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Anovelprofile error model to calculate contact error

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Journal of Beijing Institute of Technology 2014年第3期23卷 318-324页

作者：刘钦吴伟仁张之敬金鑫 School of Mechanical engineering Beijing Institute of Technology lunar exploration and aerospace engineering center

A new profile model based on multi-scale asperities is developed and contact error is cal- culated. After stratified sampling, the model can get the distribution law of entity points on each cross section. Asperity radius of curvature is estimated by the relationship between circle radius and the section interval. Contact error is related to surface form error. A model equation of contact error plane is calculated through a method based on static equilibrium theory. Three contact asperities which determine the contact error plane on the rough surface are studied. The simulation results show that contact error can be accurately calculated according to the profile error model.

关键词： profile error multi-scale asperities model contact error

Investigation on the development of deep space exploration

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Science China(Technological Sciences) 2012年第4期55卷 1086-1091页

作者： WU WeiRen LIU WangWang QIAO Dong JIE DeGang School of aerospace engineering Beijing Institute of TechnologyBeijing 100081China center of lunar exploration and aerospace engineering Beijing 100037China

Deep space exploration is the term used for the exploration of the Moon and the celestial bodies or space beyond the Moon, which is an important part of human space activities. Firstly, the development of deep space exploration (not including the Moon) during the last few decades is summarized. Secondly, the development trend of different space countries and regions is analyzed. Then the experience and enlightenment of deep space exploration are briefly discussed. Some suggestions for China's future deep space exploration are given in the end.

关键词： deep space exploration space program trend of development enlightenment

Roundness error evaluation by minimum zone circle via microscope inspection

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Journal of Beijing Institute of Technology 2013年第2期22卷 185-190页

作者：姜黎张之敬吴伟仁金鑫节德刚 School of Mechanical and Vehicular engineering Beijing Institute of Technology lunar exploration and aerospace engineering center

Utilizing the convex hull theory, a novel minimum zone circle （MZC） method, named im- proved minimum zone circle （IMZC） was developed in this paper. There were three steps for IMZC to evaluate the roundness error. Firstly, with the convex hull algorithm, data points on the circle contour were categorized into two sets to determine two concentric circles which contained all points of the contour. Secondly, vertexes of the minimum circumscribed circle and the maximum inscribed circle were found out from the previously determined two sets, and then four tangent points for de- termining the two concentric circles were also found out. Lastly, according to the evaluation using the MZC method, the roundness error was figured out. In this paper l IMZC was used to evaluate roundness errors of some micro parts. The evaluation results showed that the measurement precision using the IMZC method was higher than the least squared circle （LSC） method for the same set of data points, and IMZC had the same accuracy as the traditional MZC but dramatically shortened com- putation time. The computation time of IMZC was 6. 89% of the traditional MZC.

关键词： microscope inspection roundness error minimum zone circle (MZC) convex hull

Design of communication relay mission for supporting lunar-farside soft landing

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Science China(Information Sciences) 2018年第4期61卷 73-86页

作者： Weiren WU Yuhua TANG Lihua ZHANG Dong QIAO lunar exploration Program and Space engineering center School of aerospace engineering Beijing Institute of Technology Dong Fang Hong Satellite Co.Ltd. Key Laboratory of Autonomous Navigation and Control for Deep Space exploration Ministry of Industry and Information Technology

Chang’E-IV will be the first soft-landing and rover mission on the lunar farside. The relay satellite, which is located near the Earth-Moon L2 point for relay communication, is the key to the landing mission. Based on an analysis of the characteristics of the task and the technical difficulties associated with the relay satellite system, the overall design scheme of the relay communication mission is proposed in terms of trajectory design and communication system design among other aspects. First, according to the complex dynamic environment, a mission orbit that serves as an uninterrupted communication link is presented. A short-duration and low-energy transfer trajectory with lunar flyby is discussed. Orbital correction and a low-cost control strategy for orbit maintenance in the Earth-Moon L2 point region are provided. Second,considering the existing technical constraints, the requirement of relay communication in different stages and the design schemes of frequency division and redundant relay communication system are introduced. Finally,based on the trajectory design index and the performance of the communication system, the overall design scheme of the relay communication mission is proposed. This mission will provide the technical support and reference required for the Chang’E-IV mission.

关键词： lunar farside soft landing relay communication Earth-Moon Lagrange point

Improving Joint Features and Mechanical Properties of Pinless Fiction Stir Welding of Alcald 2A12-T4 Aluminum Alloy

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Journal of Materials Science & Technology 2016年第12期32卷 1372-1377页

作者： Zhenlei Liu Hutao Cui Shude Ji Minqiang Xu Xiangchen Meng Harbin Institute of Technology Deep Space Exploration Research Center Faculty of aerospace engineering Shenyang Aerospace University

As a new solid state welding,pinless friction stir welding（PFSW） can be used to join thin-wall *** this study,four new pinless tools with different groove distributions were designed and manufactured in order to enrich technological storage of PFSW and obtain sound joint with high quality of alclad 2A12-T4 *** results show that the small-obliquity tool is detrimental to the transfer of plasticized materials,resulting in the formation of kissing bond *** the through-groove tool or the large-curvature tool,bigger flashes form on the joint surface and alclad layer is observed in the nugget zone（NZ）,deteriorating mechanical *** with the above-mentioned three tools,using the six-groove tool with rational curvature and obliquity can not only yield sound joint with small flashes and thickness reduction,but also prevent alclad from flowing into NZ,which has potential to weld thin alclad aluminum ***,the tensile strength and elongation of joint using the six-groove tool reach the maximum values of 362 MPa and 8.3%,up to 85.1% and 64% of BM.

