• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.2
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• pp.114-121
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• 2019

Tailless aircraft have advantages of low visibility compared to conventional aircraft, but drawback of poor stability as well which makes designing controller difficult. The controller design is more difficult, especially when the center of gravity moves due to store release or fuel consumption during flight. In this paper, an L1 adaptive controller is proposed as a way to overcome these problems. The reliability and performance of the controllers were verified by non-linear simulations. RPV Flying Quality Design criteria were used for design criteria. Using the simulation, it is shown that the adaptive controller maintains stability of the unmanned aircraft for sudden large change in the inertial properties. It is also shown that the calculation burden can be reduced when it is used with the gain scheduling method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.4
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• pp.188-195
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• 2002

We proposed the design of SVC adaptive fuzzy logic controller(AFLC) using Tabu search and neural network. We tuned the gains of input-output variables of fuzzy logic controller(FLC) and weights of neural network using Tabu search. Neural network was used for adaptively tuning the output gain of FLC. The weights of neural network was learned from the back propagation algorithm in real-time. To evaluate the usefulness of AFLC, we applied the proposed method to single-machine infinite system. AFLC showed the better control performance than PD controller and GAFLS[10] for three-phase fault in nominal load which had used when tuning AFLC. To show the robustness of AFLC, we applied the proposed method to disturbances such as three-phase fault in heavy and light load. AFLC showed the better robustness than PD controller and GAFLC[10].

• Physical Therapy Korea
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• v.2 no.2
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• pp.73-84
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• 1995

Spasticity has been defined as a motor disorder characterised by a velocity-dependent increase in tonic stretch reflexes with exaggerated tendon jerks resulting in hyperexcitability of the stretch reflexes as one component of the upper motor neuron syndrome. Weakness and loss of dexterity, however, are considered to be more disabling to the patient than changes in muscle tone. The discussion includes the important role that alterations in the physiology of motor units, notably changes in firing rates and muscle fiber atrophy, play in the manifestation of muscle weakness. This paper considers both the neural and mechanical components of spasticity and discusses, in terms of clinical intervention, the implications arising from recent research. Investigations suggest that the resistance to passive movement in individuals with spasticity is due not only to neural mechanisms but also to changes in mechanical properties of muscle. The emphasis is on training the individual to gain control over the muscles required for different tasks, and on preventing secondary and adaptive soft tissue changes and ineffective adaptive motor behaviours.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.11
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• pp.1053-1060
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• 2016

This paper proposes an adaptive equalizer with the digitally controlled active variable capacitor. An equalizing amplifier consists of a main amplifier and a source degeneration RC filter which is implemented using the digitally controlled active variable capacitor for area efficiency and linear loss compensation. The active capacitor changes its capacitance by the amplifier gain control, which is based on miller effect. In the simulated results, the proposed equalizer compensates the high frequency loss and extends the data eye width from 0.31 UI to 0.64 UI.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.305-311
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• 2017

In this paper, the LLC resonant converter battery charger, using adaptive turn ratio scheme, is proposed to achieve high efficiency and wide range output voltage. The LLC converter high frequency transformer has an adaptively changed turn ratio by the auxiliary control circuitry. As a result, the optimal converter design with a large magnetizing inductance is easily achieved to minimize the conduction and the turn-off losses while providing widely regulated voltage gain capability to properly charge the Li-ion battery. The proposed converter operational principle and the optimal design considerations are illustrated in detail. Finally, several simulation results verify the proposed LLC resonant converter's effectiveness.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.124-132
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• 2018

This paper proposes an LLC resonant converter based battery charger which utilizes an adaptive turn ratio scheme to achieve a wide output voltage range and high efficiency. The high frequency transformer of the LLC converter of the proposed strategy has an adaptively changed turn ratio through the auxiliary control circuit. As a result, an optimized converter design with high magnetizing inductance is possible, while minimizing conduction and turn-off losses and providing a regulated voltage gain to properly charge the lithium ion battery. For a step-by-step explanation, operational principle and optimal design considerations of the proposed converter are illustrated in detail. Finally, the effectiveness of the proposed strategy is verified through various experimental results and efficiency analysis based on prototype 300W Li-ion battery charger and battery pack.

• Smart Structures and Systems
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• v.13 no.2
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• pp.281-303
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• 2014

In order to suppress the wind-induced vibrations of the Canton Tower, a pair of active mass driver (AMD) systems has been installed on the top of the main structure. The structural principal directions in which the bending modes of the structure are uncoupled are proposed and verified based on the orthogonal projection approach. For the vibration control design in the principal X direction, the simplified model of the structure is developed based on the finite element model and modified according to the field measurements under wind excitations. The AMD system driven by permanent magnet synchronous linear motors are adopted. The dynamical models of the AMD subsystems are determined according to the open-loop test results by using nonlinear least square fitting method. The continuous variable gain feedback (VGF) control strategy is adopted to make the AMD system adaptive to the variation in the intensity of wind excitations. Finally, the field tests of free vibration control are carried out. The field test results of AMD control show that the damping ratio of the first vibration mode increases up to 11 times of the original value without control.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2099-2105
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• 2017

In a power system that has a high wind penetration, the output power fluctuation of a large-scale wind turbine generator (WTG) caused by the varying wind speed increases the maximum frequency deviation, which is an important metric to assess the quality of electricity, because of the reduced system inertia. This paper proposes a stable power-smoothing scheme of a doubly-fed induction generator (DFIG) that can suppress the maximum frequency deviation, particularly for a power system with a high wind penetration. To do this, the proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while guaranteeing the stable operation of a DFIG, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. The simulation results based on the IEEE 14-bus system demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WTG under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1274-1285
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• 2015

This paper deals with model reference adaptive system (MRAS) speed estimators based on a secondary flux for linear induction motors (LIMs). The operation of these estimators significantly depends on an adaptation mechanism. Fixed-gain PI controller is the most common adaptation mechanism that may fail to estimate the speed correctly in different conditions, such as variation in machine parameters and noisy environment. Two adaptation mechanisms are proposed to improve LIM drive system performance, particularly at very low speed. The first adaptation mechanism is based on fuzzy theory, and the second is obtained from an LIM mechanical model. Compared with a conventional PI controller, the proposed adaptation mechanisms have low sensitivity to both variations of machine parameters and noise. The optimum parameters of adaptation mechanisms are tuned using an offline method through chaotic optimization algorithm (COA) because no design criterion is given to provide these values. The efficiency of MRAS speed estimator is validated by both numerical simulation and real-time hardware-in-the-loop (HIL) implementations. Results indicate that the proposed adaptation mechanisms improve performance of MRAS speed estimator.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1147-1155
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• 2000

The installation of wireless communication system for various services of ITS at 5.8 GHz generates mutual interference. The representative example, the sharing of frequency between DSRC system and ETC system is a cause of communication error or disturbance both sides or one side owing to mutual interference. As a solution, a Shield Plate, Antenna Directionality, Power Control is proposed, but these are not perfect solution, because a RSU doesn't have the information of position of interferer. This paper applies an adaptive array antenna which makes a gain for desired users, makes a null for interferer, to up-link, down-link of DSRC and ETC system. The analysis of BER performance shows the effect of reduced interference about 20 dB.