A novel extraction method for combustion feature of CI engine in electric hybrid power based on engine instantaneous speed

Hybrid power systems represent a crucial avenue for the advancement of vehicle power, offering a novel framework and context for the intelligent evolution of internal combustion engines. The governance of internal combustion engines stands as the cornerstone of power intelligence, with in-cylinder combustion control serving as a pivotal research focus within the realm of internal combustion engine regulation. The accurate assessment of cylinder state in hybrid power systems forms the foundation for effective in-cylinder combustion control. This paper introduces an approach to extract cylinder combustion state (cylinder work and CA50) based on instantaneous speed signals. First, the instantaneous speed signal undergoes processing using synthetic speed algorithms, followed by an evaluation of algorithm effectiveness. Subsequently, the theoretical derivation of the relationship between synthesized speed signals and cylinder state is established based on conservation of energy principles, leading to a method for extracting cylinder state. Finally, experimental validation is conducted at 270 steady-state operating points (varied speeds and load ratios) and 2 dynamic processes to verify prediction accuracy using the proposed method. The results demonstrate precise prediction capabilities for both cylinder work and CA50, with prediction errors falling within ≤10 % for CA50 and ≤9 % for cylinder work; moreover, 97 % of steady-state operating points exhibit error ranges within 5 % or less and the average error of dynamic process is 5 %.