基于VMD与时间序列分析的滚动轴承故障特征提取方法

为了在非线性、非平稳的滚动轴承故障振动信号中有效提取出敏感的故障特征,提出了基于变分模态分解(VMD)与时间序列分析相结合的特征提取方法。首先通过VMD将原始信号分解为不同预设尺度的本征模态分量(IMF),对各个IMF分量建立时间序列预测模型,通过叠加重构得到最终的预测模型,比较评价指标确定最优参数的选取。最后,通过仿真信号与滚动轴承实际故障数据分析,并与经验模式分解(EMD)进行对比,结果表明该方法能够有效的提取到故障特征频率。     

7号连铸机的NKK液位PID控制参数及结晶器流场优化

本钢三连铸的单流宽板坯连铸机从达涅利公司引进,于2008年12月4日建成投产,结晶器液位控制采用NKK技术。介绍了7号连铸机生产超低碳钢过程中,结晶器液位出现不稳定性波浪的原因,并通过改进NKK液位控制工艺,微调PID控制参数,以及优化结晶器流场等措施,提高了宽幅汽车板生产时的结晶器液位控制精度,并且解决和消除了不稳定型波浪的问题,使宽幅汽车板的轧制成材率大幅提升。     

煤矿井下防爆胶轮车湿式制动器结构优化*

针对胶轮车湿式制动器的碟簧使用中发生的碎裂现象，运用标准GB/T 1972中方法对碟簧进行验算，发现在变负荷作用下的碟簧寿命≤105次，属于有限寿命。在保持制动性能不变情况下，采取增加碟簧厚度的改进方案对碟簧结构进行优化。优化后碟簧的设计循环寿命≥2×106次，达到GB/T 1972标准规定的无限寿命，并与工业制动器JB/T 10917中规定碟簧设计循环寿命一致。     

Automatic Segmentation and Detection System for Varicocele Using Ultrasound Images

The enlarged veins in the pampiniform venous plexus, known as varicocele disease, are typically identified using ultrasound scans. The medical diagnosis of varicocele is based on examinations made in three positions taken to the right and left testicles of the male patient. The proposed system is designed to determine whether a patient is affected. Varicocele is more frequent on the left side of the scrotum than on the right and physicians commonly depend on the supine position more than other positions. Therefore, the experimental results of this study focused on images taken in the supine position of the left testicles of patients. There are two possible vein structures in each image: a cross-section (circular) and a tube (non-circular) structure. This proposed system identifies dilated (varicocele) veins of these structures in ultrasound images in three stages: preprocessing, processing, and detection and measurement. These three stages are applied in three different color modes: Grayscale, Red-Green-Blue (RGB), and Hue, Saturation, and Value (HSV). In the preprocessing stage, the region of interest enclosing the pampiniform plexus area is extracted using a median filter and threshold segmentation. Then, the processing stage employs different filters to perform image denoising. Finally, edge detection is applied in multiple steps and the detected veins are measured to determine if dilated veins exist. Overall implementation results showed the proposed system is faster and more effective than the previous work.     

基于经验模态分解方法的拉曼光谱信号处理研究

经验模态分解(EMD)方法是一个以信号内在物理频率成分为对象的自适应时频分析方法,而常见的非平稳信号分析方法,比如小波分析,它需要选择小波基,不同小波基的分析结果不同;拉曼光谱信号是典型的非线性和非平稳信号,EMD方法充分地保留了信号本身的非线性和非平稳的特征,适应于拉曼光谱信号的分析。实验在自行研制的拉曼光谱测试平台上获得了原始的拉曼光谱信号,并通过经验模态分解将信号分解成不同频率的10个本征模式分量,信号能量集中在750cm^-1和1500cm^-1左右,最后进行了频率成分分析和去噪处理,并和小波分析方法进行了对比,验证了EMD方法的有效性和实用性,该方法在拉曼光谱信号分析中有较好的应用前景。     

Actuator fault tolerant control using adaptive RBFNN fuzzy sliding mode controller for coaxial octorotor UAV

In this paper, a robust controller for a Six Degrees of Freedom (6 DOF) coaxial octorotor helicopter control is proposed in presence of actuator faults. Radial Base Function Neural Network (RBFNN), Fuzzy Logic Control approach (FLC) and Sliding Mode Control (SMC) technique are used to design a controller, named Fault Tolerant Control (FTC), for each subsystem of the octorotor helicopter. The proposed FTC scheme allows avoiding difficult modeling, attenuating the chattering effect of the SMC, reducing the rules number of the fuzzy controller, and guaranteeing the stability and the robustness of the system. The simulation results show that the proposed FTC can greatly alleviate the chattering effect, good tracking in presence of actuator faults.     

Structural optimization with an automatic mode identification method for tracking the local vibration mode

Traditional optimization methods, which take a specific order of modal frequency as the design constraint, could fail to obtain the desired solution because of modal substitution. An improved optimization model with continuous sizing variables is established to solve this problem, in which the minimum weight and a given local modal frequency are considered as the objective and the constraint. To capture accurately the expected mode of vibration, a local mode identification technique is proposed based on the strain energy ratio between the local area and the whole structure. With that scheme, an optimization system is developed, in which the local mode can be effectively identified and the constraint can be updated with it in the iteration process. Two numerical examples, of a reinforced plate and a satellite structure, are applied to illustrate the effectiveness and efficacy of the proposed method.     

基于ANSYS的带簧油封径向力分析

提出一种考虑弹簧初应力的油封径向力有限元计算方法,即通过二维轴对称模型实现带簧油封的径向力计算。该模型中通过圆管来等效油封弹簧,并可以实现弹簧初应力现象的模拟;圆管模型的材料属性由2种状态下(弹簧装配在油封上和油封装配在轴上)弹簧的拉力转换得到,转换关系通过试验与仿真相结合的办法获得,最终实现了带簧油封2种状态下的径向力有限元计算。通过径向力测量仪验证计算结果的正确性,同时发现弹簧所产生的径向力并非百分之百转化为油封径向力。