非接触供电旋转超声加工系统负载特性研究

在旋转超声波加工过程中负载的变化会引起振幅衰减,进而造成加工精度和加工效率降低。本文针对非接触供电旋转超声加工系统在加工过程中振幅衰减的问题,首先,通过静态加载实验,获得了负载对超声振子电学参数的影响规律;其后,在此基础上进行了超声振子的非接触能量传输系统的加载实验,得到负载对能量传输特性的影响规律。实验结果表明,超声振子的电学参数受负载力大小、负载力方向和被加工材料特性的共同影响而发生改变,超声振子电参数改变引起了非接触供电超声系统输出功率的改变,进而导致了振幅衰减的问题;本文采用了串联谐振下主边串联电容、副边并联电容的电路补偿方式来减小振幅的衰减。本文的研究成果为解决振幅衰减问题提供了实验依据。     

钣金件快速精确加工中的激光切割工艺分析

针对δ0．5mm～δ6mm钣金件的结构特点,通过比较常用加工工艺和激光切割过程工艺．选出适合实际的优化方案。验证了不同切割参数对切割质量的影响。在工艺参数为：脉冲功率2．4kW、脉冲宽度约10ms、功率密度10^7W/cm^2的情况下,激光切割δ0．5mm～δ6mm钣金件获得了良好的切割质量,尺寸精度控制在误差（±100μm）范围内。工艺方案合理,生产率高。     

高速端面铣削加工引入残余压应力场的试验研究

为研究高速铣削加工表面残余应力分布,在统计试验设计指导下,使用X射线衍射/电解抛光方法对试样表层、次表层残余应力分布进行测量,得出残余应力分布曲线经验预报公式,探讨切削参数对残余压应力场特征指标的影响规律。研究结果表明,合理的高速切削工艺将在加工表面内引入类似喷丸强化效果的残余压应力场;(3,1)有理式模型与三阶多项式模型是描述高速铣削引入残余应力分布曲线的有效拟合公式;高速切削工艺参数对加工表面残余应力场的产生有直接影响,每齿进给量是决定残余压应力分布的关键因素,每齿进给量的变化将引起残余应力场形成机理的改变。     

基于光纤双环网的高精度时频同步技术研究

本文介绍了一种基于光纤双环网的时频同步技术设计方法，针对时频设备协同使用时如何获得高精度同步指标这一问题提出了一种设计思路。以系统时间源使用北斗/GPS/GLONASS，本系统同步精度优于5E-13，频率稳定度优于5E-13@1d；以UTC(BIRMM)输出的TOD+1PPS做系统时间源，本系统同步精度优于4E-13，频率稳定度优于6E-14@1d。本方案提出的方法原理简单，系统可根据使用情况进行裁剪，相比卫星双向等手段成本低廉，适合在时频同步领域推广。     

基于边缘计算和VPRS的火箭设备单机双层判读与实时诊断

为提高参数自动判读的效率，增强设备单机状态诊断的时效性和准确性，提出一种基于边缘计算和变精度粗糙集(VPRS)的运载火箭设备单机双层判读与实时诊断方法。首先构建了边缘层-判读服务器层的双层判读架构。然后，基于边缘计算技术设计了边缘层判读方法，对参数原始数据进行阈值判断与数据筛选。随后，在判读服务器层，定义AIPL(AutoIP Language)判据描述语言设计高阶判据并进行高阶判读；基于VPRS建立了实时诊断模型，对设备单机的历史数据进行约简，挖掘出了简化后的状态诊断规则。最后，以XX火箭设备单机遥测数据自动判读系统升级改造为例，验证了所提方法的可行性与有效性。     

Chatter stability and precision during high-speed ultrasonic vibration cutting of a thin-walled titanium cylinder

