Adaptive identifier with a self-tuning filter

It is shown that the performance of the adaptive identifier of equation error type can be improved substantially by updating the filter online. It is known that, in the presence of uncertainty, the equation error method would not produce an estimate which has a good fit at low frequencies. To fix the problem, the identification schemes are modified by making filters time varying, and these time varying filters are updated online such that the estimate converges to a value that would be obtained by the output error method. In this way, the effects of the uncertainty are reduced