• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.174-178
• /
• 2001

An improved stationary frame-based digital current control technique for a permanent magnet (PM) synchronous motor is presented. Generally, the stationary frame current controller is known to provide the advantage of a simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state. On the other hand, in the synchronous frame current regulator, the regulated currents are dc quantities and a zero steady-state error can be obtained through the integral control. However, the need to transform the signals between the stationary and synchronous frames makes the implementation of a synchronous frame regulator complex. Although the PI controller in the stationary frame gives a steady-state error and a phase delay, the control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF, resulting in an ideal steady-state control characteristics irrespective of an operating condition as in the synchronous PI decoupling controller. However, its steady-state response may be degraded due to the inexact cancellation inputs under the parameter variations. To improve the control performance in the stationary frame, the disturbance is estimated using the time delay control. The proposed scheme is implemented on a PM synchronous motor using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

• Journal of Power Electronics
• /
• 제1권2호
• /
• pp.88-98
• /
• 2001

An improved stationary frame-based digital current control technique for a permanent magnet(PM) synchronous motor is presented. Generally, the stationary frame current controller is known to provide the advantage of a simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state. On the other hand, in the synchronous frame current regulator the regulated currents are dc quantities and a zero steady-state error can be obtained through the integral control. However, the need to transform the signals between the stationary and synchronous frames makes the implementation of a synchronous frame regulator complex. Although the PI controller in the stationary frame gives a steady-state error and a phase delay, the control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF., resulting in an ideal steady-state control characteristics irrespective of an operating condition as in the synchronous PI decoupling controller. However, its steady-state response may be degraded due to the inexact cancellation inputs under the parameter variations. To improve the control performance in the stationary frame, the disturbance is estimated using the time delay control. The proposed scheme is implemented on a PM synchronous motor using DSP TMS320C31 and the effectiveness is verified through the comparative simulations and experiments.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
• /
• pp.1255-1258
• /
• 2006

PM OLED has the line-disturbance when eyes can detect the driving line status in the shaking situation. It is closely related with the lighting intensity and the lighting time during the line driving. .In this paper we suggest the frame part method for eliminating lineflash appearance. Frame part is a driving method of PM OLED, which divides one frame into several inner-frame parts to reduce the color interference between closely related pixels and to lessen the lineflash appearance which disturbs viewer to perceive the images. Frame part groups one frame into several inner-frame parts and have inner-frame rate higher than the frame rate. Frame part could be used in most of applications in PM OLED systems to enhance the total performance of screen quality.

• 한국지구과학회지
• /
• 제40권4호
• /
• pp.353-381
• /
• 2019

The general world model for homogeneous and isotropic universe has been proposed. For this purpose, we introduce a global and fiducial system of reference (world reference frame) constructed on a (4+1)-dimensional space-time, and assume that the universe is spatially a 3-dimensional hypersurface embedded in the 4-dimensional space. The simultaneity for the entire universe has been specified by the global time coordinate. We define the line element as the separation between two neighboring events on the expanding universe that are distinct in space and time, as viewed in the world reference frame. The information that determines the kinematics of the geometry of the universe such as size and expansion rate has been included in the new metric. The Einstein's field equations with the new metric imply that closed, flat, and open universes are filled with positive, zero, and negative energy, respectively. The curvature of the universe is determined by the sign of mean energy density. We have demonstrated that the flat universe is empty and stationary, equivalent to the Minkowski space-time, and that the universe with positive energy density is always spatially closed and finite. In the closed universe, the proper time of a comoving observer does not elapse uniformly as judged in the world reference frame, in which both cosmic expansion and time-varying light speeds cannot exceed the limiting speed of the special relativity. We have also reconstructed cosmic evolution histories of the closed world models that are consistent with recent astronomical observations, and derived useful formulas such as energy-momentum relation of particles, redshift, total energy in the universe, cosmic distance and time scales, and so forth. The notable feature of the spatially closed universe is that the universe started from a non-singular point in the sense that physical quantities have finite values at the initial time as judged in the world reference frame. It has also been shown that the inflation with positive acceleration at the earliest epoch is improbable.

