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171.
M. Grasso A. Renga G. Fasano M.D. Graziano M. Grassi A. Moccia 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3909-3923
The paper focuses on space system design aspects related to an end-to-end demonstration mission, aiming at showing the feasibility of a Formation Flying Synthetic Aperture Radar (FF-SAR) with microsatellite class platforms (~100 kg). Trajectory design approaches that can fulfil payload requirements are addressed to enable selected FF-SAR applications. The exploitation of these applications relies on suitable combinations of FF-SAR techniques like Signal-to-Noise Ratio (SNR) enhancement, High-Resolution Wide Swath (HRWS) SAR imaging, and Coherence Resolution Enhancement (CRE). In this framework, a cluster of 3 micro-satellites, working in X-band, flying in a Low Earth Orbit (LEO) close-formation, has been designed as a candidate end-to-end system demonstration mission. One satellite embarks a Transmitting-Receiving (Tx/Rx) radar, i.e. it is a monostatic SAR. The other two satellites are Receiving-only platforms. Critical design aspects related to spacecraft subsystems and formation-flying analysis are addressed to confirm the technical feasibility of the spaceborne distributed system implementing the FF-SAR principle. 相似文献
172.
Andrzej Tomczyk 《Aerospace Science and Technology》2005,9(8):692-700
The handling qualities of an aircraft will be improved if the Direct Lift Control (DLC) system is applied. In this paper, an attempt has been made to evaluate the influence of DLC-type system parameters on the aircraft's maneuverability and to determine the desired values of these parameters for the purpose of obtaining required values of the handling maneuverability criteria. Published papers which deal with direct lift control do not list requirements for evaluating handling qualities and maneuverability of aircraft equipped with DLC system. In this paper, three new criteria permitting the evaluation of results of employing DLC have been defined. Analysis of influence of DLC system parameters on selected known handling qualities criteria (for example CAP, C*), as well as new DLC efficiency coefficients, have been illustrated with a numeric example of A4D “Skyhawk” fighter aircraft and PZL M-18 “Dromader” agricultural airplane control system modification. 相似文献
173.
The primary objective of the Proba-3 mission is to build a solar coronagraph composed of two satellites flying in close formation on a high elliptical orbit and tightly controlled at apogee. Both spacecraft will embark a low-cost GPS receiver, originally designed for low-Earth orbits, to support the mission operations and planning during the perigee passage, when the GPS constellation is visible. The paper demonstrates the possibility of extending the utilization range of the GPS-based navigation system to serve as sensor for formation acquisition and coarse formation keeping. The results presented in the paper aim at achieving an unprecedented degree of realism using a high-fidelity simulation environment with hardware-in-the-loop capabilities. A modified version of the flight-proven PRISMA navigation system, composed of two single-frequency Phoenix GPS receivers and an advanced real-time onboard navigation filter, has been retained for this analysis. For several-day long simulations, the GPS receivers are replaced by software emulation to accelerate the simulation process. Special attention has been paid to the receiver link budget and to the selection of a proper attitude profile. Overall the paper demonstrates that, despite a limited GPS tracking time, the onboard navigation filter gets enough measurements to perform a relative orbit determination accurate at the centimeter level at perigee. Afterwards, the orbit prediction performance depends mainly on the quality of the onboard modeling of the differential solar radiation pressure acting on the satellites. When not taken into account, this perturbation is responsible for relative navigation errors at apogee up to 50 m. The errors can be reduced to only 10 m if the navigation filter is able to model this disturbance with 70% fidelity. 相似文献
174.
175.
Jordan Maxwell Hanspeter Schaub 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(11):3478-3488
The feasibility of using electrostatic forces to stabilize a close-proximity leader-follower formation is investigated. The leader craft is equipped with a set of affixed spheres whose charge is modulated to hold the charged follower craft along a proscribed trajectory to its nominal leader-relative position. This charge structure and the follower craft are constrained to remain in the plasma wake generated behind all LEO craft because the more-dense ambient plasma outside the wake prevents object charging and electric field propagation. Once the formation is achieved, a controlled electric field is generated by the leader to counter relative accelerations from perturbations like differential drag and solar radiation pressure, holding the follow near its nominal position. Two controllers are derived for the system described, incorporating Coulomb accelerations and linearized gravity and drag accelerations. Simulations are run under unmodeled perturbations and sensor noise for different scenarios, demonstrating the challenges and benefits associated with electrostatic actuation. 相似文献
176.
177.
俄ЦАГИ在地面飞行模拟试验和飞行试验数据的统计分析基础上,提出了一个频域最佳C*响应操纵灵敏度——A值的概念,并找出了驾驶杆特性(pχ)和静态操纵灵敏度(pny、χny)最佳值与A值的表达式,以及它们偏离最佳值时飞行品质评分(PR)与人机耦合振荡(PIO)评分(PIOR)随相对偏离量的关系曲线。 A 将此关系曲线用于预测评估人感系统相关参数对PIO趋势的影响,称之为A准则。本文从应用的角度详细地进行了计算公式的推导,讨论了准则在推导过程中所采用的假设和其适用情况,重新整理和校核了计算步骤和算例,以便于我国航空界使用。 相似文献
178.
飞翼布局组合舵面航向控制特性综合研究 总被引:2,自引:0,他引:2
寻求高效实用的航向控制措施一直是飞翼布局飞行器设计的难点。提出了一种由外翼上翼面嵌入式阻力舵和其相对应的后缘副翼组成的组合舵航向控制措施,通过CFD方法、风洞试验和模型飞行试验3种研究手段,综合研究了单独部件和组合舵在低速、亚声速时的航向控制特性。结果表明:单独阻力舵的航向控制能力比较强,但与纵横向力矩耦合严重,需与其他舵组合使用;单独副翼的航向控制能力很弱,且与纵横向力矩耦合非常严重,建议不单独作为航向控制措施使用;组合舵的航向控制能力强,选取阻力舵与副翼的舵偏角角度差在0°~5°范围的组合舵方案,可以大幅度削弱与纵横向的力矩耦合程度,实现操纵舵面解耦设计;无论单独部件,还是组合舵,舵偏角为0°~6°范围的力矩变化规律较差,建议通过预置舵偏角等方式避开此角度区域。 相似文献
179.
通过对某飞翼飞机输油顺序的研究,分析了在不同输油顺序下飞机重心的变化情况及在不同重心位置下升降舵偏转角和飞翼飞机的配平状况.通过对最小配平阻力和飞机最佳重心位置的研究可知,改进飞机的输油顺序,可以增加飞机的巡航时间并改善飞机的操纵能力. 相似文献
180.
带时延和拓扑切换的编队卫星鲁棒协同控制 总被引:5,自引:0,他引:5
综合考虑了存在通信时延、拓扑结构切换、参数不确定性和外部扰动等情况下的编队卫星协同控制问题,分别提出了鲁棒位置和姿态协同控制器。采用Lyapunov直接法,通过恰当地选取公共的Lyapunov函数,保证了所设计的位置协同控制器对于通信时延和拓扑切换具有鲁棒性。控制器中设计了一个自适应项,用于在线补偿卫星质量的不确定性。进一步,引入了一个含有时变参数的非线性饱和函数向量项,保证了位置协同控制器对于外部扰动的鲁棒性,并且控制器是连续的。然后,将协同控制器推广到了姿态协同的情况,提出了类似的鲁棒姿态协同控制器。仿真结果表明了本文协同控制方案的有效性。 相似文献