• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.16-20
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• 2010

The dynamic characteristics of flight sensors is obtained by a simple method that deploys a pendulum with a rotary encoder. The encoder output is used with kinematic relations to derive reference signals for various flight sensors, including position, velocity, attitude, and angular rate sensors as well as accelerometer and magnetic sensors. A time delay of 0.4 seconds is found in the position output of the flight sensor under investigation. A logic to compensate for the time delay using a velocity information is proposed and validated in flight tests.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2317-2319
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• 2000

This paper presents a feedback controller for compensation time delay in the distributed control systems. In using network, controllers and sensors are distributed on a communications network, there exist time delays on communication lines between the system components. So, we deal with the controller using Smith predictor controller design issue for such systems. Particularly compensated for the time delay of the plant or controller involved integrator using Modified Smith predictor. Simulation and the results show the good performance for the modified Smith predictor control systems.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.84-84
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• 1998

• Journal of the Korea Computer Industry Society
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• v.3 no.5
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• pp.631-640
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• 2002

The internet phones that are currently available in use adopt packet exchange system, transferring through various routes and lacking sufficient band width with a result that there is an accompanied delay for packet transmission since the traffic is increased, accordingly affecting a lot in sound quality and speed. Two solutions for such troubles are suggested in this study to improve sound quality of internet phones. Firstly, we minimize the delay and damage regarding packet size based on traffic size by using the data algorithm from variable packets in order to supplement decreased sound quality due to the delay and damage of sound data. The second suggestion is to employ a method of Jitter compensation by giving an appropriate initial delay time with regenerating buffers to bypass troubles from Jitter, From employing the Jitter compensation method, we found that there is a sound quality improvement due to the less stoppage phenomenon.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1061-1070
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• 2009

In this paper, we have designed TDL(True-time Delay Line) for eliminating beam-squint occurring in active phased array antenna with large electrical size operated in wide bandwidth, and have tested its electrical performance. The proposed TDL device is composed of 4-bit microstrip delay line structure and MMIC amplifier for compensation of the delay-line loss. The measured results of gain and phase versus delay state satisfy the electrical requirements, also P1dB output power and noise figure meet the requirement. To verify the performance of fabricated TDL, we have simulated the beam patterns of wide-band active phased array antenna using the measured results and have certified the beam pattern compensation performance. As a result of simulated beam pattern compensation with respect to the 675.8 mm size antenna which is operated in X-band, 800 MHz bandwidth, we have reduced the beam squint error of ${\pm}1^{\circ}$ with ${\pm}0.1^{\circ}$. So this TDL module is able to be applied to active phase array antenna system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.895-902
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• 2012

In this paper, we propose a novel equalizer to compensate for the group delay including AM/PM nonlinear distortion characteristics by the nonlinear power amplifier (PA). The group delay characteristic is a nonlinear non-constant time delay that appears differently depending on each frequency component. The phase distortion by AM/PM characteristics arising from the power amplifier is a major factor to increase group delay. By the group delay distortion, the signal in the constellation expands and is rotated. Considering the problem mentioned above, the nonlinear time delay that appears differently depending on each frequency component is classified as a static group delay and AM/PM characteristic of PA, the different phase transitions depending on the size of input signal as a dynamic group delay. Static group delay estimates and compensate for phase distortions in the frequency domain with type-based method and dynamic group delay compensates for phase rotation in the time domain. We confirmed that the group delay compensation techniques were enough to compensate the group delay characteristics including AM/PM characteristics of the power amplifier.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.1
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• pp.58-66
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• 1991

In inverters, time delays are inserted in the switching signals to prevent the dc lind shortage. This causes detrimental effects on the performance of the inverters, that is, the fundamental voltage drop and the generation of low order harmonics. This paper derives simple formula to describe the time delay effects in PWM inverters, where the effects may become significant because of relatively high switching frequencies. To compensate the tice delay effects, this paper presents two methods which are suitable for sinusoidal PWM and memory-based PWM respectively. Both are simple, easy to implement, and are shown to be effective, through the experiments, in improving the output waveform of PWM inverters.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2028-2032
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• 1997

When a high performance current control is desired, a computation time delay of a digital control system may deteriorate the control performance of a current controller. Such a non-negligible effect can be considerable in transient state. This paper deals with the modified predictive current control that compensates the time delay effects of a conventional predictive current control. The method is closely related to a local average current control and a symmetrical PWM pattern generation. Also some theoretical approaches are presented to describe the voltage saturation boundary of the power converter. For validation, the proposed method is applied to an active power filter system. The experimental results show considerable improvement in current tracking capability.

• Journal of Mechanical Science and Technology
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• v.15 no.6
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• pp.699-708
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• 2001

This paper presents a new approach to the AFR (Air-to-Fuel Ratio) control problem, which is based on the wide-band oxygen sensor output. The dedicated nonlinear controller is based on the feedback lineaization technique. It is well known that the feedback linearizing control technique requires an exact model of the plant for the cancellation of plant nonlinearities. A sliding mode control scheme is applied which can effectively compensate the modeling uncertainties. The measurement time delay of an oxygen sensor limits the gain of the feedback controller. Hence, time delay compensation procedure is necessary for the improvement of control performance. The Smith predictor is adopted to compensate the effects of time delay. The simulation and experimental results show that the proposed controllers can effectively reduce the transient peaks of AFR in spite of fast tip-in and tip-out maneuvers of the throttle.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.2 no.3
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• pp.231-236
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• 2002

In this paper, we present an analysis and design method fur the control of input-saturated nonlinear systems with the time-delay. The target system is represented by Takagi-Sugeno (T-S) fuzzy model and the parallel distributed compensation (PDC) controller is designed to guarantee the local stability of the equilibrium point. We derive the sufficient condition for the local stability by applying Lyapunov-krasovskii theorem and this condition is converted into the LMI problem.