【作者】 张夕林；

【导师】 朱小良；

【作者基本信息】 东南大学 ， 测试计量技术及仪器， 2004， 硕士

【摘要】 涡街流量计作为一种发展中的流量检测设备,在工业现场中有着越来越多的应用,其涡街流量信号能否正确检测出来直接关系着测量结果的准确度。论文在肯定FFT算法易于工程实现的同时,指出其测量结果误差较大的弱点,因而在此基础上提出ZOOM-FFT算法。即通过数字低通滤波,得到一包含涡街频率的窄频带,通过对此窄带信号进行整数倍抽取以降低采样速率,然后进行同样点数的FFT运算,达到细化频谱的目的。在实现ZOOM-FFT算法的过程中,对窄带信号抽取的倍数直接关系到最后结果的精确度。为此,论文提出了运用模糊算法实现抽取倍数在线自动调整的方案。首先由FFT运算得到涡街频率的近似值,并以此作为模糊逻辑系统的输入,通过合理构建输入、输出的论域及各自语言变量的隶属度函数,并在一组根据实际抽取原则制定的模糊规则的作用下,得到对应于涡街频率的抽取倍数。论文还讨论了用于智能涡街流量计的现场总线系统的整体设计。设计思想包括传输介质、网络拓扑结构以及数据传输方式的选择,并特别提出了网络接口模件中冗余配置的概念,且针对不同的应用要求给出了不同的冗余配置方案。论文还对通过建立主时钟实现总线系统同步通信机制进行了探讨,并给出了主时钟故障时防止系统崩溃的解决方案。更多还原

【Abstract】 Vortex flow-meter is a developing device for measuring flow rate, and it has more and more application in industrial field, and the accuracy of measuring result is directly determined by vortex signal. Though FFT algorithm is easy to be realized in engineering field, it has a shortage of bigger error. After considering several kinds of advanced signal processing algorithm, ZOOM-FFT is selected to process vortex signal. After the signal is treated by digital low-pass filter, a narrow band containing vortex signal is obtained. Meanwhile, the narrow band is extracted with integer multiple to decrease sample rate before calculated by FFT with the same points as the original signal processing by means of FFT only. Using this method, the frequency spectrum is got refinement.During the process of ZOOM-FFT, the extracting multiple of narrow band is firmly related to the final result. So, fuzzy algorithm is put forth to realize on-line automatic adjustment of extracting multiple. In the fuzzy logistical system, the approximate value of vortex frequency obtained by FFT calculation is taken as the system input, and the interval of input and output varieties and their membership functions is built by simulation, and finally the extracting multiple is obtained by fuzzy rules determined by actual extracting principle.A field-bus system for intelligent vortex flow-meter is discussed also. The design content includes the selection of transmission media, topological structure and data transmission mode. The concept of redundant configuration is brought forth in network interface module, and varied redundant configurations are to meet varied requirements. Meanwhile, the synchronizing communication realized by main clock is discussed, and the solution is brought forth to prevent system from breakdown due to main clock’s fault.更多还原