Enhancement on parallel unstructured overset grid method for complex aerospace engineering applications

In the present study, an efficient overset grid method by means of parallel implicit hole-cutting is proposed for the sake of simulating unsteady flows in aerospace engineering involving multiple bodies in relative movement. In view of the degraded computational efficiency and robustness for conventional overset grid assembly, several innovative techniques are developed within the overset grid assembly process, viz., a bookkeeping alternative digital tree method to speed up the donor-cell search...     

基于机器视觉的搅拌摩擦焊缝装配质量评测方法

搅拌摩擦焊常采用无坡口焊缝,焊缝装配质量对搅拌摩擦焊装配质量影响较大,通过焊缝的特征,可以对搅拌摩擦焊缝的装配质量进行评判。线结构光是提取焊缝特征的常用手段,基于结构光传感器扫描获得的焊缝轮廓信息多通过离散的点进行表示,如何高效地从轮廓点中提取焊缝轮廓信息,是焊缝特征识别的新挑战。本文提出一种基于机器视觉的焊缝装配质量评测方法,将离散的轮廓点转换为位图,通过抗锯齿算法提高轮廓直线特征的识别可靠性,并计算对应焊缝的装配质量信息,进而实现对整条焊缝的装配质量的量化评价。与传统的离散点拟合方法相比,本方法具有较为明显的效率优势。     

六西格玛在军用飞机发动机总装质量控制中的应用

国内某军用飞机主机厂C 发动机装机后存在间隙尺寸超差、装机一次合格率低的问题，为了解决该问题，引入六西格玛质量管理模式的DMAIC 方法对发动机装机流程进行研究。运用多元回归分析、机理分析等确定影响间隙尺寸的关键因子及其影响程度，采用线性拟合得出关键因子最优参数范围，并制定详细控制计划。通过对控制图进行分析，发现改善后的间隙尺寸处于工序稳定状态，发动机装机一次合格率由改善前的65.2% 提升至95%，表明基于六西格玛DMAIC 方法的质量控制对减小生产流程变异，提高生产效率有积极作用。     

A policy iteration method for improving robot assembly trajectory efficiency

Bolt assembly by robots is a vital and difficult task for replacing astronauts in extra-vehicular activities (EVA), but the trajectory efficiency still needs to be improved during the wrench insertion into hex hole of bolt. In this paper, a policy iteration method based on reinforcement learning (RL) is proposed, by which the problem of trajectory efficiency improvement is constructed as an issue of RL-based objective optimization. Firstly, the projection relation between raw data and state-action space is established, and then a policy iteration initialization method is designed based on the projection to provide the initialization policy for iteration. Policy iteration based on the protective policy is applied to continuously evaluating and optimizing the action-value function of all state-action pairs till the convergence is obtained. To verify the feasibility and effectiveness of the proposed method, a noncontact demonstration experiment with human supervision is performed. Experimental results show that the initialization policy and the generated policy can be obtained by the policy iteration method in a limited number of demonstrations. A comparison between the experiments with two different assembly tolerances shows that the convergent generated policy possesses higher trajectory efficiency than the conservative one. In addition, this method can ensure safety during the training process and improve utilization efficiency of demonstration data.     

加工装配误差影响下偏转射流压力伺服阀静态特性分析

电液压力伺服阀是电液压力伺服控制系统的核心控制元件，广泛应用于航空、航天、军事等领域。区别于流量伺服阀，压力伺服阀在滑阀放大器的设计上多采用带有压力控制容腔的三通阀结构，不同的滑阀结构使得现有的偏转射流流量伺服阀仿真模型难以满足压力伺服阀性能预测的需求。本文基于AMESim平台建立了偏转射流压力伺服阀的仿真模型，并通过实验对仿真模型进行了验证，验证结果表明仿真模型能够准确地描述压力伺服阀的静态特性。最后，通过仿真模型分析了加工装配误差影响下压力伺服阀输出性能差异，仿真结果可为偏转射流压力伺服阀的性能预测和结构设计提供参考。     

A Robotic TeleoperationSystem for Precise Robotic Manipulation by Human-Machine Interaction

Teleoperation is of great importance in the area of robotics， especially when people are unavailable in the robot workshop. It provides a way for people to control robots remotely using human intelligence. In this paper， a robotic teleoperation system for precise robotic manipulation is established. The data glove and the 7-degrees of freedom (DOFs) force feedback controller are used for the remote control interaction. The control system and the monitor system are designed for the remote precise manipulation. The monitor system contains an image acquisition system and a human-machine interaction module， and aims to simulate and detect the robot running state. Besides，a visual object tracking algorithm is developed to estimate the states of the dynamic system from noisy observations. The established robotic teleoperation systemis applied to a series of experiments， and high-precision results are obtained， showing the effectiveness of the physical system.     

基于B1c/B2a/B3I北斗三频实时 高采样率动态PPP分析

为了分析北斗三号新信号的三频实时动态PPP定位性能，首先推导了三频两两组合无电离层模型和三频非差非组合模型的观测方程。基于山东建筑大学CORS站观测得到的北斗三号B1c/B2a/B3I三频信号1s采样率数据，使用iGMAS提供的超快速精密星历预报部分，制定了基于B1cB3I-B2aB3I三频无电离层两两组合、B1cB2aB3I三频非差非组合以及用于对比分析的B1cB2a、B1IB3I两种双频无电离层共四种定位方案。然后利用Net_Diff软件进行实时动态PPP实验，对超快速精密轨道和钟差预报部分的精度和稳定度以及实验解算结果进行分析，对比不同定位方案的定位性能。实验分析表明，两种三频定位方案定位性能均优于B1cB2a双频定位方案，定位精度能达到0.462m和0.479m，收敛至分米所需时间能达到45.8min和62.8min；B1IB3I方案定位性能优于两种三频定位方案，定位精度和收敛速度能达到0.228m和6.6min。