Design And Implementation Of Calibrating Timing Advance Processor

Application of natural gas is increasingly valued by various countries in the world in the automobile industry due to its economic value and the shortage of petroleum energy.Currently,more and more taxis in China choose to use the natural gas,and meanwhile large-scale auto makers also study the natural gas automobiles intensively.However,the bi-fuel engine modified based on a gasoline engine may have declined dynamic properties due to different physicochemical characteristics of the natural gas and the gasoline and cannot comply with the demand of a driver.Aiming at the microcomputer control ignition CNG/gasoline bi-fuel engine,the correct timed ignition of the engine was achieved by adjusting the ignition advance angle according to the characteristics of high octane value and low flame propagation velocity of the natural gas;based on analysis of the working principle of the bi-fuel engine electric control ignition system and the electric control system,the engine was calibrated under different conditions to acquire the optimum ignition advance angle,thus the automobile can achieve good dynamic properties.This design selected PIC16F873 A.In terms of hardware design,sensor signals were processed.Information such as engine speed,top dead center and intake pressure value was acquired by processing crankshaft position sensor signals,camshaft position sensor signals and throttle position sensor signals.The information was subsequently sent to the PC end via the communication module processing loop.A test was performed by utilizing the built test platform and the designed ignition advance angle regulator design program to obtain the optimum ignition advance angle at different speeds and intake pressure values,and then the optimum ignition advance angle was written into the MCU of the ignition advance angle regulator via the communication module processing loop.When the automobile ran under a certain working condition,the optimum ignition advance angle stored in the MCU was chosen to perform ignition.After adjustment,the ignition advance angle regulator could achieve ignition of the bi-fuel engine at the optimum time when the natural gas was used,thereby complying with the technical requirements of the early design phase,stabilizing system operation and achieving good application.