Predictive associative search models found a wide application in advanced control systems, decision making systems, play a fundamental role in any activity concerned with the signal processing process. In the paper, associative search identification models in variable structure control systems are considered. The application of this approach is especially effective whilst compensating for insufficient lab data for model development. In such a case, fuzzy specification of certain process variables using process knowledge base is practiced. A methodology of the synthesis of a variable structure control system is presented, as well issues of the stability of a model built by use of the associative search are considered, in the aspect of the spectrum analysis of the multi-scale wavelet expansion.