Abstract
As a crucial and critical factor in monitoring the internal state of an engine, cylinder pressure is mainly used to monitor the burning efficiency, to detect engine faults, and to compute engine dynamics. Although the intrusive type cylinder pressure sensor has been greatly improved, it has been criticized by researchers for high cost, low reliability and short life due to severe working environments. Therefore, aimed at low-cost, real-time, non-invasive, and high-accuracy, this paper presents the cylinder pressure identification method also called a virtual cylinder pressure sensor, involving Frequency-Amplitude Modulated Fourier Series (FAMFS) and Extended-Kalman-Filter-optimized (EKF) engine model. This paper establishes an iterative speed model based on burning theory and Law of energy Conservation. Efficiency coefficient is used to represent operating state of engine from fuel to motion. The iterative speed model associated with the throttle opening value and the crankshaft load. The EKF is used to estimate the optimal output of this iteration model. The optimal output of the speed iteration model is utilized to separately compute the frequency and amplitude of the cylinder pressure cycle-to-cycle. A standard engine’s working cycle, identified by the 24th order Fourier series, is determined. Using frequency and amplitude obtained from the iteration model to modulate the Fourier series yields a complete pressure model. A commercial engine (EA211) provided by the China FAW Group corporate R&D center is used to verify the method. Test results show that this novel method possesses high accuracy and real-time capability, with an error percentage for speed below 9.6% and the cumulative error percentage of cylinder pressure less than 1.8% when A/F Ratio coefficient is setup at 0.85. Error percentage for speed below 1.7% and the cumulative error percentage of cylinder pressure no more than 1.4% when A/F Ratio coefficient is setup at 0.95. Thus, the novel method’s accuracy and feasibility are verified.
Highlights
The development of cleaner and more efficient engines requires the continuous measurement of in-cylinder pressure which is of fundamental importance for combustion optimization, air-fuel ratio control, noise and pollutant reduction
The amount of air and fuel trapped in the cylinder is relatively influenced by engine speed through the volumetric efficiency, and mainly depends on the engine load
Theof validity of the cylinder proposedpressure method issensor verified by comparing the identification value cylinder pressure sensor
Summary
The development of cleaner and more efficient engines requires the continuous measurement of in-cylinder pressure which is of fundamental importance for combustion optimization, air-fuel ratio control, noise and pollutant reduction. Cylinder pressure is a fundamental intermediate variable that indicates engine state and drives models for engine combustion control. High-bandwidth control of ignition and the air-fuel ratio may permit these engines to operate reliably near the lean-burn limit, with significant improvements in efficiency and decreased emission of CO and NOx. High-bandwidth control of ignition and the air-fuel ratio may permit these engines to operate reliably near the lean-burn limit, with significant improvements in efficiency and decreased emission of CO and NOx Utilizing this technology requires a key factor: real-time cylinder pressure [1]. Control of torque balance can improve drivability and can suppress noise from light-duty diesel engines, but as a crucial part of the control algorithm, obtaining pressure data necessitates expensive pressure sensors and demands considerable computational time [3]
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