Titanium alloys are widely used in the aviation and aerospace industries due to their unique mechanical and physical properties. Specifically, thin-walled titanium (Ti) cylinders have received increasing attention for their applications as rocket engine casings, aircraft landing gear, and aero-engine hollow shaft due to their observed improvement in the thrust-to-weight ratio. However, the conventional cutting (CC) process is not appropriate for thin-walled Ti cylinders due to its low thermal conductivity, high strength, and low stiffness. Instead, high-speed ultrasonic vibration cutting (HUVC) assisted processing has recently proved highly effective for Ti-alloy machining. In this study, HUVC technology is employed to perform external turning of a thin-walled Ti cylinder, which represents a new application of HUVC. First, the kinematics, tool path, and dynamic cutting thickness of HUVC are evaluated. Second, the phenomenon of mode-coupling chatter is analyzed to determine the effects and mechanism of HUVC by establishing a critical cutting thickness model. HUVC can increase the critical cutting thickness and effectively reduce the average cutting force, thus reducing the energy intake of the system. Finally, comparison experiments are conducted between HUVC and CC processes. The results indicate that the diameter error rate is 10% or less for HUVC and 51% for the CC method due to a 40% reduction in the cutting force. In addition, higher machining precision and better surface roughness are achieved during thin-walled Ti cylinder manufacturing using HUVC.     

High precision dynamic model and control considering J2 perturbation for spacecraft hovering in low orbit

For spacecraft hovering in low orbit, a high precision spacecraft relative dynamics model without any simplification and considering J₂ perturbation is established in this paper. Using the derived model, open-loop control and closed-loop control are proposed respectively. Gauss's variation equations and the coordinate transformation method are combined to deal with the relative J₂ perturbation between the two spacecraft. The sliding mode controller is adopted as the closed-loop controller for spacecraft hovering. To improve the control accuracy, the relative J₂ perturbation is regarded as a known parameter term in the closed-loop controller. The external uncertainty perturbations except J₂ perturbation are estimated by numerical difference method, and the boundary layer method is used to weaken the impact of chattering on the sliding mode controller. The open-loop control of spacecraft hovering with the relative J₂ perturbation and without the relative J₂ perturbation are simulated and compared, and the results prove that the accuracy of open-loop control with relative J₂ perturbation has been significantly improved. Similarly, the simulation of the closed-loop control are presented to validate the effectiveness of the designed sliding mode controller, and the results demonstrate that the designed sliding mode controller including the derived relative J₂ perturbation can guarantee the high accuracy and robustness of spacecraft hovering in long-term mission.     

一种用于机载设备的高精度转动型柔性铰链

 传统铰链应用于机载设备时会产生摩擦、磨损、接触面热梯度等问题,而利用材料变形产生运动的柔性铰链可避免此类缺陷,获得高性能的同时,降低维护成本。现阶段使用的交叉簧片柔性铰链无法满足某些超精密航空机载设备的定位精度要求,因此将交叉点推广到任意位置以改善性能。首先,考虑机械接口,建立了广义交叉簧片柔性铰链的刚度和轴漂模型,从而分析了各个参数与刚度及轴漂的关系,并评估了由于加工因素造成的簧片不等长给性能带来的影响,得到了具有等值刚度和较小轴漂特性的柔性铰链。然后,通过有限元仿真验证了所分析特性的有效性。最后,通过组合提出了一种更大行程的复合柔性铰链,当转角为15°时,且在垂直力作用下,轴漂小于3 μm,精度优于在国外已得到应用的蝶形铰链。     

纳米胶体射流抛光技术综述

纳米胶体射流抛光技术是一种超光滑表面加工方法,加工范围广,具有广泛的应用前景。本文回顾了纳米胶体射流抛光技术的提出以及目前的研究现状,最后对其今后的发展进行了简单展望。     

负载对超声加工声学系统特性的影响

以一维超声振动系统为研究对象,以点、线、面三种不同的加载方式对工件进行加载,研究了负载对超声加工声学系统特性的影响。实验表明,当以点、线的加载方式对工件进行加载时,载荷的变化对声学系统特性各参数的影响不大;而当加载方式为面接触时,机械品质因数Qm、谐振频率fs和动态电阻R随着载荷F的增大有明显的增大趋势,动态电容C和最大电导Gmax却随着载荷F的增大而减小。