analysis of the systems under consideration. As an application example, a LQTI circuit is examined by using the concept of eigenstructure of LQTI system. The LQTI filter processes the sinusoidal signals modulated by some functions.

• Structural Engineering and Mechanics
• /
• v.26 no.6
• /
• pp.635-650
• /
• 2007

In this paper, the equivalent exciting force caused by electric excitation is derived. By dividing load and displacement vectors into mean values and time-varying ones, the dynamic equations of the system are transformed into linear ones for time-varying portion of the displacements. The analytical equations of the forced time responses of the drive system to electric excitations are obtained. Using the Laplace transformation, the transfer function of the drive system is obtained. These equations are used to analyze the time and frequency responses of the drive system to the electric excitation. It is known that electric excitation can cause forced responses of the drive system, the total dynamic responses are decided by three phase exciting voltages, exciting frequency and natural frequencies of the drive system, and the drive parameters have obvious influence on the time and frequency responses.

• 제어로봇시스템학회:학술대회논문집
• /
• 1987.10a
• /
• pp.842-846
• /
• 1987

This paper proves that a filter for scramble spectrum is realized by a periodically time-varying digital filter. Further, we propose a design method of this filter by using a bi-frequency map. As an example, we implemented this filter with Digital Signal Processor.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.1
• /
• pp.52-57
• /
• 1987

In this paper, a methodology is developed to remove the reaching phase and the high frequency chattering phenomenon which are the common drawbacks of variable structrue control (VSC) system. A time varying switching surface is proposed to achieve sliding motion during the entire control process and a continuous control law whose terms are continuous functions inside a boundary layer neighbouring the time varying switching surface is developed to remove the high frequency chattering phenomenon of VSC. The methodology developed in this paper is applied to the 2'nd order time varying system and the simulated results are compared with those of typical VSC methodology.

• Proceedings of the KIPE Conference
• /
• 2014.07a
• /
• pp.383-384
• /
• 2014

This paper investigates the experimental and simulated time-varying magnetic field generation in a chlor-alkali manufacturing process. 19kA thyristor-based rectifier is modeled and analyzed. The performance is compared and evaluated on the basis of exposure guidelines from ICNIRP. The mechanical structure of current carrying conductor is simplified as an infinite long busbar model and low frequency harmonic contents up to 65kHz are considered. Thyristor rectifier generates a significant amount of low frequency magnetic field harmonic contents both at ac and dc busbar of rectifier infringing the limit of ICNIRP. Along with simulation analysis the experimental measurement of the time-varying magnetic field in ac input busbar, rectifier block, dc load and busbar are presented. The experimental test results partly confirm the simulation results.