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Chao Wu Jun Yang Shihua Li Qi Li Lei Guo 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(9):2457-2471
Facing the complex aerodynamic environment of Mars atmosphere, a composite atmospheric entry trajectory tracking strategy is investigated in this paper. External disturbances, initial states uncertainties and aerodynamic parameters uncertainties are the main problems. The composite strategy is designed to solve these problems and improve the accuracy of Mars atmospheric entry. This strategy includes a model predictive control for optimized trajectory tracking performance, as well as a disturbance observer based feedforward compensation for external disturbances and uncertainties attenuation. 500-run Monte Carlo simulations show that the proposed composite control scheme achieves more precise Mars atmospheric entry (3.8?km parachute deployment point distribution error) than the baseline control scheme (8.4?km) and integral control scheme (5.8?km). 相似文献
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When Bioregenerative Life Support System (BLSS) is used for long-term deep space exploration in the future, it is possible to perform closed-loop control on growth of microalgae to effectively regulate O2 production process in emergencies. However, designing controller of microalgae cultivating device (MCD) by means of traditional methods is very difficult or even impossible due to its highly nonlinearity and large operation scope. In our research, the Artificial Neural Network Model Reference Control (ANN-MRC) method was therefore utilized for model identification and controller design for O2 production process of a specific MCD prototype—photo bioreactor (PBR), based on actual experiment and computer simulation. The results demonstrated that the ANN-MRC servo controller could robustly and self-adaptively control and regulate the light intensity of PBR to make O2 concentrations in vent pipe be in line with step reference concentrations with prescribed dynamic response performance. 相似文献
115.
Due to the difficulty and expense it costs to resupply manned-spacecraft habitats, a goal is to create a closed loop atmosphere revitalization system, in which precious commodities such as oxygen, carbon dioxide, and water are continuously recycled. Our aim is to test other sorbents for their capacity for future spacecraft missions, such as on the Orion spacecraft, or possibly lunar or Mars mission habitats to see if they would be better than the zeolite sorbents on the 4-bed molecular sieve. Some of the materials being tested are currently used for other industry applications. Studying these sorbents for their specific spacecraft application is different from that for applications on earth because in space, there are certain power, mass, and volume limitations that are not as critical on Earth. In manned-spaceflight missions, the sorbents are exposed to a much lower volume fraction of CO2 (0.6% volume CO2) than on Earth.LiLSX was tested for its CO2 capacity in an atmosphere like that of the ISS. Breakthrough tests were run to establish the capacities of these materials at a partial pressure of CO2 that is seen on the ISS. This paper discusses experimental results from benchmark materials, such as results previously obtained from tests on Grade 522, and the forementioned candidate materials for the Carbon Dioxide Removal Assembly (CDRA) system. 相似文献
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Yuming Fu Hui Liu Lingzhi Shao Minjuan Wang Yu A. Berkovich A.N. Erokhin Hong Liu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Vegetable cultivation plays a crucial role in dietary supplements and psychosocial benefits of the crew during manned space flight. Here we developed a ground-based prototype of horn-type sequential vegetable production facility, named Horn-type Producer (HTP), which was capable of simulating the microgravity effect and the continuous cultivation of leaf–vegetables on root modules. The growth chamber of the facility had a volume of 0.12 m3, characterized by a three-stage space expansion with plant growth. The planting surface of 0.154 m2 was comprised of six ring-shaped root modules with a fibrous ion-exchange resin substrate. Root modules were fastened to a central porous tube supplying water, and moved forward with plant growth. The total illuminated crop area of 0.567 m2 was provided by a combination of red and white light emitting diodes on the internal surfaces. In tests with a 24-h photoperiod, the productivity of the HTP at 0.3 kW for lettuce achieved 254.3 g eatable biomass per week. Long-term operation of the HTP did not alter vegetable nutrition composition to any great extent. Furthermore, the efficiency of the HTP, based on the Q-criterion, was 7 × 10−4 g2 m−3 J−1. These results show that the HTP exhibited high productivity, stable quality, and good efficiency in the process of planting lettuce, indicative of an interesting design for space vegetable production. 相似文献
118.
介绍了可重构机床对通信系统的要求,提出了一种基于宽带电力线通信(PLC,Power Line Communication)技术的新型通信系统.通过对机床电力线的信道特性和噪声频谱的分析与测量,选定了通信系统的载波频率和带宽等参数.为了对抗电力线信道的多径效应,提高频谱利用率,实现可靠高效的数据传输,采用正交频分复用技术(OFDM,OrthogonalFrequency Division Multiplex)作为调制解调方式.开发了PLC调制解调器,定义了物理层帧结构.最后以机床主轴伺服系统为例对该通信系统进行了实验验证.实验结果表明,该系统实现了有效数据传输率10 Mbit/s,误比特率(BER,Bit Error Rate)小于10-8的高效数据传输. 相似文献
119.
ZHAO Hongshenga XU Xiaohaob ZHANG Juna ZHU Yanboa YANG Chuansenc HONG Shengd aSchool of Electronics Information Engineering Beihang University Beijing China bCollege of Air Traffic Management Civil Aviation University of China Tianjin China cCollege of Civil Aviation Nanjing University of Aeronautics Astronautics Nanjing China dSchool of Reliability System Engineering China 《中国航空学报》2011,(3):329-336
Flight technical error (FTE) combined with navigation system error (NSE) is the main part of total system error (TSE) in performance based navigation (PBN).The implementation of PBN requires pre-flight prediction and en-route short-term dynamical prediction of the TSE.Once the sum of predicted lateral FTE and NSE is greater than the specified PBN value,the PBN cannot operate.Thus,accurate modeling and thorough analysis of lateral FTE are indispensible.Multiple-input multiple-output (MIMO) lateral track control system of a transport aircraft is designed using linear quadratic Gaussian and loop transfer recovery (LQG/LTR) method,and the lateral FTE of a turbulence disturbed approach operation is analyzed.The error estimation mapping function of latera FTE and its bound estimation algorithm are proposed based on singular value theory.According to the forming mechanism of lateral FTE,the algorithm considers environmental turbulence fluctuation disturbance,aircraft dynamics and control system parameters.Real-data-based Monte-Carlo simulation validates the theoretical analysis of FTE.It also shows that FTE is mainly caused by turbulence fluctuation disturbance when automatic flight control system (AFCS) is engaged and would increase with escalating environmental turbulence intensity. 相似文献
120.
Tear Resistance of Orthogonal Kevlar-PWF-reinforced TPU Film 总被引:1,自引:0,他引:1
This work seeks to investigate the notch sensitivity and fracture behaviour of orthogonal Kevlar-plain woven fabric (PWF)-reinforced thermoplastic polyurethanes (TPU) film applied to high altitude balloon. Four types of specimens are implemented to measure notched strength and fracture toughness by conducting static tension and tear tests on an MTS system respectively. The damage and failure mechanisms are discussed and the results for notched strength and tear resistance are evaluated and compared with each other. From the experiments, it is found that the notch sensitivity of the film increases with the increase in the size of the hole, but the notch sensitivity and the stress concentration of the notch are insignificant and there is a decrease of only about 4%-10% in tensile strength for the notched specimens with different hole sizes in diameter compared with the unnotched specimen. In contrast, the tear resistance containing a central slit with only 1 mm length is about half of tensile strength of the unnotched film, which implies that the tear resistance exists an significant notch sensitivity. The results of this study provide an insight into notch sensitivity and fracture behaviour of the Kevlar-PWF-reinforced TPU film and constitute a fundamental basis for the design of high altitude balloon. 相似文献