6 实验七 前馈-反馈调节系统(模拟系统)解析

前馈反馈控制串级控制的主回路和副回路都是闭环负反馈控制系统。

前馈反馈控制系统的前馈控制是一开环控制，反馈控制是一闭环负反馈控制。

串级是调节被控量使其不偏离给定值，而前馈是专门针对干扰量的，前馈控制一般用在变量无法控制的场合串级控制的副变量和主变量之间一般都有相互干扰因素，这种干扰因素有多大可以简单或者大约量化。

相反，前馈控制变量是不可控的，不仅对调节变量影响大，而且有可能会干扰对主变量的判断，也就是造成假象。

而且，一条前馈路径只能针对一个可测干扰、最常见的过程控制系统有DCS、PLC等，DCS侧重模拟量控制，PLC侧重开关量控制，PLC的开关量控制周期相对DCS来说具有较大优势，能够达到几个毫秒，但是目前2种系统都对自己的弱项进行了强化，因此相互之间差异的越来越小了。

2、反馈控制属于闭环控制，将被控对象的值采集并与设定值进行比较，根据差值来决定控制输出变化，形成闭环。

3、如果在这个差值上叠加可能造成被控对象值变化的另一个对象参数的值与作用系数的乘积，以提前预知被控对象可能的变化趋势并提前做出响应，那么就成了前馈控制。

4、FCS 是现场总线，可以作为DCS系统的现场设备管理层网络，能够通过1根总线连接现场设备，通过专用协议卡接入DCS系统，能够节省大量电缆。

5、串级控制是指由2个PID控制回路组成，分为外环和内环，其中外环的控制输出值作为内环的输入设定值。

前馈反馈控制的原理：前馈控制又称扰动补偿，它与反馈调节原理完全不同，是按照引起被调参数变化的干扰大小进行调节的。

在这种调节系统中要直接测量负载干扰量的变化，当干扰刚刚出现并能被测出时，调节器就能发出调节信号使调节量作相应的变化，使两者在被调量发生偏差之前抵消。

因此，前馈调节对干扰的客服比反馈调节及时。

但是前馈控制是开环控制，其控制效果需要通过反馈加以检验。

前馈控制器在测出扰动之后，按过程的某种物质或能量平衡条件计算出校正值。

如果前馈支路出现扰动，经过流量计测量之后，测量得到干扰的大小，然后在反馈支路通过调整调节阀开度，直接进行补偿。

过程控制课程设计--前馈-反馈控制系统的设计与整定北华航天工业学院课程设计报告（论文）设计课题：过程控制专业班级：学生姓名：指导教师：设计时间：201311.25-2013.12.06北华航天工业学院电子工程系过程控制课程设计任务书指导教师：教研室主任：2013年12月6日内容摘要自本世纪30年代以来，自动化技术获得了惊人的成就，已在工业和国民经济各行各业起着关键的作用。

自动化水平已成为衡量各行各业现代化水平的一个重要标志。

自动控制按输入量的变化规律分类，可分恒值控制系统（Fixed Set-Point Control System）、随动控制系统（Follow-up Control System）、过程控制系统（Process Control System）。

前馈-反馈控制系统的设计与整定，采用自动控制技术，实现对水箱液位的过程控制。

首先对被控对象的模型进行分析。

然后，根据被控对象模型和被控过程特性并加入PID调节器设计流量控制系统，采用动态仿真技术对控制系统的性能进行分析。

关键词：自动化过程控制PID目录一概述 (1)二方案设计与论证 (2)2．1 前馈控制 (2)2．2 反馈控制 (2)2．3 前馈-反馈控制 (3)2．4前馈-反馈控制系统PID算法 (4)2．5 控制方案的论证 (5)2．5．1控制方案的可靠性 (5)2．5．2控制方案的安全性 (5)2．5．3控制方案的经济性 (5)三仪表的选择与参数的设定………………………………………………………6 3．1 设备型号 (6)3．2 调节器及其参数的设置 (7)3．3 仪器仪表的组合安装 (8)3．4 计算机的参数设置 (9)四实验步骤…………………………………………………………………………9 五实验结果………………………………………………………………………10 六结论 (11)七心得体会………………………………………………………………………12 八参考文献………………………………………………………………………13一、概述PCT—I型过程控制实验装置是基于工业过程物理模拟对象，它集自动化仪表技术，计算机技术，通讯技术，自动控制技术为一体的多功能实验装置。

