Pipelines are widely employed in the petroleum, natural gas, and chemical industries due to their high efficiency and low cost. However, leakage frequently occurs at components such as valves and flanges in complex pipeline structures due to sealing failures or impact fractures, posing significant safety risks. This study conducts experimental research on leak source localization in complex pipelines using acoustic emission (AE) technology. Lead break tests are performed to analyze the propagation velocity and attenuation characteristics of AE signals. A multi-level analysis combining time-domain, frequency-domain, and wavelet transform methods reveals that the amplitude and frequency band distribution of leakage signals attenuate progressively during propagation. To enhance signal quality, a parameter optimization method based on vector weighted averaging is proposed and validated within the framework of variational mode decomposition (VMD). Effective signal modes are selected using sample entropy and correlation coefficients, followed by signal reconstruction through a wavelet thresholding denoising algorithm, resulting in a significant improvement in localization accuracy. Furthermore, the impact of signal attenuation on localization errors is investigated, and an optimized sensor placement scheme tailored for complex pipelines is proposed and experimentally verified.

To realize the automatic tightening of nuts, a nut tightening robot system strategy based on machine vision was designed in this work. The strategy was based on three stages: nut image calibration, nut identification, and nut pose estimation. In the first stage, the template pose image of the nut and the coordinates of the nut center in this nut image were obtained by calibration. In the second stage, a nut identification algorithm based on improved the backbone feature extraction network and area generation network of Faster-RCNN was presented, which improved the efficiency and accuracy of nut identification. In the last stage, a nut pose estimation algorithm based on Fourier and log-polar coordinate transformation was presented to solve the rotation angle, translation, and scale of the nut relative to the template nut image and then obtain the rotation angle of the sleeve and the central coordinate of the nut. An experimental nut tightening robot platform was also set up in this work. The results of 50 tests showed that the proposed detection methods could identify nuts with 100 x and y directions was ± 0.05 mm and of z direction was ± 0.5 mm. The experimental results showed that the nut tightening robot scheme and algorithm designed in this work were feasible in nut identification and pose estimation and met the requirements of insertion accuracy in the process of nut tightening.

法兰接头在高温环境中工作时,接头各个部件的蠕变松弛会加剧,然而在法兰接头的研究中,大多没有考虑垫片的蠕变松弛.以金属石墨缠绕垫片为例,在不同温度及不同初始密封比压情况下进行蠕变松弛性能试验;将试验结果进行拟合得到垫片蠕变松弛性能计算公式,将其代入法兰接头变形协调方程中,计算得到接头蠕变2年的螺栓力随时间的变化情况.使用ANSYS软件建立法兰接头有限元模型,并计算不同部件蠕变2年所造成的螺栓力的松弛情况.理论计算结果与有限元计算结果相近,表明建立的理论模型可用于接头螺栓力松弛的评估.研究结果表明:初始密封比压相同时,温度越大则垫片的蠕变量越大,温度相同时,初始密封比压越大则垫片的蠕变量越大;垫片蠕变对法兰接头有显著影响,在一些情况下仅垫片蠕变就能使螺栓力下降40％,因此垫片蠕变对法兰接头的影响不能忽略.

Threaded fastening operations are widely used in assembly and are typically time-consuming and costly. In low-volume, high-value manufacturing, fastening operations are carried out manually by skilled workers. The existing approaches are found to be less flexible and robust for performing assembly in a less structured industrial environment. This paper introduces a novel algorithm for detecting the position and orientation of threaded holes and a new method for tightening bolts. First, the elliptic arc fitting method and the three-point method are used to estimate the initial position and orientation of the threaded hole, and the force impact caused by switching from the free space to the constrained space during bolt tightening is solved. Second, by monitoring the deformation of passive compliance, the position information is introduced into the control process to better control the radial force between the bolt and the threaded hole in the tightening process. The constant force controller and orientation compliance controller are designed according to the adaptive control theory. A series of experiments are carried out. The results show that the proposed method can estimate the initial position and orientation of an M24 bolt with an average position error of 0.36 mm, 0.43 mm and 0.46 mm and an orientation error of 0.65°, 0.46° and 0.59°, and it can tighten the bolt with a success rate of 98.5%.

