A study of reaction wheel configurations for a 3-axis satellite attitude control

The satellite reaction wheel’s configuration plays also an important role in providing the attitude control torques. Several configurations based on three or four reaction wheels are investigated in order to identify the most suitable orientation that consumes a minimum power. Such information in a coherent form is not summarized in any publication; and therefore, an extensive literature search is required to obtain these results. In addition, most of the available results are from different test conditions; hence, making them difficult for comparison purposes. In this work, the standard reaction wheel control and angular momentum unloading schemes are adopted for all the reaction wheel configurations. The schemes will be presented together with their governing equations, making them fully amenable to numerical treatments. Numerical simulations are then performed for all the possible reaction wheel configurations with respect to an identical reference mission. All the configurations are analyzed in terms of their torques, momentums and attitude control performances. Based on the simulations, the reaction wheel configuration that has a minimum total control torque level is identified, which also corresponds to the configuration with minimum power consumption.     

ELID超精密镜面磨削过程中磨削力变化规律的试验分析

通过对ＥＬＩＤ磨削过程中磨削力变化规律的试验分析,并对试验结果进行了讨论,得出ＥＬＩＤ磨削力与磨削深度、磨粒粒度、磨削时间等之间的变化规律。     

航空机轮轮毂的静力和疲劳分析及其结构改进

以航空机轮轮毂为研究对象,采用Hypermesh、Ansys、MSC.Fatigue软件进行联合仿真。相比采用Ansys软件,联合仿真理论上得到的网格质量更好、计算时间更短、结果与实际情况更吻合。本文在仿真的不同阶段采用不同的软件,完成了模型的网格划分、静强度分析以及疲劳寿命分析的仿真。仿真结果表明:最大应力均未超过材料的强度极限,仿真和理论估算得到的疲劳寿命相差10%左右,符合设计要求。基于此提出了轮毂结构的改进建议。     

磨料有序排布钎焊金刚石砂轮磨削硬质合金的性能研究

通过优化排布金刚石磨料研制出钎焊单层金刚石端面砂轮.以硬质合金为加工对象,研究了该砂轮的磨削性能.结果显示连续干磨时,金刚石磨粒的失效形式主要是磨耗磨损和断裂两类,没有出现传统的电镀和烧结工具磨粒大量脱落的现象.这表明钎料合金对磨粒的高强度把持和砂轮的高耐用度.此外,工件的磨削表面获得了良好的粗糙度,理论预测的粗糙度数值和试验数值基本一致.     

Model Development and Adaptive Imbalance Vibration Control of Magnetic Suspended System

对星载磁悬浮单框架控制力矩陀螺,建立其转子的平动与转动的动力学方程。所建模型反映了转子的动、静不平衡特性,以及转子运动与框架、星体运动的耦合关系。模型是主动磁悬浮控制与动框架效应分析的基础。对动、静不平衡量未知的转子,设计了自适应对中控制器。在分散PD、比例交叉反馈控制器与高低通滤波器的基础上,通过动、静不平衡量的辨识与补偿控制,使转子绕其惯量主轴旋转,衰减角动量交换执行机构高速转子因不平衡而对基座产生的干扰力,消除星上主要颤振源,达到降低卫星姿态抖动的目的。     

Profile error compensation in precision grinding of ellipsoid optical surface

Optical glass elements with the ellipsoidal surface are used in many critical aerospace instruments, such as satellites, telescope and cameras. Their optical performance is mainly affected by profile accuracy and surface quality. In this paper, a rectangular ellipsoid surface is precisely ground on a BK7 optical glass blank by grating scanning grinding path with a three-axis CNC precision surface grinder. A profile error compensation procedure for ellipsoidal grinding is proposed based on the error analysis about the primary error sources in the XY and YZ projection planes during the grinding process. The mathematical prediction models of the wheel arc profile error, the measurement and wear error of the grinding wheel radiuses are established. By applying the proposed error compensation procedure, the profile accuracy of the ellipsoidal surface was improved from 4 μm to 2 μm in the XY plane, and improved from 15 μm to 5 μm in the YZ plane.     

关于汽车前轮定位参数的分析

本文由前轮定位参数的作用出发，详细分析了影响其作用的诸多因素，为合理选择汽车的前轮定位参数提供依据。     

复杂固态反应动力学的热分析研究

本文从独立平行反应和竞争反应两种模型出发,对TG和DSC研究复杂固态反应动力学作了分析.指出了不能用等转化率一类多升温速率法求取动力学参数的情况及其主要原因.     

磨削钛合金时砂轮磨损机理的研究

 磨削钛合金时砂轮磨损严重,磨削比很低。为了改善钛合金的磨削加工性,本文着重分析了造成砂轮磨损的主要原因,论述了粘附磨损、扩散磨损以及磨粒破碎、脱落所造成的磨损,并分析了磨削条件对砂轮磨损的影响。     

航空机轮刹车系统的半实物仿真实现

针对航空机轮刹车系统的现有模拟实验方法,提出了一种机轮刹车系统半实物仿真的实现方案,给出了系统方案的具体硬件环境和仿真软件的开发过程,探讨了半实物仿真实现中的关键技术。