一、前馈控制系统设计1、前馈控制系统选择原则1.1扰动量可测不可控原则 (2)1.2控制系统精确辨识原则 (2)1.3被控系统自衡原则 (3)1.4优先性原则 (3)1.5经济性原则 (4)2、工程整定2.1整定的总体原则2.1.1稳定性 (4)2.1.2 快快速性 (5)2.1.3反馈控制的静差 (5)3、前馈-反馈复合系统工程整定 (5)二、实例仿真 (6)2.1前馈控制系统整定 (7)2.2反馈控制系统前向通道稳定性分析 (7)2.3、反馈控制系统整定 (8)2.4、系统仿真 (9)三、................................................. 心得体会11四、................................................. 参考文献12一、前馈控制系统设计1.1前馈控制系统选择原则前馈控制系统的选择主要有一下原则：1.1.1扰动量可测不可控原则扰动量的可测性是补偿的前提条件，不可测的扰动量无法设计前馈补偿器。

如果干扰可控，则可通过控制方法消除扰动对系统的影响，而没有必要采用前馈这种迂回的方式，在被控系统“腹中”消除干扰的影响了。

例如在很多过程控制中，温度是一个主要干扰源。

温度可以测量（直接测量或间接测量），满足可测条件。

而在某些环境如实验室中，温度可以通过空调等进行调节（不满足不可控条件），将温度对控制对象的影响降到最低，这时就没有必要对温度采取前馈控制方式消除影响了。

而在很多现场情况下（如被控对象在室外等），温度不易调节（满足不可控条件），这时应米取前馈控制方式消除由于温度对系统的影响。

1.1.2控制系统精确辨识原则控制中的每一个环节的传递特性都应能精确辨识。

作为开环控制，构成前馈控制系统中的任何一个环节都应尽可能准确，因为开环控制系统中的任何一环节对系统的控制精确度都有一定影响。

相比之下，闭环控制对系统中环节的要求要“松”得多。

前馈控制与反馈控制前馈控制前馈控制是在前苏联学者所倡导的不变性原理的基础上发展⽽成的。

20世纪50年代以后，在⼯程上，前馈控制系统逐渐得到了⼴泛的应⽤。

前馈控制系统是根据扰动或给定值的变化按补偿原理来⼯作的控制系统，其特点是当扰动产⽣后，被控变量还未变化以前，根据扰动作⽤的⼤⼩进⾏控制，以补偿扰动作⽤对被控变量的影响。

前馈控制系统运⽤得当，可以使被控变量的扰动消灭在萌芽之中，使被控变量不会因扰动作⽤或给定值变化⽽产⽣偏差，它较之反馈控制能更加及时地进⾏控制，并且不受系统滞后的影响。

单纯的前馈控制是开环的，是按扰动进⾏补偿的，因此根据⼀种扰动设置的前馈控制就只能克服这⼀扰动对被控变量的影响，⽽对于其他扰动对被控变量的影响，由于这个前馈控制器⽆法感受到，也就⽆能为⼒了。

所以在实际⼯业过程中单独使⽤前馈控制很难达到⼯艺要求，因此为了克服其他扰动对被控变量的影响，就必须将前馈控制和反馈控制结合起来，构成前馈反馈控制系统。

前馈反馈控制系统有两种结构形式，⼀种是前馈控制作⽤与反馈控制作⽤相乘；另⼀种是前馈控制作⽤与反馈控制作⽤相加，这是前馈反馈控制系统中最典型的结构形式。

采⽤前馈控制系统的条件是：1、扰动可测但是不可控。

2、变化频繁且变化幅度⼤的扰动。

3、扰动对被控变量的影响显著，反馈控制难以及时克服，且过程控制精度要求⼜⼗分严格的情况。

反馈控制反馈控制是指在某⼀⾏动和任务完成之后，将实际结果进⾏⽐较，从⽽对下⼀步⾏动的进⾏产⽣影响，起到控制的作⽤。

其特点是：对计划决策在实施过程中的每⼀步骤所引起的客观效果，能够及时做出反应，并据此调整、修改下⼀步的实施⽅案，使计划决策的实施与原计划本⾝在动态中达到协调。

当然，反馈控制主要是对后果的反馈，⽽已铸成的事实是难以改变，且⽤新计划代替旧计划、⽤新决策代替原有决策有⼀个过程需要⼀定的时间，由于系统不能适应情况的变化，将会给⼯作带来不必要的损失。

