混凝土快速冻融试验机温度控制系统研究

发布时间：2018-06-15 19:31

本文选题：混凝土快速冻融机 + 温度控制　；参考：《河北农业大学》2015年硕士论文

【摘要】：农业工程建设是现代农业建设的重要内容,混凝土是农业工程建设的重要原材料,其耐久性直接关系到农业工程中房屋构筑物的结构安全,以及道路、水池、沤肥池、排水沟等基础设施的使用寿命。为保障工程建设的安全性和可靠性,对混凝土耐久性能的研究越来越深入。混凝土快速冻融试验机是检测混凝土在水和负温的共同作用下的耐久性能的实验仪器,其性能的好坏直接关系到混凝土质量检验的结果。本文通过分析国标中对混凝土快速冻融试验的实验方法的要求,给出了冻融循环试验的目标温度曲线,以及对温度的控制要求,介绍了冻融试验机的工作原理和冻融循环控制过程。根据控制要求,完成了系统主要硬件的选型工作,介绍了控制系统的电气原理,并给出了PLC与主要硬件的电气接线图。冻融试验时试件置于冻融箱内的防冻液中,通过与防冻液的热传递来改变温度,通过压缩机制冷或加热管加热使试验机的箱温变化实现冻融循环过程。该温度系统是带纯滞后的大惯性系统,目前用的控制方法都是根据实验数据,和经验进行调整控制参数,来设定控制参数的变化规律,控制精度和效果并非十分理想。为实现对试件芯温变化的高精度控制,本文采用了模糊控制方法,为了验证控制规律的有效性,实现系统精确控制,因而建立了试验机温度系统的数学模型,采用MATLAB对系统进行仿真。由于制冷与加热阶段的控制机制不同,本文采用实验建模法,分别建立了制冷和加热阶段系统的数学模型,并利用实验数据,完成了对模型的校验。对制冷阶段,通过建立描述变频压缩机频率与制冷功率、制冷功率与试验机箱温、箱温与试件芯温之间关系的传递函数,进而建立描述试件芯温与压缩机频率的传递关系的数学模型,通过调节压缩机的频率,实现对试件芯温的控制。对加热阶段,通过建立描述加热管的加热占空比与加热功率、加热功率与试验机箱温、箱温与试件芯温之间关系的传递函数,进而建立描述试件芯温与加热管加热占空比的传递关系的数学模型,通过调节加热占空比,实现对试件芯温的控制。根据所建试验机的数学模型,为了使系统对模型不敏感,在系统控制策略上,本文采用采用模糊控制方案。根据模糊控制器的设计原理,对混凝土快速冻融试验机的模糊控制规则进行了设计,并利用MATLAB软件对模糊控制系统进行了仿真研究,并根据仿真结果调整模糊控制规则。最后,本文还对系统的PLC控制程序和触摸屏界面进行了编写和设计,并对本文内容进行了总结和展望。
[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.
【学位授予单位】：河北农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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