• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.188-195
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• 2004

This paper presents neural load torque observer that is used to deadbeat load torque observer and gain compensation by parameter estimator As a result, the response of the PMSM(permanent magnet synchronous motor) follows that nominal plant. The load torque compensation method is composed of a neural deadbeat observer To reduce the noise effect, the post-filter implemented by MA(moving average) process, is adopted. The parameter compensator with RLSM (recursive least square method) parameter estimator is adopted to increase the performance of the load torque observer and main controller The parameter estimator is combined with a high performance neural load torque observer to resolve the problems. The neural network is trained in on-line phases and it is composed by a feed forward recall and error back-propagation training. During the normal operation, the input-output response is sampled and the weighting value is trained multi-times by error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. As a result, the proposed control system has a robust and precise system against the load torque and the Parameter variation. A stability and usefulness are verified by computer simulation and experiment.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.126-134
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• 2005

Reducing energy consumption in mobile hosts (MHs) is one of the most critical issues in wireles/mobile networks. IP paging protocol at network layer and power saving mechanism (PSM) at link layer are two core technologies to reduce the energy consumption of MHs. First, we investigate the energy efficiency of the current IEEE 802.11 power saving mechanism (PSM) when IP paging protocol is deployed over IEEE 802.11 networks. The result reveal that the current IEEE 802.11 PSM with a fixed wakeup interval (i.e., the static PSM) exhibits a degraded performance when it is integrated with IP paging protocol. Therefore, we propose an adaptive power saving mechanism in IEEE 802.11-based wireless IP networks. Unlike the static PSM, the adaptive PSM adjusts the wake-up interval adaptively depending on the session activity at IP layer. Specifically, the MH estimates the idle periods for incoming sessions based on the exponentially weighted moving average (EWMA) scheme and sets its wake-up interval dynamically by considering the estimated idle period and paging delay bound. For performance evaluation, we have conducted comprehensive simulations and compared the total cost and energy consumption, which are incurred in IP paging protocol in conjunction with various power saving mechanisms: The static PSM, the adaptive PSM, and the optimum PSM. Simulation results show that the adaptive PSM provides a closer performance to the optimum PSM than the static PSM.

• Journal of Power Electronics
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• v.8 no.4
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• pp.354-362
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• 2008

This paper presents neural load torque compensation method which is composed of a deadbeat load torque observer and gains compensation by a parameter estimator. As a result, the response of the PMSM (permanent magnet synchronous motor) obtains better precision position control. To reduce the noise effect, the post-filter is implemented by a MA (moving average) process. The parameter compensator with an RLSM (recursive least square method) parameter estimator is adopted to increase the performance of the load torque observer and main controller. The parameter estimator is combined with a high performance neural load torque observer to resolve problems. The neural network is trained in online phases and it is composed by a feed forward recall and error back-propagation training. During normal operation, the input-output response is sampled and the weighting value is trained multi-times by the error back-propagation method at each sample period to accommodate the possible variations in the parameters or load torque. As a result, the proposed control system has a robust and precise system against load torque and parameter variation. Stability and usefulness are verified by computer simulation and experiment.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.809-824
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• 2009

Hydrological system forecasting, which is the short term runoff historical data during the limited period in dam site, is a conditional precedent of hydrological persistence by stochastic analysis. We have forecasted the monthly hydrological system from Andong dam basin data that is the rainfall, evaporation, and runoff, using the seasonal ARIMA (autoregressive integrated moving average) model. Also we have conducted long term runoff simulations through the forecasted results of TANK model and ARIMA+TANK model. The results of analysis have been concurred to the observation data, and it has been considered for application to possibility on the stochastic model for dam inflow forecasting. Thus, the method presented in this study suggests a help to water resource mid- and long-term strategy establishment to application for runoff simulations through the forecasting variables of hydrological time series on the relatively short holding runoff data in an object basins.

• Journal of Korean Society of Transportation
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• v.21 no.6
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• pp.57-65
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• 2003

Traffic congestion on the streets is the major concern of Metropolitan areas in Korea. Especially the signalized intersections are the main spots where traffic congestion is to be created. Currently the subway construction has been on the process in Taegu Metropolitan city. The subway stations are usually located at the intersections where a large number of vehicles and people are moving. During the constructional period, such an intersection creates profoundly a great deal of traffic congestion due to the open-cut constructional method. Under circumstance of the constructional method, the lane configurations should be changed frequently and the surface conditions make drivers uncomfortable. The propose of this study is to propose the improved method of traffic operation at the large circled intersection under the construction. The Signalized Modern Roundabout(SMR) is applied modifying from the modern roundabout. The geometric design and signal operation of SMR is developed in this study. To verify the operation of SMR the comparative study is conducted between the operation of the open-cut method and SMR method using the micro-simulation program, NETSIM. The result of simulation shows that the delay caused by the operation of SMR is not higher than that under the open-cut method. SMR makes also the constructional period shorten, makes the cost of construction lessened and makes drivers more comfortable as well than the method of open-cut. Therefore, the study concludes that the operation of SMR is more efficient, economic and safer method than that of open-cut method at the large circled intersection under construction.