关键词： Pinless friction stir welding Groove distribution 2A12-T4 aluminum alloy Macrostructures Mechanical property

New celestial assisted INS initial alignment method for lunar explorer

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Journal of Systems engineering and Electronics 2013年第1期24卷 108-117页

作者： Weiren Wu Xiaolin Ning Lingling Liu lunar exploration and aerospace engineering center School of Instrument Science and Opto-electronics engineering Beihang University Science and Technology on Inertial Laboratory Fundamental Science on Novel Inertial Instrument and Navigation System Technology Laboratory

In the future lunar exploration programs of China, soft landing, sampling and returning will be realized. For lunar explorers such as Rovers, Landers and Ascenders, the inertial navigation system （INS） will be used to obtain high-precision navigation information. INS propagates position, velocity and attitude by integration of sensed accelerations, so initial alignment is needed before INS can work properly. However, traditional ground-based initial alignment methods cannot work well on the lunar surface because of its low rotation rate （0.55°/h）. For solving this problem, a new autonomous INS initial alignment method assisted by celestial observations is proposed, which uses star observations to help INS estimate its attitude, gyroscopes drifts and accelerometer biases. Simulations show that this new method can not only speed up alignment, but also improve the alignment accuracy. Furthermore, the impact factors such as initial conditions, accuracy of INS sensors, and accuracy of star sensor on alignment accuracy are analyzed in details, which provide guidance for the engineering applications of this method. This method could be a promising and attractive solution for lunar explorer＇s initial alignment.

关键词： lunar exploration initial alignment inertial navigation,celestial navigation.

Optimization of multi-revolution low-thrust transfer based on modified direct method

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Journal of Harbin Institute of Technology(New Series) 2008年第6期15卷 814-818页

作者：崔平远尚海滨任远栾恩杰 Deep Space exploration center Habin Institute of Technology Commission of Science Technology and Industry for National Defence Lunar Exploration Engineering Center

A modified direct optimization method is proposed to solve the optimal multi-revolution transfer with low-thrust between Earth-orbits. First, through parameterizing the control steering angles by costate variables, the search space of free parameters has been decreased. Then, in order to obtain the global optimal solution effectively and robustly, the simulated annealing and penalty function strategies were used to handle the constraints, and a GA/SQP hybrid optimization algorithm was utilized to solve the parameter optimization problem, in which, a feasible suboptimal solution obtained by GA was submitted as an initial parameter set to SQP for refinement. Comparing to the classical direct method, this novel method has fewer free parameters, needs not initial guesses, and has higher computation precision. An optimal-fuel transfer problem from LEO to GEO was taken as an example to validate the proposed approach. The results of simulation indicate that our approach is available to solve the problem of optimal muhi-revolution transfer between Earth-orbits.

关键词： low-thrust optimal transfer modified direct method hybrid algorithm simulated annealing

Spacecraft angular velocity estimation method using optical flow of stars

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Science China(Information Sciences) 2018年第11期61卷 99-112页

作者： Xiaolin NING Zonghe DING Pingping CHEN Weiren WU Jiancheng FANG Gang LIU School of Instrumentation Science & Opto-electronics engineering Beihang University lunar exploration and Space Program center China National Space Administration

Angular velocity is a crucial parameter for spacecraft navigation, which, at present, is mainly obtained by using gyroscopes. Several studies have been performed on angular velocity estimation using star sensors when data from gyroscopes are not available. Most of the previous angular velocity estimation methods using star sensors are based on information on the attitude or star vector measurements. In this paper,an angular velocity estimation method using the optical flow(OF) directly from the star images is proposed,which, unlike the previous methods, requires star coordinates in two consecutive images only. Because the procedure of star identification is eliminated, the corresponding high computation requirement is *** demonstrate that the proposed method has a robust performance in terms of computational cost and the number of stars in the field of view(FOV) compared with the previous methods. Finally, certain affecting factors are analyzed, including lens distortion, star senor instantaneous FOV(IFOV), star number,and accuracy of the star sensor.

关键词： angular velocity star sensor optical flow star images Kalman filter

Angular velocity estimation using characteristics of star trails obtained by star sensor for spacecraft

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Science China(Information Sciences) 2021年第1期64卷 201-214页

作者： Xiaolin NING Pingping CHEN Yueqing HUANG Weiren WU Jiancheng FANG School of Instrumentation Science & Opto-electronics engineering Beihang University lunar exploration and Space Program center China National Space Administration

Many studies have been conducted about angular velocity estimation using star sensors, and fairly good performance is achieved when the spacecraft is working at low-dynamic environments. However,when the spacecraft rotates at a large angular velocity, the star image will become blurred, which makes it difficult to identify and recognize star centroids, which, in turn, reduces the accuracy of angular velocity estimation. Therefore, to solve the problem with angular velocity estimation in highly dynamic situations,this research studies a method of angular velocity estimation using blurred star images. The length and ending point coordinates of star trails obtained from these blurred star images are used for a series of processes, which includes the pre-processing of blurred star images, determination of starting and ending points, thinning and selection of star trails, and calculation of trail lengths. Simulations show that the effectiveness of the proposed method in highly dynamic situations and the angular velocity estimation errors in constant and sinusoidal variation are reduced by at least 66% and 62%, respectively, compared with those of the traditional method.

关键词： angular velocity estimation star sensor blurred star images star trail characteristics unscented Kalman filter