• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.68.1-68
• /
• 2001

This paper discusses tracking position control of linear actuator that has a time delay. The time delay happens when the process reads the sensor data and sends the control input to the plant located at a remote site in distributed control system. In this thesis, the time delay between the linear actuator and the discrete PID controller has constant value due to buffer device so the time delay can be modeled by Pade approximation but the large position error of the linear actuator is generated by the time delay. Therefore, the Smith predictor is used for tracking position control of the linear actuator with the time delay in order to minimize the effect of the time delay. The experimental and simulation results show that the ...

• Journal of Communications and Networks
• /
• v.18 no.1
• /
• pp.105-111
• /
• 2016

Trust models in the literature of MANETs commonly assume that packets have different security requirements. Before a node forwards a packet, if the recipient's trust level does not meet the packet's requirement level, then the recipient must perform certain security association procedures, such as re-authentication. We present in this paper an analysis of the epidemic broadcast delay in such context. The network, mobility and trust models presented in this paper are quite generic and allow us to obtain the delay component induced only by the security associations along a path. Numerical results obtained by simulations also confirm the accuracy of the analysis. In particular, we can observe from both simulation's and analysis results that, for large and sparsely connected networks, the delay caused by security associations is very small compared to the total delay of a packet. This also means that parameters like network density and nodes' velocity, rather than any trust model parameter, have more impact on the overall delay.

• Journal of Positioning, Navigation, and Timing
• /
• v.10 no.4
• /
• pp.271-278
• /
• 2021

In this paper, a tropospheric delay error was calculated by using meteorological data collect from weather station and Saastamoinen model, and an empirical variogram of the tropospheric delay in the Korean peninsula was estimated. In order to estimate the empirical variogram of the tropospheric delay according to weather condition, sunny day, rainy day, and typhoon day were selected as analysis days. Analysis results show that a maximum correlation range of the empirical variogram on sunny day was about 560 km because there is overall trend of the tropospheric delay. On the other hand, the maximum correlation range of the empirical variogram on rainy was about 150 km because the regional variation was large. Although there is regional variation when the typhoon exists, there is a trend of the tropospheric delay due to a movement of the typhoon. Therefore, the maximum correlation range of the empirical variogram on typhoon day was about 280 km which is between sunny and rainy day.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.5A
• /
• pp.457-465
• /
• 2010

When a sensor network is used for monitoring environments in large area or transmitting information in a u-City the number of nodes becomes very large. One of the problems with this application is the increased time delay, especially in reverse direction. In this paper, we propose a new algorithm that can minimize the latency of reverse packet in large sensor network. Analysis shows that the proposed scheme can reduce the latency by more than 90% when compared to Zigbee, while the energy consumption is maintained.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.14 no.4
• /
• pp.684-693
• /
• 2011

Measurement time delay in the transfer alignment is very important. It has been well known that the time delay degrades the alignment performance and makes some navigation errors on the transfer alignment of slave INS(SINS). Therefore there are many schemes to eliminate that time delay but the compensation technique through the estimation by Kalman filter through modeling the time delay as a random constant is generally used. In the case of change over measurement time delay or the large measurement time delay, estimation performance in the existing compensation technique is degraded because model of time delay is not correct any more. In this paper, we propose the method to keep the time delay almost constant even though in the abnormal communication state and very small through feedback compensation using double buffer. Double buffer consists of two moving window to temporarily store measurements from master INS and slave INS in real time.

• Current Optics and Photonics
• /
• v.3 no.5
• /
• pp.438-444
• /
• 2019

In this theoretical study, a line-defect photonic-crystal waveguide hosted in an annular photonic crystal was demonstrated to provide high-performance slow light with a wide band, low group-velocity dispersion, and a large normalized delay-bandwidth product. Combined with structural-parameter optimization and selective optofluid injection, the normalized delay-bandwidth product could be enhanced to a large value of 0.502 with a wide bandwidth of 58.4 nm in the optical-communication window, for a silicon-on-insulator structure. In addition, the group-velocity dispersion is on the order of $10^5$ ($ps^2/km$) in the slow-light region, which could be neglected while keeping the signal transmission unchanged.

• Journal of electromagnetic engineering and science
• /
• v.3 no.2
• /
• pp.140-146
• /
• 2003

In this paper, the design of a channel filter and its group-delay-and-amplitude equalizer is carried out for the Ka-band satellite transponder subsystem. The 8th order dual-mode filter is employed for high selectivity around the band-edges with an elliptic-integral function response and has an in-line configuration. The 2-pole, reflection-type, group-delay equalizer is designed and manufactured to reduce the group-delay and amplitude variation, which can be large for such a high order filter. It is noted that in both the filter and equalizer, adopting the dual-mode coupling mechanism leads to less mass and volume. Through measurement, the performance of the realized group-delay-equalized filter is shown to meet the equipment requirements and to be appropriate for the satellite input multiplexer.

• International journal of advanced smart convergence
• /
• v.7 no.4
• /
• pp.19-26
• /
• 2018

One of the distinct features of Wireless Sensor Networks (WSNs) is duty cycling mechanism, which is used to conserve energy and extend the network lifetime. Large duty cycle interval introduces lower energy consumption, meanwhile longer end-to-end (E2E) delay. In this paper, we introduce an energy consumption minimization problem for duty-cycled WSNs. We have applied Q-learning algorithm to obtain the maximum duty cycle interval which supports various delay requirements and given Delay Success ratio (DSR) i.e. the required probability of packets arriving at the sink before given delay bound. Our approach only requires sink to compute Q-leaning which makes it practical to implement. Nodes in the different group have the different duty cycle interval in our proposed method and nodes don't need to know the information of the neighboring node. Performance metrics show that our proposed scheme outperforms existing algorithms in terms of energy efficiency while assuring the required delay bound and DSR.

• Proceedings of the KIEE Conference
• /
• 2007.04a
• /
• pp.152-154
• /
• 2007

Anew discretization method for the input-driven nonlinear continuous-time system with time delay is proposed. It is based on the combination of Taylor series expansion and first-order hold assumption. The mathematical structure of the new discretization scheme is explored. The performance of the proposed discretization procedure is evaluated by case studies. The results demonstrate that the proposed discretization scheme can assure the system requirements even though under a large sampling period. A comparison between first order hold and zero-order hold is simulated also.

• Journal of Navigation and Port Research
• /
• v.35 no.9
• /
• pp.701-706
• /
• 2011

Radio waves including GPS signals, various TV communications, and radio broadcasting can be disturbed by a strong solar storm, which may occur due to solar flares and produce an ionospheric delay anomaly in the ionosphere according to the change of total electron content. Electron density irregularities can cause deep signal fading, frequently known as ionospheric scintillation, which can result in the positioning error using GPS signal. This paper proposes a detection algorithm for the ionosphere delay anomaly during a solar storm by using multi-reference stations. Different TEC grid which has irregular electron density was applied above one reference station. Then the ionospheric delay in zenith direction applied different TEC will show comparatively large ionospheric zenith delay due to the electron irregularity. The ionospheric slant delay applied an elevation angle at reference station was analyzed to detect the ionospheric delay anomaly that can result in positioning error. A simulation test was implemented and a proposed detection algorithm using data logged by four reference stations was applied to detect the ionospheric delay anomaly compared to a criterion.