这就是反馈控制不及预先控制之处。

过程控制实验指导书授课学时：16课时授课专业：自动化授课教师：姜倩倩目录过程控制实验项目一览表 ............................................................................................ - 1 - 实验一：一阶系统数学模型的建立 ............................................................................ - 2 - 实验二：PID控制器参数自整定............................................................................... - 4 - 实验三水箱液位PID控制........................................................................................ - 8 - 实验四水箱压力的PID调节控制 .......................................................................... - 14 - 实验五串级水位控制系统设计 ............................................................................ - 17 - 实验六前馈-反馈控制系统仿真实验 .................................................................... - 19 - 实验七单片机液位控制系统 .................................................................................. - 22 - 实验八单容液位PLC控制 ...................................................................................... - 25 -过程控制实验项目一览表实验参考书：GK-1型操作说明书.实验指导书实验一：一阶系统数学模型的建立一、实验目的1．熟悉利用计算法建立系统一阶惯性环节加纯迟延的近似数学模型的方法；2．学会利用MATLAB/Simulink对系统建模的方法。

摘要 可编程序控制器(PLC)是一种集自动化技术、计算机技术和通信技术为一体的高可靠性的工业计算机，应用很广泛，现在已经越来越成熟，小批量、多品种、多规格、低成本和高质量的产品不断涌入市场。

本设计主要是在西门子编程软件S7-300的基础上实现PLC的前馈反馈系统的设计，并通过具体的实例，即对加热炉温度的前馈反馈控制的实现来说明前馈反馈的具体流程。

加热炉内的实时温度经过温度传感器、温度变送器将模拟量传送给PLC的模拟量输入模块，模拟量输入模块将模拟量转换成数字量送到PLC内部处理，再由模拟量输出模块将数字量转换为模拟量输出控制阀门的开度以达到炉内温度稳定的控制。

本文研究的重点是如何用PLC以及WinCC对现场的前馈-反馈控制系统进行控制的，如何将前馈-反馈控制系统得到的数据经过PLC后传送到上位机，用组态软件WinCC进行实时监控。

