电子膨胀阀数字控制系统设计及其流量特性实验研究

发布时间：2018-06-02 12:52

本文选题：电子膨胀阀 + 建模仿真　；参考：《山东科技大学》2011年硕士论文

【摘要】：电子膨胀阀(EEV)是制冷系统中的节流元件,它在系统中的主要作用是调节系统制冷剂流量、节流降压及控制过热度。深入全面了解电子膨胀阀流量输出响应特性、电子膨胀阀的开度-流量控制调节特性,对于合理设计电子膨胀阀流量与开度控制规律,获得热泵空调系统良好的运行品质具有重要的学术与工程指导意义。本文在探讨电子膨胀阀数字控制特征的基础上,建立了电子膨胀阀控制系统的数学模型,据此搭建了电子膨胀阀数字控制仿真实验平台,并进行计算机数字仿真分析。揭示了电子膨胀阀数字控制系统开度与流量特性；通过系统仿真分析获得电子膨胀阀的流量负反馈控制的稳态响应特性与间隙特性对系统稳态输出的影响规律。通过实验测试验证了本文所建数学模型的合理性。在电子膨胀阀数字控制系统中,引入PID控制算法,建立了含PID调节器的控制系统数学模型,并对控制系统的输出稳态特性与常规系统进行比较分析。仿真结果表明：PID调节系统相比于常规控制系统能够缩短系统响应时间,降低系统开机响应波动性并抑制系统超调现象。为深入分析电子膨胀阀流量特性,搭建了基于PLC控制步进电机,实现阀口开度数字调节的流量-开度测试系统。设计了具有过载保护与短路保护的步进电机驱动电路,采用PLC直接驱动步进电机驱动方式与四相八拍控制方式,实现对电子膨胀阀开度的精确控制。采用FS4000质量流量传感器、HITEK压力变送器以及PT100铂电阻分别测量系统管路中气体流量、压力、温度等物理量,设计了电压信号与电流信号采集电路与PT100电阻测量电路,实现对系统各参数的测量。计算机辅助测试(CAT)实验系统的软件设计主要包括PLC梯形图程序设计与工业组态软件世纪星监控界面设计。PLC控制程序实现对04AD模块与04PT模块传感器测量数据采集,实现对步进电机转速、转向的逐个脉冲输出的数字控制。监控界面设计了系统工作主界面,实时模拟电子膨胀阀的工作现场,控制并记录电子膨胀阀的开度脉冲数,实时显示系统中各个物理参数状态。设计了数据采集、实时曲线、历史曲线等多种测试辅助界面,采集与处理传感器的信号数据,记录分析实验测试数据,增强流量测试实验的功能性与可实验性。本文通过仿真与实验对比研究电子膨胀阀的流量特性,改善变频空调系统中蒸发器的热负荷匹配,实现对一拖多制冷机组的制冷剂流量分配,改善制冷系统的整机性能,提高能源利用率,降低能耗,促进制冷技术的不断向前发展和创新。CAT系统的多功能与可视化功能,为研究电子膨胀阀的流量特性提供一条新的途径。系统同时具有监测与控制功能,对于制冷系统控制技术的发展有着重要的指导意义。
[Abstract]:Electronic expansion valve (EEV) is a throttle element in the refrigeration system. Its main function in the system is to regulate the refrigerant flow, throttling the pressure and controlling the superheat. Deeply and comprehensively understand the response characteristics of the electronic expansion valve flow output, the opening and flow control regulation characteristics of the electronic expansion valve, and the reasonable design of the electronic expansion valve flow and opening control law, It is of great academic and engineering significance to obtain good operation quality of heat pump air-conditioning system. Based on the discussion of the digital control characteristics of the electronic expansion valve, the mathematical model of the electronic expansion valve control system is established in this paper. According to this model, the simulation experiment platform of the electronic expansion valve digital control is built, and the computer digital simulation analysis is carried out. The open and flow characteristics of digital control system of electronic expansion valve are revealed, and the steady state response characteristics and clearance characteristics of negative feedback control of electronic expansion valve are obtained by system simulation. The rationality of the mathematical model is verified by experiment. In the digital control system of electronic expansion valve, the mathematical model of control system with PID regulator is established by introducing PID control algorithm, and the output steady state characteristic of the control system is compared with that of the conventional system. The simulation results show that compared with the conventional control system, the response time of the system can be shortened, the response volatility of the system can be reduced and the overshoot phenomenon can be restrained. In order to deeply analyze the flow characteristics of electronic expansion valve, a flow-opening testing system based on PLC is built to realize digital adjustment of valve opening. The stepper motor drive circuit with overload protection and short circuit protection is designed. The PLC direct drive stepper motor driving mode and the four phase eight beat control mode are adopted to realize the accurate control of the opening degree of the electronic expansion valve. By using FS4000 mass flow sensor HITEK pressure transmitter and PT100 platinum resistance to measure the physical quantities of gas flow, pressure and temperature in the system respectively, a voltage signal and current signal acquisition circuit and a PT100 resistor measuring circuit are designed. The measurement of system parameters is realized. The software design of CAT-based computer aided testing (CAT) experiment system mainly includes PLC ladder diagram program design and industrial configuration software century star monitor interface design. PLC control program realizes the data acquisition of 04AD module and 04PT module sensor. Realize the digital control of step motor speed and steering pulse output one by one. The main interface of the system is designed to simulate the working field of the electronic expansion valve in real time. The opening pulse number of the electronic expansion valve is controlled and recorded. The physical parameters of the system are displayed in real time. The data acquisition, real-time curve and history curve are designed to collect and process the signal data of the sensor, to record and analyze the experimental test data, and to enhance the function and experimentability of the flow test experiment. In this paper, the flow characteristics of electronic expansion valve are studied by comparing simulation and experiment, the heat load matching of evaporator in frequency conversion air conditioning system is improved, the refrigerant flow distribution is realized for one towing and multiple refrigeration units, and the whole performance of refrigeration system is improved. To improve energy efficiency, reduce energy consumption, promote the continuous development of refrigeration technology and innovate the multi-function and visual function of cat system, which provides a new way to study the flow characteristics of electronic expansion valve. The system has the function of monitoring and controlling at the same time, which has important guiding significance for the development of refrigeration system control technology.
【学位授予单位】：山东科技大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：TH134

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