A Fuzzy Logic Based Multiple Reference Model Adaptive Control

This paper presents a fuzzy logic approach for switching multiple reference models, within the Model Reference Adaptive Control (MRAC) framework, in response to major changes in the plant operating conditions. Following a rule base, the fuzzy switching scheme effectively monitors changes in operating conditions or such drastic changes in plant. A fuzzy inference engine then fires appropriate rules, which gives a fuzzified output value. Defuzzification is then performed to switch the reference model in a predefined domain. The whole process is conducted on line, monitoring the plant auxiliary inputs at selected control intervals. The main contribution of the paper is that the proposed fuzzy switching scheme can be performed online and is very well suitable for multi modal jump systems. Unlike, static multiple model algorithms for switching (non-interacting individual model-based filters) or switching dynamic algorithms (susceptible to numerical overflow), this scheme provides an interactive multiple model environment with soft switching. The scheme is computationally feasible, effective and efficient. The proposed scheme is applied to an example system with disturbed model parameters to show its effectiveness.