经仿真运行后，本系统能实现控制要求。

关键字：前馈-反馈控制；可编程控制器；WinCC;加热炉promoted development, and The ability to resolve conflicts and constantly improve, our ... 6. on the building of Socialist culture in China. A country, a nation strong, always supported by culture flourished, the inheritance and development of civilization, without culture to develop and prosper, there will be no realization of the dream of China. 18 big yilai, XI General Secretary around "foster and promote Socialist core values" "promote China excellent traditional culture" "firmly master ideology work led right and discourse right", aspects do has series important speech, main including put publicity thought work do have better for achieved China dream condensed powerful moral support improve national culture soft strength foster and promote Socialist core values youth to consciously practice line Socialist core values Childhood actively cultivate and practice the core values of socialism and the party's important speech on the press conference. 7. promote the reform and development of social undertakings and social management. 18 big yilai, Central insisted put guarantees and improved livelihood as ruling acting political of starting point and foothold, Xia big pneumatic solution masses most care most directly most reality of interests problem, 3 years cumulative reduction poverty more than 50 million people, equivalent to a medium national population of total, annual added town employment more than 10 million people, starts construction supportability housing engineering near 4 million sets, built world Shang scale maximum, and cover universal of basic medical guarantees network and pension guarantees network, urban and rural residents income continued growth, The lives of the people of all ethnic groups have more on both material and spiritual thriving. This aspects XI General Secretary of speech main including promoted poverty area poverty, and speed up development let 1.3 billion people enjoys better more fair of education speed up advance housing guarantees and supply system construction always put people life security put in first bit efforts put China construction became network power insisted general national security views, go China features national security road effective maintenance national security and social settled,. 8. with regard to comprehensive strictly administering the party. Party of 18 big yilai, Central station in party and national survival of height, firmly grasp strengthening party of ruling capacity construction, and advanced purity construction this article mainline, to style construction for breakthrough, to developed introduced eight items provides started start, put discipline and rules is in front, organization carried out has party of mass line education practice activities and "three strict three real" topic education, insisted "zero tolerance, and full cover, and no area", insisted "Tiger" "flies" with playing, style political wind society continued improved, More perfect system of laws within the party, discipline of authoritative seriousness increasing, for the history of winning has a lot of new features provide a strong politicalAbstractProgrammable Logic Controller (PLC) is a set of automation technology, computer technology and communication technology as one of the high reliability industrial computer，and PLC is widely used. Now it is more and more mature，smaller quantities, more kinds ,lower cost and higher quality in the market. This design is abased on the programming software of Siemens to implement PLC-based feedforward-feedback control system. This design introduces an example to explain the procedure of feedforward-feedback system. The example is that through temperature control in heating furnace which is used feedforward and feedback control system.Real-time temperature, inside the furnace, after the temperature sensors, temperature transmitters discovered will be sent to the analog input module of PLC. Analog input modules convert analog to digital, and sent the digital data to CPU of PLC to process. Then analog output modules convert digital to analog to control valve, so the system achieves a stable furnace temperature control. Focus of this study is about that how to use PLC and WINCC to control feedforward-feedback system of on-scene, and how to make feedforward-feedback system convey the date to computer via PLC, then, using configuration software Wincc implement real-time monitoring.Keywords：feedforward-feedback；Programmable Logic Controller；WinCC；heating furnacepromoted development, and The ability to resolve conflicts and constantly improve, our ... 6. on the building of Socialist culture in China. A country, a nation strong, always supported by culture flourished, the inheritance and development of civilization, without culture to develop and prosper, there will be no realization of the dream of China. 18 big yilai, XI General Secretary around "foster and promote Socialist core values" "promote China excellent traditional culture" "firmly master ideology work led right and discourse right", aspects do has series important speech, main including put publicity thought work do have better for achieved China dream condensed powerful moral support improve national culture soft strength foster and promote Socialist core values youth to consciously practice line Socialist core values Childhood actively cultivate and practice the core values of socialism and the party's important speech on the press conference. 7. promote the reform and development of social undertakings and social management. 18 big yilai, Central insisted put guarantees and improved livelihood as ruling acting political of starting point and foothold, Xia big pneumatic solution masses most care most directly most reality of interests problem, 3 years cumulative reduction poverty more than 50 million people, equivalent to a medium national population of total, annual added town employment more than 10 million people, starts construction supportability housing engineering near 4 million sets, built world Shang scale maximum, and cover universal of basic medical guarantees network and pension guarantees network, urban and rural residents income continued growth, The lives of the people of all ethnic groups have more on both material and spiritual thriving. This aspects XI General Secretary of speech main including promoted poverty area poverty, and speed up development let 1.3 billion people enjoys better more fair of education speed up advance housing guarantees and supply system construction always put people life security put in first bit efforts put China construction became network power insisted general national security views, go China features national security road effective maintenance national security and social settled,. 