Identification of Continuous Systems – Practical Issues of Insensitivity to Perturbations

In this paper the issue of continuous systems estimation, insensitive to certain perturbations, is presented and discussed. Such an approach has rational advantages, especially when robust schemes are used to assist a target system responsible for industrial diagnostics. This requires that estimated model parameters are generated on-line, and their values are reliable and to a great extent accurate. Practical hints are suggested to challenge the consistency problem of estimates. Namely, the technique of instrumental variables can improve the asymptotic behavior of estimators. With a weighting mechanism, in turn, tracking the time-varying parameters of non-stationary processes is realistic. Yet, evident insensitivity to destructive outliers in the measurement data is guaranteed by the applied estimation routine in the sense of the least sum of absolute errors. Finally, premises for a proper selection of persistently exciting input signals, as well as the directions of further research are summarized in the paper.