目前被广泛应用的平面环填料组被压紧后,填料内部的应力沿轴向衰减,因此距离压盖近的环对密封的贡献较大.然而柔性石墨填料组中起主要密封作用的纯石墨环通常位于填料组的中间,两端加固石墨环的密封能力较弱.为提升柔性石墨填料的密封性能,对平面环石墨填料组进行结构优化,通过制造应力集中改变填料组受压后的应力分布,从而增大纯石墨环所受应力以提升填料密封性能.测定柔性石墨相关材料参数,利用ANSYS软件、Fluent软件对优化前后填料组的受力及密封性能进行分析.结果表明:平面环填料组在优化为V形填料组后,纯石墨环内部的应力得到提升,且整组填料与阀杆间的摩擦力更小,填料密封寿命明显更长.

The 3D reconstruction of vermiculite-based sealing material was carried out based on CT scanning experiments and Avizo software. The precision and representation of the reconstructed digital core were tested by calculating the pore structure parameters and comparing them with the experimental results of mercury compression. Avizo is a perfect interface with Fluent software to perform micro-scale seepage simulation to explore the distribution of pressure and velocity fields during fluid transport. In this paper, a new approach is proposed to study the penetration leakage of non-metallic gaskets by using equivalent pore networks.

针对传统双向改进快速扩展随机树(RRT*)算法采样速度较慢以及产生路径较粗糙的问题,对6轴机械臂的运动规划进行分析,提出了一种基于目标采样和局部路径优化改进的双向RRT*算法.首先,应用目标采样思想,在对扩展点进行筛选时,考虑随机扩展点与目标点的距离,保留距离目标点最近的随机搜索点;然后,对该搜索点进行扩展,减少不必要区域的搜索,使采样更加高效,搜索路径更优;最后,在此基础上,结合局部路径优化算法,对RRT*算法中重布线随机树过程引入优化函数概念,计算两个节点之间最小距离所需节点,并连接该节点以降低路径曲折程度.将所提改进算法与原始双向RRT*算法在不同测试环境下用机器人操作系统(ROS)进行仿真实验,实验结果表明,所提算法能有效优化算法规划路径,并提高规划效率.

文章在回顾过程装备与控制工程专业发展历程的基础上，辨析了新经济形势下该专业存在的问题，并提出“四位一体”的专业升级模式及具体举措。该模式的实施，有助于提高学生的工程实践能力、创新能力及跨界整合能力，同时有助于提升本专业的影响力。

阀门定位器是工业领域重要的控制仪器,能够有效改善气动调节阀的动静态特性.电/气(I/P)转换器作为阀门定位器内的核心部分,用于控制定位器的输出气压.为探究喷嘴挡板结构参数对定位器的影响、提高控制精度,对阀门定位器I/P转换器中的喷嘴挡板模块工作原理进行了研究,并建立了数学模型.基于该数学模型,对喷嘴挡板的恒节流孔与喷嘴孔直径作了参数优化,并利用ANSYS FLUENT仿真软件进行流场分析.基于流场分析的结果,对喷嘴挡板的其余结构参数进行优化.优化结果表明,合理的结构参数可获得更宽的线性范围与更高的灵敏度,从而提升阀门定位器的控制效果.利用ANSYS FLUENT进行仿真分析,可有效降低设计成本.该研究对定位器国产化替代工作具有参考意义.

