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1.
《中国航空学报》2020,33(11):2907-2920
This paper investigates a time-varying anti-disturbance formation problem for a group of quadrotor aircrafts with time-varying uncertainties and a directed interaction topology. A novel Finite-Time Convergent Extended State Observer (FTCESO) based fully-distributed formation control scheme is proposed to enhance the disturbance rejection and the formation tracking performances for networked quadrotors. By adopting the hierarchical control strategy, the multi-quadrotor system is separated into two subsystems: the outer-loop cooperative subsystem and the inner-loop attitude subsystem. In the outer-loop subsystem, with the estimation of disturbing forces and uncertain dynamics from FTCESOs, an adaptive consensus theory based cooperative controller is exploited to ensure the multiple quadrotors form and maintain a time-varying pattern relying only on the positions of the neighboring aircrafts. In the inner-loop subsystem, the desired attitude generated by the cooperative control law is stably tracked under a FTCESO-based attitude controller in a finite time. Based on a detailed algorithm to specify the cooperative control protocol, the feasibility condition to achieve the time-varying anti-disturbance formation tracking is derived and the rigorous analysis of the whole closed-loop multi-quadrotor system is given. Some numerical examples are conducted to intuitively demonstrate the effectiveness and the improvements of the proposed control framework. 相似文献
2.
《中国航空学报》2020,33(11):2851-2863
Recent years have witnessed a booming of the industry of civil Unmanned Aircraft System (UAS). As an emerging industry, the UAS industry has been attracting great attention from governments of all countries and the aviation industry. UAS are highly digitalized, informationized, and intelligent; therefore, their integration into the national airspace system has become an important trend in the development of civil aviation. However, the complexity of UAS operation poses great challenges to the traditional aviation regulatory system and technical means. How to prevent collisions between UASs and between UAS and manned aircraft to achieve safe and efficient operation in the integrated operating airspace has become a common challenge for industry and academia around the world. In recent years, the international community has carried out a great amount of work and experiments in the air traffic management of UAS and some of the key technologies. This paper attempts to make a review of the UAS separation management and key technologies in collision avoidance in the integrated airspace, mainly focusing on the current situation of UAS Traffic Management (UTM), safety separation standards, detection system, collision risk prediction, collision avoidance, safety risk assessment, etc., as well as an analysis of the bottlenecks that the current researches encountered and their development trends, so as to provide some insights and references for further research in this regard. Finally, this paper makes a further summary of some of the research highlights and challenges. 相似文献
3.
Fault mode probability factor based fault-tolerant control for dissimilar redundant actuation system
This paper presents a Fault Mode Probability Factor (FMPF) based Fault-Tolerant Control (FTC) strategy for multiple faults of Dissimilar Redundant Actuation System (DRAS) composed of Hydraulic Actuator (HA) and Electro-Hydrostatic Actuator (EHA). The long-term service and severe working conditions can result in multiple gradual faults which can ultimately degrade the system performance, resulting in the system model drift into the fault state characterized with parameter uncertainty. The paper proposes to address this problem by using the historical statistics of the multiple gradual faults and the proposed FMPF to amend the system model with parameter uncertainty. To balance the system model precision and computation time, a Moving Window (MW) method is used to determine the applied historical statistics. The FMPF based FTC strategy is developed for the amended system model where the system estimation and Linear Quadratic Regulator (LQR) are updated at the end of system sampling period. The simulations of DRAS system subjected to multiple faults have been performed and the results indicate the effectiveness of the proposed approach. 相似文献
4.
针对一类非线性动力学系统,本文推导出二次型性能指标下的微分对策解,由此得到一组含有非线性因素的最环风模型,这一模型特别适用于研究作空间机动飞行的飞机受外界环境扰动的灵敏性问题。最后考察了这一变化风场对飞机突防航迹非线性解耦跟踪的影响。 相似文献
5.
本文用自制的装有 BaF_2探头的高探测效率的正电子湮没寿命谱仪测量了在室温下正电子素 o-Ps 与 p-RPhG 及 m-RPhG(R=NO_2,Cl,H,CH_3,cH_3O)在20%(V/V)二氧六环水溶液中的络合形成速度常数。实验结果表明,这些o-Ps-M 络合形成速度常数 K 值均与作为配位体的 p-RPhG、m-RPhG 的碱性解离常数 K 的负对数 pK_2 呈线性函数。这表明上述瞬态络合反应满足线性自由能关系,由此可推断出上述络合反应的一些重要性质。 相似文献
6.
依据Ту-154М变稳飞机的特点,主要进行了不同操纵器、不同控制律和不同显示画面的飞行试验研究。特别是通过中央杆和侧杆、电传系统不同控制律飞行品质特性之间、两种先进控制方案及不同显示方式的比较,不仅掌握了这方面的试飞技术和评定技术,还亲身体验到变稳飞机在发展仿真技术,新机预研及提高试飞员试飞技术和评定技术等方面的巨大作用。 相似文献
7.
The significance of external influences on the environment of Earth and its atmosphere has become evident during recent years.
Especially, on time scales of several hundred years, the cosmogenic isotope concentration during the Wolf-, Spoerer-, Maunder-
and Dalton-Minimum indicates an increased cosmic ray flux. Because these grand minima of solar activity coincide with cold
periods, a correlation of the Earth climate with the cosmic ray intensities is plausible. Any quantitative study of the effects
of energetic particles on the atmosphere and environment of the Earth must address their transport to Earth and their interactions
with the Earth’s atmosphere including their filtering by the terrestrial magnetosphere. The first problem is one of the fundamental
problems in modern cosmic ray astrophysics, and corresponding studies began in the 1960s based on Parker’s cosmic ray modulation
theory taking into account diffusion, convection, adiabatic deceleration, and (later) the drift of energetic particles in
the global heliospheric magnetic field. It is well established that all of these processes determining the modulation of cosmic
rays are depending on parameters that are varying with the solar magnetic cycle. Therefore, the galactic cosmic ray intensities
close to Earth is the result of a complex modulation of the interstellar galactic spectrum within the heliosphere. The modern
view of this cosmic ray modulation is summarized in our contribution. 相似文献
8.
P.B. Marty S. Bardeau O. Czoske H. Ebeling J.P. Kneib R. Sadat I. Smail 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,34(12):2509-2515
We present an analysis of seven clusters observed by XMM-Newton as part of our survey of 17 most X-ray luminous clusters of galaxies at z 0.2 selected for a comprehensive and unbiased study of the mass distribution in massive clusters. Using the public software FTOOLS and XMMSAS we have set up an automated pipeline to reduce the EPIC MOS and pn spectro-imaging data, optimized for extended sources analysis. We also developped a code to perform intensive spectral and imaging analysis particularly focussing on proper background estimate and removal. XMM-Newton deep spectro-imaging of these clusters allowed us to fit a standard β-model to their gas emission profiles as well as a standard MEKAL emission model to their extracted spectra, and test their inferred characteristics against already calibrated relations. 相似文献
9.
电子商务及其基本法律问题 总被引:1,自引:0,他引:1
周绍安 《华北航天工业学院学报》2002,12(2):22-24
本文简单阐述了电子商务的概念、模式、基本流程及其基本法律问题和目前的立法现状,弄清这些问题,无论是对于从事电子商务还是IT产业的经营、管理以及进行相关的科研开发,都具有十分重要的意义。 相似文献
10.
本文研究了快速响应的电液位置伺服系统动态试验,着重讨论了在实践中如何选择伪随机二位式最大长度序列(PRBS)参数的问陋,并提出快速响应系统PRBS参数选择的原则,使系统辨识精度提高约15%。 相似文献