• Journal of the Society of Disaster Information
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• v.16 no.4
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• pp.650-657
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• 2020

Purpose: In this study, the effectiveness of pilot project of PLSP (Priority Lane and Signal Preference) system, which was operated in Cheongju City, was analyzed. Method: The priority signal was operated by a police officer switching to a blue signal when approaching a fire truck through CCTV, and the priority lane of emergency vehicles was displayed on the road to enable preferential traffic. VISSIM simulation analysis was performed for the 1.2km section (3.8km) of the pilot project section and vehicle data was analyzed for some of the test operation sections. Result: Simulation analysis shows that the moving speed of the emergency vehicle can be increased by 42 km/h with the introduction of PLSP, which can be increased by approximately twice the speed. Travel time was reduced by about 3 minutes, and considerable improvements of 69% compared to cities that are not operating was analyzed. The pilot operation of Cheongju City showed a time-shortening effect of about two minutes on average, with the average time reaching 4 minutes and 14 seconds in the first period and the average time reaching 5 minutes and 40 seconds in the second period. Conclusion: The system has been shown to be effective in minimizing time-to-site arrival of emergency vehicles.

• Atmosphere
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• v.25 no.1
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• pp.1-18
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• 2015

The most objective way to overcome the limitation of numerical weather prediction model is to represent the uncertainty of prediction by introducing probabilistic forecast. The uncertainty of the numerical weather prediction system developed due to the parameterization of unresolved scale motions and the energy losses from the sub-scale physical processes. In this study, we focused on the growth of model errors. We performed ensemble forecast to represent model uncertainty. By employing the multi-physics scheme (PHYS) and the stochastic kinetic energy backscatter scheme (SKEBS) in simulating typhoon Rusa (2002), we assessed the performance level of the two schemes. The both schemes produced better results than the control run did in the ensemble mean forecast of the track. The results using PHYS improved by 28% and those based on SKEBS did by 7%. Both of the ensemble mean errors of the both schemes increased rapidly at the forecast time 84 hrs. The both ensemble spreads increased gradually during integration. The results based on SKEBS represented model errors very well during the forecast time of 96 hrs. After the period, it produced an under-dispersive pattern. The simulation based on PHYS overestimated the ensemble mean error during integration and represented the real situation well at the forecast time of 120 hrs. The displacement speed of the typhoon based on PHYS was closest to the best track, especially after landfall. In the sensitivity tests of the model uncertainty of SKEBS, ensemble mean forecast was sensitive to the physics parameterization. By adjusting the forcing parameter of SKEBS, the default experiment improved in the ensemble spread, ensemble mean errors, and moving speed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1193-1199
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• 2014

To achieve safe and high-speed navigation of a mobile service robot, velocity of dynamic obstacles should be considered while planning the trajectory of a mobile robot. Trajectory planning schemes without considering the velocity of the dynamic obstacles may collide due to the relative velocities or dynamic constraints. However, the general planning schemes that considers the dynamic obstacle velocities requires long computational times. This paper proposes a velocity control scheme by scaling the time step of trajectory to deal with dynamic obstacle avoidance problem using the RNLVO (Robot Nonlinear Velocity Obstacles). The RNLVO computes the collision conditions on the basis of the NLVO (Nonlinear Velocity Obstacles). The simulation results show that the proposed scheme can deal with collision state in a short period time. Furthermore, the RNLVO computes the collisions using the trajectory of the robot. As a result, accurate prediction of the moving obstacles trajectory does not required.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.4
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• pp.450-461
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• 1998

The spatial distribution of multipath fading using miniaturized experimental setup was analyzed. The spatial Fourier transform was carried out for the analysis of the period of fading and we could find out spatial frequency component of fading. Thus the analysis using this method shows the validity of miniaturized experimental setup. The miniaturized experimental setup was made by 5 times reducing of the real size. The simulation was performed at 2 GHz and the measurement was carried out at 10 GHz. Automatic antenna moving system was made for exact measurement of the multipath fading. Both simulated and measured results in miniaturized experimental setup were shown by electric field distribution and spatial frequency density distribution curves.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.5
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• pp.531-537
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• 2018

A novel PLL with a delta-sigma modulator and a spur reduction circuit is proposed. delta-sigma modulator makes the LF remove noise easily by moving the spur noise to a higher frequency band. Therefore, the magnitude of spur can be reduced the reasonable bandwidth. The spur reduction circuit reduces the spur size by reducing the LF voltage change generated during the period of reference signal. The spur reduction circuit is designed as simple as possible not to increase the size of PLL. The proposed PLL with the previous two techniques is designed with a supply voltage of 1.8V in a 0.18um CMOS process. Simulation results show an almost 20dB reduction in the magnitude of spur. The spur reduced PLL can be used in narrow bandwidth communication system.