外文翻译-触摸屏与PLC构架下的水温PID控制.doc

毕业设计(论文)中英文资料 题目 触摸屏与PLC构架下的水温PID控制 系 别： 信息工程系 专业名称： 自动化 班级学号： 108202230 学生姓名： 谢恩哉 指导教师： 刘君二O一 四 年 三 月 2008年国际计算机、电子工程会议基于智能PID调节的连续烧结炉温度控制系统曹树坤,张亚兰,张亨 （济南大学机械工程学院中国济南）摘要：为满足在多个炉床的连续烧结炉精确温度控制精度的要求，该系统是由电脑XMT624和对温度场控制的固态继电器组成。根据烧结炉加热过程中的温度惯性、时滞的特点,采用智能PID算法来实现大范围温度调节,克服了传统PID控制的局限。通过在线实时设置智能指令单元, 该系统可以达到2的温度控制精度目标。关键词：PID 固态继电器1 引言连续烧结炉是一种常用的为金属粉末注射塑料件加热设备,它包含了脱脂和调试的过程。在粗糙的部分通过脱脂炉后,然后通过一个封闭的输送带进入水平连续烧结炉。脱脂炉和烧结炉由两台炉子门分隔。其主要部分被分为加热、烧结、冷却三部分。连续烧结炉的烧结质量取决于温度的均匀性和烧结过程的稳定性,连续烧结炉的温度控制系统是一个大时滞、非稳定、非线性复杂系统,烧结温度也受到外部因素的影响,如炉门开关、燃气流量。因此,使用传统的控制方法不能满足连续烧结炉温度控制要求1-2。在逻辑控制系统中,PID控制是最成熟，应用最广泛的技术3-4。但该算法在烧结炉温度控制系统中具有一定的局限性，该烧结炉温度控制系统具有大惯性、纯延迟, 非线性、时变特性,以及由此带来的折射出炉子过度控制和动态性能不稳定。例如,单向自然的加热归于烧结炉使用灯丝电阻、冷却依赖的是自然环境，如果温度很高，它是很困难迅速冷却。同时，建立精确的数学模型和方法,及确定该模型的参数是困难的,这也无法有效的控制温度。计算机电脑和智能控制理论的发展为复杂控制方法和动态不确定度系统控制提供了一种新方法。采用智能控制技术提升智能PID控制。2 控制系统框架多段连续烧结炉温度控制系统主要由PC和XMT624智能仪器组成，其执行机构是固态继电器。炉子被分为三段去控制温度，这意味着每段有三个温度点。连续烧结炉温度控制框架如图1。针对烧结炉的每个温度段和每个温度点仅仅采用智能PID控制。根据设定值和阅读测量值，XMT624计算温度误差,然后智能PID控制器控制固态继电器error-off时间来控制熔炉温度和设定值的稳定。3 控制算法智能PID控制算法是基于常规PID控制的控制算法，这种算法对对象具有延迟,时变和非线性系统的特点和在不同环节有不同的算法。它有棒-棒快速控制，延迟控制，稳定性控制和抗干扰的能力。由于智能PID控制算法不依赖数学模型和对参数变化不敏感，所以这种算法更适合现场使用。3.1 PID算法实现的数字在模拟系统,表示PID算法表达式是: （1）离散方程(1)、数字形式的微分方程代替连续系统微分方程，则微积分能使用求和及增量形式表示： （2） （3）在递归原则下用K表示PID输出的表达式： （4）所以在方程（4）中，=/T 是积分系数， =/T 是微分系数。PID的微分方程可以表示为： （5） 在方程（5）中，是控制量，是偏差，是比例系数，是积分系数，是微分控制系数。一旦系统产生错误，PID控制器立即工作以使目标减少错误，控制功能的强大和微弱取决于比例系数,它的限制是对于有自我平衡能力的控制对象存在静态错误。增长的值可以减少静态错误，但是过大的值会导致系统动态性能变差。积分记忆误差帮助系统减少静态错误，但是积分环节的限制是使控制系统有一个滞后的特性。如果积分环节太强大，它将使控制对象的动态性能变得很差，导致闭环系统不稳定。微分误差能获得误差变化趋势，增长微分控制因素可以加快系统响应，但是它对干扰敏感和降低系统抗干扰的能力。图1 连续烧结炉温度控制系统的框图3.2 智能PID控制环节由于仅当系统模型参数不变性时，PID算法可以得到预想效果，当一个好的PID控制器应用在模型参数随时间变化的系统时，它的能力会变得不同，这个不同在于参数要好好调整，甚至不稳定。所以智能PID控制器参数能仅仅根据现实情况通过许多次计算获得。一个系统考虑到最大偏差,最小偏差,如此系统PID控制规则如下：规则1：IF THEN = (k);规则1能确保：测量值小于温度设定值时，迅速下降。规则2：IF THEN =;为减少频繁的运动和不影响温度控制的精确性，规则2为温度偏差设置了一个死区。规则3：IF THEN =+ -+;规则3不使用微分控制，根据现场控制情况去调整和。4 设置在线PID参数XMT624通信接口是以光电耦合输出隔离为主，以异步RS485为次，一般PC机仅有RS232接口，RS232和RS485接口电气特性是不兼容的，所以要使用RS232/RS485转换器ZW485C以使RS232信号变为RS485信号。该系统工作在半双工模式下，基于当前状态的PC机发送命令去读取XMT624检测到的信号和为设定参数发送一个命令给XMT624。在响应后，XMT624立即接受命令并在仪表板显示当前工作状态。温度控制器件与PC机的通讯是：通讯速度9600bps;停止位：1；数据位：8；校验位：无。XMT624定义输入，输出，状态参数和指定地址。主要参数如表1：表1 主要参数PID控制器的三个基本参数能通过PC端口在通讯地址中被直接读取和写，所以它的控制很方便。当读和写参数时，首先，我们应知道参数的代码。读参数的代码是03H，写参数的代码是10H。例如，读测定值PV，被主机传送的数据格式显示在表2：表2 传送数据的主要格式在数据格式中的第一个地址是XMT624的地址。第二个地址是PV的EMS的存储地址。如果它读取比例因子P,那么它改变第二个地址为内存地址1004H就可以了。读和写参数的数据格式是相似的。它需要将功能代码改变为写参数的功能代码10H. PID三个基本参数是相互联系和相互约束的，由物理环境因素所限制。所以它应该在物质情况和控制要求中进行折衷的选择。在实际运用中一些实例可按照如下调整：（1）温度非常快的达到目标温度，但温度的超调是巨大时：考虑减少比例系 数或增加微分系数时间。（2）温度常常达不到目标和所需时间非常长时：考虑增加比例系数或积分时间。（3）它可以在基本控制目标内波动，但是偏差是很大的，通常是无规律时：考虑增加微分系数或减少积分时间，工作周期可能被设置的更短。（4）它被周围环境和气候变化剧烈影响。很小的变化将引起在温度波动的一些变化时：考虑增加微分系数或缩短周期。5 总结随着智能控制原理的发展，PID控制技术已越来越成熟，智能PID算法是非线性的，这种非线性能被用来克服传统PID的限制。规则1和2能使系统快而稳定，规则3能使PID有适应参数变化的能力。它实现了通过编程在线设定PID参数和提高系统控制的精度。伴随着智能PID控制， P，I，D的设置能直接影响PID控制的结果，如此这些参数与控制系统本身有了紧密的联系。所以给定一个能适应任何系统的固定值是非常困难的。因此，根据实际情况，智能PID算法的使用必须在现场调试和找到一组适应系统本身的控制参数。6 感谢这篇文章得到山东省青年科学家鼓励基金（项目号：No.2005BS05007），山东自然科学基金（项目号：No.Y2006F0），山东省重点学科（实验）研究基金的支持。