• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.246-252
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• 2012

Multivariate cumulative sum (CUSUM) control charts for simultaneously monitoring both means and variances under multivariate normal process are investigated. Performances of multivariate CUSUM schemes are evaluated for matched fixed sampling interval (FSI) and variable sampling interval (VSI) features in terms of average time to signal (ATS), average number of samples to signal (ANSS). Multivariate Shewhart charts are also considered to compare the properties of multivariate CUSUM charts. Numerical results show that presented CUSUM charts are more efficient than the corresponding Shewhart chart for small or moderate shifts and VSI feature with two sampling intervals is more efficient than FSI feature. When small changes in the production process have occurred, CUSUM chart with small reference values will be recommended in terms of the time to signal.

• Journal of Power Electronics
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• v.15 no.3
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• pp.763-774
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• 2015

This study investigates the inherent influence of a DC-link voltage controller on both DC-link voltage control and the compensation performance of a three-phase, four-wire shunt active power filter (APF). A nonlinear variable-parameter DC-link voltage controller is proposed to satisfy both the dynamic characteristic of DC-link voltage control and steady-state compensation performance. Unlike in the conventional fixed-parameter controller, the parameters in the proposed controller vary according to the difference between the actual and the reference DC-link voltages. The design procedures for the nonlinear voltage controller with variable parameters are determined and analyzed so that the proposed voltage controller can be designed accordingly. Representative simulation and experimental results for the three-phase, four-wire, center-spilt shunt APF verify the analysis findings, as well as the feasibility and effectiveness of the proposed DC-link voltage controller.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1003-1006
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• 2005

Vertex shader of GPU in personal computer is advanced in functions as to be half of traditional fixed T&L functions. And, capacity of memory for saving resources to process instructions is unlimited. GPU that can be programmed by programmer is needed for mobile system as well as personal computer. In this paper, we implement software virtual machine for vertex shader using C++ Language. Our goal is designing hardware GPU that can apply to mobile system. The virtual machine consists of nVidia GPU instructions. Input Data to virtual machine is generated by Microsoft fxc compiler. That is to say, Input Data is compiled shader program written in HLSL, Cg, or ASM. The virtual machine will be a reference model for designing hardware GPU and can be used for Testbed to test added or modified instruction.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.99-105
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• 2015

In this study, displacement estimation algorithm, which is not requiring an absolute reference point unlike the conventional displacement measurement method, is developed using the geophone. To estimate displacement of the bridge, measured velocity time signal is integrated in the frequency domain. And, the estimated displacement is compared with the measured result using a conventional method. Based on the dynamic field test results, it was found that the estimated displacement by the present algorithm is similar to that of a conventional method. The displacement estimation algorithm proposed in this paper can be effectively applied to measure the displacement of a structure, which is difficult to install a displacement transducer at the fixed point.

• Journal of the Korea Society of Computer and Information
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• v.6 no.2
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• pp.41-47
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• 2001

In this paper, I propose a detection algorithm that can reliably separate moving objects from noisy background in the image sequence received from a camera at the fixed position. The proposed algorithm consists of four processes: generation of the difference image between the input image and the reference image. multilevel quantization of the difference image, and multistage merging in the quantized image, detection of the moving object using a back propagation in a neural network. The test results show that the proposed algorithm can detect moving objects very effectively in noisy environment.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.589-591
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• 2004

In this paper, we developed a laser distance measurement(LDM) system based on DSP. We applied PPD(Pulsed Phase Detection) algorithm to the LDM system. The PPD algorithm calculate the distance from the LDM system to the object by using phase detection. Reference waveform at a fixed frequency is sampled by both the inner-loop and outer-loop pulse signal. The LDM system detects the difference of phase between the sampled signals. We obtained an accuracy of ${\sigma}=25.5mm$ from the LDM system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1047-1054
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• 2007

This paper presents a high efficiency direct instantaneous torque control (DITC) of Switched Reluctance Motor(SRM) based on the nonlinear model. The DITC method can reduce the high inherent torque ripple of SRM drive system, but drive efficiency is somewhat low due to the high current and switching loss during commutations. In order to reduce a torque ripple, a fast torque reference trajectory is selected at every instantaneous rotor position. Based on the nonlinear model of SRM, the developing torque by one phase is fixed and the other phase is regulated for minimum switchings of phase switch and variation of torque. The switching during commutation can be reduced and fast commutation can be obtained in the proposed method. As a result, drive efficiency could be improved as well as torque ripple reduction. The validity of proposed method is verified by computer simulations and comparative experiments.

• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.97-100
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• 1997

A new control method for the robust position control of a brushless DC(BLDC) motor using the asymptotically stable adaptive load torque observer is presented. A precision position control is obtained for the BLDC motor system approximately linearized using the field-orientation method. And the application of the load torque observer is published in [1] using fixed gain. However, the flux linkage is not exactly known for a load torque observer. Therefore, a model reference adaptive observer is considered to overcome the problem of the unknown parameter in this paper. And stability analysis is carried out using Liapunov stability theorem. As a result, asymptotically stable observer gain can be obtained without affecting the overall system response. The load disturbance detected by the asymptotically stable adaptive observer is compensated by feedforwarding the equivalent current having the fast response.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.423-427
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• 2001

This paper describes a control scheme for direct torque and flux control of Induction machines using space vector modulation. The proposed predictive flux control scheme has directly calculated the reference voltage space vector based on Stator flux errors in order to control the torque and flux. This proposed control scheme has not the requirement of a separate current error, thereby improving transient performance and also has the advantage of less torque ripple in steady state with a fixed switching period. The effect of proposed method has been proven by simulations. It is concluded that the proposed control topology produces better results for steady state operation than the classical direct torque control.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.2
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• pp.104-111
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• 1997

In this paper, three-phase PWM AC to DC boost converter that operates with unity power factor and sinusodial input line currents is presented. The current control of this converter is based on the space vector PWM strategy with fixed switching frequency and the line currents track to reference currents within one sampling time interval. By using this control strategy low ripples in the outut current and the voltage as well as fast dynamic response are achieved with small dc link cpacitance employed.