卫星遥感图像几何质量的仿真评价

根据卫星图像摄影过程,建立了图像质量评价的数学模型。该模型包括：整机侧视和反射镜侧视两种相机侧视方案,姿态运动、轨道运动、地球自转、地图投影等因素对卫星图像几何质量的影响。并在计算机上分析了图像的几何质量,提出了几何校正方法,为遥感卫星设计提供了有价值的参考。     

Multi-parameter decoupling and slope tracking control strategy of a large-scale high altitude environment simulation test cabin

A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic control of the temperature–pressure two-parameter and overcome the control difficulties inherent to a large inertia lag link with a complex control system which is composed of turbine refrigeration device, vacuum device and liquid nitrogen cooling device. The system includes multi-parameter decoupling of the cabin itself to avoid equipment damage of air refrigeration turbine caused by improper operation. Based on analysis of the dynamic characteristics and modeling for variations in temperature, pressure and rotation speed, an intelligent controller was implemented that includes decoupling and fuzzy arithmetic combined with an expert PID controller to control test parameters by decoupling and slope tracking control strategy. The control system employed centralized management in an open industrial ethernet architecture with an industrial computer at the core. The simulation and field debugging and running results show that this method can solve the problems of a poor anti-interference performance typical for a conventional PID and overshooting that can readily damage equipment. The steady-state characteristics meet the system requirements.     

液氧/煤油高压补燃火箭发动机非线性稳态模型——考虑推进剂温升与密度变化

针对液氧／煤油高压补燃循环液体火箭发动机,考虑了推进剂供应系统中的温度与密度变化,推导建立了改进的简化非线性稳态特性数学模型。并通过数值模拟分析验证了该改进的非线性稳态模型可行性。     

靶式喷嘴雾化模型理论研究

为研究靶式喷嘴中液膜的形成和破碎以及液滴的形成机理,建立了相应的计算模型,利用该计算模型对靶式喷嘴雾化特性进行了理论计算,并与实测值进行了比较。结果表明：在气流量不变的情况下,随着气液质量比的增加,靶的作品影响越来越小,而气液作用影响越来越大,选择好气液比对充分发挥靶和气液相互作用两种雾化方式的作用很重要建立的雾化模型理论计算值与实测值吻合较好,该模型能够反映出靶式喷嘴雾化特性。     

CCD相机取样问题探讨

从理论上对ＣＣＤ相机的取样问题进行了探讨,分析了光学取样和电路取样的关系, 并提出了取样电路的设计思路。     

基于三维激光扫描的蒙皮对缝检测研究

针对传统蒙皮对缝检测方法误差大、效率低等问题以及二维激光对缝检测的缺陷,采用了一种基于三维激光扫描蒙皮对缝的检测方法并开发出相应软件。提出了蒙皮对缝三维点云数据的去噪、临界点识别及提取方法,根据蒙皮对缝间隙阶差对气动外形的影响,分析其实际几何结构,与理论结构对比,提炼出了计算蒙皮对缝间隙阶差的数学模型,并通过对试验模拟件对缝的检测,验证了其计算精度。结果表明:该检测方法可行,与二维激光检测相比精度和重复精度更高,间隙测量精度达到0.04mm,阶差测量精度达到0.02mm,可以满足蒙皮对缝检测需求,为分析间隙阶差对装配质量的影响提供数值依据。     

Haynes 282新型高温合金晶粒长大行为及数学模型研究

为了研究新型合金在高温状态下的晶粒长大行为,进行了Haynes 282合金在973～1 373 K条件下保温0～10 800 s的晶粒长大实验,通过实验分析了保温时间和保温温度对其晶粒尺寸的影响,研究了晶粒尺寸在其实验条件下的演变规律。由此构建了符合Haynes 282合金晶粒长大的数学模型,该模型的建立能够有效表征Haynes 282合金在高温下的晶粒长大行为。     

Mathematical modeling of an armature assembly in pilot stage of a hydraulic servo valve based on distributed parameters

The dynamic performance of a nozzle-flapper servo valve can be affected by several factors such as the disturbance of the input signal, the motion of the armature assembly and the oscillation of the jet force. As the part of vibrating at high frequency, the armature assembly plays a vital role during the operation of the servo valve. In order to accurately predict the transient response of the armature assembly during the vibration, a mathematical model of armature assembly is established based on the distributed parameters method (DPM) and Hamilton principle. The new mathematical model is composed of three main parts, the modal eigenfunction, modal mechanical response expressions of the spring tube and the motion equation of the other armature assembly. After programing, the purpose of using the DPM to predict the dynamic response of different positions located on the armature assembly is achieved. For verifying the validity of the mathematical model, the finite element method (FEM) and classic model (CM) of armature assembly are applicated by commercial software under the same condition. The comparison results prove that the DPM can effectively predict the axial and tangential deflection of the armature assembly different positions which the CM can’t duing to its over-simplification. A certain error is generated when predicting the axial deformation at different heights by DPM, which is caused by an approximate method to simulate the torsion of the spring tube. The comparison results of the spring tube deflection at different vibration frequencies shows that the adaptability of DPM is significantly higher than the classic model, which verify the model is more adaptable for predicting the dynamic response of the armature assembly.     

Effects of splined shaft bending rigidity on cylinder tilt behaviour for high-speed electro-hydrostatic actuator pumps

High-speed axial piston pumps are hydraulic power supplies for electro-hydrostatic actuators(EHAs). The efficiency of a pump directly affects the operating performance of an EHA, and an understanding of the physical phenomena occurring in the cylinder/valve plate interface is essential to investigate energy dissipation. The effects of the splined shaft bending rigidity on the cylinder tilt behaviour in an EHA pump need to be considered, because the deflection and radial expansion of a steel shaft rotating at a high speed cannot be ignored. This paper proposes a new mathematical model to predict the cylinder tilt behaviour by establishing a quantitative relationship between the splined shaft deflection, the cylinder tilt angle, and the tilt azimuth angle. The moments exerted by the splined shaft are included in the equilibrium equation of the cylinder. The effects of solid and hollow splined shafts equipped in an EHA pump prototype are compared at variable speeds of 5000–10,000 r/min. With a weight saving of 29.7%, the hollow shaft is experimentally found to have almost no influence on the volumetric efficiency, but to reduce the mechanical efficiency by 0.6–2.4%. The results agree with the trivial differences of the simulated central gap heights of the interface between the two shafts and the enlargement of the simulated tilt angles by the hollow shaft. The findings could guide designs of the cylinder/valve plate interface and the splined shaft to improve both the efficiency and power density of an EHA pump.