管道运输是五大运输方式之一,环境影响和人为破坏等因素会造成管道的泄漏现象,管道发生泄漏会对人民财产安全和环境造成严重危害;目前国内的管道泄漏定位研究多以单点泄漏为主,而真实的管道运行工况中往往会发生多点泄漏现象.提出一种基于时差定位法的管道多点泄漏定位法;以两点泄漏为例,在管道上下游两端分别放置两个传感器,为降低管道运行过程中的噪声干扰,利用互谱结合变分模态分解算法将采集信号分离成多个模态并提出一种基于信息熵和滤波后信号相关系数等多指标结合的模态选取法;将去噪后的信号通过快速独立成分分析(fast independent component anaysis,Fast ICA)算法分离出独立的信号源,再基于相关系数匹配出对应泄漏源产生的声发射信号,最后通过时差定位得出泄漏源位置.在此研究基础上基于实验室管道和设备开展多点泄漏定位试验并取得了可靠的试验结果,为工业实际的多点泄漏定位提供了理论思路和解决方案.

声发射技术具有灵敏度高、实时性强、覆盖范围大等优点.泄漏产生的声发射波沿管壁传播会发生衰减,通过研究衰减系数与金属晶粒散射和热流损失的关系,建立准确的声发射能量衰减模型.在此基础上,针对声发射频带宽的特点对传统衰减定位模型进行改进,提出宽频带声发射源定位模型,该方法先通过实验确定泄漏信号频带,再将滤波后的信号经过小波包分解,提取小波包能量特征进行定位.针对无法完全滤除的噪声提出三传感器定位模型,利用3组信号互相做差可减小噪声的影响.实验表明:采用宽频带定位模型比传统定位模型更具优势,定位误差平均减小5％,低泄漏率(60 mL/min)时可减小8％;增加一个传感器后定位误差为5％,几乎不受泄漏率影响,证明了该文定位模型的准确性.

为进行轴承剩余寿命(Remaining Useful Life,RUL)预测,采用小波-谱峭度分析方法,首先对轴承振动序列信号进行小波包分解,并以谱峭度作为指标,确定故障特征频带并进行信号重构,然后,根据其频谱特征判断轴承是否发生故障,最终确定轴承振动序列信号的初始故障点(Incipient Fault Point,IFP).在此基础上,将引入注意力(Attention)机制的一维深度可分离卷积神经网络用于轴承初始故障点之后振动信号特征的提取,相比传统卷积神经网络,深度可分离卷积层可减少网络训练参数个数,加快网络训练速度.实验结果表明,注意力机制的引入使网络能够聚焦信号中关键的特征,为重要特征赋予较大权重,避免人工处理特征的不足,利于有效特征提取,最终预测结果好于SVR、CNN、RNN等常用数据驱动方法.

为了构建拟合实际骨微观结构且孔隙梯度变化连贯的仿生骨支架,在对实际骨进行Micro CT扫描和ROI分析的基础上,通过梯度函数与遗传算法相结合的方法,构建出既拟合实际骨孔隙分布规律又具有一定随机性的微观孔结构负模型,再将负模型与实体模型进行布尔运算获得仿生骨支架模型.结果表明,仿生骨支架模型的孔隙率、梯度拟合度和连通性均优于其它模型,且通过梯度函数构建的仿生骨支架模型对各种形态和孔隙分布的骨骼均具有适用性,孔隙梯度变化更加连贯自然.

Backlash is a commonly non-linear phenomenon, which can directly degrade the control accuracy of a pneumatic control valve. To explain the cause and law of backlash error, and to propose an effective method, many research works on the modeling of a pneumatic control valve system have been carried out. The currently model of a control valve system can be classified as a physical model, data-driven model, and semi-physical model. However, most models only consider the force-displacement conversion process of a pneumatic diagram actuator in a pneumatic control valve system. A physical model based on the whole workflow of the pneumatic control valve system is established and a control method to eliminate the backlash error is proposed in this paper. Firstly, the physical model of the pneumatic control valve system is established, which is composed of three parts: pneumatic diaphragm actuator model, nozzle-flapper structure model and electromagnetic model. After that, the input–output relationship of the pneumatic control valve system can be calculated according to the established physical model, and the calculation results are consistent with the experimental result. Lastly, a self-calibration PID (SC-PID) control method is proposed for backlash error elimination. The proposed method can solve valve stem oscillation caused by backlash during valve control.

