基于任意长度的数据帧头搜索实现方法

为解决卫星海量数据传输多样化问题,提出一种基于任意长度帧头的数据流搜索的实现方法。首先阐述了卫星地面基带处理系统的总体设计流程,然后针对传统的搜索特点介绍了传统的数据帧头搜索方法,最后给出了一种基于任意长度帧头的数据流的实现方法,对该方法进行了详细流程介绍。结果表明,与传统的搜索机制相比较,文章提出的搜索方法具备高速率、高准确率和使用范围广的优点。     

铰链式下垂前缘机构设计与动力学仿真研究

下垂前缘是一种结构简单的增升装置,能够有效降低气动噪声,减小机构的运动空间,已被应用于A380和A350XW。为了实现下垂前缘按照给定要求定轴转动,需要设计一种机构型式,因此提出一种基于四连杆形式的铰链式下垂前缘机构的设计方法。根据设计输入要求建立下垂前缘机构的线架模型,并对该机构进行运动学和刚柔耦合动力学仿真,得到机构运动过程中角度变化参数和该机构运动过程中的驱动力矩和铰链点载荷。结果表明:随着驱动臂匀速转动,铰链式下垂前缘能够平稳下偏26°;两个驱动平面的最大驱动力矩的比值接近3∶2,且侧撑杆的设置使驱动处的横向受载得到了改善,该机构型式设计合理,为现代民用飞机设计提供了参考依据。     

Area-oriented coordinated trajectory planning of dual-arm space robot for capturing a tumbling target

The growing amount of space debris poses a threat to operational spacecraft and the long-term sustainability of activities in outer space. According to the orbital mechanics, an uncontrolled space object will be tumbling, bringing great challenge to capture and remove it. In this paper, a dual-arm coordinated ‘‘Area-Oriented Capture"(AOC) method is proposed to capture a non-cooperative tumbling target. Firstly, the motion equation of the tumbling target is established, based on which, the dynamic properties are analyzed. Then, the ‘‘Area-Oriented Capture"concept is presented to deal with the problem of large pose(position and attitude) deviation and tumbling motion. An area rather than fixed points/devices is taken as the object to be tracked and captured. As long as the manipulators' end-effectors move to a specified range of the objective areas(not fixed points on the target, but areas), the target satellite will be hugged by the two arms.At last, the proposed method and the traditional method(i.e. fixed-point oriented capture method)are compared and analyzed through simulation. The results show that the proposed method has larger pose tolerance and takes shorter time for capturing a tumbling target.     

空间红外遥感器定标机构故障应急退出装置

针对空间红外遥感器定标机构故障模式,首次设计了一种基于记忆合金的应急退出装置,以解决因电机或控制电路故障而导致的整个成像系统失效问题。该应急退出装置通过对记忆合金棒进行加热,使其受热收缩,从而驱动齿轮传动系统脱离啮合状态,完成机构复位运动。为验证该应急退出装置的功能和性能,利用研制产品进行了真空、大气环境等多种状态下的应急退出试验。结果表明:在大气和真空环境中,该装置能实现多种状态下的可靠退出功能;在28 V额定直流工作电压下,应急退出总时间可达145～152 s。该机构具有实现简便、可靠性高、退出速度快等优点,在空间机构的故障应急方面具有较大的工程应用潜力。     

硅橡胶基防热涂层动态烧蚀行为及机理研究

针对两种典型硅橡胶基防热涂层开展高温燃气流烧蚀实验，通过对烧蚀后涂层的宏观及微观形貌分析，探讨了其防隔热机理及烧蚀模型。研究结果表明：烧蚀后两种涂层均存在液态层、陶瓷层、热解层以及原始层；烧蚀过程中甲基苯基硅橡胶涂层主要发生主链“回咬”成环反应，导致树脂基体交联密度降低，力学性能下降，涂层外表面发生开裂，甲基乙烯基硅橡胶涂层则主要发生侧基交联反应，使树脂基体交联密度上升，促进涂层发生陶瓷化转变；热辐射、热容吸热、热解反应吸热以及热阻塞效应为四种主要的热耗散机制，质量损失产生的原因主要包括反应气体释放以及气动剪切力导致的机械剥蚀。     

一种四连杆机构位置综合的迭代方法

本文提出了一种四连杆机构位置综合的迭代方法,解决了一般解析法对初始点要求过高的问题。该方法对初始点要求很低,而且在计算机上也不易出现“溢出”。     

微小孔加工试验及刀具磨损机理

由于钛合金和印刷电路板的难加工性使得微小孔的加工精度和表面质量难以保证,刀具技术成为提高加工效率的主要障碍。本文应用3种不同涂层钻头对钛合金和印刷电路板进行微小孔钻削对比试验,研究了进给速度与切削力和扭矩的关系,分析了刀具的磨损特征以及孔的表面质量和孔入口处的毛刺情况。结果表明:钻削印刷电路板的临界进给速度为1 591.2 mm/m in,涂层对钻削力和扭矩的影响不明显;类金钢石(DLC)涂层硬质合金钻头比普通硬质合金钻头和T iC涂层硬质合金钻头更适合加工钛合金材料微小孔。     

关于用来确定机构速度瞬心的“三心定理”的直接证明及若干注记

本文根据三构件中两构件相对于第三构件的三种运动情况,分别讨论了机构中三构件间速度瞬心的位置关系。当构件1和2相对构件3分别以不同的角速度绕瞬心P_(13)和P_(23)转动时,则构件1和2的瞬心P_(12)位于瞬心P_(13)和P_(23)的连线上。对这一结论的讨论方法能够代替通常用于证明“三心定理”的反证法。当构件1和2相对构件3以相同的角速度分别绕瞬心P_(13)和P_(23)转动时,则瞬心P_(12)应位于瞬心P_(13)和P_(23)连线的平行线上无穷远处。当构件1和2相对构件3分别是绕瞬心P_(13)的转动和以速度V_(23)作平动时,则瞬心P_(12)位于过瞬心P_(13)且垂直于速度V_(23)的直线上。当构件1和2相对构件3都作平动时,则构件1和2之间以速度V_(12)作相对平动,其瞬心P_(12)位于V_(12)的垂线上无穷远处。文中给出了两个应用实例。     

Cutting force model and damage formation mechanism in milling of 70wt% Si/Al composite

High-mass fraction silicon aluminium composite(Si/Al composite) has unique properties of high specific strength, low thermal expansion coefficient, excellent wear resistance and weldability. It has attracted many applications in terms of radar communication, aerospace and automobile industry. However, rapid tool wear resulted from high cutting force and hard abrasion, and damaged machined surfaces are the main problem in machining Si/Al composite. This work aims to reveal the mechanisms of milli...     

Influence of deformation zone length on bending radius of SS304 tubes with small diameters manufactured via free bending-based active motion

In three and six-axis free-bending equipment, the deformation zone length(A) is a fixed mechanical structure parameter modified when the relevant structure is redesigned and manufactured. In this study, a six degree of freedom(6-DOF) parallel mechanism was used as the control mechanism of the bending die, and a new method of changing the deformation zone length(A)was proposed. Firstly, an idealized geometric model of free bending-based active motion was established. Then, the influence of the de...