Calibration System Design And Experimental Research For Electronic Controlled Gasoline Engine

Along with the exhaust of oil resources around the world and the deterioration of the global environment, the auto industry is facing a severe challenge to meet people's exacting demands for the performance of automobiles. At the same time , the rapid development of electronic technology has brought enormous changes to the automobile industry. The invention of electronically controlled engines brought light to these problems. To attaining the better power performance and economic performance, satisfying the standards and regulations of national emission and maintaining the good work operation, the matching test of the ECU(electronic control unit) and the engine needs to be done and the control parameters be calibrated and optimized in the progress of application and development of the electronic control system. As the function of the electronic control system has been continuously strengthened, the number of objects controlled has been gradually increased, a new better calibration system is needed to meet requirement of the electronic control development.Just because the above-mentioned reasons , calibration system of electronic control engines is studied carefully. The functions of the calibration system of electronic controlled gasoline engine were analyzed, and the principles of the calibration system were studied. Based on taking both the needs of the research program and the laboratory conditions , the development frame of the calibration system was advanced, which includes the hardware design, software design and the calibration process design. The system consists of a host computer (PC), electronic control unit (ECU), communication unit , date-collecting card , and exhaust gas analysis instrument. Online-calibration of the engine was realized by utilizing single host computer , all the necessary data were collected totally by the data-collecting card, through which the exhaust gas data were obtained by serial communication. In order to realize the modification of control parameters and observation of the engine, data transfer was processing through the communication card between the host computer and the ECU. This calibration system can modify the control parameters without affecting the engine's operation. That is to operate the engine under different control data, and observe the engine performance simultaneously, so that to optimize the control parameters and save all the experiment data to the expecting data-bases, which is for offline data analysis.The calibration system is designed to match the ECU, so the ECU should not only meet the requirement of controlling the engine, but also satisfy the requirement of calibration system. The design of ECU includes hardware design and software design. The hardware design consists of all the designing of input signal processing circuit, actuator driving circuit, singlechip system circuit and communication circuit; The software was designed according to the structure of one main program with several modularized subprograms, which were assigned with different functions properly. The communication unit acts the data transfer bridge between PC and ECU, so it is very important to the calibration system, and it's also a key research part for this thesis. RS-232 serial communication mode was applied to realize the communication between PC and ECU, which have the advantages of flexibility, reliability, and convenience. The communication protocol which is simple and effective was set for the calibration system, and can reduce the communication program. In order to meet the multipurpose and expansibility of system, CAN communication port was added to the calibration system.The calibration system software is Human-Computer-Interface platform with the PC performing the management center, which is also a tool for the calibration work staff to carry out calibration. A calibration system with sufficient functions and flexibility is very important for the development of an electronic control system. Based on the windows environment, applied the program method of facing the objects and utilized the software Visual C++ 6.0 produced by Microsoft, the calibration software was developed. Applied the technologies of Data base, DLL, multithreading, data operation and collection are controlled during programming, meanwhile, plenty of Classes are set to encapsulate the functional functions, and many Controls are utilized to realized the functions of graphic displacement. The GUI is friendly, simple to operate, and full of functions, and the software has powerful functions and good expansibility. It can realize online data collecting, graphic displacement, online calibration, and data saving, and the basic calibration function.After the development of calibration system, it needs to be verified. The 491QE engine produced by Liuzhou Engine Ltd is chosen as research object. The testing bench is setup and testing devices are commissioned, then the research is carried through in this bench. The senor play an important role in calibrating, therefore the output characteristic should be calibrated firstly. By completing the state points plotted before, the map of base fuel injection pulse width and base ignition advance angle are obtained. The modification coefficient of fuel injection pulse width and ignition advance angle caused by intake air temperature and coolant temperature are obtained by changing test environment. The engine characteristic test is implemented afterwards, the results of experiment indicate the system can attain expected function and fulfill the optimization and matching test between electronic control unit and engine effectively. At last, the extended communication port of the calibration system was tested. The result shows it reached its design requirement.