Valve positioner is the core component of the pneumatic control valve. A new software and hardware design scheme of intelligent valve positioner is presented in this paper. The circuit composition of each part of the intelligent valve positioner is introduced in hardware part. Based on it, a hardware solution to realize HART ‘multi-point’ communication is proposed in this research. In the software design, a novel combined PID control algorithm is proposed to solve the nonlinear problem caused by the friction between the valve stem and the packing during the control process. Simulation results show that the method proposed in this paper is better than traditional PID method and fuzzy PID method. The software and hardware design scheme of the valve positioner proposed in this paper has certain guiding significance for the development of related products.

螺栓和法兰材料的选择是影响螺栓法兰接头密封性能的重要因素,特别是在高温条件下服役,螺栓法兰发生蠕变的情况下.分别选择法兰蠕变速率大于螺栓蠕变速率以及小于螺栓蠕变速率的两组配合方式,通过传热分析、热-结构耦合分析以及高温蠕变分析,对比研究其密封性能.结果 表明:螺栓蠕变和法兰蠕变都会引起螺栓应力重新分配,随着时间延长螺栓蠕变的累积会导致螺栓截面应力越来越均匀;但法兰蠕变的累积会降低法兰刚度,致使偏转角增大进而导致螺栓内外侧受力相差越来越大;法兰蠕变速率越大,法兰整体刚度下降越快,法兰服役周期越短,因此选择高温服役的螺栓法兰接头材料时,选取的法兰材料蠕变速率不能太大,且抗蠕变性能要比螺栓材料强.

对高压自紧式法兰密封结构进行研究,推导自紧式法兰密封比压和螺栓载荷的计算公式,并通过有限元方法进行了验证.结果 表明:密封比压与内压呈一阶线性递增的关系:密封面越窄密封比压随内压递增速度越快,法兰端面与T形垫片支撑面间隙越大则初始密封比压越大.对某自紧式法兰进行结构以及热-结构耦合分析,研究内压、温度、弯矩工况的影响.结果 表明:升温对高压和低压2种工况的密封性能影响不同,低压下升温使密封比压增大,高压下升温则会使密封比压有所减小;高压自紧式法兰密封受压侧垫片密封面上应力随弯矩增大先减小,但当弯矩增大到一定值后,该应力随着弯矩的增大而增大.

The sealing performance of a brush seal is studied in this article. At present, the mostly used model to analyze the performance of a brush seal is porous medium model in which the effect of bristle deformation is not considered. Here, a combined numerical method is proposed. First, the deformation of bristle is calculated in a fluid-solid coupling model with a simplified bristle model, and then the results of the bristle deformation is imported to a porous media model as the boundary conditions. More accurate media flow and leakage variation law of the brush seal are obtained with this calculation model.

为优化传统星形拧紧方法,提出一种基于弹性交互作用系数法的法兰接头拧紧方法.运用有限元方法对优化后的拧紧方法进行仿真计算,分析其拧紧效果即螺栓载荷大小和均匀性,并通过实验验证有限元仿真结果的有效性和提出的拧紧方法可行性.结果 表明:运用优化后的拧紧方法能通过一轮拧紧将法兰螺栓载荷预紧到目标载荷的90％以上,拧紧效果超过传统拧紧方法六轮拧紧的拧紧效果,且螺栓力分布均匀;该方法适用于不同口径法兰和不同大小的目标载荷.法兰拧紧实验结果与仿真结果相符合,证明仿真结果的有效性和提出的拧紧方法可行性.

针对法兰螺栓力的计算方法,对比分析3种计算方法的计算流程和结果的差异,并运用有限元方法分析3种螺栓力计算方法在不同工况下的垫片应力,以此研究3种螺栓力计算方法对不同工况的适应情况.结果表明:3种计算方法都适用于不同内压下的工况,但m、y系数法和PVRC系数法对内压的变化更为敏感;EN1591法适用于高温以及由外加弯矩的工况,而m、y系数法和PVRC系数法不适用;对于有泄漏率要求的工况EN1591和PVRC系数法更为合适.