一种高速跳频无人机自组网终端设计与实现

随着无人机集群的作战应用日益广泛，无人机集群实现机间组网和任务协同愈发重要。在战场复杂电磁环境下，设计具有良好抗干扰性能的网络终端已成为一项重要需求。本文设计了一种基于高速跳频通信体制的无人机自组网终端，并对研制的终端产品进行了接收灵敏度、抗干扰能力和组网功能测试。测试结果表明：跳频无人机自组网终端具有良好的灵敏度和抗干扰性能，具备多节点组网能力，设备具有高集成度、低功耗、低成本、轻量化的特点。     

Interaction tonal noise generated by contra-rotating open rotors

Fast and accurate prediction of sound radiation of Contra-Rotating Open Rotors(CRORs) is an essential element of design methods of low-noise open rotor propulsion systems.In the present work, a previous frequency-domain model is extended to predict CROR noise. It builds explicitly the relationship between harmonic loadings and corresponding tonal noise, by which the influential parameters to noise generation can be clearly understood. The real distributions of steady and unsteady blade loadings ...     

Multi-parameter load sensing pump model simulation and flow rate characteristics research

Load sensing pumps have been widely used in diverse hydraulic systems. Studies show that structural parameters have undeniable impacts on the characteristics and efficiency of the load sensing pump. The main purpose of this article is to study the influence of load sensing pump structure parameters on flow characteristics. In the present study, a nonlinear multi-parameter model is proposed for this type of pump. In this model, different parameters, including spool clearance, spool covering amount, internal leakage are considered to reflect the displacement adjustment process of the load sensing pump. Moreover, a frequency sweep method is proposed to analyze the frequency domain of the nonlinear mathematical model. An experiment rig was built to study the influence of key structural parameters on the dynamic follow-up characteristics of the pump flow. The obtained results show that the diameter of the orifice d can significantly affect the working characteristics of the pump. It is found that a large diameter of the orifice d can improve the phase following ability of the system, while a small diameter of the orifice d can reduce the bypass flow rate and increase the amplitude following ability. This paper provides a new consideration to study the dynamic follow-up characteristics of the load sensing pump.     

锯切圆柱形42CrMoA的声发射监测试验

针对锯切加工中的带锯条磨损状态未知、锯切质量下降等问题，本文研究了新试制的FTCUT双金属带锯条锯切圆柱形42CrMoA合金结构钢过程中锯切行为的变化，探讨了声发射信号与单刀锯切过程、锯齿磨损和锯切表面质量变化的关联。研究表明：锯切圆柱材料时随着锯切深度的变化，参与齿数先增大后减小，带锯条约束条件不断变化，进而影响着声发射信号幅值和锯切表面质量；基于时域分析可知锯齿磨损过程分为磨合磨损、快速磨损、稳定磨损三个阶段；基于FFT频域分析发现当频谱图出现多个主频，且第一主频幅值下降时，表明声发射信号来源比较分散，即可认定带锯条失效；基于小波包频域分析发现第7频段信号占比最高，最能反映工件表面质量的变化，其波动情况与锯切表面的微纹和波纹情况可建立一定的联系。因此，可基于声发射信号时域和频域分析判断锯齿磨损和锯切表面恶化情况，为锯齿磨损和锯切表面质量的在线监测提供一定的思路。     

高冲击试验测试装置及校准技术研究

研制出Hopkinson杆（霍普金森杆）高冲击加载装置，搭建起高冲击测试校准系统，基于LabVIEW和Matlab软件开发环境，编写系统控制程序，数据分析与处理程序，以高冲击MEMS加速度传感器为被测对象，开展冲击测试与校准技术研究，解算出传感器冲击灵敏度和频率响应指标。试验结果表明：利用该试验测试装置对冲击传感器进行测试校准，满足传感器主要静态指标测试要求；对传感器频响指标进行测试校准，得到传感器幅频特性和相频特性曲线，满足传感器动态特性测试要求。该Hopkinson杆冲击试验测试校准装置及测控系统能够实现冲击加速度传感器主要静态特性和动态特特指标的测试校准要求，平均灵敏度为0.657 548 μV/g，不确定度优于4%，幅值线性度偏差≤±5%的工作频带为12.5 kHz。本研究对高冲击试验测试的应用提供一定借鉴和参考。     

Frequency steering of spaceborne clocks based on XPNAV-1 observations

Due to high stable rotations, timing of pulsars provides a natural tool to correct the frequency deviation of spaceborne atomic clocks. Based on processing the observational data about a year of Crab pulsar given by XPNAV-1 satellite, we study the possibility of correcting the frequency deviation of spaceborne atomic clocks using pulsar timing. According to the observational data in X-ray band and the timing model parameters from radio observations, the pre-fit timing residuals with a level of 6...     

面向无人集群的通信定位一体化方法研究

针对无人集群协同作战通信/定位的集约化设计需求，提出了一种单载波频域均衡（SCFDE）与直接序列扩频（DSSS）技术有机结合的通信定位一体化波形。一方面，利用SCFDE中频域均衡易于克服频率选择性衰落且便于与DSSS结合的优势，使系统具有良好的适应复杂场景的通信能力；另一方面，利用恒包络零自相关导频序列的优良自相关和互相关特性，将其作为导频序列并计算与本地导频符号的循环移位相关，检测相关峰值即可实现整数符号周期信号到达时间估计。同时，结合用于信道估计的导频序列，构建差分延时相关模型，有效解决了小数采样周期信号到达时间估计问题，实现了高精度的信号到达时间估计。