Input observer convergence and robustness: Application to compression ratio estimation

The focus of this paper is the analysis of a high-gain observer for estimating un-steady inputs, including guarantees for: (1) robustness to measurement uncertainty, and (2) transient upper bound on estimator error. A method for selecting the observer gain based on measurement uncertainty, acceptable steady-state errors, and desired estimation error convergence rates, is also described. This strategy is demonstrated in practice for internal combustion (IC) engine effective compression ratio (ECR) estimation. Experimental results are shown to be consistent with analytical guarantees—convergence within 4 engine cycles, and a steady-state error less than 0.5 ECR, in the presence of 10% measurement error.