7 参考文献【1】 Mercedes Ramirez, Rodolfo Haber, Victor Penab, and Ivan Rodriguez, “多个烧结炉的模糊控制”，工业控制计算机，第54期，第105-113页，2003【2】 Perttu Laurinen, Juha Roning，“自适应网络模型来预测在加热炉中钢板的粗磨温度”，材料加工工艺期刊，第168期，第423-430页，2005【3】 Elena Grassi, Kostas Tsakalis，“通过频率环路整形的调谐PID控制器：应用到扩散炉温度控制”，电气与电子工程师协会技术学报，第8卷，第5辑，第42847页，2000 【4】 涂乃伟, 华福, 严欣，“自调整参数模糊PID控制器在温度控制系统中的应用”，控制与自动化学，第20卷，第6辑，第8-20页，中国，2004【5】 蔡建峰，“智能仪表在加热炉控制系统中的应用”，工业加热设备协会，第5期，第31-34页，中国，2001【6】 王海舟，“YS-170智能控制器在温度控制中的应用”，江西电力职工大学学报，第16卷，第3辑，第19-24页，2003 2008 International Conference on Computer and Electrical Engineering Continuously Sintering Furnace Temperature Control System Based onIntelligent PID AdjustmentShukun Cao, Lei Shi, Xiangbo Ze, Heng ZhangSchool of Mechanical Engineering,University of Jinan, Jinan, P. R. C; ; me_; AbstractTo meet the demands of temperature control accuracy in continuously sintering furnace with multiple hearths, this system was constituted with PC, XMT624 and solid state relay for temperature field control. According to the characteristics of heating process, temperature inertia, lag of sintering furnace, adopted intelligent PID algorithm to achieve the large-scale temperature adjustments, it overcomes the limitation of traditional PID control. Through online setting intelligent instrument unit realtimely, the system achieves the target of temperature control accuracy in 2 per thousand centigrade. 1. IntroductionContinuous sintering furnace is a commonly used heating equipment for metal powder injection molding parts, it combines degrease and sintering processes. After rough parts track the degrease furnace, and then taken into horizontal continuous sintering furnace through an enclosed conveyor belt. The degrease furnace and sintering furnace are separated by two furnace doors. The main part of which is divided into heating, sintering and cooling. The sintering quality of continuous sintering furnace depends on the uniformity of temperature and the stability of sintering process, and the temperature control system of continuous sintering furnace is abig lag, great inertia, time-dependent, nonlinear complex system, the sintering temperature is also affected by external factors, such as furnace door switches, gas flows. Therefore, using the traditional control is unable to meet continuous sintering furnace temperature control demands 1-2. In analog control system, PID control is the most mature technology, and the most extensive application 3-4. But the algorithm has some limitation in sintering furnace temperature control system that has the characteristic of great inertia, pure delay, nonlinear, time-varying, and reflected in the furnace is excessive control and dynamic performance instability. For example, the one-way nature of heating up due to sintering furnace using filament resistance, cooling is relying on the natural environment, and if the temperature is high, it is difficult to cool down.It is difficult to establish precise mathematical method and determine the model parameters, and unable to control the temperature effectively. Computers and the development of intelligent control theory provide a new approach for the complex control and dynamic uncertainty systems. Using intelligent control technology promotes intelligent PID control.2. Control system frameThe temperature control system of multi-segment continuous sintering furnace is mainly consisted of PC and XMT624 intelligent instrument, the executing agency is solid-state relay. The furnace is divided into three segments to control temperature, which means that each segment of the furnace has three temperature points. The frame of temperature control of the continuous sintering furnace is shown as figure 1.In allusion to every temperature section and every temperature point of the sintering furnace, adopt intelligent PID control solely. XMT624 according to the setting value and the reading measurement value calculates temperature deviations, and then intelligent PID controller controls solid state relay error-off time to control furnace temperature and stability in the setting value. 