中小型绕线式异步电机可控硅串级调速系统的研究

本文通过分析目前国内中小型绕线式异步电机的调速现况,提出将转子电压提高,以达到取消逆变变压器及启动电阻,将转差功率直接回馈电网进行可控硅串级调速的可能性;提出了选择最佳转子开路电势的原则,并在一台改制的7.5kW 样机上进行了试验.试验结果证实,所提出的研制方案是经济实用和可靠的,电机的调速范围可达4.1∶1以上.     

异步牵引电动机最佳转差率的分析

当电力机车上一台转向架的两个轮对分别各由一台异步牵引电动机带动,并由同一台逆变器供电时,牵引电动机的额定转差率Se对电力机车的性能将产生巨大的影响。一旦Se值确定后,由于动轮直径偏差带来的牵引电动机电流偏差和牵引力偏差即可确定。此外,电动机本身参数的偏差也对转差特性产生巨大影响,本文考虑了上述所有这些非线性参数的影响,分析了异步牵引电动机的最佳额定转差率,并结合精确的等效电路进行计算,提出了额定转差率的最佳范围。     

船闸通过能力计算中的若干问题研究

随着一些大型船闸的建设并投入使用,逐渐暴露出了目前船闸通过能力研究中还存在诸多不足.结合苏北船闸的运行情况,分析船舶过闸作业程序,推导了不同情况下一次过闸时间的计算公式及其适应条件;提出了改进一次过闸平均吨位的计算方法,建立了其连续函数表达式;并讨论了通过能力计算中的单向和双向问题.     

基于概率有限元的气缸盖疲劳可靠性分析

提出了一种基于均匀试验设计和BP神经网络模型构建随机参数与结构响应之间的近似非线性关系的概率有限元方法,该方法较直接Monte-Carlo法需要的样本数据大幅减少,更适合大规模计算的结构概率有限元分析。采用该方法以某型柴油机气缸盖结构疲劳失效分析为算例,进行了可靠度期望寿命计算,并通过对影响气缸盖应力的燃烧压力、各螺栓预紧力和喷油器压紧力等22个载荷参数的均值和标准差的敏感性分析,初步确定了造成气缸盖本体结构疲劳开裂的主要影响因素。     

A statistical process control approach using cumulative sum control chart analysis for traffic data quality verification and sensor calibration for weigh-in-motion systems

Weigh-in-motion systems have been widely used by state agencies to collect the traffic data on major state roadways and bridges to support traffic load forecasting, pavement design and analysis, infrastructure investment decision making, and transportation planning. However, the weigh-in-motion system itself poses difficulties in obtaining accurate data due to sensor characteristics that can be sensitive to vehicle speed, weather conditions, and changes in surrounding pavement conditions. This study focuses on developing a systematic methodology to detect weigh-in-motion sensor bias and enhance current practices for weigh-in-motion calibration. A mixture modeling technique using an expectation maximization algorithm was developed to divide the vehicle class 9 gross vehicle weight into three normally distributed components: unloaded, partially loaded, and fully loaded trucks. Then the well-known statistical process control technique cumulative sum control chart analysis was applied to expectation maximization estimates of daily mean gross vehicle weight for fully loaded trucks to identify and estimate shifts in the weigh-in-motion sensor. Special attention was given to the presence of autocorrelation in the data by fitting an autoregressive time-series model and then performing cumulative sum control chart analysis on the fitted residuals. Results from the analysis suggest that the proposed methodology is able to estimate a shift in the weigh-in-motion sensor accurately and also indicate the time point when the system went out of calibration. This methodology can be effectively implemented by state agencies, resulting in more accurate and reliable weigh-in-motion data.     

车身一体化涂装的应用研究

为实现涂装生产中"高质量、低成本、高效率及环境友好"的目的,文中以溶剂型钻石银灰金属漆车身涂装为例,比较了不同工艺和不同面漆的涂层性能,探讨了对现行车身涂装工艺进行创新的可行性。     

Periodic preventive maintenance policy with infinite time and limit of reliability based on health index

The aging of machine can be slowed and the life of machine can be increased by implementing periodic predictive maintenance. In this article,an improvement factor considering maintenance cost,age of machine and learning effect in the process of maintaining is constructed to describe the effect of periodic preventive maintenance. The model of improvement factor can be fitted through health index. Based on improvement factor with infinite time,cost function including preventive maintenance cost,minimal repair...     

东兴场隧道水平围岩变形破坏特征研究

结合广巴高速公路东兴场隧道对公路隧道水平围岩的变形破坏特征进行了研究,结果表明:隧道水平围岩的变形破坏为结构面控制型,隧道拱顶与拱肩受结构面切割形成的不稳定块体在重力作用下易于掉块形成平拱,拱腰受岩体的夹持作用稳定性较好.     

基于SAEJ1939的车身控制系统设计

提出了基于J1939协议的车身控制系统的硬件和软件实现方法，并在实际的调试中取得良好的效果，简化汽车车身线束，提高电控单元信息利用率，实现共享传输大批量数据信息，充分证明了方案的可行性和可靠性。     

铝型材在线切割的PMSM控制系统仿真研究

介绍了铝型材在线切割的工作流程,分析了PMSM磁场定向控制策略,利用MATLAB软件建立了位置环、速度环及电流环三环串联的仿真模型,通过实际电机参数进行仿真研究,得出了预期的仿真波形。该仿真模型为该系统的硬件及软件设计提供了可靠的理论依据。