A partition of unity level set method with moving knot CS-RBFs for optimizing variable stiffness composites

A partition of unity level set method with moving knot Compactly Supported Radial Basis Functions (CS-RBFs) is proposed for optimizing variable stiffness composite structures. The iso-contours of a level set function are utilized to represent the curved fiber paths, and the tangent vector of the iso-contour defines the orientation of fiber. The level set function of the full design domain is constructed according to the Partition of Unity (POU) method by a set of local level set functions defined on an array of overlapping subdomains, and they are constructed by using the CS-RBFs. The positions of knots are iteratively changed during the optimization to improve the performance of composite structures. Several examples of compliance minimization are presented.     

旋转调制下的抗晃动干扰初始对准方法

针对晃动基座下的对准精度受限于惯性器件常值误差，提出了旋转调制下的抗晃动干扰初始对准方法。首先，分析了单轴连续旋转调制技术对常值误差的补偿机理，并在此基础上建立了晃动基座下的惯性器件输出模型;其次，详细推导了基于双重积分的惯性系粗对准算法，通过惯性坐标系下的姿态更新跟踪载体实际姿态变化消除了角晃动干扰，通过对比力进行双重积分克服了线振动影响;最后，在粗对准算法基础上，进一步建立了旋转调制下的系统状态方程和量测方程，通过反馈校正的卡尔曼滤波算法实现最优估计精对准。仿真结果表明:旋转调制下的抗晃动对准方法在克服晃动干扰的同时，能够解决对准精度受限问题，有效提高了初始对准精度。     

A new interpretable fault diagnosis method based on belief rule base and probability table

It is vital to establish an interpretable fault diagnosis model for critical equipment. Belief Rule Base (BRB) is an interpretable expert system gradually applied in fault diagnosis. However, the expert knowledge cannot be utilized to establish the initial BRB accurately if there are multiple referential grades in different fault features. In addition, the interpretability of BRB-based fault diagnosis is destroyed in the optimization process, which reflects in two aspects: deviation from the initial expert judgment and over-optimization of parameters. To solve these problems, a new interpretable fault diagnosis model based on BRB and probability table, called the BRB-P, is proposed in this paper. Compared with the traditional BRB, the BRB-P constructed by the probability table is more accurate. Then, the interpretability constraints, i.e., the credibility of expert knowledge, the penalty factor and the rule-activation factor, are inserted into the projection covariance matrix adaption evolution strategy to maintain the interpretability of BRB-P. A case study of the aerospace relay is conducted to verify the effectiveness of the proposed method.     

往复节流式正脉冲发生器性能分析CSCD

在石油开采与钻探领域,脉冲发生器作为旋转导向系统井下信号传输系统的重要组成部分,提高压力脉冲幅值有助于提升旋转导向系列产品的市场竞争力。为了揭示其工作原理及提高压力脉冲幅值,基于计算流体动力学,利用用户自定义函数(UDF)、动网格技术、非牛顿流体模型,借助Fluent平台对往复节流式正脉冲发生器进行了动态数值实验。利用离散形式的动量方程将主阀体与电磁阀的被动运动转变为主动运动,选择适用于k-ε湍流模型的赫-巴非牛顿流体本构方程描述泥浆,提高了计算的收敛性与运动的可控性。基于非牛顿流体的流固耦合方法,更真实地模拟了脉冲器在井下工作过程。结果表明限流环内径越小或入口排量越大,则压力脉冲幅值与信号发生频率越大。     

基于XTCE标准的遥测参数装订与核对研究

面对我国现代航天高密度发射的需求，精准高效的遥测参数装订与核对尤为重要。本文基于XTCE标准定义的遥测参数格式，构建了XTCE标准对遥测参数数据底座，实现遥测参数的统一标准、统一管理和统一平台。阐述了XTCE标准的结构、火箭遥测数据库的生成和数据底座的构造。实现了对大型火箭遥测参数的自动装订，大幅提高了工作效率。     

柔性基座冗余机械臂的最优反作用控制

针对柔性基座冗余机械臂的末端轨迹跟踪问题，提出一种反作用最优控制方法，该算法将轨迹跟踪视为高优先级任务，而反作用优化控制在高优先级任务零空间内进行。由于冗余机械臂的自运动能在不影响末端运动的前提下改变关节运动，利用冗余机械臂的自运动消除振动系统中的低阶模态力，使机械臂在完成轨迹跟踪的同时激起的弹性振动大幅减小，从而提高了系统的稳定性。以平面3自由度柔性基座机械臂和空间7自由度柔性基座机械臂为例进行数值仿真，证实了方法的有效性。     

A novel combination belief rule base model for mechanical equipment fault diagnosis

Due to the excellent performance in complex systems modeling under small samples and uncertainty, Belief Rule Base(BRB) expert system has been widely applied in fault diagnosis. However, the fault diagnosis process for complex mechanical equipment normally needs multiple attributes, which can lead to the rule number explosion problem in BRB, and limit the efficiency and accuracy. To solve this problem, a novel Combination Belief Rule Base(C-BRB) model based on Directed Acyclic Graph(DAG) structu...     

5G微基站环境下GNSS接收机性能及观测质量分析

我国已全面进入5G时代，为研究5G微基站电磁环境对全球卫星导航系统（GNSS）接收机工作性能及观测数据质量的影响，基于自主建设差分基准站的零基线观测数据，采用静态相对定位方法，通过观测数据质量分析、载波与伪距的双差残差序列、对比相对静态定位结果，综合评估5G微基站对GNSS接收机工作性能及观测数据质量的影响。实验表明：当前环境下，GNSS差分基准站及接收机处于近距离建设的5G微基站时，载波相位观测噪声变化范围为5cm，伪距观测噪声变化范围为15cm，零基线测试结果变化范围为1mm。在实验距离内，5G微基站对于GNSS接收机工作性能及数据观测质量影响较小，可以忽略。