Function development of real-time detection for engine misfire fault based on adaptive threshold diagnosis
To address the limitations of the current on-board diagnostic system(OBD)misfire diagnosis strategy in functional logic,result output and threshold calibration,this paper proposes a diagnosis strategy of adaptive threshold algorithm without additional calculations and hardware resources.This strategy,based on the angle domain recogni-tion method,uses the relative divergence analysis to find the misfire-sensitive area in real time and obtain the calcu-lation time segment.To construct the misfire characteristic signals,the change value of each segment is calculated based on each working cylinder time segment and using the weighted average.The signals are then used as the diag-nosis and analysis object.For the threshold adaptive process,the basic threshold is defined according to the engine speed and load,the actual threshold with the working cylinder time segment change for random misfire mode is cor-rected,along with the minimum value of the misfire characteristic signal with separated-cylinder filtering in the cur-rent working cycle for continuous misfire mode.The actual vehicle verification results showed that the diagnosis threshold can be adjusted adaptively in real-time with the changes of engine operation points by the misfire character-istic signals in this strategy.Furthermore,the misfire diagnosis effect was also improved under high-speed and low-load conditions.The diagnosis results could also be outputted in the current operation cylinder time,and the diagno-sis real-time performance was promoted by 89%.In addition,under the continuous misfire mode,the positive ampli-tude of the misfire characteristic signal with separated-cylinder filtering was increased by more than 25%.Various misfire types were detected in the whole operation range of the engine,and it did not need to set the diagnosis thresh-old with vehicle driving status and conditions,thus reducing a large amount of calibration work and decreasing the impact of the vehicle difference.
adaptive thresholdon-board diagnostics(OBD)misfire detectionrandom misfirecontinuous mis-firemultiple misfirediagnosis algorismstrategy development
国家科技期刊平台
NSTL
万方数据
维普
