本文選題：混凝土快速凍融機 + 溫度控制��； 參考：《河北農業(yè)大學》2015年碩士論文

【摘要】：農業(yè)工程建設是現(xiàn)代農業(yè)建設的重要內容,混凝土是農業(yè)工程建設的重要原材料,其耐久性直接關系到農業(yè)工程中房屋構筑物的結構安全,以及道路、水池、漚肥池、排水溝等基礎設施的使用壽命。為保障工程建設的安全性和可靠性,對混凝土耐久性能的研究越來越深入。混凝土快速凍融試驗機是檢測混凝土在水和負溫的共同作用下的耐久性能的實驗儀器,其性能的好壞直接關系到混凝土質量檢驗的結果。本文通過分析國標中對混凝土快速凍融試驗的實驗方法的要求,給出了凍融循環(huán)試驗的目標溫度曲線,以及對溫度的控制要求,介紹了凍融試驗機的工作原理和凍融循環(huán)控制過程。根據(jù)控制要求,完成了系統(tǒng)主要硬件的選型工作,介紹了控制系統(tǒng)的電氣原理,并給出了PLC與主要硬件的電氣接線圖。凍融試驗時試件置于凍融箱內的防凍液中,通過與防凍液的熱傳遞來改變溫度,通過壓縮機制冷或加熱管加熱使試驗機的箱溫變化實現(xiàn)凍融循環(huán)過程。該溫度系統(tǒng)是帶純滯后的大慣性系統(tǒng),目前用的控制方法都是根據(jù)實驗數(shù)據(jù),和經驗進行調整控制參數(shù),來設定控制參數(shù)的變化規(guī)律,控制精度和效果并非十分理想。為實現(xiàn)對試件芯溫變化的高精度控制,本文采用了模糊控制方法,為了驗證控制規(guī)律的有效性,實現(xiàn)系統(tǒng)精確控制,因而建立了試驗機溫度系統(tǒng)的數(shù)學模型,采用MATLAB對系統(tǒng)進行仿真。由于制冷與加熱階段的控制機制不同,本文采用實驗建模法,分別建立了制冷和加熱階段系統(tǒng)的數(shù)學模型,并利用實驗數(shù)據(jù),完成了對模型的校驗。對制冷階段,通過建立描述變頻壓縮機頻率與制冷功率、制冷功率與試驗機箱溫、箱溫與試件芯溫之間關系的傳遞函數(shù),進而建立描述試件芯溫與壓縮機頻率的傳遞關系的數(shù)學模型,通過調節(jié)壓縮機的頻率,實現(xiàn)對試件芯溫的控制。對加熱階段,通過建立描述加熱管的加熱占空比與加熱功率、加熱功率與試驗機箱溫、箱溫與試件芯溫之間關系的傳遞函數(shù),進而建立描述試件芯溫與加熱管加熱占空比的傳遞關系的數(shù)學模型,通過調節(jié)加熱占空比,實現(xiàn)對試件芯溫的控制。根據(jù)所建試驗機的數(shù)學模型,為了使系統(tǒng)對模型不敏感,在系統(tǒng)控制策略上,本文采用采用模糊控制方案。根據(jù)模糊控制器的設計原理,對混凝土快速凍融試驗機的模糊控制規(guī)則進行了設計,并利用MATLAB軟件對模糊控制系統(tǒng)進行了仿真研究,并根據(jù)仿真結果調整模糊控制規(guī)則。最后,本文還對系統(tǒng)的PLC控制程序和觸摸屏界面進行了編寫和設計,并對本文內容進行了總結和展望。
[Abstract]:Agricultural engineering construction is an important content of modern agricultural construction. Concrete is an important raw material for agricultural engineering construction. Its durability is directly related to the structural safety of housing structures in agricultural engineering, as well as roads, pools and compost ponds. Service life of infrastructure such as gutters. In order to ensure the safety and reliability of engineering construction, the research on durability of concrete is more and more thorough. The concrete rapid freeze-thaw testing machine is an experimental instrument for testing the durability of concrete under the joint action of water and negative temperature, and its performance is directly related to the result of concrete quality inspection. Based on the analysis of the requirements of the national standard for the rapid freeze-thaw test of concrete, the target temperature curve of the freeze-thaw test and the control requirements for the temperature are given in this paper. The working principle of freeze-thaw testing machine and the control process of freeze-thaw cycle are introduced. According to the control requirements, the selection of the main hardware of the system is completed, the electrical principle of the control system is introduced, and the electrical wiring diagram between PLC and the main hardware is given. In the freeze-thaw test, the specimen is placed in the antifreeze liquid in the freeze-thaw box. The temperature is changed by heat transfer with the antifreeze, and the freeze-thaw cycle is realized by the refrigeration of compressor or the heating of heating tube. The temperature system is a large inertial system with pure delay. The current control methods are based on the experimental data and experience to adjust the control parameters to set the control parameters change law. The control precision and effect are not very ideal. In order to realize the high precision control of the core temperature change of the specimen, the fuzzy control method is adopted in this paper. In order to verify the validity of the control law and realize the accurate control of the system, the mathematical model of the temperature system of the testing machine is established. MATLAB is used to simulate the system. Because the control mechanism of refrigeration and heating stage is different, the mathematical model of refrigeration and heating stage system is established by the method of experimental modeling, and the calibration of the model is completed by using the experimental data. For the refrigeration stage, a transfer function describing the relationship between frequency and cooling power of frequency conversion compressor, refrigeration power and test box temperature, box temperature and specimen core temperature is established. Then a mathematical model describing the transfer relationship between the core temperature and the frequency of the compressor is established, and the core temperature of the specimen can be controlled by adjusting the frequency of the compressor. For the heating stage, the transfer function describing the relationship between heating duty cycle and heating power, heating power and test box temperature, box temperature and specimen core temperature is established. Then a mathematical model describing the transfer relationship between the core temperature of the specimen and the heating duty cycle of the heating tube is established. The control of the core temperature of the specimen can be realized by adjusting the heating duty cycle. According to the mathematical model of the test machine, in order to make the system insensitive to the model, the fuzzy control scheme is adopted in the system control strategy. According to the design principle of fuzzy controller, the fuzzy control rules of concrete rapid freeze-thaw testing machine are designed, and the fuzzy control system is simulated by MATLAB software, and the fuzzy control rules are adjusted according to the simulation results. Finally, the PLC control program and touch screen interface of the system are written and designed, and the content of this paper is summarized and prospected.
【學位授予單位】：河北農業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU528

【相似文獻】

相關碩士學位論文 前1條

1 高蒙蒙;混凝土快速凍融試驗機溫度控制系統(tǒng)研究[D];河北農業(yè)大學;2015年

，

本文編號：2023295