Development Of Control Device For Novel Absorption Refrigeration System

Since the monitoring sites of the actual absorption refrigeration system are scattered, there are few researches on the controller of this system, and no perfect detection and control device is formed. In this thesis, therefore, a set of intelligent control device is designed to collect the data of monitoring points in the running process of the system, and a PI controller is designed to realize the real-time control of the electronic expansion valve. The main research works of this thesis include:First of all, a decentralized data acquisition system based on CAN bus is developed. On the basis of analyzing the complicated structures of the absorption refrigeration system, the PeliCAN communication protocol based on CAN bus was studied. This research employs STC15F260S22 as the controlling core of the micro-controller to design CAN node modules, data acquisition and control modules. Moreover, the bottom hardware driver is design using the PeliCAN protocol to realize communication between any two CAN nodes. Therefore, a complete system of the bottom data communication platform is set up for the decentralized monitor of the absorption refrigeration system.Then, the data acquisition and monitoring system based on LabVIEW is developed on the PC. The graphical interface of the absorption refrigeration system is built by DSC module, and the real-time data acquisition, display and storage of the absorption refrigeration system is realized by using the function of LabVIEW. A transfer function model for the superheat control can be identified by the step response of the superheat of evaporator outlet with the electronic expansion valve. PID function modules in LabVIEW software are employed to realize the real-time automatic control of superheat of the evaporator outlet using electronic expansion valves.Finally, the data acquisition and monitoring system of the upper computer based on the embedded Linux operating system is developed on the ARM9. The man-machine friendly interface of the absorption refrigeration system is designed with Qt/Embedded, and the real-time data acquisition and display of the system is realized by using its slot function. The SQLite is employed as the database of the PC, in which the collected data is stored, and the superheat data is analyzed by the callback function. The PI controller is embedded in the Qt/Embedded program on the ARM9 development board to realize the real-time data collection and monitoring of the absorption refrigeration system, so the superheat of the system can stabilize at 5℃ quickly.This kind of control device developed in this thesis can realize the data acquisition, display, storage and real-time control of the absorption refrigeration system. It provides a real platform for the absorption refrigeration system optimization and control and it has important significance for the real-time control of the system.