• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.456-460
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• 1996

A nonlinear control scheme for preventing limit cycle due to the nonlinearity of themulti-step bang-bang actuator in mechanical position control systems is proposed. A linearized model, SIDF, fora multi-step bang-bang actuator is introduced to compensate the nonlinearity of the multi-step bang-bang actuator. Using that model, a $H_{\infty}$robust controller for position control systms with a bang-bang actuator is proposed by loop shaping tecniques with normalized coprime factorization stabilization to address the robustness. The proposed scheme needs a smaller deadband as a result of compensating the nonlinearity of the bang-bang actuator. A single-axis servo system is served in order to verify the proposed control scheme experimentally. Experimental results show that the controller can satisfy the special intersts, silent contact switching of the actuator.r.

• Journal of KSNVE
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• v.6 no.6
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• pp.763-770
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• 1996

This paper proposes a method to determine the initial shape and size of the suspension beam of an optical pickup actuator subjected to specified dynamic characteristics. For the analysis, a simplified model consisting of a concentrated mass, rotational springs and beams is developed. Based on this model, the key dimensionless design parameters are introduced, which govern low-frequency vibration characteristics i. e., the resonant frequencies in the tracking and focusing directions. A systematic procedure for sizing and shaping the actuator suspension beams is described and applied to a sample case. The effectiveness of the present technique is verified through the comparison of the present and the finite element results.

• Nuclear Engineering and Technology
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• v.29 no.4
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• pp.280-290
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• 1997

The robust controller for the nuclear reactor power control system is designed. The nuclear reactor is modeled by use of the point kinetics equations and the singly lumped energy balance equations, Since the model is not exact, the controller which can make the actual system robust is necessary. The perturbed plant is investigated by employing the uncertainties of the initial power level and the physical properties, and by introducing the delay into the modeled plant The overall system is configured into the two port model and the H$\infty$ controller is designed. In designing the H$\infty$ controller, two factors of the loop shaping and the permissible magnitude of control input are taken into account The designed controller provides the sufficient margins for the robustness, and the transients of the system output power and the control input satisfy their associated requirement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.251-256
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• 2000

This paper presents dynamic modeling and controller design of a tracked vehicle installed with the double-rod type ERSU(electro-rheological suspension unit). A 16 DOF(degree-of-freedom) model for the tracked vehicle is established by Lagrangian method. After showing the spring and damping characteristics of the proposed ERSU, equivalent 2 DOF 1/12 tracked vehicle model is then formulated by regarding the spring and viscous damping coefficients under the static state as constant values. A robust LSDP(loop-shaping design procedure) $H_{\infty}$ controller compensating spring and damping parameter variations is then designed in order to suppress unwanted vibration of the vehicle. The control responses such as vertical and pitch acceleration are presented in time domain.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.102-109
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• 1997

A two-degree-of freedom (TDF) $H_{\infty}$controller for a seeker scan loop is presented for the purpose of improving scanning performances. The perturbed plant model is characterized via the normalized coprime factorization. The TDF $H_{\infty}$controller is designed based on the loop shaping design procedure and model matching approach, and its performances are evaluated and compared with those of a previous work. It is demonstrated that the proposed TDF $H_{\infty}$controller is more effective to the control of the seeker scan loop than the previous controller.oller.

• The Journal of Society for e-Business Studies
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• v.8 no.3
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• pp.219-239
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• 2003

The world of business is being profoundly transformed by the Internet and electronic commerce. E-commerce is driven by Internet and e-commerce technology. That is, the new e-commerce is commonly associated with highly developed technical elements, ranging from web , graphic design. payment systems and network infrastructure. Thus, it is necessary to decide which technologies are important and how they are related to each other. To anticipate the future of each information communication technology and electronic commerce accurately , we have attempted to develop a classification model of electronic commerce technology. A classification model for EC technologies consists of three categories: basic technology, base technology, and application technology. This model can play a role as a guideline in classifying EC technologies into three hierarchical category and in comparing the relative relationships of each electronic commerce technology. It will also provide an impetus for the study of electronic commerce technologies and for the shaping process of electronic commerce generally.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1381-1388
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• 1993

