【作者】 朱珍；

【导师】 周洪煜；

【作者基本信息】 重庆大学 ， 热能工程， 2003， 硕士

【摘要】 换热器是一种标准工艺设备。被广泛应用于动力工程领域以及其它一些过程工业部门。当换热器在较大温差范围内运行时，换热器出口介质温度控制仍面临着挑战。系统非线性性在很大程度上取决于介质的流速和介质的温度。本文中，换热器的控制任务主要有两个，首先通过控制水箱进口水阀门开度，进而控制水箱水位，进而控制换热器进口水流量。其次，通过控制蒸汽阀门开度，进而控制换热器蒸汽流量，进而控制被蒸汽加热的换热器出口水温。传统的PID控制在换热器系统控制中一直占有主导地位，原因在于它的结构简单，易于设计。但是，传统的PID控制也在控制中遇到了不少问题，例如系统超调量大、震荡周期多、在控制具有较大时延的对象时稳定性能差等。最近几年里，大量的先进控制技术得到了发展，模糊逻辑控制就是其中之一。它在工业实际应用中非常引人注目。因为模糊逻辑控制能模仿人思考和处理问题的方式，抓住对象的不确切信息，所以模糊逻辑控制往往能够取到令人满意的控制效果。在大多数模糊控制器中，偏差和偏差变化率的论域以及隶属函数必须提前确定。通常，这就需要不断的试验。本文设计了以蒸汽/水为介质的换热器，以及相对应的系统，并对用到的数据采集卡板作了介绍。在进口水速的控制中，应用了PID-模糊双模控制。在出口水温控制中，本文提出了比例-模糊双模控制，其中模糊控制器是基于Takagi-Sigeno模糊推理系统构建，用以解决系统存在的滞后问题。从它发展来的数字控制器非常简单，因为具有简明的解析表达式，并且只有几个需要调整的参数。在控制初期引入比例控制的作用是提高系统的响应速度。仿真结果证明，本文所提出的控制策略在抑制超调、减少震荡周期、提高系统的稳定性上都得到提高，优于单纯常规PID控制。更多还原

【Abstract】 Heat exchangers are standard components in the field of Power Engineering, and also other process industry. Temperature control is still a major challenge if the heat exchanger is operated over a wide range. The nonlinear behavior depends strongly on the flow rates and on the temperature of the media. In this paper, a cross-flow steam/water heat exchanger is considered. The goal is to control the water outlet temperature by manipulating the flow rate of the steam and control the water inlet rate by manipulating the height of the water level in the water tank.Conventional PID-type controllers have played a dominant role in the heat exchanger systems due to its simple control structure and ease of design. However, PID-type controllers may encounter problems such as lager overshoot and even poor stability in the control of plants with time delay.In recent year, plenty of advanced control techniques have been developed. Fuzzy Logical Control is one of these new paradigms and has become very attractive in industrial practices. Because of its capability to emulate human thinking and human inference and to capture the inexact information of the plant, Fuzzy Logical Controller (FLC) often yields satisfactory performances. In most FLCS, the universes of discourse of the error and the change of the error and the membership function of their fuzzy sets have to be determined in advance. Usually, this is not easy and requires the trial and error method.This paper designs a cross-flow steam/water heat exchanger and the according system and the sampling card. In the water inlet rate control, a PID-Fuzzy two-mode controller is used. In the outlet temperature control, this paper proposes to use Takagi-Sigeno Type Fuzzy System to construct controller for plants with time delay. The developed digital controller in this way is very simple because it has a compact analytical expression and includes only a few adjustable parameters. To improve the response speed, a P controller is added in the initial stages. So a P-Fuzzy two-mode controller bring out. Simulation results illustrate that the proposed controllers are effective in suppressing the maximum overshoot and in reducing the decaying oscillation cycles and also superior then PID controllers.更多还原