• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.663-668
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• 1990

This paper deals with the application of a Generalized Predictive Control (CPC) to a Pressurized Water Reactor (P.W.R) Nuclear Power Plant. Generalized Predictive Control is a sort of Explicit Self-Tuning Control. Current self-tuning algorithms lack robustness to prior choices of either dead-time (input time delay of a plant) or model order. GPC is shown by simulation studies to be superior to accepted self-tuning techniques such as minimum variance and pole-placement from the viewpoint that it is robust to prior choices of dead-time or model order. In this paper a GPC controller is designed to control the P.W.R. nuclear power rlant with varying dead-time and through the designing procedure the designer is free from the constraint of knowing the exact dead-time. The controller is constructed based on the 2nd order linear model approximated in the vicinity of operating point. To ensure that this low-order model describes the complex real dynamics well enough for control purposes, model parameters are updated on-line with a Recursive Least Squares algorithm. Simulation results are successful and show the possibilities of the GPC control application to actual plants with varying or unknown dead-time.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.21-31
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• 2007

Relaxed Static Stability (RSS) concept has been applied to improve aerodynamic performance of modern version supersonic jet fighter aircraft. The T-50 advanced supersonic trainer employs the RSS concept in order to improve the aerodynamic performance. And the flight control system stabilizes the unstable aircraft and provides adequate handling qualities. The T-50 longitudinal control laws employ a proportional-plus-integral type controller based on a dynamic inversion method. The longitudinal dynamic modes consist of short period with high frequency and phugoid mode with low frequency. The design goal of longitudinal control law is optimization of short period damping ratio and frequency using Lower Order Equivalent System (LOES) complying the requirement of MIL-F-8785C. This paper addresses phugoid mode characteristics such as damping ratio and natural frequency that is affected by the nonlinear control laws such as angle of attack limiter, auto pitch attitude command system and autopilot of pitch attitude hold.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.2
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• pp.168-172
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• 2015

In general, open-loop fiber-optic gyroscopes (FOG) are less stable than closed-loop FOGs but they offer simpler implementation. The typical operation time of line-of-sight (LOS) stabilization systems is a few seconds to one hour. In this paper, a open-loop fiber optic gyroscope (FOG) for LOS applications is designed and implemented. The design goal is aimed at implementing a low cost, compact FOG with low Angle Random Walk (ARW) (< $0.03deg/\sqrt{h}$) and bias instability (< 0.25deg/h). The FOG uses an open-loop all-fiber configuration with 100M PM fiber wound on a small diameter spool. In order to get the design goal, digital signal processing techniques for signal detection, modulation control and compensation are designed and implemented in FPGA.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.179-184
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• 1993

In general, for underwater vehicles in low speed, depthkeeping operations are carried out by using the variation of the weight in the seaway tank. The depthkeeping control of underwater vehicles is difficult because of the deadzone effect in the flow rate control valve. In this paper, the nonlinear multivariable QLQG/LTR control system using a seaway tank and bow planes is synthesized in order to improve the performance of the depth control system. The computer simulation results show the multivariable QLQG/LTR control system has good depth control performance under the deadzone effect.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.830-837
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• 2015

A study which is to develop the low-cost urban railway system for low-density line such as Gwang-ju subway Line 2 is in progress, and its TCS(Train Control System) is required as an economic system which is able to train operation suitable in low-density line. We have developed the signaling equipment which is configured with automatic block system between stations, and the control center's equipment in order to meet the requirements of TCS mentioned above. In this paper, we propose the control procedure of ATS to be required for train operation management in the low-density line such as Gwang-ju subway Line 2. The control procedure of ATS considered all features such as the requirements analysis for train operation management, the functions of train control system to be applied and the block type. Also, it considered the station(interlocking, passenger, turn-back) type, station control(stop, route, departure, turn-back departure, turn-back) type, and train operation management for exiting and entering depot. The ATS control procedure proposed in this paper has an advantage in the cost and efficiency through unification and optimization of its function. And in cost of operating and maintenance, the ATS system has a feature that can be significantly reduced.

