• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.421-421
• /
• 2000

In this paper, robust two-degree-of-freedom controller for satellite antenna system which tracks reference signal is designed. Two-degree-of-freedom controller consists of a prefilter and a feedback controller to solve trade-off between robust stability and command response. The feedback controller is designed from specifications like stability, disturbance rejection and robustness via H$_{\infty}$ design technique. In the sequel, H$_2$ optimal prefilter is introduced to improve the command response. This suggests a two-step design, with different types of performance specifications at each stage. In practical problems, this may easily lead to a prefilter of unacceptably high order. In order to avoid high order prefilter we use a particular structure in which both the prefilter and the feedback controller share the same dynamics. H$_2$-prefilter technique proposed in this paper is verified by simulation.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.501-505
• /
• 2001

The parallel operation system of UPS is used to increase reliability of power source at critical load. But parallel UPS system has a few defects, impedance is different from each other and circulating current occurs between UPSs, due to line impedance and parameter variation, though controlled by the same synchronization signal. According to such characteristic of parallel UPS, balanced load-sharing control is the most important technique in parallel UPS operation. In this paper, a novel power deviation compensation algorithm is proposed. it is composed of voltage controller to compensate power deviation that be calculated by using active and reactive current deviation between inverters on synchronous d-q reference frame.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.6
• /
• pp.585-592
• /
• 2003

The parallel operation system of UPS is used to increase reliability of power source at critical load. But parallel UPS system has a few defects, impedance is different from each other and circulating current occurs between UPSs, due to line impedance and parameter variation, though controlled by the same synchronization signal. According to such characteristic of parallel UPS, balanced load-sharing control is the most important technique in parallel UPS operation. In this paper, a novel power deviation compensation algorithm is proposed. it is composed of voltage controller to compensate power deviation that be calculated by using active and reactive current deviation between Inverters on synchronous d-q reference frame.

• Journal of Ocean Engineering and Technology
• /
• v.34 no.6
• /
• pp.481-488
• /
• 2020

Composite materialsuch as glass-fiber reinforced plastic and carbon-fiber reinforced plastic (CFRP) shows anisotropic property and have been widely used for structural members and outfitings of ships. The structural safety of composite structures has been generally evaluated via finite element analysis. This paper presents a technique for updating the finite element model of anisotropic beams or plates via natural frequencies. The finite element model updates involved a compensation process of anisotropic material properties, such as the elastic and shear moduli of orthotropic structural members. The technique adopted was based on a discrete genetic algorithm, which is an optimization technique. The cost function was adopted to assess the optimization problem, which consisted of the calculated and referenced low-order natural frequencies for the target structure. The optimization process was implemented with MATLAB, which includes the finite element updates and the corresponding natural frequency calculations with MSC/NASTRAN. Material properties of a virtual cantilevered orthotropic beam were estimated to verify the presented method and the results obtained were compared with the reference values. Furthermore, the technique was applied to a cantilevered CFRP beam to successfully estimate the unknown material properties.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.37 no.2
• /
• pp.60-68
• /
• 2000

This paper describes a design methodology for the CMOS current source which can be implemented in standard memory process. The proposed techniques provide a good characteristic against the power-supply variation by utilizing a self-bias circuit and the reduction of the first-order component of the temperature variation through the new temperature compensation technique and include a new current-sensing start-up circuit enabling a robust operation against the voltage noise generated during the operation of the chip. In addition to the circuit-design technology, techniques where the proposed CMOS current-reference circuit can be applied to the clocking circuits of a very high-speed DRAM are presented. The feasibility of the suggested design methodology for the CMOS current reference is demonstrated by both the analytical method and the circuit simulation.

• Journal of Power Electronics
• /
• v.18 no.3
• /
• pp.863-870
• /
• 2018

The traditional power control theories for the harmonic reduction methods in multilevel inverters are found to be unreliable under unbalanced load conditions. The unreliability in harmonic mitigation is caused by voltage fluctuations, non-linear loads, the use of power switches, etc. In general, the harmonics are reduced by filters. However, such devices are an expensive way to provide a smooth and fast response to secure power systems during dynamic conditions. Hence, the Decoupled Double Synchronous Reference Frame (DDSRF) theory combined with a State Delay Controller (SDC) is proposed to achieve a harmonic reduction in power systems. The DDSRF produces a sinusoidal harmonic that is the opposite of the load harmonic. Then, it injects this harmonic into power systems, which reduces the effect of harmonics. The SDC is used to reduce the delay between the compensation time for power injection and the generation of a reference signal. The proposed technique has been simulated using MATLAB and its reliability has been verified experimentally under unbalanced conditions.