3. Control algorithmIntelligent PID control algorithm 5-6 is the control algorithm base on conventional PID control algorithm for the object that has characteristic of delay, time-varying and nonlinear systems, and in different segments has different algorithm. It has both Bang-Bang fast control and the lag control stability control and anti-jamming capability.As intelligent PID control algorithm is not dependent on the mathematical model, and is not sensitive to changes in parameters, therefore is more suitable for field use.3.1. PID algorithm to achieve the figuresIn the analog system, the expression of PID algorithm is: （1） Discrete equation (1), digital form of differential equations instead of the continuous system differential equations, differential and integral can be expressed using sum and incremental form: （2） （3）Under the principle of recursion may write PID output expression with k: （4）In the equation (4), =/T is integral coefficient, =/T d is differential coefficient. So the differential equation of PID can be expressed: （5）In the equation (5), is control value, is deviation, is proportion factor, is integration control factor, is differential control factor.Once the system generates error, PID controller immediately works to make the object reduce errors, the strength and feebleness of control function depend on proportion factor , and its limitation is existing static error for control objects with self-balancing ability. Increasing value can reduces static errors, but the big value has led to the dynamic performance of the system weaker.Integral memory error helps the system eliminate static errors, but the limitation of integral role is that makes a control system have lag characteristics. If the integral role is too strong, it would make dynamic quality of the object weaker and lead to the closed-loop system instability. The differential error can get the trend of error change, and increasing differential control factoraccelerate the system response, but it will be sensitive to interference, and reducing the anti-jamming ability of the system.3.2. Intelligent PID control rulesBecause the PID algorithm gets the desired effect only when the system model parameters are non-denaturing, when a okay PID controller is applied in the model parameters time-changing system, its capability can become difference which parameters are adjusted well, and even instability. Therefore, the intelligent PID controller parameters can only be got by many times calculation according to the factsituation. A system allows for the maximum deviation , minimum deviation , so the PID control rules of system as follow:Rule 1:IF THEN = (k);The rule 1 can guarantee that a measured value is less than the temperature setting value, rapidly fall.Rule 2: IF THEN =;To eliminate the frequent motion and not affect precision temperature control, the rule 2 set a dead zone for temperature deviations. Rule 3:IF THEN=+ -+;Rule 3 does not use differential controls, and according the scene control situation to adjust and.4. Setting of PID on-line parametersThe communications interface of XMT624 instrument is optoelectronic output isolation principal and subordinate asynchronous RS485, and general PC only has RS232 interface, RS232 and RS485 interface electrical characteristics are