Current-mode fuzzy linguistic hedge circuits

In this paper, a current-mode design methodology to implement a set of fuzz y linguistic hedge circuits is proposed. The so-called fuzzy linguistic hed ge is a fuzzy operation applied to adjust the membership function of a fuzz y set. The fuzzy membership function of control variable and the control ru les are very important in a fuzzy logic controller because they dominate th e control strategies. If the control results fail to meet the system requir ements, the control objective can still be achieved by adjusting the member ship function of the fuzzy set or the control rules. Moreover, the adjustme nt effect of the control strategies through the modifications of the fuzzy membership function is the same as that of the system control rules. In thi s paper, we propose a set of fuzzy linguistic hedge circuits, including abs olutely, very, much more, more, plus minus, more or less, slightly, and con trast intensification, which has been fabricated in 0.8 mu m CMOS process. Experimental results show that the average error of the circuits is within 1% of the full scale current. Under the power supply voltage of 3.3 V, the operating dynamic range is 50 mu A. Furthermore, these circuits still work well even when the power supply voltage is down to 2.5 V. In addition, in r eal world application, we can incorporate a membership function generator, a fuzzification unit, a multi-input maximum/minimum circuit, and a defuzzif ication unit with the linguistic hedge used to modify the membership functi on in order to develop a real-time adaptive fuzzy logic controller.