磁带机运转对星载CCD相机成像的影响

利用Ｌａｇｒａｎｇｅ方程,建立了磁带轮转动和卫星姿态振动相互影响的仿真模型,并用数值计算方法计算了卫星的姿态振动,仿真分析了对星载线阵ＣＣＤ成像质量的影响。     

外缘预旋进气的旋转空腔主盘局部换热及流阻特性研究

某型发动机的实际涡轮盘腔冷却结构被简化成外缘预旋进气的旋转空腔模型,以实验方法研究了旋转雷诺数（Ｒｅω）、冷气雷诺数（Ｒｅｚ）、哥拉晓夫数（Ｇｒ＊）对主盘局部换热及流阻特性的影响。实验发现,冷气雷诺数、旋转雷诺数的增大,使主盘局部换热系数在盘缘附近迅速增大,而在接近盘心时出现负值;阻力系数随旋转雷诺数的增大而减小,随冷气雷诺数的增大而增大。     

一种采用速度控制模式的动量轮控制系统

针对以无刷力矩电机驱动的动量轮提出了利用旋转变压器直接求差进行位置反馈闭路控制及以脉冲输入作为加速度给定量输入的控制系统。控制电路由FPGA芯片集成 ,结构简单、有效。初步实验结果表明 ,系统实现了动量轮在± 30 0 0r/min转速范围内速度控制精度优于 2× 10 - 5且加速度响应时间优于 2 0 0ms的预期要求     

片切磨削方法构造的自由曲面磨削支持系统

以操作者高效准确操作数控磨削中心为目的,开发了自由曲面磨削支持系统,进行了基于球头磨具的磨削中心基础研究。讨论了获得高精度曲面的加工要点,并提出了片切磨削方法。     

速率模式飞轮姿态控制系统飞轮组合平稳切换方法

对速率模式飞轮姿态控制系统的能控性、稳定性和飞轮组合切换过程进行了研究,揭示了在飞轮组合切换过程中引起卫星姿态抖动的原因,提出了通过对残余角动量进行卸载并将卸载函数同时前馈到系统输入的方法,以保持卫星姿态的稳定度。从理论上证明了可引入残余角动量进行卸载,将卸载函数同时前馈到系统输入,并且不改变原系统的能控性和稳定性。给出了某卫星飞轮切换应用实例,说明了飞轮组合平稳切换方法的有效性。     

Modeling and experiment of grinding wheel axial profiles based on gear hobs

Hobbing is one of the crucial gear manufacturing processes with high precision and high efficiency. In order to improve the accuracy of hobbing and hob relief grinding, more precise grinding wheels are demanded for relief grinding in the production of gear hobs. In this paper, a new and accurate mathematical method for calculating the axial profile of grinding wheel based on the corresponding gear hob to be ground is proposed. Considering that most researches have been conducted to focus on the optimization of hob geometric feature and only can be applied to a specific type of hand of helix and rake angle of gear hobs. The method in this paper can be served as a general algorithm for generating axial profile of grinding wheels on the basis of the spatial envelope theory, the principle of coordinate system transformation, and studies on normal profile of single-tooth. The accuracy of grinding hobs is based on applying the approach in practical manufacturing. Taking two typical different kinds of pre-grinding gear hobs as examples for calculation and experiment, the results of tooth profile errors strengthen the position that the validity and feasibility of this method, it can be employed for gear hob design and grinding processing.     

Nonlinear H∞ based underactuated attitude control for small satellites with two reaction wheels

Underactuated attitude control is supposed to be used on spacecraft when failure happens with onboard actuators. One main problem with existing underactuated attitude control designs is their limited capabilities against disturbances. In order to solve this problem, an approach based on the theory of H∞$H\infty$ is proposed in this paper. Two propositions are derived from the H∞$H\infty$ theory to improve the robustness of one popular underactuated attitude control design, which was presented by Tsiotras et al. It is proved mathematically that the controller satisfying these two propositions respectively can stabilize the underactuated attitude system locally or globally. The numerical simulations show that the improved controllers based on the H∞$H\infty$ theory could provide higher pointing accuracy for small satellites against disturbances. This validates the effectiveness of the proposed H∞$H\infty$ based approach to improve existing underactuated attitude control designs.     

大型民机双作动筒式前轮转弯操纵系统设计与仿真分析

为了提高飞机起降性能,当前飞机起落架逐步发展为采用电传操纵技术。而为了满足对低速大转角机动和大转弯力矩的要求,现代大部分大型民机都装配了双作动筒式前轮转弯系统。本文以大型民机的双作动筒式电传前轮转弯操纵系统为研究对象,针对双作动筒式前轮转弯机构设计一种随动转阀式换向阀,以满足其在死点位置时液压源换向的要求;随后基于双作动筒式前轮转弯系统对操纵控制的要求,设计了集手轮低速大角度转弯、脚蹬快速小角度转弯以及减摆功能于一体的飞机前轮操纵电液伺服系统,并建立仿真模型,进行动态仿真分析,以检验系统的各项功能。仿真结果表明,系统能够满足工程使用的要求。     

基于GSPN的飞机前轮转弯系统安全性评估

为解决在缺乏统计数据时无法对系统安全性进行评估的问题,提出将系统广义随机Petri网(GSPN,Generalized Stochastic Petri Nets)与经典评估相结合的方法.以某型尚处于设计阶段的飞机前轮转弯系统为研究对象,通过分析该系统结构功能图,建立出系统故障类型和影响分析(FMEA,Failure Modes and Effects Analysis)表;依照经典公式,求出系统各单元及其故障类型的故障率、维修度、平均无故障时间和平均维修时间等数据;将求得的数据与前轮转弯系统的GSPN模型相结合,利用TimeNET软件求得系统各故障类型的稳态失效概率;联立经验公式及危险度矩阵图对系统的安全性进行评估.经测评,该型飞机前轮转弯系统安全性符合设计要求.      

A320飞机在低速滑行中滑偏的处理

A320系列飞机在运行中有时会出现低速滑行时滑偏的现象,给航班的安全、正点运行带来了很大的压力.本文分析了引起滑偏的原因,给出针对此类故障的快速处理建议及排故方法,以期节省排除此类故障的时间,对缓解航班运行压力提供帮助.