• International Journal of Fuzzy Logic and Intelligent Systems
• /
• v.8 no.3
• /
• pp.185-191
• /
• 2008

In this paper, experimental studies of a neural network (NN) control technique for non-model based position control of the x-y table robot are presented. Decentralized neural networks are used to control each axis of the x-y table robot separately. For an each neural network compensator, an inverse control technique is used. The neural network control technique called the reference compensation technique (RCT) is conceptually different from the existing neural controllers in that the NN controller compensates for uncertainties in the dynamical system by modifying desired trajectories. The back-propagation learning algorithm is developed in a real time DSP board for on-line learning. Practical real time position control experiments are conducted on the x-y table robot. Experimental results of using neural networks show more excellent position tracking than that of when PD controllers are used only.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1098-1101
• /
• 2004

The ordinary stereo image of an object consists of data of left and right views. Therefore, the left and right image pairs have to be transmitted simultaneously in order to display 3-dimentional video at the remote site. However, due to the twice data in comparing with a monoscopic image of the same object, it needs to be compressed for fast transmission and resource saving. Hence, it needs an effective coding algorithm for compressing stereo image. It was found previously that compressing left and right frames independently will achieve the compression ratio lower than compressing by utilizing the spatial redundancy between both frames. Therefore, in this paper, we study the stereo image compression technique based on the multiresolution wavelet transform using varied disparity-block size for estimation and compensation. The size of disparity-block in the stereo pair subbands are scaling on a coarse-to-fine wavelet coefficients strategy. Finally, the reference left image and residual right image after disparity estimation and compensation are coded by using SPIHT coding. The considered method demonstrates good performance in both PSNR measures and visual quality for stereo image.

• Journal of Biomedical Engineering Research
• /
• v.28 no.4
• /
• pp.449-454
• /
• 2007

An electrohydraulic (EH) pump-driven closed-loop blood pressure regulatory system was developed based on flow-mediated vascular occlusion using the vascular occlusive cuff technique. It is very useful for investigating blood pressure-dependant physiological variability, in particular, that could identify the principal mediators of renal autoregulation, such as tubuloglomerular feedback (TGF) and myogenic (MYO), during blood pressure regulation. To address this issue, renal perfusion pressure (RPP) should be well regulated under various experimental conditions. In this paper, we designed a new EH pump-driven RPP regulatory system capable of implementing precise and rapid RPP regulation. A closed-loop servo-controlwas developed with an optimal proportional plus integral (PI) compensation using the dynamic feedback RPP signal from animals. An in vivo performance was evaluated in terms of flow-mediated RPP occlusion, maintenance, and release responses. Step change to 80 mmHg reference from normal RPP revealed steady state error of ${\pm}3%$ during the RPP regulatory period after PI action. We obtained rapid RPP release time of approximately 300 ms. It is concluded that the proposed EH RPP regulatory system could be utilized in in vivo performance to study various pressure-flow relationships in diverse fields of physiology, and in particular, in renal autoregulation mechanisms.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.5
• /
• pp.82-91
• /
• 2014

The combined generator system by integrating several renewable energy sources can share the electrical infrastructure and therefore have the advantage of constructing not only the transmission system but also the power conversion system. Among the various combined renewable system, the wind power and wave power has a high possibility of future growth due to the economic feasibility in offshore environment. This kind of large-scale combined systems might be follow the determination by the transmission system operator's directions and control the output profile by focusing at PCC. However, both renewable energies are depend on the unpredictable environmental variation; it is needed to do the compensation devices. In this paper, the ESS compensation plan is proposed to do output determination of the combined generator system by paying attention to active power of utility grid with the analysis of the controllable elements of the wind and wave power generator. The improvement of the new application technique of the combined system is confirmed through using the PSCAD/EMTDC. The entire simulation process was designed by adopting the active power control according to the reference signal of TSO.