过程控制课程设计之液位流量串级控制系统

红河学院过控课程设计 1 目录 第一章 概述 ························································································ 4 1.1本课程设计的研究意义 ··········································································· 4 1.2本课程设计的目的和内容 ········································································ 4 第二章 系统结构的控制方案··········································································· 5 2.1控制系统在世界应用中的重要意义 ···························································· 5 2.2系统结构设计························································································ 5 2.3控制系统的总体方框图及工作过程 ···························································· 6 2.3.1被控对象的分析 ············································································· 6 第三章 PID参数整定 ················································································ 7 3.1控制规律的比较与选择 ··········································································· 8 3.1.1常见控制规律的类型及优缺点的比较 ······················································· 8 第四章 设备的选型 ······················································································ 11 4.1液位传感器 ·························································································· 11 4.2电磁流量传感器···················································································· 11 4.3电动调节阀 ·························································································· 11 4.5变频器 ································································································12 4.6模块选择 ·····························································································12 4.7适合本系统的检测转换元件 ····································································12 4.8液位检测转换元件 ················································································13 4.9执行元件的选择性能参数 ·······································································13 第五章 系统仿真和结果分析··········································································14 红河学院过控课程设计 2 第六章 实际控制系统的运行与调试 ································································15 6.1实际控制系统的组成的动态运行图 ···························································15 6.2实际控制系统的运行调试方法 ·································································15 6.3实际控制系统的调试步骤 ·······································································17 6.4运行调试中的问题及解决方法 ·································································18

第一章 概述 1.1 本课程设计课题研究的意义 随着现代工业生产过程向着大型、连续和强化方向发展，对控制系统的控制品质提出了日益增长的要求。在这种情况下，简单的单回路控制已经难以满足一些复杂的控制要求。在单回路控制方案基础上提出的串级控制方案，则对提高过程控制的品质有极为明显的效果。串级控制系统具有单回路控制系统的全部功能，而且还具有许多单回路控制系统所没有的优点。因此，串级控制系统的控制质量一般都比单回路控制系统好，而且串级控制系统利用一般常规仪表就能够实现，所以，串级控制是一种易于实现且效果又较好的控制方法。 红河学院过控课程设计 3 本课程设计课题讨论了一个简单的液位流量串级控制系统的设计方法及步骤。液位和流量是工业生产过程中最常用的两个测控参数，因此本课程设计课题具有较大的现实意义。 1.2 本论文的目的和内容 1.2.1 目的 通过课程设计，加深对所学传感器技术、转换技术、电子技术、自动控制原理以及过程控制的基本原理、基本知识的理解和应用，掌握串级控制系统的设计步骤和方法，掌握工程整定参数方法，培养创新意识，增强动手能力，为今后工作打下一定的理论和实践基础。 1.2.2 内容 一、题目： 液位流量串级控制系统 二、设计指标： 液位在0～500mm内给定一个值，＜5%，稳定时间＜300s,稳态误差≤∣±2mm∣。 三、主要任务： 以严谨的态度对待课程设计，认真复习有关基础理论和技术知识，认真查阅参考资料，仔细分析被控对象的工作原理、特性以及控制要求。能在指导老师的帮助下解决设计中的各种问题，按计划完成课程设计各阶段的任务，使设计的系统的各项指标达到要求。重视理论与实际结合，并以积极、认真的态度参加课程设计答辩。 第二章 系统的控制方案

2.1控制系统在实际应用中的重要意义 单回路控制系统是过程控制中结构最简单的一种形式，它只用一个调节器，调节器也只有一个输入信号，从系统方框图看，只有一个闭环。在大多数情况下，这种简单系统已经能够满足工艺生产的要求。但有些调节对象的动态特性虽然并不复杂，但控制的任务却比较特殊，则单回路控制系统就无能为力了。另外，随着生产过程向着大型、连续和强化方向发展，对操作条件要求更加严格，参数间相互关系更加复杂，对控制系统的精度和功能提出许多新的要求，对能源消耗和红河学院过控课程设计 4 环境污染也有明确的限制。为此，需要在单回路的基础上，采取其它措施，组成复杂控制系统，而串级控制系统就是其中一种改善和提高控制品质的极为有效的控制系统。 液位和流量是工业生产过程中最常用的两个参数，对液位和流量进行控制的装置在工业生产中应用的十分普遍。液位的时间常数T一般很大，因此有很大的容积迟延，如果用单回路控制系统来控制，可能无法达到较好的控制质量。而串级控制系统可以用一般常规仪表来实现，成本增加也不大，却可以起到十分明显的提高控制质量的效果，因此往往采用串级控制系统对液位进行控制。一般情况下，流量是影响液位的主要因素，其时间常数较小，将它纳入副回路进行控制，不仅有效地克服了流量对液位造成的干扰，而且使系统工作频率提高，能够对液位实行较快的控制。 2.2 系统结构设计

整个过程控制系统由控制器、调节器、测量变送、被控对象组成。在本次控制系统中控制器为计算机，采用算法为PID控制规律，调节器为电磁阀，测量变送为HB、FT两个组成，被控对象为流量PV。结构组成如下图2.2所示。 当系统启动后，水泵开始抽水，通过管道分别将水送到上水箱和下水箱，由HB返回信号，是否还需要放水到下水箱。若还需要（即水位过低），则通过电磁阀控制流量的大小，加大流量，从而使下水箱水位达到合适位置；若不需要（即水位过高或刚好合适），则通过电磁阀使流量保持或减小。其过程控制系统图如图2.1所示。

图2.1 控制系统框图 过程控制系统由四大部分组成，分别为控制器、调节器、被控对象、测量变

送。本次设计为流量回路控制，即为闭环控制系统，如下图2.2

控制器控制阀被控对象测量元件变送器

干扰作用 f 被控变量 y控制作用偏差e给定值

s

z