Pressure signal processing algorithm for fuel oil leakage diagnosis

Abstract

A pressure signal processing algorithm for fuel oil leakage diagnosis comprises the following steps: for a filtered fuel tank pressure signal, identifying periodically fluctuating wave crests and wavetroughs, evaluating the stable state of the fuel tank pressure signal, and identifying a pressure gradient calculation starting point; classifying the initial oil tank pressure signals: when the pressure fluctuates upwards and has obvious wave troughs and wave crests and the fluctuation energy has convergence characteristics, respectively identifying two wave crests and two wave troughs to calculate the slope, and calculating the average value of the slope; only recognizing one wave crest and one wave trough, recalculating the starting point of only one wave crest and one wave trough, calculating the slope with the starting point every unit time in a certain time period, and solving the slope average value; not recognizing wave troughs and wave crests within a certain time, calculating the slope with the starting point every unit time, and solving the slope average value for diagnosis; indicating that no fluctuation exists in pressure ascending, at the moment, enabling the pressure change energy of the oil tank to tend to be 0 due to the fluctuation of the liquid level; in a certain time period, calculating the slope with the starting point every unit time, and calculating the average value of the slope for diagnosis.

Description

technical field [0001] The invention relates to a method for diagnosing fuel oil leakage, in particular to an algorithm for processing fuel tank pressure signals during the fuel oil leakage diagnosis stage. Background technique [0002] "GB18352.6-2016 Light Vehicle Exhaust Pollutant Emission Limits and Measurement Methods (China Six Stages)" revised the technical requirements for monitoring items, thresholds and monitoring conditions of on-board diagnostic systems. When the vehicle has the following conditions, the OBD system should detect the failure of the evaporation system: (1) There are one or more leakage points in the entire evaporation system, and the leakage of these leakage points is greater than or equal to the leakage generated by a small hole with a diameter of 1mm . (2) The fuel tank cap of the fuel tank is not tightened or the fuel tank cap is missing. [0003] The previous fuel leakage diagnosis method uses the pressure decay gradient calculation: pressure...

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Problems solved by technology

(2) The fuel tank cap of the fuel tank is not tightened or the fuel tank cap is missing

[0003] The previous fuel leakage diagnosis method uses the pressure decay gradient calculation: pressure decay gradient = (end point fuel tank pressure - start point pressure) / pressure holding time, so when the start point and end point pressure appear peaks or troughs will cause pressure decay Inaccurate gradient calculation

Due to the structure of the fuel tank of a certain project, it is flat and long. Due to the avoidance of the frame beam, the liquid level of the fuel tank is above 45L, so it is divided into two cavities by its groove. In addition, the fuel tank is arranged longitudinally. When the vehicle changes its motion state, the inside of the fuel tank The oil shakes back and forth, which will periodically squeeze the front and rear cavities, resulting in periodic fluctuations in the fuel tank pressure, and the fluctuations are large, and cannot be stabilized for a long time, resulting in inaccurate calculation of the fuel tank pressure decay gradient calculated when entering the diagnosis. Risk of False Positive and Missing Negative 1mm Leakage Failures

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