• Journal of information and communication convergence engineering
• /
• 제14권1호
• /
• pp.21-25
• /
• 2016

N-screen is a promising technology to improve support for multimedia multicasting, content sharing, content mobility, media scalability, and seamless mobility. In this paper, the WiMedia distributed-MAC (D-MAC) protocol is adopted for development of a seamless N-screen wireless service. Furthermore, to provide a multi-hop, one source multi-use N-screen service through point to point streaming in a seamless D-MAC protocol, a dynamic multi-frame transmission technology is proposed. In this technology, a dynamic time slot allocation scheme and a multi-hop resource reservation scheme are combined. In the proposed dynamic time slot allocation scheme, two thresholds, a hard threshold and a soft threshold, are included to satisfy the power consumption and delay requirements. A multi-frame DRP reservation scheme is proposed to minimize end-to-end delay during the multi-hop transmissions between N-screen devices. The proposed dynamic multi-frame transmission scheme enhances N-screen performance in terms of the multi-hop link establishment success rate and link establishment time compared to the conventional WiMedia D-MAC system.

• 대한수학회지
• /
• 제51권5호
• /
• pp.897-918
• /
• 2014

This paper addresses multi-window Gabor frames with rational time-frequency product. Such issue was considered by Zibulski and Zeevi (Appl. Comput. Harmonic Anal. 4 (1997), 188-221) in terms of Zak transform matrix (so-called Zibuski-Zeevi matrix), and by many others. In this paper, we introduce of a new Zak transform matrix. It is different from Zibulski-Zeevi matrix, but more direct and convenient for our purpose. Using such Zak transform matrix we characterize rational time-frequency multi-window Gabor frames (Riesz bases and orthonormal bases), and Gabor duals for a Gabor frame. Some examples are also provided, which show that our Zak transform matrix method is efficient.

• Advances in concrete construction
• /
• 제9권4호
• /
• pp.407-412
• /
• 2020

Due to the influence of nonlinearity and time-variation, it is difficult to establish an accurate model of concrete frame structures that adopt active controllers. Fuzzy theory is a relatively appropriate method but susceptible to human subjective experience to decrease the performance. To guarantee the stability of multi-time delays complex system with multi-interconnections, a delay-dependent criterion of evolved design is proposed in this paper. Based on this criterion, the sector nonlinearity which converts the nonlinear model to multiple rule base of the linear model and a new sufficient condition to guarantee the asymptotic stability via Lyapunov function is implemented in terms of linear matrix inequalities (LMI). A numerical simulation for a three-layer reinforced concrete frame structure subjected to earthquakes is demonstrated that the proposed criterion is feasible for practical applications.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 추계 학술논문 발표대회
• /
• pp.92-93
• /
• 2014

Green Frame is a method for Rahmen structure construction composed of composite PC members. The composite PC members of Green Frame which are based on in-situ production can reduce the construction cost and are more likely to secure quality when compared to production in factories. Previous studies developed forms for in-situ production of Green Frame composite PC members and proposed algorithms to arrange them on site. However, it requires not only their arrangement, but also calculation of an accurate production period to produce the required PC members in a limited space and supply them in a timely manner. In particular, it is necessary to clearly define the properties of detailed processes for in-situ production of PC members and to calculate the time required for respective process. To do so, this study is a basic research on calculating the time for in-situ production using a linear scheduling method.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
• /
• pp.27-34
• /
• 2002

In the case of reinforced concrete structures, the knowledge of load transfer in the long-term behavior analysis considering construction sequence is very important. Even though long-term behavior of concrete structures has been widely studied, the studies on the time-dependent axial force variation of shore have been scarce to date. In order to investigate the shore behaviors under actual construction conditions, a three-story test frame was constructed on a construction site. The entire construction schedule for the test frame was made to follow the schedule of an actual three-story frame. To analyze the data collected from the test frame, an analysis method based on the Winkler foundation model was developed. This analysis method accurately Predicts the time-dependent behavior of shore. The analysis results coincide well with those obtained by the Midas GENw program

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.61-64
• /
• 1999

The turbo code appropriate to IMT-2000 is known to have a good performance whenever the size of frame increases. But it is not appropriate to a sort of video service to need real time because of decoding complexity and long delay time by the size of frame. Therefore this paper proposes decoding decision algorithm of short frame in which soft output is weighted according to iteration number in turbo decoder. Performance of the proposed algorithm is analysed in the AWGN channel when short length of frame is 100, 256, 640. As the result. it is appeared that the proposed decoding decision algorithm has improved in BER other than in the existing MAP decoding algorithm.