• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.76-82
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• 2004

A method of designing a state feedback gam achieving a specified insensitivity of the closed-loop trajectory by the singularly perturbed unified system using the operators is proposed. The order of system is reduced by the singular perturbation technique by ignoring the fast mode in it. The proposed method takes care of the actual trajectory variations over the range of the singular perturbation parameter. Necessary conditions for optimality are also derived. The previous study was done in the continuous time system The present paper extends the previous study to the discrete system and the ${\delta}-operating$ system that unifies the continuous and discrete systems. Advantages of the proposed method are shown in the numerical example.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.405-412
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• 2012

A flow control on airfoil installed a vortex cell for high efficiency wind turbine blade in stationary and dynamic stall conditions have been numerically investigated by solving the compressible Navier-Stokes equations. The numerical scheme is based on a node-based finite-volume method with Roe's flux-difference splitting and an implicit time-integration method coupled with dual time step sub-iteration. The computed result for the airfoil in the stationary showed that lift-drag ratio increases due to low pressure by the vortex cell. The oscillating airfoil with the vortex cell showed that the magnitude of hysteresis loop is reduced due to the enhanced vortex in the cell.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.11
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• pp.1134-1142
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• 2003

This paper presents a hardware implementation of the STS diversity system, utilizing FPGAs and introduces the function and the design method of each of the modules of the system. In order to improve the performance of the implemented STS system which is an open loop transmit diversity system under fading environment, the exact estimation of the communication channel is essential. Therefore, we propose the optimal forgetting factor to estimate pilot channel in this paper, It is shown in this paper that the pilot channel is estimated using the forgetting factor of 0.7 without increasing the integration range of the pilot channel even when the power of pilot channel is not sufficiently large in CDMA 2000 1x signal environment.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.1
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• pp.60-65
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• 2008

In this paper, we concern the stability of smart space by using the robust digital controller. The proposed methodologies are based on the intelligent digital redesign (IDR). More precisely, we represent the nonlinear and uncertain analog system as the Takaki-Sugeno (T-S) fuzzy model. Then the IDR problem can be reduced to find the digital gains minimizing the norm distance between the closed-loop states of the analog and digital control. Its constructive conditions are expressed as the linear matrix inequalities (LMIs). At last, a numerical example, HVAC system, is demonstrated to visualize the feasibility of the proposed methodology.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.2
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• pp.187-192
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• 2009

Telecommand & telemetry control equipment is needed for the testing of the transponders during the development of satellite. This equipment must have a loopback function to perform the self testing without satellite. The fabrication of the designed system is easier and cheaper than the conventional testing system using direct modulation method. The measured results of fabricated equipment are satisfied with required specifications. A overall path loss of uplink and downlink is 47.8 dB and 42.6 dB, respectively. Also, IMD3 of uplink has measured 60.68 dBc at an output of -50 dBm.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.548-554
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• 2012

Verification and validation of operational software of the flight control computer, which is flight safety critical, is very important to prove correctness and faultness of the software. To verify the real-time softare requirement on operational software of flight control computer, real-time software internal parameter and variable monitoring technics on hardware-in-the-loop environment, similar to on-flight environment, is required. This paper describes flight safety critical software validation and verificiation environment using standard debugging interface, NEXUS 5001.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.565-573
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• 2017

This paper presents a multistage in-flight alignment (MIFA) method for a strapdown inertial navigation system (SDINS) suitable for moving vehicles with no initial attitude references. A SDINS mounted on a moving vehicle frequently loses attitude information for many reasons, and it makes solving navigation equations impossible because the true motion is coupled with an undefined vehicle attitude. To determine the attitude in such a situation, MIFA consists of three stages: a coarse horizontal attitude, coarse heading, and fine attitude with adaptive Kalman navigation filter (AKNF) in order. In the coarse horizontal alignment, the pitch and roll are coarsely estimated from the second order damping loop with an input of acceleration differences between the SDINS and GPS. To enhance estimation accuracy, the acceleration is smoothed by a scalar filter to reflect the true dynamics of a vehicle, and the effects of the scalar filter gains are analyzed. Then the coarse heading is determined from the GPS tracking angle and yaw increment of the SDINS. The attitude from these two stages is fed back to the initial values of the AKNF. To reduce the estimated bias errors of inertial sensors, special emphasis is given to the timing synchronization effects for the measurement of AKNF. With various real flight tests using an UH60 helicopter, it is proved that MIFA provides a dramatic position error improvement compared to the conventional gyro compass alignment.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2705-2710
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• 2011

With the rapid development of information and communication technology, CBTC system based on the wireless communication is widely applied in the railway signal system recently. CBTC system has advantages of lower installation space and maintenance fee than existing systems and the increase of transportation capacity and improvement of operating efficiency etc. due to the short headway. Based on the continuous wireless data communication between onboard and wayside equipment, CBTC system not only locates the train and transmits the information required for the train control, but also implements the moving block function by calculating the brake curves continuously according to distance from the preceding train. CBTC system can use either inductive loop (IL-CBTC) or radio frequency transmissions (RF-CBTC). In this paper, we propose RF-CBTC system architecture based on the functional modules, in which the CAN bus network is applied for the interfaces between the modules.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.46-52
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• 2016

Quasi-Orthogonal STBC (QO-STBC) scheme is proposed conventionally achieving approximate full rate and full diversity in more than 3 transmit antenna and open-loop environmen.. But, conventional QO-STBC has disadvantage that performance degradation by interference terms of detection matrix and high decoding complexity. Recently, this interference cancellation scheme of low decoding complexity by multiplying specific rotation matrix is proposed. We propose more general interference cancellation scheme by using EVD(Eigenvalue Decompostion).

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.56-59
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• 1996

Worst-case state estimation will be proposed in this paper. By using the worst-case disturbance and worst-case state estimation, we can obtain right/left constrained coprime factors. If constrained coprime factors are used in designing a controller, the infinity-norm of closed-loop transfer matrix can be smaller than any constant .gamma.(> .gamma.$_{opt}$) without matrix dilation optimization. The derivation of left/right constrained coprime factors is achieved by doubly coprime factorization for the plant constrained by the infinity norm. And the parameterization of stabilizing controllers gives us easily understanding for H$_{\infty}$ control theory.ry.