incompatible with each other, so using RS232 /RS485 converter ZW485C, to change RS232 signal into RS485 signal. The system works in half-duplex mode, the PC based on the current state sends orders in order to read the signal that XMT624 instrument detected, and sends an order to XMT624 for setting parameters. XMT624 receives the order immediately after the response, and on the instrument panel vision the current operating state. The communication of temperature control instrument and PC is: communication speed of 9600bps; stopping bits: 1; data bits: 8; parity bits: none. XMT624 defines input, output and state parameters, and assigns the address. The main parameters as listed in Table 1: With the development of intelligent control theory, PID control technology is more and more mature. The intelligent PID algorithm is nonlinear, which can be used to conquer the limitation of the traditional PID. The rule 1 and rule 2 can make the system fast.Three basic parameters of the PID controller can be directly read and wrote in the corresponding address through the PC interface, so it is controlled expediently. When read and write parameters, firstly, we should know the parameters code. The reading parameters code is 03 and the writing parameters code is 10H. For example, reading measurements PV, the data format sent by the main frame is shown as Table 2: The first address in the data format is the XMT624s address. The second address is the PVs EMS memory address. If it reads the ratio factor P, it changes the second address to EMS memory address1004H is OK. The reading and writing parameters data format is similar. And it needs to change the functional code to the writing parameters functional code 10H.Three basic parameters of PID are interaction and mutual constraints and are restricted by the physical environmental factors. So it should decide the eclectic choice between the material circs and control requires. Some instance in actual use can be adjusted as follows:(1) The temperature reaches target very quickly, but the temperature overshoot is great: consider reducing proportions coefficients or increasing differential coefficient time.(2) The temperature often fails to the target and the time is great: consider increasing the proportions coefficients or integral time.(3) It can fluctuate at the basic control goals, but deviation is oversize, and it is often volatile: consider increasing differential coefficient or reducing integral time, and the work cycle may be set shorter.(4) It is affected greatly by the surrounding environment or the weather changes. Little change will cause some changes in the temperature fluctuations: consider increase differential coefficient or shorten the cycle time.5. ConclusionsWith the development of intelligent control theory, PID control technology is more and more mature. The intelligent PID algorithm is nonlinear, which can be used to conquer the limitation of the traditional PID. The rule 1 and rule 2 can make the system fast and stability, and the rule 3 makes the PID adaptive capability with the variable parameters. It realizes the parameters of PID setting on-line through programming, and increases system control accuracy. With intelligent PID control, the result of PID control can be directly affected by the set of P, I, D etc, and such several parameters have close relation with the control system itself. So it is difficult to give a fixed value which adapts to any system. Therefore, the use of the in