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51.
An input filter is frequently employed between a switching regulator and its power source. However, its presence often results in degradation of dynamic performances and stability. The detrimental interaction is between an input filter and a switching regulator and is a function of the input filter parameters and also of the supply voltage. An earlier paper presented an analysis and design procedure aimed at developing a feed-forward loop to cancel this undesirable interaction. The feed-forward design is extended here to encompass a scheme that automatically accounts for changes in the supply voltage; the result is an adaptive compensation that tracks the input voltage variations. Experimental results are presented that confirm the adaptive nature of the design. 相似文献
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Plaschke Ferdinand Hietala Heli Archer Martin Blanco-Cano Xóchitl Kajdič Primož Karlsson Tomas Lee Sun Hee Omidi Nojan Palmroth Minna Roytershteyn Vadim Schmid Daniel Sergeev Victor Sibeck David 《Space Science Reviews》2018,214(5):1-66
Space Science Reviews - Particles are accelerated to very high, non-thermal energies in solar and space plasma environments. While energy spectra of accelerated electrons often exhibit a power law,... 相似文献
54.
Chae Kyung Sim Huynh Anh Nguyen Le Soojong Pak Hye-In Lee Wonseok Kang Moo-Young Chun Ueejeong Jeong In-Soo Yuk Kang-Min Kim Chan Park Michael D. Pavel Daniel T. Jaffe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
We present a Python-based data reduction pipeline package (PLP) for the Immersion GRating INfrared Spectrograph (IGRINS), an instrument that covers the complete H- and K-bands in one exposure with a spectral resolving power of 40,000. The reduction steps carried out by the PLP include flat-fielding, background removal, order extraction, distortion correction, wavelength calibration, and telluric correction using spectra of A type standard stars. As the spectrograph has no moving parts, the PLP automatically reduces the data using predefined functions for the processes of order extraction, distortion correction, and wavelength calibration. Before the telluric correction of the target spectra, the intrinsic hydrogen absorption features of the standard A star are removed with a Gaussian fitting algorithm. The final result is the flux of the target as a function of wavelength. Users can customize the predefined functions for the extraction of the spectrum from the echellogram and adjust the parameters for the fitting functions for the spectra of celestial objects, using “fine-tuning” options, as necessary. Presently, the PLP produces the best results for point-source targets. 相似文献
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Eun-Jung Choi Jae-Cheol Yoon Byoung-Sun Lee Sang-Young Park Kyu-Hong Choi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Spaceborne GPS receivers are used for real-time navigation by most low Earth orbit (LEO) satellites. In general, the position and velocity accuracy of GPS navigation solutions without a dynamic filter are 25 m (1σ) and 0.5 m/s (1σ), respectively. However, GPS navigation solutions, which consist of position, velocity, and GPS receiver clock bias, have many abnormal excursions from the normal error range for space operation. These excursions lessen the accuracy of attitude control and onboard time synchronization. In this research, a new onboard orbit determination algorithm designed with the unscented Kalman filter (UKF) was developed to improve the performance. Because the UKF is able to obtain the posterior mean and covariance accurately by using the second-order Taylor series expansion through the sampled sigma points that are propagated by using the true nonlinear system, its performance can be better than that of the extended Kalman filter (EKF), which uses the linearized state transition matrix to predict the covariance. The dynamic models for orbit propagation applied perturbations due to the 40 × 40 geo-potential, the gravity of the Sun and Moon, solar radiation pressure, and atmospheric drag. The 7(8)th-order Runge–Kutta numerical integration was applied for orbit propagation. Two types of observations, navigation solutions and C/A code pseudorange, can be used at the user’s discretion. The performances of the onboard orbit determination were verified using real GPS data of the CHAMP and KOMPSAT-2 satellites. The results of the orbit determination were compared with the precision orbit ephemeris (POE) of the CHAMP and KOMPSAT-2 satellites. 相似文献
57.
航空航天复合材料应用的最新进展 总被引:3,自引:0,他引:3
文章介绍了先进复合材料的最新进展情况,内容包括用于最新复合材料体系的各种增强纤维、树脂基体,及复合材料结构设计的一些新概念。重点介绍了低成本和高效的制造技术。复合材料重要结构件的制造技术在不断改进,制造出的部件不仅精度和强度更高,而且更显成本效益。文章还介绍了航空航天领域一些新研发的复合材料结构件。 相似文献
58.
Forced vibration analysis including a vortex lattice prediction given an external aerodynamic force is conducted in this paper based on a standing wave formulation. The starting point of the standing wave formulation is a set of blade disk normal modes that incorporate all forms of the blade, disk, and shroud elastic coupling. The Küssner gust function was used in a few previous investigations of forced vibration based on the standing wave formulation. However, it was found to be valid only for low engine-order excitation. Therefore, a two-dimensional unsteady vortex lattice method is employed in this paper to predict the gust excitation up to higher engine-order excitation. Thus, the present unsteady vortex lattice analytical model is capable of capturing compressibility and higher engine-order excitation. It features advantages in terms of its computational time and level of accuracy. The effects of mistuning a cascaded blade are also examined in the present aeroelastic analysis to determine the possible advantages obtained by doing this. Numerical results for the mistuned bladed disk are presented regarding its forced response characteristics. In a low engine-order excitation condition, it is shown that similar predictions are obtained between the present and earlier analyses. The maximum discrepancy in the blade amplitude is 70% for a single-blade mistuned rotor and 62.6% for an alternately mistuned rotor, in the worst case, compared to a completely tuned rotor. Single-peak frequencies are presented and analyzed in the higher engine-order excitation levels. 相似文献
59.
Korea’s space development program was created almost 40 years behind those of the advanced countries but it has nevertheless made remarkable progress. Korean space development has been focused on technology catch-up, where commercialization and growth of industrial competitiveness are important rationales. However, the program has several problems, including: lack of a space equipment manufacturing industry, total system companies in the space manufacturing industry and communication between industry and researchers, and much concentration of projects and initiatives in the Korean Aerospace Research Institute (KARI). This study analyzes the problem by comparing space agencies and programs in Korea and other countries, particularly Japan and the USA. It is shown that the role of a national laboratory is critical in space industry development and argued that KARI should make greater efforts to promote the Korean space industry by encouraging technology transfer, sharing equipment and communication between companies. For successful space development, the main organization – usually the national research institute – should change its role from a research-only laboratory to manager and supporter of space development and industry. Such a move would invigorate Korea’s space industry and allow it to catch up with countries with a similar environment. 相似文献
60.
The paper presents a novel noncertainty-equivalent adaptive (NCEA) control system for the pitch attitude control of satellites in elliptic orbits using solar radiation pressure (SRP). The satellite is equipped with two identical solar flaps to produce control moments. The adaptive law is based on the attractive manifold design using filtered signals for synthesis, which is a modification of the immersion and invariance (I&I) method. The control system has a modular controller–estimator structure and has separate tunable gains. A special feature of this NCEA law is that the trajectories of the satellite converge to a manifold in an extended state space, and the adaptive law recovers the performance of a deterministic controller. This recovery of performance cannot be obtained with certainty-equivalent adaptive (CEA) laws. Simulation results are presented which show that the NCEA law accomplishes precise attitude control of the satellite in an elliptic orbit, despite large parameter uncertainties. 相似文献