Analog Circuit Implementation of a Variable Universe Adaptive Fuzzy Logic Controller

A novel analog integrated circuit implementation of an adaptive fuzzy logic controller (AFLC), called variable universe fuzzy logic controller (VFLC), is presented which has not been reported before. The VFLC is a stable controller which has fewer on-line adapting parameters than the conventional AFLCs based on adapting fuzzy rules, thus it is more suitable for hardware implementation. The input and output universes of discourse of the VFLC are adaptively changed according to the input variables to improve the control effect. A novel peaky-triangle membership function is presented to realize the complex input universe variation. The absolute value of the integral of the input variables is used for the output universe variation, and then it is multiplied with the output of the conventional fuzzy logic controller to form the final output. The other parts are minimization circuits and a center of gravity defuzzification circuit that does not use a division circuit. An analog VFLC with 2 inputs, 1 output, and 9 rules is designed and fabricated using a 0.6-mum CMOS standard technology. It can work either in a non-adaptive or an adaptive mode. The measurements show that it completes the VFLC functions.