Identification and control of nonlinear systems using multiple models: relay feedback approach

The relay feedback autotuning is extended to handle process nonlinearity. Local models from relay feedback tests are scheduled using the Takagi-Sugeno fuzzy modeling. The characteristics of the fuzzy implications are analyzed and an even simpler model is explored. The importance of the selection of the scheduled parameters is emphasized. One transfer function example and a recycle plant are used to illustrated the advantage of the simple model scheduling method. More importantly, the improved control performance can be achieved using already known process knowledge.