Study On The Testing And Diagnosing Method Of Engine Ignition System Based On The Virtual Instrument

Engine as the power source of vehicle, has great effect to vehicle performance. Engine Ignition System is one of electric accessories systems that have great influencing to engine performance, which both has highly fault ratio.Sometimes engine performance test starts from Ignition System, so research in testing and diagnosing method of Ignition System has important meaning.Along with development of testing and diagnosing technology, computer software and testing system integrates even more closely.Both frame conception and design means of instrument have breakthroughly change, appear a new-style instrument conception- virtual instrument(VI). VI's trait lies in internet application, which integrate many functions such as data gather, control, data analyse, output of result and so on. It realizes closely combination of computer and testing technology, represents development direction of instrument technology.In common use ignition System has three categories, their ignition principle are similar.Performances of ignition System are mostly describe and analyse by character parameters, common use character parameters including primary circuit voltage, sub-circuit voltage, closed angle of touch nod and overlap angle, advance ignition angle etc. Ignition System performance test commonly consist of two parts,measure voltage wave and advance ignition angle.By test evaluate ignition System performance all-round,and use in fault diagnose.This paper's research involves mainly the following aspects:1. Analyse and transact ignition voltage wave with means of wave analysis.In the interest of compare, array multi-cylinder engines'waves in term of ignition order to parallel wave, paratactic wave and overlap wave for display. In wave analysis, ordinarily divide sub-circuit voltage wave into four fault reflecting sections comprising ignition section, burning section, surging section and vibrant section, in convenient for analysis reflecting fault instance of subsection. All analyse means hereinbefore could be carry out by application of virtual instrument technology.Adjusting function of just-time Control in ignition system is evaluated currently by measure of advance ignition angle. The optimal ignition angle isn't a fixed value, it changes with engine rotate speed and load etc., ordinarily measure by just-time instrument.The paper consult principle of measure method of air pressure in cylinder, make research for application of virtual instrument technology in ignition time testing.2. For need of diagnose method research, apply Fault Tree Analysis to analyse imaginabale fault in ignition system, take three fault events which are be expected taken place least of all, as top event to protract fault tree analysis. According as compare and analysis of voltage wave occupy biggish proportion in the paper's research, introduce wave image matching theory into research of diagnose method. Use frame mode identify theory decompound complicated mode into some simple modes which are apt to analyse and calculate, consult partition method of wave fault analysis, divide wave into four subsections for expediently matching calculation, devise simplified matching arithmetic that select characteristic points to compare.3. Testing and diagnosing method which research based on virtual instrument technology, commonly involve two parts as hardware devise and software devise. According to research needs, in several choice data gather hardware composings, choose PC-DAQ instrument composing that based on computer PCI bus. For need of data gather, select type of head sensors especially engine rotate speed sensor and cylinder pressure sensor, and make research for signal pretreatment system. Data gather board is the most important part of data gather hardware composings, select product of Zhongtaiyanchuang in the paper, introduce technology parameter and setting technipue of the board detailed. Lastly analyse anti-jamming measures of data gather system.4. Virtual instrument software design is the hard core of method research, main function as data gather, data analyse and transact are fulfill by software. The research of the paper select graphical programme language LabVIEW of NI Company as study tool, make use of its merits as be prone to implement data gather and instrument control. The software designed by LabVIEW could commonly separate into three layers'hiberarchy, first software layer is make up of User interface and measure implement part, second software layer take charge of validate of logic relation and set down correlative decision-making, third software layer take charge of communicate between instrument and measured equipments or application. The main research of the paper is the first software layer designed, the second and third software layer implement mostly by LabVIEW's interrelated setting. Softpanel is designed for ultimate manipulator, softpanel designed in the paper take principia of easy-useing and nice-looking, manipulate mostly by menu from main interface stepwise to sub-interface with idiographic function ,to fulfill testing or diagnosing function of whole system. Software drive layer's function are fulfilled by setting with MAX. The holistic software design in term of modularization, could be drived into data gather module, data analyse module and assiatant function modules. We should know difference between each module and every manipulating layer are not absolute independence, in fact are contact and dependence with definite logic connection, by these to fulfill whole function of the system.5. Research of trial and simulation are crucial step of validate research method which designed by virtual instrument. In the paper, we choose a sort of familiar vehicle to test its ignition system, limit to trail condition we devise several typical fault types of ignition system with simulating research, present analysis and outcome of testing trail and simulating diagnose mostly with wave image and data table.Through these research steps, elementarily validate feasibility and validity of studied testing and diagnosing methods.The virtual instrument testing and diagnosing system in this paper should be improved in future, for some factors like time restrictions and financial shortage, and so on.