• Journal of Power Electronics
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• v.13 no.3
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• pp.479-486
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• 2013

This paper presents a control strategy for distributed systems, which can be used in islanded microgrids. The control strategy is based on the droop method, which uses locally measured feedback to achieve load current sharing. Instead of the traditional droop method, an improved one is implemented. A virtual inductor in the synchronous frame for three-phase inverters is proposed to deal with the coupling of the frequency and the amplitude related to the active and reactive power. Compared with the traditional virtual inductor, the proposed virtual inductor is not affected by high frequency noises because it avoids differential calculations. A model is given for the distributed generation system, which is beneficial for the design of the droop coefficients and the value of the virtual inductor. The effectiveness of the proposed control strategy is verified by simulation and experiment results.

• Journal of Power Electronics
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• v.18 no.1
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• pp.103-115
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• 2018

Parametric uncertainties and inverter nonlinearity exist in the permanent magnet synchronous motor (PMSM) drive system of electrical vehicles, which may lead to performance degradation or failure, and eventually threaten reliable operation. Therefore, a model-free deadbeat predictive current controller (MFDPCC) for PMSM drive systems is proposed in this study. The data-driven ultra-local model of a surface-mounted PMSM (SMPMSM) drive system that consists of parametric uncertainties and inverter nonlinearity is first established through the input and output data of a SMPMSM drive system. Subsequently, MFDPCC is designed. The performance comparisons and analyses of the proposed MFDPCC, the conventional proportional-integral controller, and the model-based deadbeat predictive current controller for SMPMSM drive systems are implemented via system simulation and experimental tests. Results show the effectiveness and technical advantages of the proposed MFDPCC.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.04a
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• pp.1139-1143
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• 2000

세계 각국의 우정사업 기관들은 우편번호에 대한 우편서비스의 질을 향상시키기 위하여 많은 노력을 기울이고 있다. 이의 일환으로 실시하고 있는 "우편번호 바코드 인쇄 제도"는 우편물을 저렴하고 신속.정확히 처리함으로써 우편 이용자들의 욕구를 충족시켜주기 위한 제도이다. 이 제도는 우편을 이용하는 우편번호가 자신의 우편물에 우편번호에 해당하는 흑백의 바코드를 인쇄해서 접수하게 되면 서비스 제공자는 인증절차를 거쳐 합격한 업체에 대해 소정의 요금을 할인해 주는 제도이다. 우리나라도 1998년부터 이 제도를 도입하여 운영 중에 있으며, 1999년도에 개국한 6개의 우편집중국에 대해서도 개국과 함께 이 제도를 시행할 예정으로 있다. 기존에는 소형통상 우편물에 대해서만 이 제도를 적용하였으나 대형통상 우편물인 플랫우편물에 대해서도 적용하도록 하고 있다. 이에 따라, 본 고에서는 우편번호 바코드 인쇄 제도가 소기의 목적을 달성할 수 있도록 플랫우편물에 대해 연구한 내용을 다루었다.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1071-1087
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• 2017

This paper introduces a DC/AC converter, which can be connected in parallel with a diode rectifier for regenerative applications. The DC/AC converter is supposed to transmit regenerative energy to the power grid when a motor is braking. Isolation transformers are not needed in the topology, which can reduce the size and cost. An analysis of the zero-order current existing in the system is carried out. In addition, algorithms to minimize the zero-order current, control the power factor and keep the DC bus voltage stable are discussed. A 55kW industrial prototype is built to verify the proposed analysis and control strategies.

• Journal of Power Electronics
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• v.19 no.1
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• pp.168-178
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• 2019

Discrete space vector modulation (DSVM) is an effective method to improve the steady-state performance of the finite control set predictive control for permanent magnet synchronous motor drive systems. However, it requires complex computations due to the presence of numerous virtual voltage vectors. This paper proposes an improved finite control set model-free predictive control using DSVM to reduce the computational burden. First, model-free deadbeat current control is used to generate the reference voltage vector. Then, based on the principle that the voltage vector closest to the reference voltage vector minimizes the cost function, the optimal voltage vector is obtained in an effective way which avoids evaluation of the cost function. Additionally, in order to implement double-objective control, a two-level decisional cost function is designed to sequentially reduce the stator currents tracking error and the inverter switching frequency. The effectiveness of the proposed control is validated based on experimental tests.

