【作者】 荆荣霞；

【导师】 万金领；

【作者基本信息】 山东轻工业学院 ， 机械电子工程， 2007， 硕士

【摘要】 液体流量是工业生产中的一个重要参数。随着现代工业技术的快速发展,测量环境日益复杂化,人们对流量测量的要求也越来越高,许多流量测量技术问题亟待解决,其中测量精度就是一个重要方面。对于容积式流量计液体小流量的测量,测量误差的主要来源是内部泄漏。本文首先分析了容积式流量计误差的特性,根据流体力学原理,提出了一种提高容积式流量计液体小流量测量精度的新方法—差压补偿法,阐述了差压补偿法的设计思想,即在流量计的转轴上增加一个起补偿作用的控制电机,控制电机通过定比传动与流量计的转子连接,其转速由流量计入口与出口的压差决定,使流量计转子的转速紧随压差的变化自动调节。结合检测与控制理论,给出了检测系统的总体设计方案。然后,分别对本检测系统的几个组成部分:压差检测、信号采集与转换、控制方法和电机驱动部分作了详细的阐述和设计。压差检测部分主要任务是完成非电量到电量的转换,使用电容式压差变送器将流量计入口和出口的压差信号△P转换成标准的4～20mA的电流信号输出。信号采集与转换部分主要完成功率放大和A/D转换,由美国ATMEL公司生产的AT89C51AC2微处理器实现。在电机驱动部分的分析中使用步进电机作为执行机构,设计了步进电机驱动器和功率放大器。另外,抗干扰设计保证了系统的安全性和稳定性。控制方法是本文的重点内容,在分析了流体控制领域常用的几种控制方法,比较了各自的优缺点之后,选择了结合常规PID控制和模糊控制的新的控制策略—模糊自整定PID控制,这种复合型控制方式既能充分体现PID控制的结构简单、控制精度高和稳态无误差的优点,又可以充分发挥模糊控制的动态性能好和擅长解决非线性问题方面的特长。在控制器的变量和变量隶属度确定之后,给出了控制规则表,应用MATLAB仿真软件对控制过程进行了仿真,仿真结果表明所设计的控制系统能取得良好的控制性能。更多还原

【Abstract】 Liquid flow is an important parameter of industry. Along with the fast development of modern industrial technology, and the measuring environment complicates day by day, the requirement of flow measurement comes higher and higher, many technical problems await to be solved, measuring precision is one of the keys. For liquid low flow measurement of volumetric flowmeter, the erroris mainly from leakage.In this thesis, the error characteristics were analyzed firstly, and a full new measuring method, differential-pressure compensation method, is arising to improve the measuring precision according to the principle of hydromechanics. And it elaborates the design idea and integrating the theory of examination and control, provides the construction of examination and test system. And then, it gives detailed illustration and design of the partials of the system, differential pressure examination and test, signal gathering and transforming, controlling method and motor driving.The function of differential pressure examination and test part is to complete the transformation from non-electric signal to electric signal. Using capacitive differential pressure transformer, the differential pressure△P between entrance and exit of flowmeter is transformed to a standard electric current signal in 4~20mA for output. The function of the signal gathering and transforming is power amplifying and A/D transformation, processed by AT89C51AC2 CPU of ATMEL USA. The thesis analyses the motor driving part, by step-motor, designs the step-motor driver and its power amplifier. Moreover, the anti-jamming design guarantees the system’s security and stability. The control method is the keystone in this thesis. After analyzing several regular control methods in fluid control field and contrasting their advantage and shortcoming, a new fuzzy self-adjusting PID control method, united the advantages of normal PID control and fuzzy control, comes out. It owns not only the advantages, simple structure, high precision and no error of normal PID control, but also the advantages, excellent dynamic and non-linear performance of fuzzy control. Once the variable and relation to it are made certain, the control table comes out. The simulating result by MATLAB shows the good control performance of this control system.更多还原