8. with regard to comprehensive strictly administering the party. Party of 18 big yilai, Central station in party and national survival of height, firmly grasp strengthening party of ruling capacity construction, and advanced purity construction this article mainline, to style construction for breakthrough, to developed introduced eight items provides started start, put discipline and rules is in front, organization carried out has party of mass line education practice activities and "three strict three real" topic education, insisted "zero tolerance, and full cover, and no area", insisted "Tiger" "flies" with playing, style political wind society continued improved, More perfect system of laws within the party, discipline of authoritative seriousness increasing, for the history of winning has a lot of new features provide a strong political2目录1 绪论 (1)1.1 国内外研究现状 (1)1.2 本课题研究内容及方法 (2)2 基于PLC的双闭环流量比值控制系统设计 (3)2.1 系统的工艺流程 (3)2.2 控制系统的硬件选型 (4)2.2.1 PLC的发展及特点 (4)2.2.2 PLC的内部结构 (5)2.2.3 西门子公司的S7系列PLC (7)2.2.4 CPU的选型 (8)2.2.5 I/O模块的选型 (8)2.2.6 电源模块的选型 (9)2.3 系统各部分硬件选型 (9)2.3.1 温度传感器的选择 (10)2.3.2 温度变送器的选择 (10)2.3.3 流量计与压力变送器的选择 (10)2.4 软件设计方案 (11)2.4.1 STEP 7编程软件的简介 (11)2.4.2 系统控制方案的选择 (11)2.4.3 加热炉前馈-反馈系统控制流程图 (12)2.4.4 PID控制及其控制算法 (13)2.5 程序的编写 (15)3 WinCC组态与仿真 (20)3.1 新建工程 (20)3.2 建立Wincc与PLC的通信连接 (21)3.3 创建供料系统的过程画面 (25)3.3.1 创建画面 (25)3.3.2 仿真结果 (27)结束语 (33)致谢 (35)参考文献 (36)reform results, economy, and political system, and culture system, and social system, and discipline check system, and party of construction system reform solid advance, tax, and financial, and price, and administrative approval, and State-owned enterprises, and ecological civilization, important field and key link reform made major progress, market in resources configuration in the of decisive role significantly enhanced, Unprecedented burst of momentum and vitality of economic and social development. XI General Secretary's speech in this regard include the reform only when there is no complete, the < decisions of the CPC Central Committee on some major problems in deepening reform > notes on the 18 session of ideas into the party's spirit of the reforms more difficult to move forward, the increasing use of the Socialist system with Chinese characteristics such as the ability to run the country. 4. with regard to promoting sustained and healthy economic development. Face complex changeable of international situation and difficult heavy of domestic reform development stable task, XI General Secretary made China economic development into new normal of science judge, proposed innovation, and coordination, and green, and open, and shared five big development concept, implementation macro policy to stability, and industry policy to associate, and micro policy to live, and reform policy to real, and social policy to backing five big pillar sex policy, vigorously advance supply side structural reform, new concept, achieved has 2013 to 2015 during, Domestic production total annual growth 7.3%, obviously fast Yu earlier world economic 2.3% of annual growth, on world economic growth of contribution over 25%, tertiary industry accounted for domestic production total share over 50%, eventually consumption on economic growth of contribution rate reached 66%, economic structure adjustment made important progress, development of quality and benefits significantly upgrade, China economic show out huge of swing room and broad of development prospects. This aspects XI General Secretary of speech main including economic growth must is real and no water of growth improve open type economic level "see missing of hand" and "see have see of hand" are to with good speed up from elements drive, and investment scale drive development mainly to to innovation drive development mainly of change active promoted China energy production and consumption revolution,. 5. with regard to building the rule of law in China. 18 big yilai, Central tightly around full advance law ruling, put party of led, and people masters, and law ruling organic unified up, insisted law ruling, and law ruling, and law administrative common advance, insisted rule of law national, and rule of law Government, and rule of law socialone construction, full advance science legislation, and strictly law enforcement, and just judicial, and universal law-abiding, China features socialist legal system further sound perfect, leaders at all levels cadres using rule of law thinking and rule of law way deepening reform, and附录 (37)1.完整程序 (37)2.整体仿真画面 (42)promoted development, and The ability to resolve conflicts and constantly improve, our ... 6. on the building of Socialist culture in China. A country, a nation strong, always supported by culture flourished, the inheritance and development of civilization, without culture to develop and prosper, there will be no realization of the dream of China. 18 big yilai, XI General Secretary around "foster and promote Socialist core values" "promote China excellent traditional culture" "firmly master ideology work led right and discourse right", aspects do has series important speech, main including put publicity thought work do have better for achieved China dream condensed powerful moral support improve national culture soft strength foster and promote Socialist core values youth to consciously practice line Socialist core values Childhood actively cultivate and practice the core values of socialism and the party's important speech on the press conference. 7. promote the reform and development of social undertakings and social management. 18 big yilai, Central insisted put guarantees and improved livelihood as ruling acting political of starting point and foothold, Xia big pneumatic solution masses most care most directly most reality of interests problem, 3 years cumulative reduction poverty more than 50 million people, equivalent to a medium national population of total, annual added town employment more than 10 million people, starts construction supportability housing engineering near 4 million sets, built world Shang scale maximum, and cover universal of basic medical guarantees network and pension guarantees network, urban and rural residents income continued growth, The lives of the people of all ethnic groups have more on both material and spiritual thriving. This aspects XI General Secretary of speech main including promoted poverty area poverty, and speed up development let 1.3 billion people enjoys better more fair of education speed up advance housing guarantees and supply system construction always put people life security put in first bit efforts put China construction became network power insisted general national security views, go China features national security road effective maintenance national security and social settled,. 8. with regard to comprehensive strictly administering the party. Party of 18 big yilai, Central station in party and national survival of height, firmly grasp strengthening party of ruling capacity construction, and advanced purity construction this article mainline, to style construction for breakthrough, to developed introduced eight items provides started start, put discipline and rules is in front, organization carried out has party of mass line education practice activities and "three strict three real" topic education, insisted "zero tolerance, and full cover, and no area", insisted "Tiger" "flies" with playing, style political wind society continued improved, More perfect system of laws within the party, discipline of authoritative seriousness increasing, for the history of winning has a lot of new features provide a strong political4广西工学院2011届毕业论文基于PLC的前馈-反馈控制系统的设计1 绪论1.1 国内外研究现状现代社会要求生产厂商能对市场的需求做出迅速反应，生产出小批量、多品种、多规格、低成本和高质量的产品。

