An aircraft brake control algorithm with torque compensation based on RBF neural network

The wheel brake system of an aircraft is the key to ensure its safe landing and rejected takeoff. A wheel’s slip state is determined by the brake torque and ground adhesion torque, both of which have a large degree of uncertainty. It is this nature that brings upon the challenge of obtaining high deceleration rate for aircraft brake control. To overcome the disturbances caused by the above uncertainties, a braking control law is designed, which consists of two parts: runway surface recognition a...     

Directional Filtering Due to Mesospheric Wind Shear on the Propagation of Acoustic-gravity Waves

Gravity waves with periods close to the Brunt-V?is?l? period of the upper troposphere are often observed at mesopause altitudes as short period, quasi-monochromatic waves. The assumption that these short period waves originate in the troposphere may be problematic because their upward propagation to the mesosphere and lower thermosphere region could be significantly impeded due to an extended region of strong evanescence above the stratopause. To reconcile this apparent paradox, an alternative explanation is proposed in this paper. The inclusion of mean winds and their vertical shears is sufficient to allow certain short period waves to remain internal above the stratopause and to propagate efficiently to higher altitudes. A time-dependent numerical model is used to demonstrate the feasibility of this and to determine the circumstances under which the mesospheric wind shears play a role in the removal and directional filtering of short period gravity waves. Finally this paper concludes that the combination of the height-dependent mean winds and the mean temperature structure probably explains the existence of short period, quasi-monochromatic structures observed in airglow images of mesopause region.      

Corrosion Resistance of Ni-P Composite Coating on Mg Alloy： Critical Role of the Intermediate Phosphate Conversion Coating Layer for Suppressing Galvanic Couple Formation

Electroless nickel (EN) plating can give rise to the severe galvanic corrosion of the magnesium (Mg) alloy matrix, owing to its nobler electrochemical potential than Mg alloy. To hinder the formation of galvanic couple, an intermediate phosphate conversion coating (PCC) layer is introduced between the EN layer and the Mg alloy matrix. Since the ceramic-like PCC layer cannot be catalyzed, a low-cost Ag-activation technique is used to process the PCC layer before electroless plating. The cross-section morphology and element distribution of the PCC-EN composite coating indicate that the PCC intermediate layer can effectively separate the Mg alloy from the EN layer. Moreover, the results of electrochemical tests suggest that the PCC-EN composite coating has a better corrosion resistance in comparison with the EN coating and AZ91D Mg alloy.     

China Space Environment Development

This paper presents Chinese space environment detection and parts of results,and gives a short perspective of space environment observations on Chinese future satellites.      

Space Life Science of China

With the human space exploration activities, space life science is an emerging interdiscipline, which covers a wide range of researches. Based on our country's manned space station and recoverable satellite science experimental platform, the development of space life science research is very important to acquire new knowledge or new technological innovation, to give further services to the human space exploration activities, to improve the national economic and social development. Both ground-based and flight applied studies were continuously performed in the previous 2 years. Here, we review and summarize the researches on space life sciences contributed by Chinese scientists.      

Materials Experiment on Tiangong-2 Space Laboratory

During the China's Tiangong-2 (TG-2) flight mission, the experiments of 18 kinds of material samples were conducted in space by using a Multiple Materials Processing Furnace (MMPF) mounted in the orbital module of the TG-2 space laboratory. After the experiments of 12 kinds of samples of the first and second batches were completed successfully, astronauts packed and brought them back to the ground by ShenzhouⅡ spacecraft. By studying processing and formation on semiconductor and optoelectronics materials, metal alloys and metastable materials, functional single-crystal, micro-and nano-composite materials encapsulated in sample ampoules both in space and on Earth, we expect to explore some physical and chemical processes and mechanism of the materials formation that are normally obscured and therefore are difficult to study quantitatively on the ground due to the gravity-induced convection, to obtain the processing and synthesis technology for preparing high quality materials, and lead to the improvement and development of materials processing techniques on Earth, and also develop the experiment device and comprehensive ability for materials experiment in microgravity environment. This report briefly introduces the main points of each research work and preliminary comparative analysis results of 12 samples carried out by scientists undertaking research task.      

Linear Shaped Charge Cutting Property and Charge Cutting Mechanism of Mg-Gd-Y-Zn Alloy

The linear shaped charge cutting technology is an effective technology for aircraft separation. It can separate invalid components from aircrafts timely to achieve light-weight. Magnesium alloy is the lightest metal material, and can be used to cast effective light-weight components of an aircraft construction. However, the application study of the linear shaped charge cutting technology on magnesium alloy components is basically blank. In response to the demand for the linear separation of magnesium alloys, the Mg-12Gd-0.5Y-0.4Zn alloy is selected to carry out the target shaped charge cutting test. The effects of the shaped charge line density, cutting thickness, and mechanical properties on the cutting performance of the alloy are studied. The shaped charge cutting mechanism is analyzed through the notch structure. The results show that the linear shaped charge cutting performance is significantly affected by the penetration and the collapse. The higher the linear density is, the stronger the ability of the linear shaped charge cutter is, and the greater the penetration depth is, which is advantageous. However, the target structure will be damaged when it is too large (e.g., 4.5 g?m-1). Within 12 mm, when the cutting thickness of the target increases, the penetration depth increases. The lower the tensile strength is, the greater the penetration depth is, and the more conducive the penetration depth to the shaped charge cutting is. When the elongation (EL) increases to 12%, the collapse of the target is incomplete and the target cannot be separated. When the tensile strength of the Mg-Gd-Y-Zn alloy is less than 350 MPa, the EL is less than 6.5%, the cutting thickness is less than 12 mm, and the linear shaped charge cutting of the magnesium alloy can be achieved stably.     

面向商业小卫星的记忆合金星箭分离装置研制（英文）

Non-pyrotechnic separation devices have been fully recognized for their high performance and high reliability. The focus of this paper is mainly around the development of memory alloy satellite and rocket separation devices. Due to the increasing demand for small-sized rockets and satellites, some suggestions and experiments for developing this new type of non-pyrotechnic device are proposed and conducted.     

一种对流层软式飞艇设计体积估算方法的商榷

出于对对流层软式飞艇动态受力平衡的考虑,分别从一般情况、特定任务和限制飞艇地面净重(轻)情况三个角度分析,尝试建立了飞艇设计体积与携带燃油量的数学关系模型,并利用仿真曲线相交的方法,对飞艇设计体积进行区间估算,以此作为设计目标值的依据.     

神经网络PID算法在BTT导弹度控制中的应用

提出一种基于神经网络PID的控制系统,为缺乏精确数学模型的非线性对象--BTF导弹,提供了一种有效的控制方案.仿真及实验结果表明,该控制方法可实现导弹三通道的解耦控制和输出渐近无差跟踪,可获得满意的控制效果.