This paper presents a method for the simultaneous optimal design of structural and control systems. Sensitivities of performance index with respect to structural design variables are analyzed. The structural design variables are optimized to minimize the performance index by use of conjugate gradient method. The method is applied to a half model of an active vehicle suspension system with elastic body moving on a randomly profiled road. The suspension control force of an optimally controlled system in the presence of measurement errors are calculated by use of linear quadratic Gaussian control theory and Kalman filter theory. The performance index contains ride comfort, road holding and working space of suspension. The structural design variables taken are stiffness, daming properties and the position of the suspension system. The random road profile considered as colored noise is shaped from white noise by use of shaping filter. The performance of an optimal simultaneous structure/control system is compared with that of an optimal controlled system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1279-1288
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• 2004

In this paper, the DMR(Digital Microwave Radio) system-based OFDM(Orthogonal Frequency Division Multiplexing) scheme in microwave channel environments has been proposed and system performances have been evaluated. The existing single carrier DMR system has a complex system structure due to using high-level QAM(Quadrature Amplitude Modulation) modulation scheme and so charmel capacity is limited by sensitive effects from fading. Therefore, in the proposed DMR system, it uses that the OFDM scheme for enhancement of fading distortion and also uses that the band-limited pulse shaping filter instead of windowing for no additional data such as GI/GB and for using efficient of IFFT/FFT block. The performance of OFDM/QPSK-DMR system and single carrier DMR system are analysed by computer simulation using two-ray model under the microwave channel environments The computer simulation results confirm that the fade margin of the proposed OFDM/QPSK-DMR system is highly increased as the number of sub-carriers is larger.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.567-572
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• 2011

A sensitivity analysis of the methods used to evaluate the transport properties of a CdZnTe detector was performed using two different radiations (${\alpha}$ particle and gamma-ray) emitted from an $^{241}Am$ source. The mobility-lifetime products of the electron-hole pair in a planar CZT detector ($5{\times}5{\times}2\;mm^3$) were determined by fitting the peak position as a function of biased voltage data to the Hecht equation. To verify the accuracy of these products derived from ${\alpha}$ particles and low-energy gamma-rays, an energy spectrum considering the transport property of the CZT detector was simulated through a combination of the deposited energy and the charge collection efficiency at a specific position. It was found that the shaping time of the amplifier module significantly affects the determination of the (${\mu}{\tau}$) products; the ${\alpha}$ particle method was stabilized with an increase in the shaping time and was less sensitive to this change compared to when the gamma-ray method was used. In the case of the simulated energy spectrum with transport properties evaluated by the ${\alpha}$ particle method, the peak position and tail were slightly different from the measured result, whereas the energy spectrum derived from the low-energy gamma-ray was in good agreement with the experimental results. From these results, it was confirmed that low-energy gamma-rays are more useful when seeking to obtain the transport properties of carriers than ${\alpha}$ particles because the methods that use gamma-rays are less influenced by the surface condition of the CZT detector. Furthermore, the analysis system employed in this study, which was configured by a combination of Monte Carlo simulation and the Hecht model, is expected to be highly applicable to the study of the characteristics of CZT detectors.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.1-9
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• 2018

In this study, a hybrid control method that adjusts for the existing force control technique has been presented for consideration. The proposed hybrid control technique does away with the chattering phenomenon occurring in existing force control technique and provides high shock absorption efficiency. In order to design the controller for the landing gear with MR damper, the equation of motion of the landing gear was derived. The hybrid controller was designed after constructing a simulation model using Recur-Dyne, multi-body dynamic analysis software. The hybrid controller can reduce the maximum strut force and displacement based on the skyhook controller, and is able to get the high efficiency by making it work for the additional force control technique. In addition, an effective switching control technique and input shaping technique was applied to prevent the chattering in the drop simulation. Finally, the performance of the landing characteristics was evaluated throughout the various drop simulations.