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771.
Quantitative and robust speed control for a switched reluctance motor (SRM) drive is considered to be rather difficult and challenging owing to its highly nonlinear dynamic behavior. A speed control scheme having two-degree-of-freedom (2DOF) structure is developed here to improve the speed dynamic response of an SRM drive. In the proposed control scheme, the feedback controller is quantitatively designed to meet the desired regulation control requirements first. Then a reference model and a command feedforward controller based on an inverse plant model are employed to yield the desired tracking response at nominal case. As the variations of system parameters and operating conditions occur, the prescribed control specifications may not be satisfied any more. To improve this, the inverse model is adaptively tuned by a fuzzy control scheme so that the model-following tracking error is significantly reduced. In addition, a simple disturbance cancellation robust controller is added to improve the tracking and regulation control performances further. 相似文献
772.
The mosaic structure of the magnetic field in the heliosphere is described. It is formed by multiple corotating and propagating
magnetic domains which are especially numerous during solar maximum years.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
773.
V. I. Karpman 《Space Science Reviews》1974,16(3):361-388
This paper is a review of nonlinear theory of ELF waves propagating along the magnetic field in the magnetosphere. The following subjects are covered: (1) Main peculiarities of the Quasi-linear Approximation. (2) Nonlinear interaction of monochromatic waves with the resonant particles. (3) Side-band instability. (4) Quasimonochromatic wave packets. (5) Effects due to the inhomogeneity of the medium. 相似文献
774.
The effect of adjacent channel interference on the probability of error in a binary bandpass communication system with an integrating and dumping detector is investigated. Narrowband filters are assumed in the receiver of the main signal and transmitters of both main and interfering signals. Plots of the probability of error as a function of signal to noise ratio in the main channel or as a function of carrier frequency difference between the main and interfering signals are presented, assuming that the filters are of the Butterworth type. These figures are helpful in the selection of minimal frequency spacing of adjacent channels. 相似文献
775.
K. Sezaki S. Enya M. Morioka J. Ochiai I. Tanasawa T. Maekawa 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(5):85-88
In this paper, the Marangoni convection including buoyancy convection in two-dimensional fluid model was investigated experimentally and theoretically. The transparent liquid in the test cell was heated and cooled under various conditions. The fluid flow driven by surface tension and by buoyancy force was visualized and measured. The flow patterns, velocity distributions and temperature field were obtained and they were compared with the results of the numerical solutions. The effect of the configuration and the convection in microgravity on crystal growth was discussed. The temperature field of the crystallizing surface was predicted. 相似文献
776.
V. I. LukyashchenkoS. O. TverdokhlebovN. A. Brukhanov 《Acta Astronautica》1999,44(7-12):525-529
A concept of a universal fitting-out module applicable for space flight test of a solar-powered electric propulsion (EP) as well as for the assembly and deployment of small spacecraft (S/C) from the international space station (ISS) is proposed. 相似文献
777.
Steered beam adaptive arrays for multiple simultaneous desired signals are discussed. It is shown that the performance of a steered beam adaptive array depends upon the range of input signal strengths and the choice of the steering vector. Optimum steering vectors for various input signal strengths are given. All choices of steering vectors are equally effective in the rejection of jammers. 相似文献
778.
K.L. Majumder R. Ramakrishnan I.C. Matieda G. Sharma A.K.S. Gopalan D.S. Kamat 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(2):283-286
Indian Space Research Organisation (ISRO) plans to launch a Remote Sensing Satellite around 1985 for acquiring resources information in the visible and near infrared region. For this a number of projects under Joint Experiments Program (JEP) were taken up between ISRO and various departments under Government of India to define the mission parameters including the spectral bands. This paper presents the results obtained in the selection of spectral bands and their widths for IRS program. 相似文献
779.
D.K. Kondepudi I. Prigogine 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(5):171-176
We note that far-from-equilibrium chemical systems can respond very sensitively to gravity. The response could be in selection of possible structures or in the formation of propagating bands. In these cases the sensitivity is characterized by the factor , where n=2 or 3, Eg the interaction energy, k the Boltzmann constant and T, the temperature. Also, taking the thermodynamic fluctuations into account, we obtain the theoretical limit for the minimum field strength measurable by such systems. 相似文献
780.
V.I. Polezhaev S.A. Nikitin A.I. Fedyushkin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(5):65-78
Investigations conducted earlier by the authors have established that due to the steady-state field of body forces, convection is capable of giving rise to macroinhomogeneity in transverse impurity distribution in crystals. In the case of semiconductor materials the maximal value of this inhomogeneity is due to a weak convection in the melt, typical of low-gravity conditions. However, in addition to steady gravitational convection, other factors ignored previously, may also be employed in conducting experiments in low-g environments. The present paper discusses the results of theoretical studies of some factors influencing impurity distribution in the melt and the crystal. 相似文献