• Journal of IKEEE
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• v.13 no.3
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• pp.32-38
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• 2009

Ultrasonic motor (USM) is a new type motor which is driven by the ultrasonic vibration of piezoelectric elements. It possess many useful features that electromagnetic motors do not have, such as low speed and high torque. However, ultrasonic motor has heavy nonlinear speed characteristics and is sensitive to the change of drive conditions. In order to solve these problems, we present a smooth position control scheme for ultrasonic motor using fuzzy logic control with human expertise and without the need of any precise mathematical model. A "smooth operation" consideration is included when constructing the fuzzy rule base in order to achieve a most smooth response. An experimental position control system is constructed to show the effectiveness of the proposed control scheme.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1286-1294
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• 2015

Capacitor current feedback active damping is extensively used in grid-connected converters with an LCL filter. However, systems tends to become unstable when the digital control delay is taken into account, especially in low switching frequencies. This paper discusses this issue by deriving a discrete model with a digital control delay and by presenting the stable region of an active damping loop from high to low switching frequencies. In order to overcome the disadvantage of capacitor current feedback active damping, this paper proposes a modified approach using grid current and converter current for feedback. This can expand the stable region and provide sufficient active damping whether in high or low switching frequencies. By applying the modified approach, the active damping loop can be simplified from fourth-order into second-order, and the design of the grid current loop can be simplified. The modified approach can work well when the grid impedance varies. Both the active damping performance and the dynamic performance of the current loop are verified by simulations and experimental results.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.421-424
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• 2000

Direct Torque Control(DTC) of AC motor has the fast torque and flux dynamic responses even though it has very simple scheme to implement. However DTC do not show good performance at low speed range with conventional open loop stator flux observer when stator resistance varied. So authors proposed nonlinear stator flux obsever in order to flux estimation at low speed and show its simulation results.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.11
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• pp.1096-1103
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• 2010

This paper proposes CDC (Continuous Damping Control) algorithm and verifies in multi-body dynamic vehicle. In order to distinguish a road profile on driving, waviness calculated by the filtered vertical-accelerations of sprung and unsprung masses is introduced. Sky-hook control is used at a low waviness road and constant damping level control is used at a high waviness road, where the hard damping level is determined by waviness, roll rate, acceleration, and deceleration. The damping levels of ride, anti-roll, anti-squat, and anti-dive modules are calculated by tuning parameters which is dependent upon vehicle velocity. Therefore this high tunable algorithm is useful to improve the ride and handling performance under various driving conditions. In the simulations, tire and dampers are modelled by SWIFT (Short Wavelength Intermediate Frequency Tire) model and 1st order delay model, and results are compared with conventional damper's.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.28.2-28.2
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• 2008

Recently, star sensors have been successfully used as main attitude sensors for attitude control in many satellites. This research presents the star visibility analysis for star trackers and the goal of this analysis is to make sure that the star tracker implementation is suitable to the mission profile and scenario and satisfies the requirement of attitude orbit control system. As a main optical attitude sensor imaging stars, accomodations of a star tracker should be optimized in order to improve the probability of the usage by avoiding the blinding (the unavailability) by the Sun and the Earth. For the analysis, a statistical approach and a time simulation approach are used. The statistical approach is based on the generation of numerous cases, to derive relevant statistics about Earth and Sun proximity probabilites for different lines of sight. The time simulation approach is performed for one orbit to check the statistical result and to refine the statistical result and accomodations of star trackers. In order to perform simulations first of all, an orbit and specific mission profiles of a satellite are set, next the earth proximity probability and the sun proximity probability are calculated by considering the attitude maneuvers and the geometry of the orbit, and then finally the unavailability positions are estimated. As a result, the optimized accomodations of two star trackers are suggested for the low earth orbit satellite.