【作者】 王宁；

【导师】 李春茂；

【作者基本信息】 西南交通大学 ， 电力电子与电力传动， 2011， 硕士

【摘要】 回流焊炉属于表面贴装技术(SMT)中的一套重要的焊接设备,它是将温度提升至焊锡融化的温度后,将贴片元器件固化在PCB板的焊盘上,从而实现了印制板和元器件的电气连接。其工作时,必须保证温度曲线按照贴片元件焊接时的标准温度曲线进行控制,控制的要求是温度上升的速度和稳定的温度值,控制温度值的精确性和平稳性是保证生产良好产品的关键。本文在已有回流焊简易加工设备的基础上,采用工作效率高、运算速度快的ATmega 128(L)微处理器作为控制器的核心,采用K型热电偶作为前端温度采样工具,配合转换精度高并带有冷端补偿的A/D温度转换芯片MAX6675,将采集到的现场参数送到微处理器中,由单片机根据控制算法作出控制决策,送到执行单元--固态继电器(MGR-1D4810)去控制电阻丝的功率。整套监控系统可靠性高、操作简单、易于扩展,便于升级和改造。为了实现精确的控制,需要建立该回流焊炉的数学模型,从而在该模型的基础上完成控制器的设计。精确模型的获得可以从热力学的角度建立,得到的模型有利于系统分析,便于回流焊设备的改造,不过模型的建立需要了解工艺过程,建立过程复杂并且实用性不强；也可以通过实验法建立,借助MATLAB等辅助工具使得数学建模过程变得简单有效。MATLAB在其多年的发展变化中,形成了很多解决实际问题的方法,用MATLAB进行建模,可以解决从数据获取到模型建立需要经过反复探索和计算的劣势。于是,在复杂的控制系统的设计过程中,设计者只需要先获得对象的数据,然后对数据进行检验,再选择模型结构、参数估计和模型检验后,通过系统辨识理论就可以获得对象的数学模型。在用MATLAB进行辨识的过程中,只要保证采集数据的准确性和可靠性,根据经验选定要辨识系统的结构,最后通过MATLAB计算出模型的参数,最终得到实用性强、可靠性高的数学模型。本文以回流焊为研究背景,对现阶段温度系统建模的研究现状进行概述和分析后,指出需要解决的问题；结合MATLAB工具软件,用免机理分析建模法和辨识工具箱对回流焊炉进行了数学建模。本文首先介绍了免机理分析建模法的基本理论思想,给出免机理分析建模的实现过程和快速解决方案；然后对系统建模所需要的基础数据作出结构定义,并根据系统的需求设计制作数据采集电路的硬件部分和软件部分；介绍了大林算法的基本原理,以及如何用大林算法设计与该模型相吻合的数字控制器；最后用仿真和实验的方法验证该模型和控制器的有效性。更多还原

【Abstract】 The equipment of reflow oven plays an important part in welding equipment of surface-mount technology (SMT). The aim of this equipment is to control the temperature to the seting point following the temperature curve of the SMT components so as to the SMT components can fix on the soldering plate of PCB. The precision and stability of controlling on temperature is the key factor to ensure a well product can produced.Based on the existing equipment of reflow oven, this paper adopt microprocessor of ATmega 128 (L) as its controller to provide with high efficiency and performance, even as the high speed of operation, and employ K type thermocouple as front-end sampling tools of temperature, cooperating with the A/D conversion chip named MAX6675, which take the cold end compensation, and some other advantages such as high precision, reliability, strong transformation. The A/D will send the datas collecting from field parameters to microprocessor. According to control algorithm, the microprocessor will calculate the sampled datas and make a decision of controlling, and send the control orders to the unit used to execute orders-Solid-state relay (MGR-1 D4810) to control the resistance of power. The whole set of monitoring system has some advantages such as high performance of reliability, simple operation, easy to expand, facilitate the promotion and the transformation.In order to achieve more accurate control effect, it needs to establish a mathematical model of reflow oven, and then to design a controller based on this model.A accurate model can established by the equation of thermodynamic equilibrium, but it has to understand the process of the system.So the establishing models is relatively complicated and has not a strongly practicability, but it can be used to analyze the system from the mechanism, and easy to modify the equipment for the reflow oven; With the emergence and continuous development in recently years, the MATLAB gradually formed a lot of methods to solve practical problems. In the process of establishing a model, the MATLAB solves the disadvantage from repeated explorations, large amount of calculation, difficult to complete and so on, and firstly it only to obtain the data from the practice of the object and then test the data, choose a model structure, estimate the parameter and test this model, and finally get the mathematical model of the object through system identification theory, making the complex control system designing more convenient. During the process of identification using MATLAB, the veracity and reliability of the sampled data must be guarantee. And according to the experience to select a system structure, finally calculates model structure and parameters through MATLAB. As the research background in reflow oven, this paper combines with the modern temperature modeling study status of summary and analysis, then points out what the problems needed to be solved; Combined with MATLAB tool software, adopts the way of one-order inertial system modeling method and the toolbox of recognition and analysis to establish a mathematical modeling of reflow oven. Firstly this paper introduces the theory and method about the modeling avoiding analysis, and gives the realization and quick solutions of obtaining mathematic model of the system; then defines a data structure based on the system needed during the modeling process. After that, it introduces the basic principle of Dalin algorithm, and how to design the controller with this algorithm; Finally, test the model by experiments and the effectiveness of the designed controller.更多还原