我国创业板的设立与风险投资退出渠道的选择

风险投资对于一国的经济增长特别是高新技术的发展有十分重要的意义 ,而风险投资的退出对于风险投资的发展则起到了决定性的作用。通过对风险投资的退出渠道及其影响因素的分析认为 ,创业板的设立对于一国风险投资的发展具有决定性的作用 ,因而我国应积极推进创业板的设立 ,同时应采取各种措施来防范创业板市场的风险。     

Reconfigurable fault-tolerant control for supersonic missiles with actuator failures under actuation redundancy

Aircraft undergoing actuator failures into under-actuation have been seldom studied in literature. Aiming at addressing actuator failures of Total Loss of Effectiveness (TLOE) as well as Partial Loss of Effectiveness (PLOE) resulting in different system actuations, reconfigurable Fault-Tolerant Control (FTC) is proposed for supersonic wingless missiles under actuation redundancy. The under-actuated system of TLOE failure patterns is solved by transformation to cascade systems through a ‘shape variable’. Meanwhile, actuator TLOE faults of different unknown failure patterns from proper actuation to under-actuation are accommodated by a reconfigurable adaptive law on a multiple-model basis. The backstepping technique with the Extended State Observer (ESO) method adopted as a basic strategy is applied to an established symmetric coupled missile system with actuator PLOE faults, modeling errors, and external disturbances. Additionally, the nonlinear saturation characteristics of actuators are settled by an auxiliary system with the Nussbaum function technique. The stability of the control system is analyzed and proven through Lyapunov theory. Numerical simulations are implemented in the presences of aerodynamic uncertainties, gust disturbance, and actuator failures. Results demonstrate the effectiveness of the proposed method with satisfactory tracking performance and actuator fault tolerance capacity.     

Performance analysis and application on Ti-6Al-4V of micro-forging system

Micro-forging (MF) is a novel surface modification technology which is capable of smoothening and strengthening the workpiece surface simultaneously. Based on analysis of the mechanism and energy conversion of micro-forging process, an electromagnetically driven micro-forging system is developed. To further grasp the kinetic characteristic of the equipment, a simulation model is established and its accuracy is verified. With the help of simulation and experimental results, we propose an input voltage optimization method, which drives the micro-forging head moving in a uniform and stable way. In this study, the influence of MF on surface integrity of Ti-6Al-4V (TC4) is firstly reported. Experimental results show that MF treatment reduces surface roughness (R_a) and increases micro-hardness by 48% and 11.8% at most, respectively. Besides, a compressive stress layer with an amplitude of −1000 MPa and a depth of 0.8 mm is observed. This study analyzes the performance and reveals the potential of micro-forging technology, which lays a solid foundation for expanding its application in TC4 surface modification.     

飞机软油箱舱底板的力学模型与设计方法研究

某型号飞机软油箱舱的底板出现裂纹,维修时局部加强后,故障重复出现。本文通过建立力学模型,从理论上对故障原因进行分析,提出了该型号飞机软油箱舱底板的设计方法和改进措施,并得到验证。     

基于归一化神经网络的航天器自适应姿态跟踪控制

针对以变速控制力矩陀螺（VSCMGs）为姿态控制执行机构的航天器在同时考虑惯性参数和执行机构不确定性情况下的姿态跟踪控制问题,提出了一种基于归一化神经网络的自适应姿态跟踪控制方法。设计一个非线性反馈控制器作为航天器姿态控制的基本控制器,利用归一化神经网络设计补偿控制器,用以在线估计和消除包含系统不确定参数的未知不确定函数的影响,避免了标准自适应控制方法需要进行大量不确定参数估计的缺陷。采用神经网络输入归一化技术,简化了闭环系统复杂的稳定性分析过程。理论分析证明了闭环系统的稳定性和姿态跟踪误差的收敛性。仿真结果表明,所提出的控制方法能满足航天器在惯性参数和执行机构不确定性及外干扰存在情况下的高精度姿态跟踪控制要求。
     

民机结构维修大纲抽样检查原则与方法研究

民机结构维修中的抽样检查是保证飞机持续适航的关键措施。结构抽样检查是为了掌握同一时期下线飞机的结构损伤情况,以便更好地修订维修计划。针对民机结构维修的抽样是非随机抽样的特点,本文研究了结构维修抽样的原则,结合空客A320抽样经验,给出了我国自主设计大飞机结构维修抽样准则和抽样的具体步骤。     

CubeSail: A low cost CubeSat based solar sail demonstration mission

CubeSail is a nano-solar sail mission based on the 3U CubeSat standard, which is currently being designed and built at the Surrey Space Centre, University of Surrey. CubeSail will have a total mass of around 3 kg and will deploy a 5 × 5 m sail in low Earth orbit. The primary aim of the mission is to demonstrate the concept of solar sailing and end-of-life de-orbiting using the sail membrane as a drag-sail. The spacecraft will have a compact 3-axis stabilised attitude control system, which uses three magnetic torquers aligned with the spacecraft principle axis as well as a novel two-dimensional translation stage separating the spacecraft bus from the sail. CubeSail’s deployment mechanism consists of four novel booms and four-quadrant sail membranes. The proposed booms are made from tape-spring blades and will deploy the sail membrane from a 2U CubeSat standard structure. This paper presents a systems level overview of the CubeSat mission, focusing on the mission orbit and de-orbiting, in addition to the deployment, attitude control and the satellite bus.     

用解题法调试某型飞机斜板系统

某型飞机是国家重点工程项目之一 ,该机进气道自动调节系统采用计算机进行结算、调节与控制 ,增加了系统调节精度和可靠性。但在首批飞机的调试中 ,极难实现技术条件的要求 ,且无规律可循。对此 ,我们通过对斜板调节机理的研究实验 ,摸索出了斜板在大小πk 时调节曲线的对比规律 ,设置了调整计算方程 ,可靠地解决了这一难题。     

模块化功能组件备分优化研究

通过对影响备分因素的分析，以费用和可靠性指标为参数，从系统观点出发，建立了模块化功能组件备分优化模型，并给出一种算法。     

Tethered towing using open-loop input-shaping and discrete thrust levels

Asteroid retrieval, satellite servicing, and debris removal concepts often rely on a thrusting vehicle to redirect and steer a passive object. One effective way to tow the object is through a tether. This study employs a discretized tether model attached to six degree-of-freedom end bodies. To reduce the risk of a post-burn collision between the end bodies, discrete thrust input shaping profiles are considered including a Posicast input and a bang-off-bang thrust profile. These input shaping techniques attain desirable collision avoidance performance by inducing a tumbling or gravity gradient motion of the tethered formation. Their performance is compared to an earlier frequency notched thruster profile.