• Current Optics and Photonics
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• v.6 no.6
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• pp.634-641
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• 2022

A frequency stable and tunable optoelectronic oscillator (OEO) incorporating an optical phase shifter and a phase-shifted fiber Bragg grating (PS-FBG) is designed and analyzed. The frequency tunability of the OEO can be realized by using a tunable microwave photonic bandpass filter consisting of a PS-FBG, a phase modulator. The optical phase compensation loop is used to compensate for the phase variations of the RF signal from the OEO by adjusting an optical phase shifter. Simulation results demonstrate that the output RF signals of the OEO can be tuned in a frequency range of 118 MHz to 24.092 GHz. When the ambient temperature fluctuates within ±3.9 ℃, the frequency drifts of the output RF signals are less than 68 Hz, the side-mode suppression ratios are more than 69.39 dB, and the phase noise is less than -92.49 dBc/Hz at a 10 kHz offset frequency.

• Current Optics and Photonics
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• v.5 no.6
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• pp.641-651
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• 2021

To handle the servo delay in a real-time adaptive optics system, a linear subspace system identification algorithm was employed to model the system, and the accuracy of the system identification was verified by numerical calculation. Experimental verification was conducted in a real test bed system. Through analysis and comparison of the experimental results, the convergence can be achieved only 200 times with prediction and 300 times without prediction. After the wavefront peak-to-valley value converges, its mean values are 0.27, 4.27, and 10.14 ㎛ when the communication distances are 1.2, 4.5, and 10.2 km, respectively. The prediction algorithm can effectively improve the convergence speed of the peak-to-valley value and improve the free-space optical communication performance.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.237-241
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• 2009

Automation and robotic technology (ART) has been successfully applied in the manufacturing and allied industries to achieve on-time delivery of quality products at increasingly reduced costs. Meeting time, quality and cost targets still remains a big challenge in the global construction industry with prevalence of time and cost overruns. Application of ART in the construction industry could contribute to significant improvement in the efficient and effective delivery of projects to meet and exceed client expectations. However, the uptake of ART is still low in the construction industry. This study investigates the various ways in which ART could be applied to improve construction project delivery, potential areas of applications, and constraints to the uptake of the technology in the construction industry. Recommendations are made for improving the uptake of ART in the construction industry.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.12
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• pp.30-47
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• 1997

This paper encompasses a general technology in robot deburring automation using solid rotaing burr tools. Deburring is a cumbersome area in finishing technology, where design concept and system implementation is based on knowhows and experiences rather then theoretical development. In the field engineering it is diffcult to find a clue to where and how to start the system design. This paper presents a guide inselection of tool concept of geometry and material. Also, the concept of tool compliance system is introduced, which is one of the most important factor in robot deburring. Typical problems encountered in the field are classified into 20 categories and the solutions are suggested by the proven technology from the expertise. Special problems in polymer and diecasting areas are also briefly mentioned.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.1100-1105
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• 2022

Denoising, registering, and detecting changes of 3D digital map are generally conducted by skilled technicians, which leads to inefficiency and the intervention of individual judgment. The manual post-processing for analyzing 3D point cloud data of construction sites requires a long time and sufficient resources. This study develops automation technology for analyzing 3D point cloud data for construction sites. Scanned data are automatically denoised, and the denoised data are stored in a specific storage. The stored data set is automatically registrated when the data set to be registrated is prepared. In addition, regions with non-homogeneous densities will be converted into homogeneous data. The change detection function is developed to automatically analyze the degree of terrain change occurred between time series data.