第13讲前馈--反馈控制系统分析一、前馈——反馈复合控制系统1 前馈——反馈复合控制系统的基本概念前馈——反馈复合控制系统：系统中既有针对主要扰动信号进行补偿的前馈控制，又存在对被调量采用反馈控制以克服其它的扰动信号，这样的控制系统就是前馈——反馈复合控制系统。

2 概念的理解：(1) 复合控制是指系统中存在两种不同的控制方式，即前馈控制和反馈控制；(2) 前馈控制的作用是对主要的扰动信号进行完全补偿，可以针对主要的扰动信号，设计相应的前馈控制器；(3) 引入反馈控制，是为了使系统能克服所有扰动信号对被调量产生的影响；因为除了已知的主要的扰动信号以外，系统中还存在其它的扰动信号，这些扰动信号对被调量的影响比较小，有的是我们能够考虑到的，有的我们根本就考虑不到或无法测量，都通过反馈控制加以克服；(4) 系统中需要测量的信号既有被调量，又有扰动信号；3 前馈——反馈复合控制系统实例分析混合水温的前馈——反馈复合控制系统（如图3－12所示）。

热水调节阀冷水调节阀混合水温θ图3－12 混和水温复合控制示意图流量测量变送器前馈控制器温度测量变送器调节器执行器4前馈——反馈复合控制系统的组成前馈——反馈复合控制系统主要由以下环节构成：(1) 扰动信号测量变送器：对扰动信号进行测量并转换成统一的电信号； (2) 被调量测量变送器：对被调量进行测量并转换成统一的电信号； (3) 前馈控制器：对扰动信号进行完全补偿； (4) 调节器：反馈控制调节器，对被调量进行调节； (5) 执行器和调节机构(6) 扰动通道对象：扰动信号通过该通道对被调量产生影响；(7) 控制通道对象：调节量通过该通道对被调量进行调节；前馈——反馈复合控制系统的原理方框图如图3－13所示。

C++ 图3－13 前馈反馈复合控制系统原理图Z++-R +W D (s)W B (s)K z K fW ob (s)K mW r (s)K m为便于分析，通常可将前馈——反馈复合控制系统原理图进行简化，如图3－14所示。

