The dynamical environments analysis of surface particles for different shaped asteroids

Asteroids are coming to be a popular topic in the areas of astrophysical studies and deep space exploration recently. However, surface dynamics of asteroids is still a difficult problem. This paper aims at the motion analysis of surface particles for different asteroids. The dynamical analysis method of particles’ movement is given for three parts: global motion trend, local motion trend and static analysis. A dimensionless parameter ζ is defined to distinguish the predominant term to determine the distribution of effective potential. Three kinds of common asteroids: spheroidal asteroid, spindle-shaped asteroid and dumbbell-shaped asteroid are all discussed for those three parts with different parameter ζ. The motion trend of particles on the surface of each kind of asteroid is given. The static analysis of surface particles for different asteroids is also illustrated. Based on them, some common rules for different shaped asteroids are revealed. This paper could not only provide a reference for asteroid exploration missions but also be meaningful for the research of morphologic evolution of asteroids.     

Auto-normalization algorithm for robotic precision drilling system in aircraft component assembly

A novel approach is proposed to detect the normal vector to product surface in real time for the robotic precision drilling system in aircraft component assembly, and the auto-normalization algorithm is presented based on the detection system. Firstly, the deviation between the normal vector and the spindle axis is measured by the four laser displacement sensors installed at the head of the multi-function end effector. Then, the robot target attitude is inversely solved according to the auto-normalization algorithm. Finally, adjust the robot to the target attitude via pitch and yaw rotations about the tool center point and the spindle axis is corrected in line with the normal vector simultaneously. To test and verify the auto-normalization algorithm, an experimental platform is established in which the laser tracker is introduced for accurate measurement. The results show that the deviations between the corrected spindle axis and the normal vector are all reduced to less than 0.5°, with the mean value 0.32°. It is demonstrated the detection method and the auto-normalization algorithm are feasible and reliable.     

Aeroservoelastic modeling and analysis of a canard-configured air-breathing hypersonic vehicles

Air-breathing hypersonic vehicles (HSVs) are typically characterized by interactions of elasticity, propulsion and rigid-body flight dynamics, which may result in intractable aeroservoelastic problem. When canard is added, this problem would be even intensified by the introduction of low-frequency canard pivot mode. This paper concerns how the aeroservoelastic stability of a canard-configured HSV is affected by the pivot stiffnesses of all-moveable horizontal tail (HT) and canard. A wing/pivot system model is developed by considering the pivot torsional flexibility, fuselage vibration, and control input. The governing equations of the aeroservoelastic system are established by combining the equations of rigid-body motion, elastic fuselage model, wing/pivot system models and actuator dynamics. An unsteady aerodynamic model is developed by steady Shock-Expansion theory with an unsteady correction using local piston theory. A baseline controller is given to provide approximate inflight characteristics of rigid-body modes. The vehicle is trimmed for equilibrium state, around which the linearized equations are derived for stability analysis. A comparative study of damping ratios, closed-loop poles and responses are conducted with varying controller gains and pivot stiffnesses. Available bandwidth for control design is discussed and feasible region for pivot stiffnesses of HT and canard is given.     

玉米空间飞行处理细胞超微结构变异的研究

玉米干种子搭载于返回式卫星上，经离海平面１７６ｋｍ至３５４ｋｍ的空间条件处理，发现处理后的玉米叶片超微结构发生各种变异。主要变异包括：细胞质壁分离，液泡增大，细胞壁加厚、扭曲，胞间连丝增多，出现叶绿体基粒盘和基质类囊体的变异，细胞核和叶绿体变形，内质网的数量增多、体积增大，以及其它细胞内膜系统与其它超微结构的变化。     

涡喷发动机H_∞控制参数化Ricati方程的解

由分块矩阵的奇异值不等式关系，给出了初猜值γ０、λ０的对半求解法，在此基础上直接给出带参数的Ｒｉｃｃａｔｉ方程迭代求解法。用此方法对涡喷发动机不确定性系统设计了控制器，并在发动机气动热力学非线性模型上进行了仿真验证，结果表明控制系统能够取得满意的鲁棒性能、抗干扰性能和伺服跟踪性能。     

气体渗碳过程中的计算机两级全过程动态控制

利用仿真数学模型推导出的渗层碳浓度分布与渗碳时间、渗碳温度、气氛碳势之间的关系式以及三点自调整控制原理，编制了气体渗碳的全过程动态控制软件，并且安装、调试了两级全过程动态控制系统的硬件，从而开发了气体渗碳过程的计算机两级全过程动态控制系统。     

质量计划四题

简述了质量计划编制应注意的４ 个问题： 哪些情况需要编制质量计划；编写哪些内容；采用哪种编写形式；如何在管理上保证质量计划得到良好的贯彻实施。     

通氨滴醇软氮化工艺试验

介绍了通氨滴醇气体软氮化工艺的试验过程,并在分析试验结果的基础上确定了最佳软氮化工艺条件.     

如何提高飞机表面质量

探讨了提高飞机表面质量的方法。提出提高飞机表面质量是个系统工程，必须从优化设计结构、提高零件和工装的制造准确度及协调准确度，采用合理的铆接装配工艺方法等多方面共同采取措施。     

转盘测距仪的工作原理及其误差分析

转盘测距仪的结构简单,安装操作方便,测量精度比较高,现已得到广泛应用。简要介绍转盘测距仪的工作原理,测量误差来源与分布以及减少测量误差的方法。