Research On Key Technology Of Octane Number Measuring Machine

The anti-knock performance of gasoline is generally measured by the octane number,which is the most important indicator in gasoline detection.Octane number tester is a special instrument for detecting octane number in gasoline.However,in the current domestic octane tester,the measurement of the knock signal is unstable,and the closing angle control in the ignition system is unstable,which affects the experimental results.In order to improve the stability of the octane measuring machine in the working process,this paper has completed the design of the knock signal pre-processing circuit and the ignition controller circuit,and the knock signal filtering method and automatic search for the maximum level of the knock level The height method was studied.The main work of this article is as follows:1?The preprocessing and preliminary filtering of the knock signal were studied,and the design of the knock signal preprocessing circuit was completed.The knock signal is a weak AC signal,which is amplified and converted into a DC signal proportional to the knock intensity.It is a problem that needs to be resolved in the pre-processing of the knock signal.By calculating the characteristic frequency of the pressure wave in the cylinder,a band-pass filter is designed to filter out the ambient noise outside the characteristic frequency of the knock.Amplification,using a threshold amplification adjustable circuit for processing;finally,a half-wave rectification and integration circuit is used to retain the half-waveform of the amplified AC signal and obtain the peak value of each pulse of the signal.The DC signal meets the basic requirements for reading the knock signal.2?Using the method of compound morphological filtering,the denoising method of detonation signal is studied.The signal after the detonation signal pre-processing circuit still has a large noise.A filtering method is used to extract the real detonation signal from the noise-containing signal.Analysis of the processing results of the knocking signal by the moving average filter and the general morphological filter shows that the general morphological filter meets the requirements except that the lag time is too long.Analyze the structure of the morphological filter and its calculation principle.The first-order RC filter with a short lag time is used to replace part of the morphological filter algorithm to reduce its lag and combine to form a composite morphological filter.The algorithm of the morphological filter has directivity.When designing the first-order RC filter,it also has the corresponding directivity.Finally,through experimental analysis,it is found that the knock signal processed by the composite morphological filter is stable and has a small amount of lag,which meets the requirements of the experiment.3?By adopting the method of automatic adjustment and fuzzy control of the carburetor liquid level,an automatic search for the liquid level of the maximum knock intensity is realized.In this paper,fuzzy control method is used to automatically search the liquid level.Firstly,based on the experimental operation experience,the fuzzy controller was determined as a three-input single-output controller.The difference between three consecutive periodic detonation signals is used as the input of the fuzzy controller,and the triangular membership function is used to blur it into a fuzzy amount.The fuzzy variables and set fuzzy control rules are calculated by the sum-product fuzzy inference method to calculate the output fuzzy amount.Finally,the fuzzy average canceller is used to eliminate the blur to get the output variable,that is,the amount of change in liquid level.4?By analyzing and studying the factors and conditions that affect the stability of the ignition closure angle,the optimization design of the ignition controller is completed.The octane tester is a single-cylinder low-speed engine.Common ignition controllers used in this instrument will experience problems with excessively wide primary current pulse widths and unstable closure angle control.Observe the state of each part of the entire ignition process by observing the waveform of the Hall signal,the voltage of the closing angle,and the current in the primary coil during the ignition process.By adding a constant current source in the peripheral circuit to change the proportion of the charge-discharge current at the closed angle,the phenomenon that the primary current pulse width is too wide is reduced.By changing the closing angle capacitance,the voltage is changed to meet the closing stability conditions at low speeds.The optimized ignition control was successfully applied to the octane number measuring machine,and the operation was stable to meet the needs of use.