前馈-反馈控制系统仿真实验一、实验目的（1）掌握动态模型的创建方法.。

（2）掌握前馈控制系统的理论整定方法和工程整定方法。

（3）了解调节器参数对控制品质的影响。

二、实验仪器计算机一台三、实验步骤(1)启动计算机，运行MAILAB应用程序；(2)在MAILAB命令窗口输入Simulink,启动Simulink；(3)在Simulink库浏览窗口中，单击工具栏中的新建窗口快捷按钮或在库窗口中选择菜单命令打开一个标题为“Untitled”的空白模型编辑窗口；(4)用鼠标双击信号源模块库(Source)图标，打开信号源模块库，将光标移动到阶跃信号模块(( Step)的图标上，按住鼠标左键，将其拖放到空白模型编辑窗口中.用鼠标双击附加模块库Simulink模块库，将光标移到PID Controller图标上，按住鼠标左键，将其拖放到空白模块编辑窗口中；（5)用同样的方法从连续系统模块库、接受模块库和数学运算模块库中把传递函数模块、示波器模块(scope)和加法器模块c shin }拖放到空白模型编辑窗口中。

用鼠标单击一个模块的输出端口并用鼠标拖放到另一模块的伞入端口，完成模块间的连接，构造图1所示的前馈控制系统的仿真模型。

图1 （6）根据计算结果设置PID调节其参数。

PI参数PID参数四、实验结果（1）启动仿真，通过示波器模块观测并记录系统输出的变化曲线。

有PID环节如下：（2）启动仿真，通过示波器模块观测并记录系统输出的变化曲线。

有PI环节如下：（3）启动仿真，通过示波器模块观测并记录系统输出的变化曲线。

无反馈模块：（4）启动仿真，通过示波器模块观测并记录系统输出的变化曲线。

加PID控制，没有前馈模块：五、总结（1）通过本次实验掌握动态模型的创建方法，前馈控制系统的理论整定方法和工程整定方法，以及了解调节器参数对控制品质的影响；（2）前馈控制系统一般和反馈结合应用，能够很好的克服前馈的局限性；（3）从实验波形中可以看出，前馈控制可以把干扰在输出前处理好，从中可以看出其控制及时的优点但局限性较大，有些干扰无法处理。

控制系统中前馈控制与反馈控制的区别在自动控制系统中,反馈控制是闭环控制,所谓的闭环控制是将输出信号反送到控制器的输入端与给定值(给定控制信号)进行比较，得到偏差信号作为控制器的输入信号．（如何构成的“环路”?对整个控制系统来讲包含两条主要通路信号,一条是从控制器传送到控制对象的前向通道信号,还有一条是从控制对象反馈到控制器输入的反向信号，整个系统构成一个闭和的环路,因此称为闭环)。

前馈控制则是指不存在给定信号与控制对象的输出信号进行比较的过程,直接对控制对象进行控制的一种控制方式,是一种开环的控制方式。

它是在从给定值到控制对象的称为“前向”控制通道上加上控制信号的一种控制方式。

因此称为“前馈”。

前馈控制一般由前馈控制器完成，前馈控制器输出到“前向通道”的信号（作用在控制系统的信号)称为前馈信号。

前馈控制器的输入一般是对系统的某种扰动进行检测和处理后的信号。

那么二者之间究竟有怎么的区别和联系，笔者对此做了以下的见点介绍。

图1 反馈控制框图图2 前馈控制框图上面的两个框图分别是反馈控制框图和前馈控制框图,从图上分析可知二者之间的区别:1。

所测量的信号量不同,前馈系统中所测的信号量是干扰量,反馈系统中所测量的信号量是被控变量。

一般反馈控制系统是按照测量值与给定值比较得到的偏差进行调节的,这都属于闭环负反馈调节,其特点是在被控变量出现偏差后才进行调节。

如果干扰已经发生而没有产生偏差，调节器不会进行工作。

所以反馈系统的调节作用落后于干扰作用。

前馈调节是按照干扰作用来进行调节的。

它的特点是把干扰测量出来，直接引入调节装置。

不像反馈控制那样一定要产生偏差后再来调节,所以前馈控制系统能很好的克服干扰的作用。

2。

前馈控制根据其特定的控制规律需要用专用调节器，反馈控制一般只需采用通用调节器即可。

由于前馈控制的精确性和及时性取决于干扰通道和调节通道的特性，且要求较高，因此，要根据被控制对象的特点来确定调节规律,进而选择所需要的专用调节器,而反馈基本上不管干扰通道的特性，且允许被控变量有波动，因此，反馈调节通常采用PＩＤ调节规律,常用常规仪表或ＤＣS等控制系统实现，可采用通用调节器。