Optimal A/F Ratio Estimation Model (Synthetic UEGO) for SI Engine Cold Transient AFR Feedback Control

Paper #:
  • 980798

Published:
  • 1998-02-23
Citation:
Tang, X., Asik, J., Meyer, G., and Samson, R., "Optimal A/F Ratio Estimation Model (Synthetic UEGO) for SI Engine Cold Transient AFR Feedback Control," SAE Technical Paper 980798, 1998, https://doi.org/10.4271/980798.
Pages:
11
Abstract:
A new method to estimate instantaneous A/F ratio and use the estimation as a feedback signal to control AFR during cold transients, before the oxygen sensor is functional, has been realized by a on-board PCM for a vehicle with a 4.6L, V8, PFI engine [4, 6]. Different AFRs cause variations in flame propagation, causing fluctuations in the effective torque. When a known AFR disturbance is induced into an engine system, a corresponding crankshaft angular velocity fluctuation can be detected. A variable derived from this physical phenomenon can be used to characterize the problem. The optimal fuel perturbation signal is designed by a relaxation concept, and the system model is determined by employing a dual-direction screening multivariate stepwise regression analysis. The estimated AFR is used by the PCM in a closed loop control to correct the fuel during cold transients.
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