The Research Of Testing-controlling System For Performance Testing Of Automobile Air-Conditioner Based On Virtual Instrument

This thesis examines the characteristics of the present automobile air-conditioner testing-controlling system, points out the inevitable appearance of Virtual Instrument, and explains the concept of VI, its hardware and software structure, its characters and applications. It also compares the different features of the three most popular projects, and develops a system based on the multi-function data adapt card and the graphic programming language - LabVIEW. Then it analyses refrigeration the principle and characteristic of the automobile air-conditioner, and investigates and compares the thermodynamics theory and methods of testing of the automobile air-conditioner's performance, it introduces the method of the difference of enthalpy especially. The principle of this system is : Use DAQ card to acquire physical analog and digital data coming from couples of sensors, appropriately process the data, then transmit it to computer by PCI BUS, after the data is dealt with by the software of system, the report will be displayed and printed. In the following chapters, the testing-controlling system is illustrated at length, including the design of hardware structure, mainly the makeup of hardware part and the realization of adapting outer physical signal. And the system controls the cylinder system and electromotor by the PLC and transducer. Next, the graphic programming language - LabVIEW is introduced. In addition, the functions of virtual automobile air-conditioner testing-controlling system are listed in detail.The main point of the system is signal collects and control department. This thesis emphasizes to discuss how to be more accuracy, more sensitiveness, more on time and more economies acquisition signal that need to be collected. In the text stated how to choose transducer and meter, communication between PC and distribution control system. Control system of the system is divided into 2 parts,PC control and bottom layer distribute control, bottom layer unit mainly include PLC, electromagnetism valve control system, transducer. Subject to control real time, reliability, dependability and communication belt width, the thesis bring forward the scheme of distribute control system. Then bottom layer control operate component with the rule in control module, greatly decreased the need of communication belt width between PC and sensor, intensify real time control. The testing-controlling system based on virtual instrument can improve automobile air-conditioner design quality, shorten its development period, intensify accuracy of maintenance, improve repair quality.