一种高精度数控车床的主轴装配工艺设计

为了达到数控机床的高精度技术要求,对主轴组件的关键部件进行了严格的动平衡校核工艺规划.结合主轴组件特性,制定了主轴定向装配法方案.主轴轴承装配采用隔套双定位方法,为避免装配过程中隔套的过定位现象,对隔套进行了结构分析优化,并设计了隔套以研代磨的加工工艺,确保轴承的装配精度.实践证明主轴装配工艺的设计方案能够满足机床主轴动态特性的相关技术要求.     

数控车床主轴箱力学性能分析及拓扑优化设计

以HyperWorks为平台,对某型号数控车床主轴箱进行力学性能分析,基于变密度法,以主轴箱的相对密度为设计变量,主轴箱体积最小为目标函数,主轴箱静力变形和低阶模态为约束,建立拓扑优化数学模型。基于该方法对数控车床主轴箱进行拓扑优化设计。在保证主轴箱性能和不增加质量的前提下,找到了最优结构布局方案,为企业改进其结构提供了理论依据。     

高速主轴回转误差动态测试与分析

应用双向法设计测试系统,对主轴的回转误差进行动态测试.该系统由高精度标准棒、非接触位移传感器和LMS TEST,LAB采集器组成.阐述了回转误差的测试原理,针对机床主轴测试中标准棒的安装偏心问题,提出了有效解决方法,并进行了实验研究.     

精密卧式主轴设计研究

以HMS63型卧式加工中心主轴的设计为例,讲述主轴的设计过程,详细阐述了主轴的结构设计以及相关的理论计算.通过机床样机试验结果证明,该主轴的结构设计是合理的、设计方法是切实可行的.     

Online monitoring of transit-time ultrasonic flowmeters based on fusion of optical observation

It is well-known that transit-time ultrasonic flowmeters (TTUF) are unsuitable for bubble-contained flows. This paper presents a new online monitoring method based on optical observation, which monitors the functionality of the TTUF in the presence of bubbles in the fluid. The method avoids the unnecessary Emergency Shutdowns (ESD) due to bubble presence in the fluid by bubble detection. The proposed method accomplishes bubble identification through a combination of image processing and wavelet analysis. In addition, a new method is proposed which estimates single bubble size in horizontal pipes using a data fusion approach.     

基于门控循环单元的动态过程下两相 CO2 质量流量测量

针对碳捕集与封存条件下科里奥利质量流量计测量气液两相CO_2动态过程质量流量时误差较大的问题,本文提出了一种基于门控循环单元(GRU)的动态过程下气液两相CO_2质量流量校正方法。利用GRU适合动态过程预测的特点,使用来自CO_2气液两相流实验平台的采集数据,对GRU网络模型进行训练,并使用网格搜索法结合K折交叉验证优化模型参数。使用八组典型工况下的测试集对优化后的GRU模型在测量精度和泛化性能方面进行了评估,并与最小二乘支持向量机(LS-SVM)模型进行了对比分析。实验结果表明GRU模型优于LS-SVM模型,并且GRU模型在动态波动发生后的平稳阶段,其输出结果能够快速跟随CO_2质量流量变化,相对误差在±5%以内。     

科里奥利质量流量计检定误差分析与对策探讨

科里奥利质量流量计在能源和化工品等领域的贸易结算中应用较广,其具有测量效率高、精度准确和运行稳定可靠的特点。目前,人们对科里奥利质量流量计的使用提出了更高的精度要求,因此有必要进行其检定误差的消除处理。以万华(宁波)化学有限公司2019年的大修项目为例,在阐述流量计检定准确性影响因素的基础上,就项目检定与误差分析过程进行深入分析,指出科里奥利质量流量计检定误差处置办法,期望能进一步提升科里奥利质量流量计检定精度,继而为相关行业贸易实现和经济发展提供有效保证。     

Proposal of novel spindle speed variation profile with constant acceleration rate for improvement of chatter stability

Spindle speed variation (SSV) is one of the effective methods which suppresses regenerative chatter. However, regenerative chatter can grow even if SSV is applied. In the previous work, the chatter growth characteristics in SSV were clarified. The chatter frequency changes proportionally to the varying spindle speed, and it causes the change of the magnitude of the dynamic compliance. Hence, chatter can be suppressed through SSV since the dynamic compliance usually reduces as the chatter frequency changes. A greater compliance reduction can be obtained by a higher rate of spindle speeds in two consecutive revolutions at the same angular position, i.e., acceleration rate. From the investigations in the previous work, limitation of the conventionally utilized SSV profiles is found as follows: the acceleration rate always fluctuates with speed variation and the chatter vibration grows where the acceleration rate is insufficient for suppression, and hence suppressing chatter in all sections of SSV is difficult. In this paper, a new SSV profile with a constant acceleration rate, namely CAR-SSV, is proposed to overcome the limitation of chatter stability improvement by utilizing conventional SSV profiles. The magnitude of the acceleration rate is kept constant to realize the chatter suppression effect throughout the cutting process. Through time-domain simulation and cutting experiments, the chatter stability of CAR-SSV is investigated based on the previously introduced chatter stability evaluation indices. Influence of the parameters of CAR-SSV on the stability is investigated, and an appropriate strategy for setting SSV parameters to achieve higher stability is discussed. In addition, in order to verify the effectiveness of the proposed profile, the stabilities of conventional SSV profiles and CAR-SSV are compared through time-domain simulations and cutting experiments.     

Pitometry as a validation tool for water flow measurement in large diameter pipelines

Accurate measurement of water flow rates in large diameter pipelines is a challenge for water companies that need to produce, transport and distribute increasing quantities of water. To a large extent, this challenge results from the impossibility of recalibration of the flow meters within the periodicity established in the metrological regulations since the removal of a large size flow meter from its site of operation in the field and its transport to a calibration laboratory is in most cases technically and economically impracticable. Because of this scenario, this paper presents the pitometry technique as an interesting alternative to solve problems related to the validation of water flow measurements performed by flow measurement systems installed in large diameter conduits. The technique is based on the determination of the water flow rate by mapping the velocity profile of the water flow inside the pipe by means of Cole type Pitot tubes. The water flow rate is determined in a cross section of the pipe located near and in series to the flowmeter to be evaluated. Based on the results obtained in a great number of water flow measurements already performed by applying the pitometry technique in large diameter pipelines in the field, it is possible to conclude that this methodology is perfectly applicable in the validation of the performance of flow meters installed in these conduits solving satisfactorily the issues related to its operation.     

Applications of digital signal processing methods in TOF calculation of ultrasonic gas flowmeter

Ultrasonic gas flowmeters (UGFM) are extensively used in petroleum, chemical, natural gas and other fields because of their distinctive measurement advantages. As the core technology of the UGFM, digital signal processing technology determines its measurement accuracy and stability. This paper systematically reviews the signal processing methods for measuring the TOF (time of flight) based on the principle of time difference method. According to the stability of the feature information extracted by different digital signal processing methods, the advantages and disadvantages of each method are analyzed. Aiming at the problems of serious energy attenuation, weak echo signal amplitude, and low signal-to-noise ratio (SNR) when ultrasonic signal propagate in the gas, different signal processing methods are evaluated and compared from the aspects of calculation accuracy, response speed, anti-interference ability and sensitivity to parameter changes. Finally, some improvement ideas and directions for further research are proposed according to the analysis results.